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Types of Literature Review — A Guide for Researchers

Table of Contents

Researchers often face challenges when choosing the appropriate type of literature review for their study. Regardless of the type of research design and the topic of a research problem , they encounter numerous queries, including:

What is the right type of literature review my study demands?

• How do we gather the data?
• How to conduct one?
• How reliable are the review findings?
• How do we employ them in our research? And the list goes on.

If you’re also dealing with such a hefty questionnaire, this article is of help. Read through this piece of guide to get an exhaustive understanding of the different types of literature reviews and their step-by-step methodologies along with a dash of pros and cons discussed.

Heading from scratch!

What is a Literature Review?

A literature review provides a comprehensive overview of existing knowledge on a particular topic, which is quintessential to any research project. Researchers employ various literature reviews based on their research goals and methodologies. The review process involves assembling, critically evaluating, and synthesizing existing scientific publications relevant to the research question at hand. It serves multiple purposes, including identifying gaps in existing literature, providing theoretical background, and supporting the rationale for a research study.

What is the importance of a Literature review in research?

Literature review in research serves several key purposes, including:

• Background of the study: Provides proper context for the research. It helps researchers understand the historical development, theoretical perspectives, and key debates related to their research topic.
• Identification of research gaps: By reviewing existing literature, researchers can identify gaps or inconsistencies in knowledge, paving the way for new research questions and hypotheses relevant to their study.
• Theoretical framework development: Facilitates the development of theoretical frameworks by cultivating diverse perspectives and empirical findings. It helps researchers refine their conceptualizations and theoretical models.
• Methodological guidance: Offers methodological guidance by highlighting the documented research methods and techniques used in previous studies. It assists researchers in selecting appropriate research designs, data collection methods, and analytical tools.
• Quality assurance and upholding academic integrity: Conducting a thorough literature review demonstrates the rigor and scholarly integrity of the research. It ensures that researchers are aware of relevant studies and can accurately attribute ideas and findings to their original sources.

Types of Literature Review

Literature review plays a crucial role in guiding the research process , from providing the background of the study to research dissemination and contributing to the synthesis of the latest theoretical literature review findings in academia.

However, not all types of literature reviews are the same; they vary in terms of methodology, approach, and purpose. Let's have a look at the various types of literature reviews to gain a deeper understanding of their applications.

1. Narrative Literature Review

A narrative literature review, also known as a traditional literature review, involves analyzing and summarizing existing literature without adhering to a structured methodology. It typically provides a descriptive overview of key concepts, theories, and relevant findings of the research topic.

Unlike other types of literature reviews, narrative reviews reinforce a more traditional approach, emphasizing the interpretation and discussion of the research findings rather than strict adherence to methodological review criteria. It helps researchers explore diverse perspectives and insights based on the research topic and acts as preliminary work for further investigation.

Steps to Conduct a Narrative Literature Review

Source:- https://www.researchgate.net/figure/Steps-of-writing-a-narrative-review_fig1_354466408

Define the research question or topic:

The first step in conducting a narrative literature review is to clearly define the research question or topic of interest. Defining the scope and purpose of the review includes — What specific aspect of the topic do you want to explore? What are the main objectives of the research? Refine your research question based on the specific area you want to explore.

Conduct a thorough literature search

Once the research question is defined, you can conduct a comprehensive literature search. Explore and use relevant databases and search engines like SciSpace Discover to identify credible and pertinent, scholarly articles and publications.

Select relevant studies

Before choosing the right set of studies, it’s vital to determine inclusion (studies that should possess the required factors) and exclusion criteria for the literature and then carefully select papers. For example — Which studies or sources will be included based on relevance, quality, and publication date?

*Important (applies to all the reviews): Inclusion criteria are the factors a study must include (For example: Include only peer-reviewed articles published between 2022-2023, etc.). Exclusion criteria are the factors that wouldn’t be required for your search strategy (Example: exclude irrelevant papers, preprints, written in non-English, etc.)

Critically analyze the literature

Once the relevant studies are shortlisted, evaluate the methodology, findings, and limitations of each source and jot down key themes, patterns, and contradictions. You can use efficient AI tools to conduct a thorough literature review and analyze all the required information.

Synthesize and integrate the findings

Now, you can weave together the reviewed studies, underscoring significant findings such that new frameworks, contrasting viewpoints, and identifying knowledge gaps.

Discussion and conclusion

This is an important step before crafting a narrative review — summarize the main findings of the review and discuss their implications in the relevant field. For example — What are the practical implications for practitioners? What are the directions for future research for them?

Write a cohesive narrative review

Organize the review into coherent sections and structure your review logically, guiding the reader through the research landscape and offering valuable insights. Use clear and concise language to convey key points effectively.

Structure of Narrative Literature Review

A well-structured, narrative analysis or literature review typically includes the following components:

• Introduction: Provides an overview of the topic, objectives of the study, and rationale for the review.
• Background: Highlights relevant background information and establish the context for the review.
• Main Body: Indexes the literature into thematic sections or categories, discussing key findings, methodologies, and theoretical frameworks.
• Discussion: Analyze and synthesize the findings of the reviewed studies, stressing similarities, differences, and any gaps in the literature.
• Conclusion: Summarizes the main findings of the review, identifies implications for future research, and offers concluding remarks.

Pros and Cons of Narrative Literature Review

• Flexibility in methodology and doesn’t necessarily rely on structured methodologies
• Follows traditional approach and provides valuable and contextualized insights
• Suitable for exploring complex or interdisciplinary topics. For example — Climate change and human health, Cybersecurity and privacy in the digital age, and more
• Subjectivity in data selection and interpretation
• Potential for bias in the review process
• Lack of rigor compared to systematic reviews

Example of Well-Executed Narrative Literature Reviews

Paper title:  Examining Moral Injury in Clinical Practice: A Narrative Literature Review

Source: SciSpace

You can also chat with the papers using SciSpace ChatPDF to get a thorough understanding of the research papers.

While narrative reviews offer flexibility, academic integrity remains paramount. So, ensure proper citation of all sources and maintain a transparent and factual approach throughout your critical narrative review, itself.

2. Systematic Review

A systematic literature review is one of the comprehensive types of literature review that follows a structured approach to assembling, analyzing, and synthesizing existing research relevant to a particular topic or question. It involves clearly defined criteria for exploring and choosing studies, as well as rigorous methods for evaluating the quality of relevant studies.

It plays a prominent role in evidence-based practice and decision-making across various domains, including healthcare, social sciences, education, health sciences, and more. By systematically investigating available literature, researchers can identify gaps in knowledge, evaluate the strength of evidence, and report future research directions.

Steps to Conduct Systematic Reviews

Source:- https://www.researchgate.net/figure/Steps-of-Systematic-Literature-Review_fig1_321422320

Here are the key steps involved in conducting a systematic literature review

Formulate a clear and focused research question

Clearly define the research question or objective of the review. It helps to centralize the literature search strategy and determine inclusion criteria for relevant studies.

Develop a thorough literature search strategy

Design a comprehensive search strategy to identify relevant studies. It involves scrutinizing scientific databases and all relevant articles in journals. Plus, seek suggestions from domain experts and review reference lists of relevant review articles.

Screening and selecting studies

Employ predefined inclusion and exclusion criteria to systematically screen the identified studies. This screening process also typically involves multiple reviewers independently assessing the eligibility of each study.

Data extraction

Extract key information from selected studies using standardized forms or protocols. It includes study characteristics, methods, results, and conclusions.

Critical appraisal

Evaluate the methodological quality and potential biases of included studies. Various tools (BMC medical research methodology) and criteria can be implemented for critical evaluation depending on the study design and research quetions .

Data synthesis

Analyze and synthesize review findings from individual studies to draw encompassing conclusions or identify overarching patterns and explore heterogeneity among studies.

Interpretation and conclusion

Interpret the findings about the research question, considering the strengths and limitations of the research evidence. Draw conclusions and implications for further research.

The final step — Report writing

Craft a detailed report of the systematic literature review adhering to the established guidelines of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). This ensures transparency and reproducibility of the review process.

By following these steps, a systematic literature review aims to provide a comprehensive and unbiased summary of existing evidence, help make informed decisions, and advance knowledge in the respective domain or field.

Structure of a systematic literature review

A well-structured systematic literature review typically consists of the following sections:

• Introduction: Provides background information on the research topic, outlines the review objectives, and enunciates the scope of the study.
• Methodology: Describes the literature search strategy, selection criteria, data extraction process, and other methods used for data synthesis, extraction, or other data analysis..
• Results: Presents the review findings, including a summary of the incorporated studies and their key findings.
• Discussion: Interprets the findings in light of the review objectives, discusses their implications, and identifies limitations or promising areas for future research.
• Conclusion: Summarizes the main review findings and provides suggestions based on the evidence presented in depth meta analysis.

*Important (applies to all the reviews): Remember, the specific structure of your literature review may vary depending on your topic, research question, and intended audience. However, adhering to a clear and logical hierarchy ensures your review effectively analyses and synthesizes knowledge and contributes valuable insights for readers.

Pros and Cons of Systematic Literature Review

• Adopts rigorous and transparent methodology
• Minimizes bias and enhances the reliability of the study
• Provides evidence-based insights
• Time and resource-intensive
• High dependency on the quality of available literature (literature research strategy should be accurate)
• Potential for publication bias

Example of Well-Executed Systematic Literature Review

Paper title: Systematic Reviews: Understanding the Best Evidence For Clinical Decision-making in Health Care: Pros and Cons.

Read this detailed article on how to use AI tools to conduct a systematic review for your research!

3. Scoping Literature Review

A scoping literature review is a methodological review type of literature review that adopts an iterative approach to systematically map the existing literature on a particular topic or research area. It involves identifying, selecting, and synthesizing relevant papers to provide an overview of the size and scope of available evidence. Scoping reviews are broader in scope and include a diverse range of study designs and methodologies especially focused on health services research.

The main purpose of a scoping literature review is to examine the extent, range, and nature of existing studies on a topic, thereby identifying gaps in research, inconsistencies, and areas for further investigation. Additionally, scoping reviews can help researchers identify suitable methodologies and formulate clinical recommendations. They also act as the frameworks for future systematic reviews or primary research studies.

Scoping reviews are primarily focused on —

• Emerging or evolving topics — where the research landscape is still growing or budding. Example — Whole Systems Approaches to Diet and Healthy Weight: A Scoping Review of Reviews .
• Broad and complex topics : With a vast amount of existing literature.
• Scenarios where a systematic review is not feasible: Due to limited resources or time constraints.

Steps to Conduct a Scoping Literature Review

While Scoping reviews are not as rigorous as systematic reviews, however, they still follow a structured approach. Here are the steps:

Identify the research question: Define the broad topic you want to explore.

Identify Relevant Studies: Conduct a comprehensive search of relevant literature using appropriate databases, keywords, and search strategies.

Select studies to be included in the review: Based on the inclusion and exclusion criteria, determine the appropriate studies to be included in the review.

Data extraction and charting : Extract relevant information from selected studies, such as year, author, main results, study characteristics, key findings, and methodological approaches.  However, it varies depending on the research question.

Collate, summarize, and report the results: Analyze and summarize the extracted data to identify key themes and trends. Then, present the findings of the scoping review in a clear and structured manner, following established guidelines and frameworks .

Structure of a Scoping Literature Review

A scoping literature review typically follows a structured format similar to a systematic review. It includes the following sections:

• Introduction: Introduce the research topic and objectives of the review, providing the historical context, and rationale for the study.
• Methods : Describe the methods used to conduct the review, including search strategies, study selection criteria, and data extraction procedures.
• Results: Present the findings of the review, including key themes, concepts, and patterns identified in the literature review.
• Discussion: Examine the implications of the findings, including strengths, limitations, and areas for further examination.
• Conclusion: Recapitulate the main findings of the review and their implications for future research, policy, or practice.

Pros and Cons of Scoping Literature Review

• Provides a comprehensive overview of existing literature
• Helps to identify gaps and areas for further research
• Suitable for exploring broad or complex research questions
• Doesn’t provide the depth of analysis offered by systematic reviews
• Subject to researcher bias in study selection and data extraction
• Requires careful consideration of literature search strategies and inclusion criteria to ensure comprehensiveness and validity.

In short, a scoping review helps map the literature on developing or emerging topics and identifying gaps. It might be considered as a step before conducting another type of review, such as a systematic review. Basically, acts as a precursor for other literature reviews.

Example of a Well-Executed Scoping Literature Review

Paper title: Health Chatbots in Africa Literature: A Scoping Review

Check out the key differences between Systematic and Scoping reviews — Evaluating literature review: systematic vs. scoping reviews

4. Integrative Literature Review

Integrative Literature Review (ILR) is a type of literature review that proposes a distinctive way to analyze and synthesize existing literature on a specific topic, providing a thorough understanding of research and identifying potential gaps for future research.

Unlike a systematic review, which emphasizes quantitative studies and follows strict inclusion criteria, an ILR embraces a more pliable approach. It works beyond simply summarizing findings — it critically analyzes, integrates, and interprets research from various methodologies (qualitative, quantitative, mixed methods) to provide a deeper understanding of the research landscape. ILRs provide a holistic and systematic overview of existing research, integrating findings from various methodologies. ILRs are ideal for exploring intricate research issues, examining manifold perspectives, and developing new research questions.

Steps to Conduct an Integrative Literature Review

• Identify the research question: Clearly define the research question or topic of interest as formulating a clear and focused research question is critical to leading the entire review process.
• Literature search strategy: Employ systematic search techniques to locate relevant literature across various databases and sources.
• Evaluate the quality of the included studies : Critically assess the methodology, rigor, and validity of each study by applying inclusion and exclusion criteria to filter and select studies aligned with the research objectives.
• Data Extraction: Extract relevant data from selected studies using a structured approach.
• Synthesize the findings : Thoroughly analyze the selected literature, identify key themes, and synthesize findings to derive noteworthy insights.
• Critical appraisal: Critically evaluate the quality and validity of qualitative research and included studies by using BMC medical research methodology.
• Interpret and present your findings: Discuss the purpose and implications of your analysis, spotlighting key insights and limitations. Organize and present the findings coherently and systematically.

Structure of an Integrative Literature Review

• Introduction : Provide an overview of the research topic and the purpose of the integrative review.
• Methods: Describe the opted literature search strategy, selection criteria, and data extraction process.
• Results: Present the synthesized findings, including key themes, patterns, and contradictions.
• Discussion: Interpret the findings about the research question, emphasizing implications for theory, practice, and prospective research.
• Conclusion: Summarize the main findings, limitations, and contributions of the integrative review.

Pros and Cons of Integrative Literature Review

• Informs evidence-based practice and policy to the relevant stakeholders of the research.
• Contributes to theory development and methodological advancement, especially in the healthcare arena.
• Integrates diverse perspectives and findings
• Time-consuming process due to the extensive literature search and synthesis
• Requires advanced analytical and critical thinking skills
• Potential for bias in study selection and interpretation
• The quality of included studies may vary, affecting the validity of the review

Example of Integrative Literature Reviews

Paper Title: An Integrative Literature Review: The Dual Impact of Technological Tools on Health and Technostress Among Older Workers

5. Rapid Literature Review

A Rapid Literature Review (RLR) is the fastest type of literature review which makes use of a streamlined approach for synthesizing literature summaries, offering a quicker and more focused alternative to traditional systematic reviews. Despite employing identical research methods, it often simplifies or omits specific steps to expedite the process. It allows researchers to gain valuable insights into current research trends and identify key findings within a shorter timeframe, often ranging from a few days to a few weeks — unlike traditional literature reviews, which may take months or even years to complete.

When to Consider a Rapid Literature Review?

• When time impediments demand a swift summary of existing research
• For emerging topics where the latest literature requires quick evaluation
• To report pilot studies or preliminary research before embarking on a comprehensive systematic review

Steps to Conduct a Rapid Literature Review

• Define the research question or topic of interest. A well-defined question guides the search process and helps researchers focus on relevant studies.
• Determine key databases and sources of relevant literature to ensure comprehensive coverage.
• Develop literature search strategies using appropriate keywords and filters to fetch a pool of potential scientific articles.
• Screen search results based on predefined inclusion and exclusion criteria.
• Extract and summarize relevant information from the above-preferred studies.
• Synthesize findings to identify key themes, patterns, or gaps in the literature.
• Prepare a concise report or a summary of the RLR findings.

Structure of a Rapid Literature Review

An effective structure of an RLR typically includes the following sections:

• Introduction: Briefly introduce the research topic and objectives of the RLR.
• Methodology: Describe the search strategy, inclusion and exclusion criteria, and data extraction process.
• Results: Present a summary of the findings, including key themes or patterns identified.
• Discussion: Interpret the findings, discuss implications, and highlight any limitations or areas for further research
• Conclusion: Summarize the key findings and their implications for practice or future research

Pros and Cons of Rapid Literature Review

• RLRs can be completed quickly, authorizing timely decision-making
• RLRs are a cost-effective approach since they require fewer resources compared to traditional literature reviews
• Offers great accessibility as RLRs provide prompt access to synthesized evidence for stakeholders
• RLRs are flexible as they can be easily adapted for various research contexts and objectives
• RLR reports are limited and restricted, not as in-depth as systematic reviews, and do not provide comprehensive coverage of the literature compared to traditional reviews.
• Susceptible to bias because of the expedited nature of RLRs. It would increase the chance of overlooking relevant studies or biases in the selection process.
• Due to time constraints, RLR findings might not be robust enough as compared to systematic reviews.

Example of a Well-Executed Rapid Literature Review

Paper Title: What Is the Impact of ChatGPT on Education? A Rapid Review of the Literature

A Summary of Literature Review Types

Tools and Resources for Conducting Different Types of Literature Reviews

Online scientific databases.

Platforms such as SciSpace , PubMed , Scopus , Elsevier , and Web of Science provide access to a vast array of scholarly literature, facilitating the search and data retrieval process.

Reference management software

Tools like SciSpace Citation Generator , EndNote, Zotero , and Mendeley assist researchers in organizing, annotating, and citing relevant literature, streamlining the review process altogether.

Automate Literature Review with AI tools

Automate the literature review process by using tools like SciSpace literature review which helps you compare and contrast multiple papers all on one screen in an easy-to-read matrix format. You can effortlessly analyze and interpret the review findings tailored to your study. It also supports the review in 75+ languages, making it more manageable even for non-English speakers.

Goes without saying — literature review plays a pivotal role in academic research to identify the current trends and provide insights to pave the way for future research endeavors. Different types of literature review has their own strengths and limitations, making them suitable for different research designs and contexts. Whether conducting a narrative review, systematic review, scoping review, integrative review, or rapid literature review, researchers must cautiously consider the objectives, resources, and the nature of the research topic.

If you’re currently working on a literature review and still adopting a manual and traditional approach, switch to the automated AI literature review workspace and transform your traditional literature review into a rapid one by extracting all the latest and relevant data for your research!

There you go!

Frequently Asked Questions

Narrative reviews give a general overview of a topic based on the author's knowledge. They may lack clear criteria and can be biased. On the other hand, systematic reviews aim to answer specific research questions by following strict methods. They're thorough but time-consuming.

A systematic review collects and analyzes existing research to provide an overview of a topic, while a meta-analysis statistically combines data from multiple studies to draw conclusions about the overall effect of an intervention or relationship between variables.

A systematic review thoroughly analyzes existing research on a specific topic using strict methods. In contrast, a scoping review offers a broader overview of the literature without evaluating individual studies in depth.

A systematic review thoroughly examines existing research using a rigorous process, while a rapid review provides a quicker summary of evidence, often by simplifying some of the systematic review steps to meet shorter timelines.

A systematic review carefully examines many studies on a single topic using specific guidelines. Conversely, an integrative review blends various types of research to provide a more comprehensive understanding of the topic.

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Systematic Reviews

• Types of Literature Reviews

What Makes a Systematic Review Different from Other Types of Reviews?

• Planning Your Systematic Review
• Database Searching
• Creating the Search
• Search Filters and Hedges
• Grey Literature
• Managing and Appraising Results
• Further Resources

Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91–108. doi:10.1111/j.1471-1842.2009.00848.x

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Literature Review: Types of literature reviews

• Traditional or narrative literature reviews
• Scoping Reviews
• Systematic literature reviews
• Annotated bibliography
• Keeping up to date with literature
• Finding a thesis
• Evaluating sources and critical appraisal of literature
• Managing and analysing your literature
• Further reading and resources

Types of literature reviews

The type of literature review you write will depend on your discipline and whether you are a researcher writing your PhD, publishing a study in a journal or completing an assessment task in your undergraduate study.

A literature review for a subject in an undergraduate degree will not be as comprehensive as the literature review required for a PhD thesis.

An undergraduate literature review may be in the form of an annotated bibliography or a narrative review of a small selection of literature, for example ten relevant articles. If you are asked to write a literature review, and you are an undergraduate student, be guided by your subject coordinator or lecturer.

The common types of literature reviews will be explained in the pages of this section.

• Narrative or traditional literature reviews
• Critically Appraised Topic (CAT)
• Scoping reviews
• Annotated bibliographies

These are not the only types of reviews of literature that can be conducted. Often the term "review" and "literature" can be confusing and used in the wrong context. Grant and Booth (2009) attempt to clear up this confusion by discussing 14 review types and the associated methodology, and advantages and disadvantages associated with each review.

Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies . Health Information & Libraries Journal, 26 , 91–108. doi:10.1111/j.1471-1842.2009.00848.x

What's the difference between reviews?

Researchers, academics, and librarians all use various terms to describe different types of literature reviews, and there is often inconsistency in the ways the types are discussed. Here are a couple of simple explanations.

• The image below describes common review types in terms of speed, detail, risk of bias, and comprehensiveness:

"Schematic of the main differences between the types of literature review" by Brennan, M. L., Arlt, S. P., Belshaw, Z., Buckley, L., Corah, L., Doit, H., Fajt, V. R., Grindlay, D., Moberly, H. K., Morrow, L. D., Stavisky, J., & White, C. (2020). Critically Appraised Topics (CATs) in veterinary medicine: Applying evidence in clinical practice. Frontiers in Veterinary Science, 7 , 314. https://doi.org/10.3389/fvets.2020.00314 is licensed under CC BY 3.0

• The table below lists four of the most common types of review , as adapted from a widely used typology of fourteen types of reviews (Grant & Booth, 2009).  

Grant, M.J. & Booth, A. (2009).  A typology of reviews: An analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26 (2), 91-108. https://doi.org/10.1111/j.1471-1842.2009.00848.x

See also the Library's  Literature Review guide.

Critical Appraised Topic (CAT)

For information on conducting a Critically Appraised Topic or CAT

Callander, J., Anstey, A. V., Ingram, J. R., Limpens, J., Flohr, C., & Spuls, P. I. (2017).  How to write a Critically Appraised Topic: evidence to underpin routine clinical practice.  British Journal of Dermatology (1951), 177(4), 1007-1013. https://doi.org/10.1111/bjd.15873 

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Different Types of Literature Review: Which One Fits Your Research?

By Laura Brown on 13th October 2023

You might not have heard that there are multiple kinds of literature review. However, with the progress in your academic career you will learn these classifications and may need to use different types of them. However, there is nothing to worry if you aren’t aware of them now, as here we are going to discuss this topic in detail.

There are approximately 14 types of literature review on the basis of their specific objectives, methodologies, and the way they approach and analyse existing literature in academic research. Of those 14, there are 4 major types. But before we delve into the details of each one of them and how they are useful in academics, let’s first understand the basics of literature review.

What is Literature Review?

A literature review is a critical and systematic summary and evaluation of existing research. It is an essential component of academic and research work, providing an overview of the current state of knowledge in a particular field.

In easy words, a literature review is like making a big, organised summary of all the important research and smart books or articles about a particular topic or question. It’s something scholars and researchers do, and it helps everyone see what we already know about that topic. It’s kind of like taking a snapshot of what we understand right now in a certain field.

It serves with some specific purpose in the research.

• Provides a comprehensive understanding of existing research on a topic.
• Identifies gaps, trends, and inconsistencies in the literature.
• Contextualise your own research within the broader academic discourse.
• Supports the development of theoretical frameworks or research hypotheses.

4 Major Types Of Literature Review

The four major types include, Narrative Review, Systematic Review, Meta-Analysis, and Scoping Review. These are known as the major ones because they’re like the “go-to” methods for researchers in academic and research circles. Think of them as the classic tools in the researcher’s toolbox. They’ve earned their reputation because they have a unique style for literature review introduction , clear steps and specific qualities that make them super handy for different research needs.

1. Narrative Review

Narrative reviews present a well-structured narrative that reads like a cohesive story, providing a comprehensive overview of a specific topic. These reviews often incorporate historical context and offer a broad understanding of the subject matter, making them valuable for researchers looking to establish a foundational understanding of their area of interest. They are particularly useful when a historical perspective or a broad context is necessary to comprehend the current state of knowledge in a field.

2. Systematic Review

Systematic reviews are renowned for their methodological rigour. They involve a meticulously structured process that includes the systematic selection of relevant studies, comprehensive data extraction, and a critical synthesis of their findings. This systematic approach is designed to minimise bias and subjectivity, making systematic reviews highly reliable and objective. They are considered the gold standard for evidence-based research as they provide a clear and rigorous assessment of the available evidence on a specific research question.

3. Meta Analysis

Meta analysis is a powerful method for researchers who prefer a quantitative and statistical perspective. It involves the statistical synthesis of data from various studies, allowing researchers to draw more precise and generalisable conclusions by combining data from multiple sources. Meta analyses are especially valuable when the aim is to quantitatively measure the effect size or impact of a particular intervention, treatment, or phenomenon.

4. Scoping Review

Scoping reviews are invaluable tools, especially for researchers in the early stages of exploring a topic. These reviews aim to map the existing literature, identifying gaps and helping clarify research questions. Scoping reviews provide a panoramic view of the available research, which is particularly useful when researchers are embarking on exploratory studies or trying to understand the breadth and depth of a subject before conducting more focused research.

Different Types Of Literature review In Research

There are some more approaches to conduct literature review. Let’s explore these classifications quickly.

5. Critical Review

Critical reviews provide an in-depth evaluation of existing literature, scrutinising sources for their strengths, weaknesses, and relevance. They offer a critical perspective, often highlighting gaps in the research and areas for further investigation.

6. Theoretical Review

Theoretical reviews are centred around exploring and analysing the theoretical frameworks, concepts, and models present in the literature. They aim to contribute to the development and refinement of theoretical perspectives within a specific field.

7. Integrative Review

Integrative reviews synthesise a diverse range of studies, drawing connections between various research findings to create a comprehensive understanding of a topic. These reviews often bridge gaps between different perspectives and provide a holistic overview.

8. Historical Review

Historical reviews focus on the evolution of a topic over time, tracing its development through past research, events, and scholarly contributions. They offer valuable context for understanding the current state of research.

9. Methodological Review

Among the different kinds of literature reviews, methodological reviews delve into the research methods and methodologies employed in existing studies. Researchers assess these approaches for their effectiveness, validity, and relevance to the research question at hand.

10. Cross-Disciplinary Review

Cross-disciplinary reviews explore a topic from multiple academic disciplines, emphasising the diversity of perspectives and insights that each discipline brings. They are particularly useful for interdisciplinary research projects and uncovering connections between seemingly unrelated fields.

11. Descriptive Review

Descriptive reviews provide an organised summary of existing literature without extensive analysis. They offer a straightforward overview of key findings, research methods, and themes present in the reviewed studies.

12. Rapid Review

Rapid reviews expedite the literature review process, focusing on summarising relevant studies quickly. They are often used for time-sensitive projects where efficiency is a priority, without sacrificing quality.

13. Conceptual Review

Conceptual reviews concentrate on clarifying and developing theoretical concepts within a specific field. They address ambiguities or inconsistencies in existing theories, aiming to refine and expand conceptual frameworks.

14. Library Research

Library research reviews rely primarily on library and archival resources to gather and synthesise information. They are often employed in historical or archive-based research projects, utilising library collections and historical documents for in-depth analysis.

Each type of literature review serves distinct purposes and comes with its own set of strengths and weaknesses, allowing researchers to choose the one that best suits their research objectives and questions.

Choosing the Ideal Literature Review Approach in Academics

In order to conduct your research in the right manner, it is important that you choose the correct type of review for your literature. Here are 8 amazing tips we have sorted for you in regard to literature review help so that you can select the best-suited type for your research.

• Clarify Your Research Goals: Begin by defining your research objectives and what you aim to achieve with the literature review. Are you looking to summarise existing knowledge, identify gaps, or analyse specific data?
• Understand Different Review Types: Familiarise yourself with different kinds of literature reviews, including systematic reviews, narrative reviews, meta-analyses, scoping reviews, and integrative reviews. Each serves a different purpose.
• Consider Available Resources: Assess the resources at your disposal, including time, access to databases, and the volume of literature on your topic. Some review types may be more resource-intensive than others.
• Alignment with Research Question: Ensure that the chosen review type aligns with your research question or hypothesis. Some types are better suited for answering specific research questions than others.
• Scope and Depth: Determine the scope and depth of your review. For a broad overview, a narrative review might be suitable, while a systematic review is ideal for an in-depth analysis.
• Consult with Advisors: Seek guidance from your academic advisors or mentors. They can provide valuable insights into which review type best fits your research goals and resources.
• Consider Research Field Standards: Different academic fields have established standards and preferences for different forms of literature review. Familiarise yourself with what is common and accepted in your field.
• Pilot Review: Consider conducting a small-scale pilot review of the literature to test the feasibility and suitability of your chosen review type before committing to a larger project.

Bonus Tip: Crafting an Effective Literature Review

Now, since you have learned all the literature review types and have understood which one to prefer, here are some bonus tips for you to structure a literature review of a dissertation .

• Clearly Define Your Research Question: Start with a well-defined and focused research question to guide your literature review.
• Thorough Search Strategy: Develop a comprehensive search strategy to ensure you capture all relevant literature.
• Critical Evaluation: Assess the quality and credibility of the sources you include in your review.
• Synthesise and Organise: Summarise the key findings and organise the literature into themes or categories.
• Maintain a Systematic Approach: If conducting a systematic review, adhere to a predefined methodology and reporting guidelines.
• Engage in Continuous Review: Regularly update your literature review to incorporate new research and maintain relevance.

Some Useful Tools And Resources For You

Effective literature reviews demand a range of tools and resources to streamline the process.

• Reference management software like EndNote, Zotero, and Mendeley helps organise, store, and cite sources, saving time and ensuring accuracy.
• Academic databases such as PubMed, Google Scholar, and Web of Science provide access to a vast array of scholarly articles, with advanced search and citation tracking features.
• Research guides from universities and libraries offer tips and templates for structuring reviews.
• Research networks like ResearchGate and Academia.edu facilitate collaboration and access to publications. Literature review templates and research workshops provide additional support.

Some Common Mistakes To Avoid

Avoid these common mistakes when crafting literature reviews.

• Unclear research objectives result in unfocused reviews, so start with well-defined questions.
• Biased source selection can compromise objectivity, so include diverse perspectives.
• Never miss on referencing; proper citation and referencing are essential for academic integrity.
• Don’t overlook older literature, which provides foundational insights.
• Be mindful of scope creep, where the review drifts from the research question; stay disciplined to maintain focus and relevance.

While Summing Up On Various Types Of Literature Review

As we conclude this classification of fourteen distinct approaches to conduct literature reviews, it’s clear that the world of research offers a multitude of avenues for understanding, analysing, and contributing to existing knowledge.

Whether you’re a seasoned scholar or a student beginning your academic journey, the choice of review type should align with your research objectives and the nature of your topic. The versatility of these approaches empowers you to tailor your review to the demands of your project.

Remember, your research endeavours have the potential to shape the future of knowledge, so choose wisely and dive into the world of literature reviews with confidence and purpose. Happy reviewing!

Laura Brown, a senior content writer who writes actionable blogs at Crowd Writer.

Literature Reviews

• Types of reviews
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Types of reviews and examples

Choosing a review type.

• 1. Define your research question
• 2. Plan your search
• 3. Search the literature
• 4. Organize your results
• 5. Synthesize your findings
• 6. Write the review
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• Meta-analysis
• Systematized

Definition:

"A term used to describe a conventional overview of the literature, particularly when contrasted with a systematic review (Booth et al., 2012, p. 265).

Characteristics:

• Provides examination of recent or current literature on a wide range of subjects
• Varying levels of completeness / comprehensiveness, non-standardized methodology
• May or may not include comprehensive searching, quality assessment or critical appraisal

Mitchell, L. E., & Zajchowski, C. A. (2022). The history of air quality in Utah: A narrative review.  Sustainability ,  14 (15), 9653.  doi.org/10.3390/su14159653

Booth, A., Papaioannou, D., & Sutton, A. (2012). Systematic approaches to a successful literature review. London: SAGE Publications Ltd.

"An assessment of what is already known about a policy or practice issue...using systematic review methods to search and critically appraise existing research" (Grant & Booth, 2009, p. 100).

• Assessment of what is already known about an issue
• Similar to a systematic review but within a time-constrained setting
• Typically employs methodological shortcuts, increasing risk of introducing bias, includes basic level of quality assessment
• Best suited for issues needing quick decisions and solutions (i.e., policy recommendations)

Learn more about the method:

Khangura, S., Konnyu, K., Cushman, R., Grimshaw, J., & Moher, D. (2012). Evidence summaries: the evolution of a rapid review approach.  Systematic reviews, 1 (1), 1-9.  https://doi.org/10.1186/2046-4053-1-10

Virginia Commonwealth University Libraries. (2021). Rapid Review Protocol .

Quarmby, S., Santos, G., & Mathias, M. (2019). Air quality strategies and technologies: A rapid review of the international evidence.  Sustainability, 11 (10), 2757.  https://doi.org/10.3390/su11102757

Grant, M.J. & Booth, A. (2009). A typology of reviews: an analysis of the 14 review types and associated methodologies.  Health Information & Libraries Journal , 26(2), 91-108. https://www.doi.org/10.1111/j.1471-1842.2009.00848.x

Developed and refined by the Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre), this review "map[s] out and categorize[s] existing literature on a particular topic, identifying gaps in research literature from which to commission further reviews and/or primary research" (Grant & Booth, 2009, p. 97).

Although mapping reviews are sometimes called scoping reviews, the key difference is that mapping reviews focus on a review question, rather than a topic

Mapping reviews are "best used where a clear target for a more focused evidence product has not yet been identified" (Booth, 2016, p. 14)

Mapping review searches are often quick and are intended to provide a broad overview

Mapping reviews can take different approaches in what types of literature is focused on in the search

Cooper I. D. (2016). What is a "mapping study?".  Journal of the Medical Library Association: JMLA ,  104 (1), 76–78. https://doi.org/10.3163/1536-5050.104.1.013

Miake-Lye, I. M., Hempel, S., Shanman, R., & Shekelle, P. G. (2016). What is an evidence map? A systematic review of published evidence maps and their definitions, methods, and products.  Systematic reviews, 5 (1), 1-21.  https://doi.org/10.1186/s13643-016-0204-x

Tainio, M., Andersen, Z. J., Nieuwenhuijsen, M. J., Hu, L., De Nazelle, A., An, R., ... & de Sá, T. H. (2021). Air pollution, physical activity and health: A mapping review of the evidence.  Environment international ,  147 , 105954.  https://doi.org/10.1016/j.envint.2020.105954

Booth, A. (2016). EVIDENT Guidance for Reviewing the Evidence: a compendium of methodological literature and websites . ResearchGate. https://doi.org/10.13140/RG.2.1.1562.9842 . 

Grant, M.J. & Booth, A. (2009). A typology of reviews: an analysis of the 14 review types and associated methodologies.  Health Information & Libraries Journal , 26(2), 91-108.  https://www.doi.org/10.1111/j.1471-1842.2009.00848.x

"A type of review that has as its primary objective the identification of the size and quality of research in a topic area in order to inform subsequent review" (Booth et al., 2012, p. 269).

• Main purpose is to map out and categorize existing literature, identify gaps in literature—great for informing policy-making
• Search comprehensiveness determined by time/scope constraints, could take longer than a systematic review
• No formal quality assessment or critical appraisal

Learn more about the methods :

Arksey, H., & O'Malley, L. (2005) Scoping studies: towards a methodological framework.  International Journal of Social Research Methodology ,  8 (1), 19-32.  https://doi.org/10.1080/1364557032000119616

Levac, D., Colquhoun, H., & O’Brien, K. K. (2010). Scoping studies: Advancing the methodology. Implementation Science: IS, 5, 69. https://doi.org/10.1186/1748-5908-5-69

Example : 

Rahman, A., Sarkar, A., Yadav, O. P., Achari, G., & Slobodnik, J. (2021). Potential human health risks due to environmental exposure to nano-and microplastics and knowledge gaps: A scoping review.  Science of the Total Environment, 757 , 143872.  https://doi.org/10.1016/j.scitotenv.2020.143872

A review that "[compiles] evidence from multiple...reviews into one accessible and usable document" (Grant & Booth, 2009, p. 103). While originally intended to be a compilation of Cochrane reviews, it now generally refers to any kind of evidence synthesis.

• Compiles evidence from multiple reviews into one document
• Often defines a broader question than is typical of a traditional systematic review

Choi, G. J., & Kang, H. (2022). The umbrella review: a useful strategy in the rain of evidence.  The Korean Journal of Pain ,  35 (2), 127–128.  https://doi.org/10.3344/kjp.2022.35.2.127

Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P. (2015). Summarizing systematic reviews: Methodological development, conduct and reporting of an umbrella review approach. International Journal of Evidence-Based Healthcare , 13(3), 132–140. https://doi.org/10.1097/XEB.0000000000000055

Rojas-Rueda, D., Morales-Zamora, E., Alsufyani, W. A., Herbst, C. H., Al Balawi, S. M., Alsukait, R., & Alomran, M. (2021). Environmental risk factors and health: An umbrella review of meta-analyses.  International Journal of Environmental Research and Public Dealth ,  18 (2), 704.  https://doi.org/10.3390/ijerph18020704

A meta-analysis is a "technique that statistically combines the results of quantitative studies to provide a more precise effect of the result" (Grant & Booth, 2009, p. 98).

• Statistical technique for combining results of quantitative studies to provide more precise effect of results
• Aims for exhaustive, comprehensive searching
• Quality assessment may determine inclusion/exclusion criteria
• May be conducted independently or as part of a systematic review

Berman, N. G., & Parker, R. A. (2002). Meta-analysis: Neither quick nor easy. BMC Medical Research Methodology , 2(1), 10. https://doi.org/10.1186/1471-2288-2-10

Hites R. A. (2004). Polybrominated diphenyl ethers in the environment and in people: a meta-analysis of concentrations.  Environmental Science & Technology ,  38 (4), 945–956.  https://doi.org/10.1021/es035082g

A systematic review "seeks to systematically search for, appraise, and [synthesize] research evidence, often adhering to the guidelines on the conduct of a review" provided by discipline-specific organizations, such as the Cochrane Collaboration (Grant & Booth, 2009, p. 102).

• Aims to compile and synthesize all known knowledge on a given topic
• Adheres to strict guidelines, protocols, and frameworks
• Time-intensive and often takes months to a year or more to complete
• The most commonly referred to type of evidence synthesis. Sometimes confused as a blanket term for other types of reviews

Gascon, M., Triguero-Mas, M., Martínez, D., Dadvand, P., Forns, J., Plasència, A., & Nieuwenhuijsen, M. J. (2015). Mental health benefits of long-term exposure to residential green and blue spaces: a systematic review.  International Journal of Environmental Research and Public Health ,  12 (4), 4354–4379.  https://doi.org/10.3390/ijerph120404354

"Systematized reviews attempt to include one or more elements of the systematic review process while stopping short of claiming that the resultant output is a systematic review" (Grant & Booth, 2009, p. 102). When a systematic review approach is adapted to produce a more manageable scope, while still retaining the rigor of a systematic review such as risk of bias assessment and the use of a protocol, this is often referred to as a  structured review  (Huelin et al., 2015).

• Typically conducted by postgraduate or graduate students
• Often assigned by instructors to students who don't have the resources to conduct a full systematic review

Salvo, G., Lashewicz, B. M., Doyle-Baker, P. K., & McCormack, G. R. (2018). Neighbourhood built environment influences on physical activity among adults: A systematized review of qualitative evidence.  International Journal of Environmental Research and Public Health ,  15 (5), 897.  https://doi.org/10.3390/ijerph15050897

Huelin, R., Iheanacho, I., Payne, K., & Sandman, K. (2015). What’s in a name? Systematic and non-systematic literature reviews, and why the distinction matters. https://www.evidera.com/resource/whats-in-a-name-systematic-and-non-systematic-literature-reviews-and-why-the-distinction-matters/

• Review Decision Tree - Cornell University For more information, check out Cornell's review methodology decision tree.
• LitR-Ex.com - Eight literature review methodologies Learn more about 8 different review types (incl. Systematic Reviews and Scoping Reviews) with practical tips about strengths and weaknesses of different methods.
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Review Typologies

There are many types of evidence synthesis projects, including systematic reviews as well as others. The selection of review type is wholly dependent on the research question. Not all research questions are well-suited for systematic reviews.

• Review Typologies (from LITR-EX) This site explores different review methodologies such as, systematic, scoping, realist, narrative, state of the art, meta-ethnography, critical, and integrative reviews. The LITR-EX site has a health professions education focus, but the advice and information is widely applicable.

Review the table to peruse review types and associated methodologies. Librarians can also help your team determine which review type might be appropriate for your project. 

Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91-108.  doi:10.1111/j.1471-1842.2009.00848.x

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Literature Review: Types of Literature Reviews

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Types of Literature Reviews

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• Know the Difference! Systematic Review vs. Literature Review

It is important to think of knowledge in a given field as consisting of three layers.

• First, there are the primary studies that researchers conduct and publish.
• Second, are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the original studies.
• Third, there are the perceptions, conclusions, opinions, and interpretations that are shared informally that become part of the lore of the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews.

Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are several approaches to how they can be done, depending upon the type of analysis underpinning your study. Listed below are definitions of types of literature reviews:

Argumentative Review      This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews.

Integrative Review      Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication.

Historical Review      Few things rest in isolation from historical precedent. Historical reviews are focused on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomenon emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review      A review does not always focus on what someone said [content], but how they said it [method of analysis]. This approach provides a framework of understanding at different levels (i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques), enables researchers to draw on a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection and data analysis, and helps highlight many ethical issues which we should be aware of and consider as we go through our study.

Systematic Review      This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?"

Theoretical Review      The purpose of this form is to concretely examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomenon. The theoretical literature review help establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

* Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147.

All content is from The Literature Review created by Dr. Robert Larabee USC

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Evidence Synthesis, Systematic Review Services : Literature Review Types, Taxonomies

• Develop a Protocol
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Choosing a Literature Review Methodology

Growing interest in evidence-based practice has driven an increase in review methodologies. Your choice of review methodology (or literature review type) will be informed by the intent (purpose, function) of your research project and the time and resources of your team. 

• Decision Tree (What Type of Review is Right for You?) Developed by Cornell University Library staff, this "decision-tree" guides the user to a handful of review guides given time and intent.

Types of Evidence Synthesis*

Critical Review - Aims to demonstrate writer has extensively researched literature and critically evaluated its quality. Goes beyond mere description to include degree of analysis and conceptual innovation. Typically results in hypothesis or model.

Mapping Review (Systematic Map) - Map out and categorize existing literature from which to commission further reviews and/or primary research by identifying gaps in research literature.

Meta-Analysis - Technique that statistically combines the results of quantitative studies to provide a more precise effect of the results.

Mixed Studies Review (Mixed Methods Review) - Refers to any combination of methods where one significant component is a literature review (usually systematic). Within a review context it refers to a combination of review approaches for example combining quantitative with qualitative research or outcome with process studies.

Narrative (Literature) Review - Broad, generic term - Refers to an examination and general synthesis of the research literature, often with a wide scope; completeness and comprehensiveness may vary. Does not follow an established protocol.

Overview - Generic term: summary of the [medical] literature that attempts to survey the literature and describe its characteristics.

Qualitative Systematic Review or Qualitative Evidence Synthesis - Method for integrating or comparing the findings from qualitative studies. It looks for ‘themes’ or ‘constructs’ that lie in or across individual qualitative studies.

Rapid Review - Assessment of what is already known about a policy or practice issue, by using systematic review methods to search and critically appraise existing research.

Scoping Review or Evidence Map - Preliminary assessment of potential size and scope of available research literature. Aims to identify nature and extent of research.

State-of-the-art Review - Tend to address more current matters in contrast to other combined retrospective and current approaches. May offer new perspectives on issue or point out area for further research.

Systematic Review - Seeks to systematically search for, appraise and synthesize research evidence, often adhering to guidelines on the conduct of a review. (An emerging subset includes Living Reviews or Living Systematic Reviews - A [review or] systematic review which is continually updated, incorporating relevant new evidence as it becomes available.)

Systematic Search and Review - Combines strengths of critical review with a comprehensive search process. Typically addresses broad questions to produce ‘best evidence synthesis.’

Umbrella Review - Specifically refers to review compiling evidence from multiple reviews into one accessible and usable document. Focuses on broad condition or problem for which there are competing interventions and highlights reviews that address these interventions and their results.

*Apart from some qualifying description for "Narrative (Literature) Review", these definitions are provided in Grant & Booth's "A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies."

Literature Review Types/Typologies, Taxonomies

Grant, M. J., and A. Booth. "A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies."  Health Information and Libraries Journal  26.2 (2009): 91-108.  DOI: 10.1111/j.1471-1842.2009.00848.x  Link

Munn, Zachary, et al. “Systematic Review or Scoping Review? Guidance for Authors When Choosing between a Systematic or Scoping Review Approach.” BMC Medical Research Methodology , vol. 18, no. 1, Nov. 2018, p. 143. DOI: 10.1186/s12874-018-0611-x. Link

Sutton, A., et al. "Meeting the Review Family: Exploring Review Types and Associated Information Retrieval Requirements."  Health Information and Libraries Journal  36.3 (2019): 202-22.  DOI: 10.1111/hir.12276  Link

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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

Prevent plagiarism. Run a free check.

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

Scribbr slides are free to use, customize, and distribute for educational purposes.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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• UConn Library
• Literature Review: The What, Why and How-to Guide
• Introduction

Literature Review: The What, Why and How-to Guide — Introduction

• Getting Started
• How to Pick a Topic
• Strategies to Find Sources
• Evaluating Sources & Lit. Reviews
• Tips for Writing Literature Reviews
• Writing Literature Review: Useful Sites
• Citation Resources
• Other Academic Writings

What are Literature Reviews?

So, what is a literature review? "A literature review is an account of what has been published on a topic by accredited scholars and researchers. In writing the literature review, your purpose is to convey to your reader what knowledge and ideas have been established on a topic, and what their strengths and weaknesses are. As a piece of writing, the literature review must be defined by a guiding concept (e.g., your research objective, the problem or issue you are discussing, or your argumentative thesis). It is not just a descriptive list of the material available, or a set of summaries." Taylor, D.  The literature review: A few tips on conducting it . University of Toronto Health Sciences Writing Centre.

Goals of Literature Reviews

What are the goals of creating a Literature Review?  A literature could be written to accomplish different aims:

• To develop a theory or evaluate an existing theory
• To summarize the historical or existing state of a research topic
• Identify a problem in a field of research 

Baumeister, R. F., & Leary, M. R. (1997). Writing narrative literature reviews .  Review of General Psychology , 1 (3), 311-320.

What kinds of sources require a Literature Review?

• A research paper assigned in a course
• A thesis or dissertation
• A grant proposal
• An article intended for publication in a journal

All these instances require you to collect what has been written about your research topic so that you can demonstrate how your own research sheds new light on the topic.

Types of Literature Reviews

What kinds of literature reviews are written?

Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. The review ends with a conclusion section which summarizes the findings regarding the state of the research of the specific study, the gaps identify and if applicable, explains how the author's research will address gaps identify in the review and expand the knowledge on the topic reviewed.

• Example : Predictors and Outcomes of U.S. Quality Maternity Leave: A Review and Conceptual Framework:  10.1177/08948453211037398  

Systematic review : "The authors of a systematic review use a specific procedure to search the research literature, select the studies to include in their review, and critically evaluate the studies they find." (p. 139). Nelson, L. K. (2013). Research in Communication Sciences and Disorders . Plural Publishing.

• Example : The effect of leave policies on increasing fertility: a systematic review:  10.1057/s41599-022-01270-w

Meta-analysis : "Meta-analysis is a method of reviewing research findings in a quantitative fashion by transforming the data from individual studies into what is called an effect size and then pooling and analyzing this information. The basic goal in meta-analysis is to explain why different outcomes have occurred in different studies." (p. 197). Roberts, M. C., & Ilardi, S. S. (2003). Handbook of Research Methods in Clinical Psychology . Blackwell Publishing.

• Example : Employment Instability and Fertility in Europe: A Meta-Analysis:  10.1215/00703370-9164737

Meta-synthesis : "Qualitative meta-synthesis is a type of qualitative study that uses as data the findings from other qualitative studies linked by the same or related topic." (p.312). Zimmer, L. (2006). Qualitative meta-synthesis: A question of dialoguing with texts .  Journal of Advanced Nursing , 53 (3), 311-318.

• Example : Women’s perspectives on career successes and barriers: A qualitative meta-synthesis:  10.1177/05390184221113735

Literature Reviews in the Health Sciences

• UConn Health subject guide on systematic reviews Explanation of the different review types used in health sciences literature as well as tools to help you find the right review type
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• Next: How to Pick a Topic >>
• Last Updated: Sep 21, 2022 2:16 PM
• URL: https://guides.lib.uconn.edu/literaturereview

How to Conduct a Literature Review: A Guide for Graduate Students

• Let's Get Started!
• Traditional or Narrative Reviews
• Systematic Reviews
• Typology of Reviews
• Literature Review Resources
• Developing a Search Strategy
• What Literature to Search
• Where to Search: Indexes and Databases
• Finding articles: Libkey Nomad
• Finding Dissertations and Theses
• Extending Your Searching with Citation Chains
• Forward Citation Chains - Cited Reference Searching
• Keeping up with the Literature
• Managing Your References
• Need More Information?

What is a Literature Review?

A literature review summarizes and synthesizes material on a research topic. It provides a summary of previous research and provides context for the material presented in your thesis. The literature review is your opportunity to show what you understand about your topic area, and distinguish previous research from the work you are doing. For example, your thesis may be building on an existing theory or model and extending it a new direction. It's important to provide context for your project by providing a roadmap to previous literature.

Purpose of a Literature Review

• Identifies gaps in current knowledge
• Helps you to avoid reinventing the wheel by discovering the research already conducted on a topic
• Sets the background on what has been explored on a topic so far
• Increases your breadth of knowledge in your area of research
• Helps you identify seminal works in your area
• Allows you to provide the intellectual context for your work and position your research with other, related research
• Provides you with opposing viewpoints
• Helps you to discover research methods which may be applicable to your work
• Research methods for post graduates Full cite: Greenfield (2002) Research Methods for postgraduates. 2nd Ed. London: Arnold
• A typology of reviews: an analysis of 14 review types and associated methodologies Full cite: Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26, 91–108. doi:10.1111/j.1471-1842.2009.00848.x

Literature Reviews: An Overview for Graduate Students

This section adapted from The Literature Review, by Charles Stuart University Library. Available: https://libguides.csu.edu.au/review.

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• Next: Traditional or Narrative Reviews >>

The library's collections and services are available to all ISU students, faculty, and staff and Parks Library is open to the public .

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• URL: https://instr.iastate.libguides.com/gradlitrev

How to Conduct a Literature Review: Types of Literature Reviews

• What is a Literature Review?

Types of Literature Reviews

• Finding "The Literature"
• Organizing/Writing
• Citation Help

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Literature reviews are pervasive throughout various academic disciplines, and thus you can adopt various approaches to effectively organize and write your literature review.  The University of Southern California created a summarized list of the various types of literature reviews, reprinted here:

• Argumentative Review
• Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication.
• Historical Review Few things rest in isolation from historical precedent. Historical reviews are focused on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.
• Methodological Review A review does not always focus on  what  someone said [content], but  how  they said it [method of analysis]. This approach provides a framework of understanding at different levels (i.e. those of theory, substantive fields, research approaches and data collection and analysis techniques), enables researchers to draw on a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection and data analysis, and helps highlight many ethical issues which we should be aware of and consider as we go through our study.
• Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyse data from the studies that are included in the review. Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?"
• Theoretical Review The purpose of this form is to concretely examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review help establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.
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• Next: Finding "The Literature" >>
• Last Updated: Aug 9, 2024 11:12 AM
• URL: https://libguides.jsu.edu/literaturereview

Types of Literature Review

There are many types of literature review. The choice of a specific type depends on your research approach and design. The following types of literature review are the most popular in business studies:

Narrative literature review , also referred to as traditional literature review, critiques literature and summarizes the body of a literature. Narrative review also draws conclusions about the topic and identifies gaps or inconsistencies in a body of knowledge. You need to have a sufficiently focused research question to conduct a narrative literature review

Systematic literature review requires more rigorous and well-defined approach compared to most other types of literature review. Systematic literature review is comprehensive and details the timeframe within which the literature was selected. Systematic literature review can be divided into two categories: meta-analysis and meta-synthesis.

When you conduct meta-analysis you take findings from several studies on the same subject and analyze these using standardized statistical procedures. In meta-analysis patterns and relationships are detected and conclusions are drawn. Meta-analysis is associated with deductive research approach.

Meta-synthesis, on the other hand, is based on non-statistical techniques. This technique integrates, evaluates and interprets findings of multiple qualitative research studies. Meta-synthesis literature review is conducted usually when following inductive research approach.

Scoping literature review , as implied by its name is used to identify the scope or coverage of a body of literature on a given topic. It has been noted that “scoping reviews are useful for examining emerging evidence when it is still unclear what other, more specific questions can be posed and valuably addressed by a more precise systematic review.” [1] The main difference between systematic and scoping types of literature review is that, systematic literature review is conducted to find answer to more specific research questions, whereas scoping literature review is conducted to explore more general research question.

Argumentative literature review , as the name implies, examines literature selectively in order to support or refute an argument, deeply imbedded assumption, or philosophical problem already established in the literature. It should be noted that a potential for bias is a major shortcoming associated with argumentative literature review.

Integrative literature review reviews , critiques, and synthesizes secondary data about research topic in an integrated way such that new frameworks and perspectives on the topic are generated. If your research does not involve primary data collection and data analysis, then using integrative literature review will be your only option.

Theoretical literature review focuses on a pool of theory that has accumulated in regard to an issue, concept, theory, phenomena. Theoretical literature reviews play an instrumental role in establishing what theories already exist, the relationships between them, to what degree existing theories have been investigated, and to develop new hypotheses to be tested.

At the earlier parts of the literature review chapter, you need to specify the type of your literature review your chose and justify your choice. Your choice of a specific type of literature review should be based upon your research area, research problem and research methods.  Also, you can briefly discuss other most popular types of literature review mentioned above, to illustrate your awareness of them.

[1] Munn, A. et. al. (2018) “Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach” BMC Medical Research Methodology

  John Dudovskiy

Which review is that? A guide to review types

• Which review is that?
• Review Comparison Chart
• Decision Tool
• Critical Review
• Integrative Review
• Narrative Review
• State of the Art Review
• Narrative Summary
• Systematic Review
• Meta-analysis
• Comparative Effectiveness Review
• Diagnostic Systematic Review
• Network Meta-analysis
• Prognostic Review
• Psychometric Review
• Review of Economic Evaluations
• Systematic Review of Epidemiology Studies
• Living Systematic Reviews
• Umbrella Review
• Review of Reviews
• Rapid Review
• Rapid Evidence Assessment
• Rapid Realist Review
• Qualitative Evidence Synthesis
• Qualitative Interpretive Meta-synthesis
• Qualitative Meta-synthesis
• Qualitative Research Synthesis
• Framework Synthesis - Best-fit Framework Synthesis
• Meta-aggregation
• Meta-ethnography
• Meta-interpretation
• Meta-narrative Review
• Meta-summary
• Thematic Synthesis
• Mixed Methods Synthesis
• Narrative Synthesis
• Bayesian Meta-analysis
• EPPI-Centre Review
• Critical Interpretive Synthesis
• Realist Synthesis - Realist Review
• Scoping Review
• Mapping Review
• Systematised Review
• Concept Synthesis
• Expert Opinion - Policy Review
• Technology Assessment Review
• Methodological Review
• Systematic Search and Review

This quick reference tool provides information on a wide range of literature review types that are available for research synthesis for publication and research purposes.  

Graphic and guide based on on the work of  Sutton et al., (2019) on 'Review Families'.

*Note to students undertaking a literature review as part of coursework:

It is recommended that students undertaking a literature review as part of their coursework follow the literature review guidelines provided within their subject as they may include selected elements of full literature reviews suitable to the learning task.

References Sutton, A., Clowes, M., Preston, L., & Booth, A. (2019). Meeting the review family: exploring review types and associated information retrieval requirements.  Health Information & Libraries Journal ,  36 (3), 202-222.  Full Text

Cite this guide

Birkic, V., Celeste, T., & Cochrane, L. (2020). Which review is that? A guide to review types, Available from https://unimelb.libguides.com/whichreview

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• Last Updated: Aug 19, 2024 1:08 PM
• URL: https://unimelb.libguides.com/whichreview

• James P. Adams Library

Conducting a Literature Review

• Types of Literature Reviews
• What is a Literature Review?
• Tutorials This link opens in a new window
• Research Iteration
• Guides & Handbooks

Review Comparison Chart

A selection of the common review types found in the literature is presented and compared in the following table using the SALSA framework developed by Grant and Booth (2009).

Adapted from:

Grant, M.J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91-108.  https://doi.org/10.1111/j.1471-1842.2009.00848.x

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"Review Comparison Chart" from  Which review is that? A guide to review types  by the University of Melbourne Library is used with permission.

• Last Updated: Sep 10, 2024 2:46 PM
• URL: https://library.ric.edu/conducting-a-literature-review

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Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.

Handbook of eHealth Evaluation: An Evidence-based Approach [Internet].

Chapter 9 methods for literature reviews.

Guy Paré and Spyros Kitsiou .

9.1. Introduction

Literature reviews play a critical role in scholarship because science remains, first and foremost, a cumulative endeavour ( vom Brocke et al., 2009 ). As in any academic discipline, rigorous knowledge syntheses are becoming indispensable in keeping up with an exponentially growing eHealth literature, assisting practitioners, academics, and graduate students in finding, evaluating, and synthesizing the contents of many empirical and conceptual papers. Among other methods, literature reviews are essential for: (a) identifying what has been written on a subject or topic; (b) determining the extent to which a specific research area reveals any interpretable trends or patterns; (c) aggregating empirical findings related to a narrow research question to support evidence-based practice; (d) generating new frameworks and theories; and (e) identifying topics or questions requiring more investigation ( Paré, Trudel, Jaana, & Kitsiou, 2015 ).

Literature reviews can take two major forms. The most prevalent one is the “literature review” or “background” section within a journal paper or a chapter in a graduate thesis. This section synthesizes the extant literature and usually identifies the gaps in knowledge that the empirical study addresses ( Sylvester, Tate, & Johnstone, 2013 ). It may also provide a theoretical foundation for the proposed study, substantiate the presence of the research problem, justify the research as one that contributes something new to the cumulated knowledge, or validate the methods and approaches for the proposed study ( Hart, 1998 ; Levy & Ellis, 2006 ).

The second form of literature review, which is the focus of this chapter, constitutes an original and valuable work of research in and of itself ( Paré et al., 2015 ). Rather than providing a base for a researcher’s own work, it creates a solid starting point for all members of the community interested in a particular area or topic ( Mulrow, 1987 ). The so-called “review article” is a journal-length paper which has an overarching purpose to synthesize the literature in a field, without collecting or analyzing any primary data ( Green, Johnson, & Adams, 2006 ).

When appropriately conducted, review articles represent powerful information sources for practitioners looking for state-of-the art evidence to guide their decision-making and work practices ( Paré et al., 2015 ). Further, high-quality reviews become frequently cited pieces of work which researchers seek out as a first clear outline of the literature when undertaking empirical studies ( Cooper, 1988 ; Rowe, 2014 ). Scholars who track and gauge the impact of articles have found that review papers are cited and downloaded more often than any other type of published article ( Cronin, Ryan, & Coughlan, 2008 ; Montori, Wilczynski, Morgan, Haynes, & Hedges, 2003 ; Patsopoulos, Analatos, & Ioannidis, 2005 ). The reason for their popularity may be the fact that reading the review enables one to have an overview, if not a detailed knowledge of the area in question, as well as references to the most useful primary sources ( Cronin et al., 2008 ). Although they are not easy to conduct, the commitment to complete a review article provides a tremendous service to one’s academic community ( Paré et al., 2015 ; Petticrew & Roberts, 2006 ). Most, if not all, peer-reviewed journals in the fields of medical informatics publish review articles of some type.

The main objectives of this chapter are fourfold: (a) to provide an overview of the major steps and activities involved in conducting a stand-alone literature review; (b) to describe and contrast the different types of review articles that can contribute to the eHealth knowledge base; (c) to illustrate each review type with one or two examples from the eHealth literature; and (d) to provide a series of recommendations for prospective authors of review articles in this domain.

9.2. Overview of the Literature Review Process and Steps

As explained in Templier and Paré (2015) , there are six generic steps involved in conducting a review article:

• formulating the research question(s) and objective(s),
• searching the extant literature,
• screening for inclusion,
• assessing the quality of primary studies,
• extracting data, and
• analyzing data.

Although these steps are presented here in sequential order, one must keep in mind that the review process can be iterative and that many activities can be initiated during the planning stage and later refined during subsequent phases ( Finfgeld-Connett & Johnson, 2013 ; Kitchenham & Charters, 2007 ).

Formulating the research question(s) and objective(s): As a first step, members of the review team must appropriately justify the need for the review itself ( Petticrew & Roberts, 2006 ), identify the review’s main objective(s) ( Okoli & Schabram, 2010 ), and define the concepts or variables at the heart of their synthesis ( Cooper & Hedges, 2009 ; Webster & Watson, 2002 ). Importantly, they also need to articulate the research question(s) they propose to investigate ( Kitchenham & Charters, 2007 ). In this regard, we concur with Jesson, Matheson, and Lacey (2011) that clearly articulated research questions are key ingredients that guide the entire review methodology; they underscore the type of information that is needed, inform the search for and selection of relevant literature, and guide or orient the subsequent analysis. Searching the extant literature: The next step consists of searching the literature and making decisions about the suitability of material to be considered in the review ( Cooper, 1988 ). There exist three main coverage strategies. First, exhaustive coverage means an effort is made to be as comprehensive as possible in order to ensure that all relevant studies, published and unpublished, are included in the review and, thus, conclusions are based on this all-inclusive knowledge base. The second type of coverage consists of presenting materials that are representative of most other works in a given field or area. Often authors who adopt this strategy will search for relevant articles in a small number of top-tier journals in a field ( Paré et al., 2015 ). In the third strategy, the review team concentrates on prior works that have been central or pivotal to a particular topic. This may include empirical studies or conceptual papers that initiated a line of investigation, changed how problems or questions were framed, introduced new methods or concepts, or engendered important debate ( Cooper, 1988 ). Screening for inclusion: The following step consists of evaluating the applicability of the material identified in the preceding step ( Levy & Ellis, 2006 ; vom Brocke et al., 2009 ). Once a group of potential studies has been identified, members of the review team must screen them to determine their relevance ( Petticrew & Roberts, 2006 ). A set of predetermined rules provides a basis for including or excluding certain studies. This exercise requires a significant investment on the part of researchers, who must ensure enhanced objectivity and avoid biases or mistakes. As discussed later in this chapter, for certain types of reviews there must be at least two independent reviewers involved in the screening process and a procedure to resolve disagreements must also be in place ( Liberati et al., 2009 ; Shea et al., 2009 ). Assessing the quality of primary studies: In addition to screening material for inclusion, members of the review team may need to assess the scientific quality of the selected studies, that is, appraise the rigour of the research design and methods. Such formal assessment, which is usually conducted independently by at least two coders, helps members of the review team refine which studies to include in the final sample, determine whether or not the differences in quality may affect their conclusions, or guide how they analyze the data and interpret the findings ( Petticrew & Roberts, 2006 ). Ascribing quality scores to each primary study or considering through domain-based evaluations which study components have or have not been designed and executed appropriately makes it possible to reflect on the extent to which the selected study addresses possible biases and maximizes validity ( Shea et al., 2009 ). Extracting data: The following step involves gathering or extracting applicable information from each primary study included in the sample and deciding what is relevant to the problem of interest ( Cooper & Hedges, 2009 ). Indeed, the type of data that should be recorded mainly depends on the initial research questions ( Okoli & Schabram, 2010 ). However, important information may also be gathered about how, when, where and by whom the primary study was conducted, the research design and methods, or qualitative/quantitative results ( Cooper & Hedges, 2009 ). Analyzing and synthesizing data : As a final step, members of the review team must collate, summarize, aggregate, organize, and compare the evidence extracted from the included studies. The extracted data must be presented in a meaningful way that suggests a new contribution to the extant literature ( Jesson et al., 2011 ). Webster and Watson (2002) warn researchers that literature reviews should be much more than lists of papers and should provide a coherent lens to make sense of extant knowledge on a given topic. There exist several methods and techniques for synthesizing quantitative (e.g., frequency analysis, meta-analysis) and qualitative (e.g., grounded theory, narrative analysis, meta-ethnography) evidence ( Dixon-Woods, Agarwal, Jones, Young, & Sutton, 2005 ; Thomas & Harden, 2008 ).

9.3. Types of Review Articles and Brief Illustrations

EHealth researchers have at their disposal a number of approaches and methods for making sense out of existing literature, all with the purpose of casting current research findings into historical contexts or explaining contradictions that might exist among a set of primary research studies conducted on a particular topic. Our classification scheme is largely inspired from Paré and colleagues’ (2015) typology. Below we present and illustrate those review types that we feel are central to the growth and development of the eHealth domain.

9.3.1. Narrative Reviews

The narrative review is the “traditional” way of reviewing the extant literature and is skewed towards a qualitative interpretation of prior knowledge ( Sylvester et al., 2013 ). Put simply, a narrative review attempts to summarize or synthesize what has been written on a particular topic but does not seek generalization or cumulative knowledge from what is reviewed ( Davies, 2000 ; Green et al., 2006 ). Instead, the review team often undertakes the task of accumulating and synthesizing the literature to demonstrate the value of a particular point of view ( Baumeister & Leary, 1997 ). As such, reviewers may selectively ignore or limit the attention paid to certain studies in order to make a point. In this rather unsystematic approach, the selection of information from primary articles is subjective, lacks explicit criteria for inclusion and can lead to biased interpretations or inferences ( Green et al., 2006 ). There are several narrative reviews in the particular eHealth domain, as in all fields, which follow such an unstructured approach ( Silva et al., 2015 ; Paul et al., 2015 ).

Despite these criticisms, this type of review can be very useful in gathering together a volume of literature in a specific subject area and synthesizing it. As mentioned above, its primary purpose is to provide the reader with a comprehensive background for understanding current knowledge and highlighting the significance of new research ( Cronin et al., 2008 ). Faculty like to use narrative reviews in the classroom because they are often more up to date than textbooks, provide a single source for students to reference, and expose students to peer-reviewed literature ( Green et al., 2006 ). For researchers, narrative reviews can inspire research ideas by identifying gaps or inconsistencies in a body of knowledge, thus helping researchers to determine research questions or formulate hypotheses. Importantly, narrative reviews can also be used as educational articles to bring practitioners up to date with certain topics of issues ( Green et al., 2006 ).

Recently, there have been several efforts to introduce more rigour in narrative reviews that will elucidate common pitfalls and bring changes into their publication standards. Information systems researchers, among others, have contributed to advancing knowledge on how to structure a “traditional” review. For instance, Levy and Ellis (2006) proposed a generic framework for conducting such reviews. Their model follows the systematic data processing approach comprised of three steps, namely: (a) literature search and screening; (b) data extraction and analysis; and (c) writing the literature review. They provide detailed and very helpful instructions on how to conduct each step of the review process. As another methodological contribution, vom Brocke et al. (2009) offered a series of guidelines for conducting literature reviews, with a particular focus on how to search and extract the relevant body of knowledge. Last, Bandara, Miskon, and Fielt (2011) proposed a structured, predefined and tool-supported method to identify primary studies within a feasible scope, extract relevant content from identified articles, synthesize and analyze the findings, and effectively write and present the results of the literature review. We highly recommend that prospective authors of narrative reviews consult these useful sources before embarking on their work.

Darlow and Wen (2015) provide a good example of a highly structured narrative review in the eHealth field. These authors synthesized published articles that describe the development process of mobile health (m-health) interventions for patients’ cancer care self-management. As in most narrative reviews, the scope of the research questions being investigated is broad: (a) how development of these systems are carried out; (b) which methods are used to investigate these systems; and (c) what conclusions can be drawn as a result of the development of these systems. To provide clear answers to these questions, a literature search was conducted on six electronic databases and Google Scholar . The search was performed using several terms and free text words, combining them in an appropriate manner. Four inclusion and three exclusion criteria were utilized during the screening process. Both authors independently reviewed each of the identified articles to determine eligibility and extract study information. A flow diagram shows the number of studies identified, screened, and included or excluded at each stage of study selection. In terms of contributions, this review provides a series of practical recommendations for m-health intervention development.

9.3.2. Descriptive or Mapping Reviews

The primary goal of a descriptive review is to determine the extent to which a body of knowledge in a particular research topic reveals any interpretable pattern or trend with respect to pre-existing propositions, theories, methodologies or findings ( King & He, 2005 ; Paré et al., 2015 ). In contrast with narrative reviews, descriptive reviews follow a systematic and transparent procedure, including searching, screening and classifying studies ( Petersen, Vakkalanka, & Kuzniarz, 2015 ). Indeed, structured search methods are used to form a representative sample of a larger group of published works ( Paré et al., 2015 ). Further, authors of descriptive reviews extract from each study certain characteristics of interest, such as publication year, research methods, data collection techniques, and direction or strength of research outcomes (e.g., positive, negative, or non-significant) in the form of frequency analysis to produce quantitative results ( Sylvester et al., 2013 ). In essence, each study included in a descriptive review is treated as the unit of analysis and the published literature as a whole provides a database from which the authors attempt to identify any interpretable trends or draw overall conclusions about the merits of existing conceptualizations, propositions, methods or findings ( Paré et al., 2015 ). In doing so, a descriptive review may claim that its findings represent the state of the art in a particular domain ( King & He, 2005 ).

In the fields of health sciences and medical informatics, reviews that focus on examining the range, nature and evolution of a topic area are described by Anderson, Allen, Peckham, and Goodwin (2008) as mapping reviews . Like descriptive reviews, the research questions are generic and usually relate to publication patterns and trends. There is no preconceived plan to systematically review all of the literature although this can be done. Instead, researchers often present studies that are representative of most works published in a particular area and they consider a specific time frame to be mapped.

An example of this approach in the eHealth domain is offered by DeShazo, Lavallie, and Wolf (2009). The purpose of this descriptive or mapping review was to characterize publication trends in the medical informatics literature over a 20-year period (1987 to 2006). To achieve this ambitious objective, the authors performed a bibliometric analysis of medical informatics citations indexed in medline using publication trends, journal frequencies, impact factors, Medical Subject Headings (MeSH) term frequencies, and characteristics of citations. Findings revealed that there were over 77,000 medical informatics articles published during the covered period in numerous journals and that the average annual growth rate was 12%. The MeSH term analysis also suggested a strong interdisciplinary trend. Finally, average impact scores increased over time with two notable growth periods. Overall, patterns in research outputs that seem to characterize the historic trends and current components of the field of medical informatics suggest it may be a maturing discipline (DeShazo et al., 2009).

9.3.3. Scoping Reviews

Scoping reviews attempt to provide an initial indication of the potential size and nature of the extant literature on an emergent topic (Arksey & O’Malley, 2005; Daudt, van Mossel, & Scott, 2013 ; Levac, Colquhoun, & O’Brien, 2010). A scoping review may be conducted to examine the extent, range and nature of research activities in a particular area, determine the value of undertaking a full systematic review (discussed next), or identify research gaps in the extant literature ( Paré et al., 2015 ). In line with their main objective, scoping reviews usually conclude with the presentation of a detailed research agenda for future works along with potential implications for both practice and research.

Unlike narrative and descriptive reviews, the whole point of scoping the field is to be as comprehensive as possible, including grey literature (Arksey & O’Malley, 2005). Inclusion and exclusion criteria must be established to help researchers eliminate studies that are not aligned with the research questions. It is also recommended that at least two independent coders review abstracts yielded from the search strategy and then the full articles for study selection ( Daudt et al., 2013 ). The synthesized evidence from content or thematic analysis is relatively easy to present in tabular form (Arksey & O’Malley, 2005; Thomas & Harden, 2008 ).

One of the most highly cited scoping reviews in the eHealth domain was published by Archer, Fevrier-Thomas, Lokker, McKibbon, and Straus (2011) . These authors reviewed the existing literature on personal health record ( phr ) systems including design, functionality, implementation, applications, outcomes, and benefits. Seven databases were searched from 1985 to March 2010. Several search terms relating to phr s were used during this process. Two authors independently screened titles and abstracts to determine inclusion status. A second screen of full-text articles, again by two independent members of the research team, ensured that the studies described phr s. All in all, 130 articles met the criteria and their data were extracted manually into a database. The authors concluded that although there is a large amount of survey, observational, cohort/panel, and anecdotal evidence of phr benefits and satisfaction for patients, more research is needed to evaluate the results of phr implementations. Their in-depth analysis of the literature signalled that there is little solid evidence from randomized controlled trials or other studies through the use of phr s. Hence, they suggested that more research is needed that addresses the current lack of understanding of optimal functionality and usability of these systems, and how they can play a beneficial role in supporting patient self-management ( Archer et al., 2011 ).

9.3.4. Forms of Aggregative Reviews

Healthcare providers, practitioners, and policy-makers are nowadays overwhelmed with large volumes of information, including research-based evidence from numerous clinical trials and evaluation studies, assessing the effectiveness of health information technologies and interventions ( Ammenwerth & de Keizer, 2004 ; Deshazo et al., 2009 ). It is unrealistic to expect that all these disparate actors will have the time, skills, and necessary resources to identify the available evidence in the area of their expertise and consider it when making decisions. Systematic reviews that involve the rigorous application of scientific strategies aimed at limiting subjectivity and bias (i.e., systematic and random errors) can respond to this challenge.

Systematic reviews attempt to aggregate, appraise, and synthesize in a single source all empirical evidence that meet a set of previously specified eligibility criteria in order to answer a clearly formulated and often narrow research question on a particular topic of interest to support evidence-based practice ( Liberati et al., 2009 ). They adhere closely to explicit scientific principles ( Liberati et al., 2009 ) and rigorous methodological guidelines (Higgins & Green, 2008) aimed at reducing random and systematic errors that can lead to deviations from the truth in results or inferences. The use of explicit methods allows systematic reviews to aggregate a large body of research evidence, assess whether effects or relationships are in the same direction and of the same general magnitude, explain possible inconsistencies between study results, and determine the strength of the overall evidence for every outcome of interest based on the quality of included studies and the general consistency among them ( Cook, Mulrow, & Haynes, 1997 ). The main procedures of a systematic review involve:

• Formulating a review question and developing a search strategy based on explicit inclusion criteria for the identification of eligible studies (usually described in the context of a detailed review protocol).
• Searching for eligible studies using multiple databases and information sources, including grey literature sources, without any language restrictions.
• Selecting studies, extracting data, and assessing risk of bias in a duplicate manner using two independent reviewers to avoid random or systematic errors in the process.
• Analyzing data using quantitative or qualitative methods.
• Presenting results in summary of findings tables.
• Interpreting results and drawing conclusions.

Many systematic reviews, but not all, use statistical methods to combine the results of independent studies into a single quantitative estimate or summary effect size. Known as meta-analyses , these reviews use specific data extraction and statistical techniques (e.g., network, frequentist, or Bayesian meta-analyses) to calculate from each study by outcome of interest an effect size along with a confidence interval that reflects the degree of uncertainty behind the point estimate of effect ( Borenstein, Hedges, Higgins, & Rothstein, 2009 ; Deeks, Higgins, & Altman, 2008 ). Subsequently, they use fixed or random-effects analysis models to combine the results of the included studies, assess statistical heterogeneity, and calculate a weighted average of the effect estimates from the different studies, taking into account their sample sizes. The summary effect size is a value that reflects the average magnitude of the intervention effect for a particular outcome of interest or, more generally, the strength of a relationship between two variables across all studies included in the systematic review. By statistically combining data from multiple studies, meta-analyses can create more precise and reliable estimates of intervention effects than those derived from individual studies alone, when these are examined independently as discrete sources of information.

The review by Gurol-Urganci, de Jongh, Vodopivec-Jamsek, Atun, and Car (2013) on the effects of mobile phone messaging reminders for attendance at healthcare appointments is an illustrative example of a high-quality systematic review with meta-analysis. Missed appointments are a major cause of inefficiency in healthcare delivery with substantial monetary costs to health systems. These authors sought to assess whether mobile phone-based appointment reminders delivered through Short Message Service ( sms ) or Multimedia Messaging Service ( mms ) are effective in improving rates of patient attendance and reducing overall costs. To this end, they conducted a comprehensive search on multiple databases using highly sensitive search strategies without language or publication-type restrictions to identify all rct s that are eligible for inclusion. In order to minimize the risk of omitting eligible studies not captured by the original search, they supplemented all electronic searches with manual screening of trial registers and references contained in the included studies. Study selection, data extraction, and risk of bias assessments were performed inde­­pen­dently by two coders using standardized methods to ensure consistency and to eliminate potential errors. Findings from eight rct s involving 6,615 participants were pooled into meta-analyses to calculate the magnitude of effects that mobile text message reminders have on the rate of attendance at healthcare appointments compared to no reminders and phone call reminders.

Meta-analyses are regarded as powerful tools for deriving meaningful conclusions. However, there are situations in which it is neither reasonable nor appropriate to pool studies together using meta-analytic methods simply because there is extensive clinical heterogeneity between the included studies or variation in measurement tools, comparisons, or outcomes of interest. In these cases, systematic reviews can use qualitative synthesis methods such as vote counting, content analysis, classification schemes and tabulations, as an alternative approach to narratively synthesize the results of the independent studies included in the review. This form of review is known as qualitative systematic review.

A rigorous example of one such review in the eHealth domain is presented by Mickan, Atherton, Roberts, Heneghan, and Tilson (2014) on the use of handheld computers by healthcare professionals and their impact on access to information and clinical decision-making. In line with the methodological guide­lines for systematic reviews, these authors: (a) developed and registered with prospero ( www.crd.york.ac.uk/ prospero / ) an a priori review protocol; (b) conducted comprehensive searches for eligible studies using multiple databases and other supplementary strategies (e.g., forward searches); and (c) subsequently carried out study selection, data extraction, and risk of bias assessments in a duplicate manner to eliminate potential errors in the review process. Heterogeneity between the included studies in terms of reported outcomes and measures precluded the use of meta-analytic methods. To this end, the authors resorted to using narrative analysis and synthesis to describe the effectiveness of handheld computers on accessing information for clinical knowledge, adherence to safety and clinical quality guidelines, and diagnostic decision-making.

In recent years, the number of systematic reviews in the field of health informatics has increased considerably. Systematic reviews with discordant findings can cause great confusion and make it difficult for decision-makers to interpret the review-level evidence ( Moher, 2013 ). Therefore, there is a growing need for appraisal and synthesis of prior systematic reviews to ensure that decision-making is constantly informed by the best available accumulated evidence. Umbrella reviews , also known as overviews of systematic reviews, are tertiary types of evidence synthesis that aim to accomplish this; that is, they aim to compare and contrast findings from multiple systematic reviews and meta-analyses ( Becker & Oxman, 2008 ). Umbrella reviews generally adhere to the same principles and rigorous methodological guidelines used in systematic reviews. However, the unit of analysis in umbrella reviews is the systematic review rather than the primary study ( Becker & Oxman, 2008 ). Unlike systematic reviews that have a narrow focus of inquiry, umbrella reviews focus on broader research topics for which there are several potential interventions ( Smith, Devane, Begley, & Clarke, 2011 ). A recent umbrella review on the effects of home telemonitoring interventions for patients with heart failure critically appraised, compared, and synthesized evidence from 15 systematic reviews to investigate which types of home telemonitoring technologies and forms of interventions are more effective in reducing mortality and hospital admissions ( Kitsiou, Paré, & Jaana, 2015 ).

9.3.5. Realist Reviews

Realist reviews are theory-driven interpretative reviews developed to inform, enhance, or supplement conventional systematic reviews by making sense of heterogeneous evidence about complex interventions applied in diverse contexts in a way that informs policy decision-making ( Greenhalgh, Wong, Westhorp, & Pawson, 2011 ). They originated from criticisms of positivist systematic reviews which centre on their “simplistic” underlying assumptions ( Oates, 2011 ). As explained above, systematic reviews seek to identify causation. Such logic is appropriate for fields like medicine and education where findings of randomized controlled trials can be aggregated to see whether a new treatment or intervention does improve outcomes. However, many argue that it is not possible to establish such direct causal links between interventions and outcomes in fields such as social policy, management, and information systems where for any intervention there is unlikely to be a regular or consistent outcome ( Oates, 2011 ; Pawson, 2006 ; Rousseau, Manning, & Denyer, 2008 ).

To circumvent these limitations, Pawson, Greenhalgh, Harvey, and Walshe (2005) have proposed a new approach for synthesizing knowledge that seeks to unpack the mechanism of how “complex interventions” work in particular contexts. The basic research question — what works? — which is usually associated with systematic reviews changes to: what is it about this intervention that works, for whom, in what circumstances, in what respects and why? Realist reviews have no particular preference for either quantitative or qualitative evidence. As a theory-building approach, a realist review usually starts by articulating likely underlying mechanisms and then scrutinizes available evidence to find out whether and where these mechanisms are applicable ( Shepperd et al., 2009 ). Primary studies found in the extant literature are viewed as case studies which can test and modify the initial theories ( Rousseau et al., 2008 ).

The main objective pursued in the realist review conducted by Otte-Trojel, de Bont, Rundall, and van de Klundert (2014) was to examine how patient portals contribute to health service delivery and patient outcomes. The specific goals were to investigate how outcomes are produced and, most importantly, how variations in outcomes can be explained. The research team started with an exploratory review of background documents and research studies to identify ways in which patient portals may contribute to health service delivery and patient outcomes. The authors identified six main ways which represent “educated guesses” to be tested against the data in the evaluation studies. These studies were identified through a formal and systematic search in four databases between 2003 and 2013. Two members of the research team selected the articles using a pre-established list of inclusion and exclusion criteria and following a two-step procedure. The authors then extracted data from the selected articles and created several tables, one for each outcome category. They organized information to bring forward those mechanisms where patient portals contribute to outcomes and the variation in outcomes across different contexts.

9.3.6. Critical Reviews

Lastly, critical reviews aim to provide a critical evaluation and interpretive analysis of existing literature on a particular topic of interest to reveal strengths, weaknesses, contradictions, controversies, inconsistencies, and/or other important issues with respect to theories, hypotheses, research methods or results ( Baumeister & Leary, 1997 ; Kirkevold, 1997 ). Unlike other review types, critical reviews attempt to take a reflective account of the research that has been done in a particular area of interest, and assess its credibility by using appraisal instruments or critical interpretive methods. In this way, critical reviews attempt to constructively inform other scholars about the weaknesses of prior research and strengthen knowledge development by giving focus and direction to studies for further improvement ( Kirkevold, 1997 ).

Kitsiou, Paré, and Jaana (2013) provide an example of a critical review that assessed the methodological quality of prior systematic reviews of home telemonitoring studies for chronic patients. The authors conducted a comprehensive search on multiple databases to identify eligible reviews and subsequently used a validated instrument to conduct an in-depth quality appraisal. Results indicate that the majority of systematic reviews in this particular area suffer from important methodological flaws and biases that impair their internal validity and limit their usefulness for clinical and decision-making purposes. To this end, they provide a number of recommendations to strengthen knowledge development towards improving the design and execution of future reviews on home telemonitoring.

9.4. Summary

Table 9.1 outlines the main types of literature reviews that were described in the previous sub-sections and summarizes the main characteristics that distinguish one review type from another. It also includes key references to methodological guidelines and useful sources that can be used by eHealth scholars and researchers for planning and developing reviews.

Typology of Literature Reviews (adapted from Paré et al., 2015).

As shown in Table 9.1 , each review type addresses different kinds of research questions or objectives, which subsequently define and dictate the methods and approaches that need to be used to achieve the overarching goal(s) of the review. For example, in the case of narrative reviews, there is greater flexibility in searching and synthesizing articles ( Green et al., 2006 ). Researchers are often relatively free to use a diversity of approaches to search, identify, and select relevant scientific articles, describe their operational characteristics, present how the individual studies fit together, and formulate conclusions. On the other hand, systematic reviews are characterized by their high level of systematicity, rigour, and use of explicit methods, based on an “a priori” review plan that aims to minimize bias in the analysis and synthesis process (Higgins & Green, 2008). Some reviews are exploratory in nature (e.g., scoping/mapping reviews), whereas others may be conducted to discover patterns (e.g., descriptive reviews) or involve a synthesis approach that may include the critical analysis of prior research ( Paré et al., 2015 ). Hence, in order to select the most appropriate type of review, it is critical to know before embarking on a review project, why the research synthesis is conducted and what type of methods are best aligned with the pursued goals.

9.5. Concluding Remarks

In light of the increased use of evidence-based practice and research generating stronger evidence ( Grady et al., 2011 ; Lyden et al., 2013 ), review articles have become essential tools for summarizing, synthesizing, integrating or critically appraising prior knowledge in the eHealth field. As mentioned earlier, when rigorously conducted review articles represent powerful information sources for eHealth scholars and practitioners looking for state-of-the-art evidence. The typology of literature reviews we used herein will allow eHealth researchers, graduate students and practitioners to gain a better understanding of the similarities and differences between review types.

We must stress that this classification scheme does not privilege any specific type of review as being of higher quality than another ( Paré et al., 2015 ). As explained above, each type of review has its own strengths and limitations. Having said that, we realize that the methodological rigour of any review — be it qualitative, quantitative or mixed — is a critical aspect that should be considered seriously by prospective authors. In the present context, the notion of rigour refers to the reliability and validity of the review process described in section 9.2. For one thing, reliability is related to the reproducibility of the review process and steps, which is facilitated by a comprehensive documentation of the literature search process, extraction, coding and analysis performed in the review. Whether the search is comprehensive or not, whether it involves a methodical approach for data extraction and synthesis or not, it is important that the review documents in an explicit and transparent manner the steps and approach that were used in the process of its development. Next, validity characterizes the degree to which the review process was conducted appropriately. It goes beyond documentation and reflects decisions related to the selection of the sources, the search terms used, the period of time covered, the articles selected in the search, and the application of backward and forward searches ( vom Brocke et al., 2009 ). In short, the rigour of any review article is reflected by the explicitness of its methods (i.e., transparency) and the soundness of the approach used. We refer those interested in the concepts of rigour and quality to the work of Templier and Paré (2015) which offers a detailed set of methodological guidelines for conducting and evaluating various types of review articles.

To conclude, our main objective in this chapter was to demystify the various types of literature reviews that are central to the continuous development of the eHealth field. It is our hope that our descriptive account will serve as a valuable source for those conducting, evaluating or using reviews in this important and growing domain.

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• Cite this Page Paré G, Kitsiou S. Chapter 9 Methods for Literature Reviews. In: Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.
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• Introduction
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• Types of Review Articles and Brief Illustrations
• Concluding Remarks

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Organizing Your Social Sciences Research Paper

• 5. The Literature Review
• Purpose of Guide
• Design Flaws to Avoid
• Independent and Dependent Variables
• Glossary of Research Terms
• Reading Research Effectively
• Narrowing a Topic Idea
• Broadening a Topic Idea
• Extending the Timeliness of a Topic Idea
• Academic Writing Style
• Applying Critical Thinking
• Choosing a Title
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• Research Process Video Series
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• The C.A.R.S. Model
• Background Information
• The Research Problem/Question
• Theoretical Framework
• Citation Tracking
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• Evaluating Sources
• Primary Sources
• Secondary Sources
• Tiertiary Sources
• Scholarly vs. Popular Publications
• Qualitative Methods
• Quantitative Methods
• Insiderness
• Using Non-Textual Elements
• Limitations of the Study
• Common Grammar Mistakes
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A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have used in researching a particular topic and to demonstrate to your readers how your research fits within existing scholarship about the topic.

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . Fourth edition. Thousand Oaks, CA: SAGE, 2014.

Importance of a Good Literature Review

A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

• Give a new interpretation of old material or combine new with old interpretations,
• Trace the intellectual progression of the field, including major debates,
• Depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant research, or
• Usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

Given this, the purpose of a literature review is to:

• Place each work in the context of its contribution to understanding the research problem being studied.
• Describe the relationship of each work to the others under consideration.
• Identify new ways to interpret prior research.
• Reveal any gaps that exist in the literature.
• Resolve conflicts amongst seemingly contradictory previous studies.
• Identify areas of prior scholarship to prevent duplication of effort.
• Point the way in fulfilling a need for additional research.
• Locate your own research within the context of existing literature [very important].

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper. 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . Los Angeles, CA: SAGE, 2011; Knopf, Jeffrey W. "Doing a Literature Review." PS: Political Science and Politics 39 (January 2006): 127-132; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012.

Types of Literature Reviews

It is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally among scholars that become part of the body of epistemological traditions within the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews. Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are a number of approaches you could adopt depending upon the type of analysis underpinning your study.

Argumentative Review This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].

Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses or research problems. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication. This is the most common form of review in the social sciences.

Historical Review Few things rest in isolation from historical precedent. Historical literature reviews focus on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review A review does not always focus on what someone said [findings], but how they came about saying what they say [method of analysis]. Reviewing methods of analysis provides a framework of understanding at different levels [i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques], how researchers draw upon a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection, and data analysis. This approach helps highlight ethical issues which you should be aware of and consider as you go through your own study.

Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. The goal is to deliberately document, critically evaluate, and summarize scientifically all of the research about a clearly defined research problem . Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.

Theoretical Review The purpose of this form is to examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review helps to establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

NOTE: Most often the literature review will incorporate some combination of types. For example, a review that examines literature supporting or refuting an argument, assumption, or philosophical problem related to the research problem will also need to include writing supported by sources that establish the history of these arguments in the literature.

Baumeister, Roy F. and Mark R. Leary. "Writing Narrative Literature Reviews."  Review of General Psychology 1 (September 1997): 311-320; Mark R. Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147; Petticrew, Mark and Helen Roberts. Systematic Reviews in the Social Sciences: A Practical Guide . Malden, MA: Blackwell Publishers, 2006; Torracro, Richard. "Writing Integrative Literature Reviews: Guidelines and Examples." Human Resource Development Review 4 (September 2005): 356-367; Rocco, Tonette S. and Maria S. Plakhotnik. "Literature Reviews, Conceptual Frameworks, and Theoretical Frameworks: Terms, Functions, and Distinctions." Human Ressource Development Review 8 (March 2008): 120-130; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following in support of understanding the research problem :

• An overview of the subject, issue, or theory under consideration, along with the objectives of the literature review,
• Division of works under review into themes or categories [e.g. works that support a particular position, those against, and those offering alternative approaches entirely],
• An explanation of how each work is similar to and how it varies from the others,
• Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research.

The critical evaluation of each work should consider :

• Provenance -- what are the author's credentials? Are the author's arguments supported by evidence [e.g. primary historical material, case studies, narratives, statistics, recent scientific findings]?
• Methodology -- were the techniques used to identify, gather, and analyze the data appropriate to addressing the research problem? Was the sample size appropriate? Were the results effectively interpreted and reported?
• Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
• Persuasiveness -- which of the author's theses are most convincing or least convincing?
• Validity -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  Development of the Literature Review

Four Basic Stages of Writing 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources would be appropriate to include? 2.  What types of sources should I review (books, journal articles, websites; scholarly versus popular sources)? 3.  Should I summarize, synthesize, or critique sources by discussing a common theme or issue? 4.  Should I evaluate the sources in any way beyond evaluating how they relate to understanding the research problem? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature review sections. Read them to get a sense of the types of themes you might want to look for in your own research or to identify ways to organize your final review. The bibliography or reference section of sources you've already read, such as required readings in the course syllabus, are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make the act of reviewing easier if you first limit scope of the research problem. A good strategy is to begin by searching the USC Libraries Catalog for recent books about the topic and review the table of contents for chapters that focuses on specific issues. You can also review the indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict, or look in the index for the pages where Egypt is mentioned in the text. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is particularly true in disciplines in medicine and the sciences where research conducted becomes obsolete very quickly as new discoveries are made. However, when writing a review in the social sciences, a survey of the history of the literature may be required. In other words, a complete understanding the research problem requires you to deliberately examine how knowledge and perspectives have changed over time. Sort through other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to explore what is considered by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronology of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression revealed, for example, a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic [“conceptual categories”] A thematic literature review is the most common approach to summarizing prior research in the social and behavioral sciences. Thematic reviews are organized around a topic or issue, rather than the progression of time, although the progression of time may still be incorporated into a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it would still be organized chronologically reflecting technological developments in media. The difference in this example between a "chronological" and a "thematic" approach is what is emphasized the most: themes related to the role of the Internet in presidential politics. Note that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point being made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Internet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. However, only include what is necessary for the reader to locate your study within the larger scholarship about the research problem.

Here are examples of other sections, usually in the form of a single paragraph, you may need to include depending on the type of review you write:

• Current Situation : Information necessary to understand the current topic or focus of the literature review.
• Sources Used : Describes the methods and resources [e.g., databases] you used to identify the literature you reviewed.
• History : The chronological progression of the field, the research literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
• Selection Methods : Criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed [i.e., scholarly] sources.
• Standards : Description of the way in which you present your information.
• Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review section is, in this sense, just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence [citations] that demonstrates that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Related items that provide additional information, but that are not key to understanding the research problem, can be included in a list of further readings . Use Quotes Sparingly Some short quotes are appropriate if you want to emphasize a point, or if what an author stated cannot be easily paraphrased. Sometimes you may need to quote certain terminology that was coined by the author, is not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute for using your own words in reviewing the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each thematic paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to your own work and the work of others. Keep Your Own Voice While the literature review presents others' ideas, your voice [the writer's] should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

These are the most common mistakes made in reviewing social science research literature.

• Sources in your literature review do not clearly relate to the research problem;
• You do not take sufficient time to define and identify the most relevant sources to use in the literature review related to the research problem;
• Relies exclusively on secondary analytical sources rather than including relevant primary research studies or data;
• Uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
• Does not describe the search procedures that were used in identifying the literature to review;
• Reports isolated statistical results rather than synthesizing them in chi-squared or meta-analytic methods; and,
• Only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Cook, Kathleen E. and Elise Murowchick. “Do Literature Review Skills Transfer from One Course to Another?” Psychology Learning and Teaching 13 (March 2014): 3-11; Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . London: SAGE, 2011; Literature Review Handout. Online Writing Center. Liberty University; Literature Reviews. The Writing Center. University of North Carolina; Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: SAGE, 2016; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012; Randolph, Justus J. “A Guide to Writing the Dissertation Literature Review." Practical Assessment, Research, and Evaluation. vol. 14, June 2009; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016; Taylor, Dena. The Literature Review: A Few Tips On Conducting It. University College Writing Centre. University of Toronto; Writing a Literature Review. Academic Skills Centre. University of Canberra.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions to a problem or gaining a new perspective. Consult with a librarian about identifying research databases in other disciplines; almost every field of study has at least one comprehensive database devoted to indexing its research literature.

Frodeman, Robert. The Oxford Handbook of Interdisciplinarity . New York: Oxford University Press, 2010.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to writing this part of your paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. Some questions to ask:

• How are they organizing their ideas?
• What methods have they used to study the problem?
• What theories have been used to explain, predict, or understand their research problem?
• What sources have they cited to support their conclusions?
• How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

When you begin to write your literature review section, you'll be glad you dug deeper into how the research was designed and constructed because it establishes a means for developing more substantial analysis and interpretation of the research problem.

Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1 998.

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've thoroughly reviewed the literature:

• Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a conceptual dead end. At this point consider: Does your study extend current research?  Does it forge a new path? Or, does is merely add more of the same thing being said?
• Look at sources the authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been generated to address the research problem.
• Search Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review [see next sub-tab]. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline. Here again, if the same authors are being cited again and again, this may indicate no new literature has been written on the topic.

Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: Sage, 2016; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

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Label	Description	Search	Appraisal	Synthesis	Analysis
Critical Review	Aims to demonstrate writer has extensively researched literature and critically evaluated its quality. Goes beyond mere description to include degree of analysis and conceptual innovation. Typically results in hypothesis or model	Seeks to identify most significant items in the field	No formal quality assessment. Attempts to evaluate according to contribution	Typically narrative, perhaps conceptual or chronological	Significant component: seeks to identify conceptual contribution to embody existing or derive new theory
Literature Review	Generic term: published materials that provide examination of recent or current literature. Can cover wide range of subjects at various levels of completeness and comprehensiveness. May include research findings	May or may not include comprehensive searching	May or may not include quality assessment	Typically narrative	Analysis may be chronological, conceptual, thematic, etc.
Mapping review/ systematic map	Map out and categorize existing literature from which to commission further reviews and/or primary research by identifying gaps in research literature	Completeness of searching determined by time/scope constraints	No formal quality assessment	May be graphical and tabular	Characterizes quantity and quality of literature, perhaps by study design and other key features. May identify need for primary or secondary research
Meta-analysis	Technique that statistically combines the results of quantitative studies to provide a more precise effect of the results	Aims for exhaustive, comprehensive searching. May use funnel plot to assess completeness	Quality assessment may determine inclusion/exclusion and/or sensitivity analyses	Graphical and tabular with narrative commentary	Numerical analysis of measures of effect assuming absence of heterogeneity
Mixed studies review/mixed methods review	Refers to any combination of methods where one significant component is a literature review (usually systematic). Within a review context it refers to a combination of review approaches for example combining quantitative with qualitative research or outcome with process studies	Requires either very sensitive search to retrieve all studies or separately conceived quantitative and qualitative strategies	Requires either a generic appraisal instrument or separate appraisal processes with corresponding checklists	Typically both components will be presented as narrative and in tables. May also employ graphical means of integrating quantitative and qualitative studies	Analysis may characterise both literatures and look for correlations between characteristics or use gap analysis to identify aspects absent in one literature but missing in the other
Overview	Generic term: summary of the [medical] literature that attempts to survey the literature and describe its characteristics	May or may not include comprehensive searching (depends whether systematic overview or not)	May or may not include quality assessment (depends whether systematic overview or not)	Synthesis depends on whether systematic or not. Typically narrative but may include tabular features	Analysis may be chronological, conceptual, thematic, etc.
Qualitative systematic review/qualitative evidence synthesis	Method for integrating or comparing the findings from qualitative studies. It looks for ‘themes’ or ‘constructs’ that lie in or across individual qualitative studies	May employ selective or purposive sampling	Quality assessment typically used to mediate messages not for inclusion/exclusion	Qualitative, narrative synthesis	Thematic analysis, may include conceptual models
Rapid review	Assessment of what is already known about a policy or practice issue, by using systematic review methods to search and critically appraise existing research	Completeness of searching determined by time constraints	Time-limited formal quality assessment	Typically narrative and tabular	Quantities of literature and overall quality/direction of effect of literature
Scoping review	Preliminary assessment of potential size and scope of available research literature. Aims to identify nature and extent of research evidence (usually including ongoing research)	Completeness of searching determined by time/scope constraints. May include research in progress	No formal quality assessment	Typically tabular with some narrative commentary	Characterizes quantity and quality of literature, perhaps by study design and other key features. Attempts to specify a viable review
State-of-the-art review	Tend to address more current matters in contrast to other combined retrospective and current approaches. May offer new perspectives on issue or point out area for further research	Aims for comprehensive searching of current literature	No formal quality assessment	Typically narrative, may have tabular accompaniment	Current state of knowledge and priorities for future investigation and research
Systematic review	Seeks to systematically search for, appraise and synthesis research evidence, often adhering to guidelines on the conduct of a review	Aims for exhaustive, comprehensive searching	Quality assessment may determine inclusion/exclusion	Typically narrative with tabular accompaniment	What is known; recommendations for practice. What remains unknown; uncertainty around findings, recommendations for future research
Systematic search and review	Combines strengths of critical review with a comprehensive search process. Typically addresses broad questions to produce ‘best evidence synthesis’	Aims for exhaustive, comprehensive searching	May or may not include quality assessment	Minimal narrative, tabular summary of studies	What is known; recommendations for practice. Limitations
Systematized review	Attempt to include elements of systematic review process while stopping short of systematic review. Typically conducted as postgraduate student assignment	May or may not include comprehensive searching	May or may not include quality assessment	Typically narrative with tabular accompaniment   Reproduced from Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies . Health Info Libr J. 2009 Jun;26(2):91-108. doi: 10.1111/j.1471-1842.2009.00848.x Last Updated: Sep 24, 2024 9:42 AM URL: https://guides.lib.utexas.edu/systematicreviews Systematic Reviews: Methods & Resources Methods & Resources Protocol & Registration Search Strategy Where to Search Study selection and appraisal Data Extraction, Study Characteristics, Results Reporting the quality/risk of bias PRISMA Reporting Items Manage citations using RefWorks This link opens in a new window Covidence Guide This link opens in a new window Many organizations have created guidelines to standardize reporting of analytical research. See some of the main ones below. The NIH offers a useful chart of Research Reporting Guidelines , and you can find over 500 on the EQUATOR network PRISMA Guidelines Gold-standard guideline on how to perform and write-up a systematic review and/or meta-analysis of the outcomes reported in multiple clinical trials of therapeutic interventions AHRQ's Methods Guide for Effectiveness and Comparative Effectiveness Reviews Synthesis without meta-analysis (SWiM) in systematic reviews Campbell, M. (2020). Synthesis without meta-analysis (SWiM) in systematic reviews: reporting guideline. BMJ, 368. Guideline on how to analyze evidence for a narrative review, to provide a recommendation based on heterogenous study types Methods Manual for Community Guide Systematic Reviews Community Preventive Services Task Force (2021). The Methods Manual for Community Guide Systematic Reviews. (Public Health Prevention systematic review guidelines) Planning Worksheet for Structured Literature Reviews Cornell University Library (2019). A basic framework for a literature review. STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) statement MOOSE Reporting Guidelines for Meta-analyses of Observational Studies Brooke BS, Schwartz TA, Pawlik TM. MOOSE Reporting Guidelines for Meta-analyses of Observational Studies. JAMA Surg. 2021;156(8):787–788. doi:10.1001/jamasurg.2021.0522 Tools and Guidance Right Review Flowchart to help you choose the proper review methodology for your project Systematic Review Accelerator Catalog of tools that support various tasks within the systematic review and wider evidence synthesis process. Tools include the 'Polyglot Search Translator'. Institute of Medicine. (2011). Finding What Works in Health Care: Standards for Systematic Reviews. Washington, DC: National Academies Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly work in Medical Journals International Committee of Medical Journal Editors (2022) Cochrane Handbook for Systematic Reviews of Interventions Joanna Briggs Institute (JBI) Manual for Evidence Synthesis Provides guidance on how to analyze both quantitative and qualitative research How to do a systematic review Pollock, A., & Berge, E. (2018). International journal of stroke : official journal of the International Stroke Society, 13(2), 138–156. https://doi.org/10.1177/1747493017743796 Cochrane Qualitative & Implementation Methods Group. (2019). Training resources. Meeting the review family: exploring review types and associated information retrieval requirements Sutton, A., Clowes, M., Preston, L., & Booth, A. (2019). Health information and libraries journal, 36(3), 202–222. https://doi.org/10.1111/hir.12276 Software tools for systematic reviews Covidence Available for free to GW affiliates, this is a popular tool for facilitating screening decisions, used by the Cochrane Collaboration. Register for an account. Statistical software available at Himmelfarb SPSS, SAS, Stata, NVivo, Atlas.ti, and MATLAB RedCAP Software to create survey forms for research or data collection or data extraction. SRDR tool from AHRQ Free, web-based and has a training environment, tutorials, and example templates of systematic review data extraction forms RevMan 5 ReviewManager (RevMan) is Cochrane's bespoke software for writing Cochrane Reviews. Rayyan Free, web-based tool for collecting and screening citations. It has options to screen with multiple people, masking each other. GradePro Free, web application to create, manage and share summaries of research evidence (called Evidence Profiles and Summary of Findings Tables) for reviews or guidelines, uses the GRADE criteria to evaluate each paper under review. DistillerSR Needs subscription. Create coded data extraction forms from templates. EPPI Reviewer Needs subscription. Like DistillerSR, tool for text mining, data clustering, classification and term extraction SUMARI Needs subscription. Qualitative data analysis. Dedoose Needs subscription. Qualitative data analysis, similar to NVIVO in that it can be used to code interview transcripts, identify word co-occurence, cloud based. Forest Plot Generators Meta-Essentials a free set of workbooks designed for Microsoft Excel that, based on your input, automatically produce meta-analyses including Forest Plots. Produced for Erasmus University Rotterdam joint research institute. Neyeloff, Fuchs & Moreira Another set of Excel worksheets and instructions to generate a Forest Plot. Published as Neyeloff, J.L., Fuchs, S.C. & Moreira, L.B. Meta-analyses and Forest plots using a microsoft excel spreadsheet: step-by-step guide focusing on descriptive data analysis. BMC Res Notes 5, 52 (2012). https://doi-org.proxygw.wrlc.org/10.1186/1756-0500-5-52 For R programmers instructions are at https://cran.r-project.org/web/packages/forestplot/vignettes/forestplot.html and you can download the R code package from https://github.com/gforge/forestplot << Previous: Home Next: Protocol & Registration >> Last Updated: Aug 13, 2024 12:37 PM URL: https://guides.himmelfarb.gwu.edu/systematic_review Himmelfarb Intranet Privacy Notice Terms of Use GW is committed to digital accessibility. If you experience a barrier that affects your ability to access content on this page, let us know via the Accessibility Feedback Form . Himmelfarb Health Sciences Library 2300 Eye St., NW, Washington, DC 20037 Phone: (202) 994-2962 [email protected] https://himmelfarb.gwu.edu View  PDF Download full issue Journal of Business Research Literature review as a research methodology: an overview and guidelines. Previous article in issue Next article in issue Cited by (0) University of Michigan Library Research Guides Evidence Syntheses (Scoping, systematic, & other types of reviews) Types of Reviews Choosing a Review Type Types of literature reviews. Should You Do a Systematic Review? Work with a Search Expert Evidence in an Evidence Synthesis Information Sources Search Strategy Covidence Review Software Selection Process Data Collection Process Study Risk of Bias Assessment Reporting Results For Search Professionals This guide focuses on the methodology for systematic reviews (SRs), but an SR may not be the best methodology to use to meet your project's goals. Use the articles listed here or in the Types of Literature Reviews box below for information about additional methodologies that could better fit your project.  Haddaway NR, Lotfi T, Mbuagbaw L. Systematic reviews: A glossary for public health . Scand J Public Health. 2022 Feb 9:14034948221074998. doi: 10.1177/14034948221074998. Epub ahead of print. PMID: 35139715. Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies . Health Info Libr J. 2009 Jun;26(2):91-108. Defines 14 types of reviews and provides a helpful summary table on pp. 94-95. Sutton A, Clowes M, Preston L, Booth A. Meeting the review family: exploring review types and associated information retrieval requirements . Health Info Libr J . 2019;36(3):202–222. doi:10.1111/hir.12276 If you're not sure what type of review is right for your quantitative review, use this tool to find the best methodology for your project, What Review is Right for You? https://whatreviewisrightforyou.knowledgetranslation.net Systematic Reviews Meta-Analyses Comparative Effectiveness systematically and transparently searches for a broad range of information to synthesize, in order to find the effect of an intervention. uses a protocol  has a clear data extraction and management plan. Time-intensive and often take months to a year or more to complete, even with a multi-person team.  NOTE: The term "systematic review" is also used incorrectly as a blanket term for other types of reviews. Methodological Guidance Finding What Works in Health Care: Standards for Systematic Reviews. 2011. Institute of Medicine. http://books.nap.edu/openbook.php?record_id=13059 Cochrane Handbook of Systematic Reviews of Interventions, v. 6. 2019. https://training.cochrane.org/handbook The Joanna Briggs Reviewers Manual. 2024. https://jbi-global-wiki.refined.site/space/MANUAL The Community Guide/Methods/Systematic Review Methods. 2014. The Community Preventive Services Task Force. http://www.thecommunityguide.org/about/methods.html For issues in systematic reviews, especially in social science or other qualitative research:  Some Potential "Pitfalls" in the Construction of Educational Systematic Reviews. https://doi.org/10.1007/s40596-017-0675-7 Lescoat, A., Murphy, S. L., Roofeh, D., et al. (2021). Considerations for a combined index for limited cutaneous systemic sclerosis to support drug development and improve outcomes. https://doi.org/10.1177/2397198320961967 DeLong, M. R., Tandon, V. J., Bertrand, A. A. (2021). Review of Outcomes in Prepectoral Prosthetic Breast Reconstruction with and without Surgical Mesh Assistance.  https://pubmed.ncbi.nlm.nih.gov/33177453/ Carey, M. R., Vaughn, V. M., Mann, J. (2020). Is Non-Steroidal Anti-Inflammatory Therapy Non-Inferior to Antibiotic Therapy in Uncomplicated Urinary Tract Infections: a Systematic Review.  https://pubmed.ncbi.nlm.nih.gov/32270403/ Statistical technique for combining the findings from disparate  quantitative studies. Uses statistical methods to objectively evaluate, synthesize, and summarize results. May be conducted independently or as part of a systematic review. Cochrane Handbook, Ch 10: Analysing data and undertaking meta-analyses https://training.cochrane.org/handbook/current/chapter-10 Bauer, M. E., Toledano, R. D., Houle, T., et al. (2020). Lumbar neuraxial procedures in thrombocytopenic patients across populations: A systematic review and meta-analysis. https://pubmed.ncbi.nlm.nih.gov/31810860/ 6 Mailoa J, Lin GH, Khoshkam V, MacEachern M, et al. Long-Term Effect of Four Surgical Periodontal Therapies and One Non-Surgical Therapy: A Systematic Review and Meta-Analysis. https://pubmed.ncbi.nlm.nih.gov/26110453/ Umbrella Reviews Reviews other systematic reviews on a topic.  Often defines a broader question than is typical of a traditional systematic review. Most useful when there are competing interventions to consider. Ioannidis JP. Integration of evidence from multiple meta-analyses: a primer on umbrella reviews, treatment networks and multiple treatments meta-analyses .  https://pubmed.ncbi.nlm.nih.gov/35081993 Aromataris, E., Fernandez, R., Godfrey, C. M., Holly, C., Khalil, H., & Tungpunkom, P.  2015 Methodology for JBI Umbrella Reviews. https://ro.uow.edu.au/cgi/viewcontent.cgi?articl. Gastaldon, C., Solmi, M., Correll, C. U., et al. (2022). Risk factors of postpartum depression and depressive symptoms: umbrella review of current evidence from systematic reviews and meta-analyses of observational studies. https://pubmed.ncbi.nlm.nih.gov/35081993/ Blodgett, T. J., & Blodgett, N. P. (2021). Melatonin and melatonin-receptor agonists to prevent delirium in hospitalized older adults: An umbrella review.   https://pubmed.ncbi.nlm.nih.gov/34749057/ Comparative effectiveness  Systematic reviews of existing research on the effectiveness, comparative effectiveness, and comparative harms of different health care interventions.  Intended to provide relevant evidence to inform real-world health care decisions for patients, providers, and policymakers. “Methods Guide for Effectiveness and Comparative Effectiveness Reviews.” Methods Guide for Effectiveness and Comparative Effectiveness Reviews https://effectivehealthcare.ahrq.gov/products/collections/cer-methods-guide Main document of above guide :  https://effectivehealthcare.ahrq.gov/sites/default/files/pdf/cer-methods-guide_overview.pdf . Tanni KA, Truong CB, Johnson BS, Qian J. Comparative effectiveness and safety of eribulin in advanced or metastatic breast cancer: a systematic review and meta-analysis. Crit Rev Oncol Hematol. 2021 Jul;163:103375. doi: 10.1016/j.critrevonc.2021.103375. Epub 2021 Jun 2. PMID: 34087344. Rice D, Corace K, Wolfe D, Esmaeilisaraji L, Michaud A, Grima A, Austin B, Douma R, Barbeau P, Butler C, Willows M, Poulin PA, Sproule BA, Porath A, Garber G, Taha S, Garner G, Skidmore B, Moher D, Thavorn K, Hutton B. Evaluating comparative effectiveness of psychosocial interventions adjunctive to opioid agonist therapy for opioid use disorder: A systematic review with network meta-analyses. PLoS One. 2020 Dec 28;15(12):e0244401. doi: 10.1371/journal.pone.0244401. PMID: 33370393; PMCID: PMC7769275. ​ Scoping Review or Evidence Map Systematically and transparently collect and  categorize  existing evidence on a broad question of  policy or management importance. Seeks to identify research gaps and opportunities for evidence synthesis rather than searching for the effect of an intervention.  May critically evaluate existing evidence, but does not attempt to synthesize the results in the way a systematic review would. (see  EE Journal  and  CIFOR ) May take longer than a systematic review. For useful guidance on whether to conduct a scoping review or not, see Figure 1 in this article. Pollock, D , Davies, EL , Peters, MDJ , et al. Undertaking a scoping review: A practical guide for nursing and midwifery students, clinicians, researchers, and academics . J Adv Nurs . 2021 ; 77 : 2102 – 2113 . https://doi.org/10.1111/jan.14743For a helpful Hilary Arksey & Lisa O'Malley (2005) Scoping studies: towards a methodological framework http://10.1080/1364557032000119616 Aromataris E, Munn Z, eds. (2020) . JBI Manual for Evidence Synthesis.  JBI. Chapter 11: Scoping Reviews. https://wiki.jbi.global/display/MANUAL/Chapter+11%3A+Scoping+reviews Munn Z, Peters MD, Stern C, Tet al. (2018)  Systematic review or scoping review? Guidance for authors when choosing between a systematic or scoping review approach. https://pubmed.ncbi.nlm.nih.gov/30453902/ Tricco AC, Lillie E, Zarin W, et al.. PRISMA Extension for Scoping Reviews (PRISMA-ScR): Checklist and Explanation. Ann Intern Med. 2018 Oct 2;169(7):467-473. doi: 10.7326/M18-0850. Epub 2018 Sep 4. PMID: 30178033.  https://www.acpjournals.org/doi/epdf/10.7326/M18-0850 Bouldin E, Patel SR, Tey CS, et al. Bullying and Children who are Deaf or Hard-of-hearing: A Scoping Review. https://pubmed.ncbi.nlm.nih.gov/33438758 Finn M, Gilmore B, Sheaf G, Vallières F. What do we mean by individual capacity strengthening for primary health care in low- and middle-income countries? A systematic scoping review to improve conceptual clarity. https://pubmed.ncbi.nlm.nih.gov/33407554/ Hirt J, Nordhausen T, Meichlinger J, Braun V, Zeller A, Meyer G. Educational interventions to improve literature searching skills in the health sciences: a scoping review.  https://pubmed.ncbi.nlm.nih.gov/33013210/ ​ Rapid Review Useful for addressing issues needing timely decisions, such as developing policy recommendations.  Applies systematic review methodology within a time-constrained setting. Employs intentional, methodological "shortcuts" (limiting search terms for example) at the risk of introducing bias. Defining characteristic is the transparency of team methodological choices. Garritty, Chantelle, Gerald Gartlehner, Barbara Nussbaumer-Streit, Valerie J. King, Candyce Hamel, Chris Kamel, Lisa Affengruber, and Adrienne Stevens. “Cochrane Rapid Reviews Methods Group Offers Evidence-Informed Guidance to Conduct Rapid Reviews.” Journal of Clinical Epidemiology 130 (February 2021): 13–22. https://doi.org/10.1016/j.jclinepi.2020.10.007 . Klerings I , Robalino S , Booth A , et al. Rapid reviews methods series: Guidance on literature search. BMJ Evidence-Based Medicine. 19 April 2023. https:// 10.1136/bmjebm-2022-112079 WHO. “WHO | Rapid Reviews to Strengthen Health Policy and Systems: A Practical Guide.” World Health Organization. Accessed February 11, 2022. https://iris.who.int/handle/10665/258698 . Dobbins, Maureen. “Steps for Conducting a Rapid Review,” 2017, 25.  https://www.nccmt.ca/uploads/media/media/0001/01/a816af720e4d587e13da6bb307df8c907a5dff9a.pdf Norris HC, Richardson HM, Benoit MC, et al. (2021) Utilization Impact of Cost-Sharing Elimination for Preventive Care Services: A Rapid Review.   https://pubmed.ncbi.nlm.nih.gov/34157906/ Marcus N, Stergiopoulos V. Re-examining mental health crisis intervention: A rapid review comparing outcomes across police, co-responder and non-police models. Health Soc Care Community. 2022 Feb 1. doi: 10.1111/hsc.13731. Epub ahead of print. PMID: 35103364. Narrative ( Literature ) Review A broad term referring to reviews with a wide scope and non-standardized methodology. See Baethge 2019 below for a method to provide quality assessment, Search strategies, comprehensiveness, and time range covered will vary and do not follow an established protocol. It provides insight into a particular topic by critically examining sources, generally over a particular period of time. Greenhalgh, T., Thorne, S., & Malterud, K. (2018). Time to challenge the spurious hierarchy of systematic over narrative reviews?. https://pubmed.ncbi.nlm.nih.gov/29578574/ Baethge, C., Goldbeck-Wood, S. & Mertens, S. (2019). SANRA—a scale for the quality assessment of narrative review articles. https://doi.org/10.1186/ s41073-019-0064-8   https:// researchintegrityjournal. biomedcentral.com/articles/10. 1186/s41073-019-0064-8 Czypionka, T., Greenhalgh, T., Bassler, D., & Bryant, M. B. (2021). Masks and Face Coverings for the Lay Public : A Narrative Update. https://pubmed.ncbi.nlm.nih.gov/33370173/ Gardiner, F. W., Nwose, E. U., Bwititi, P. T., et al.. (2017). Services aimed at achieving desirable clinical outcomes in patients with chronic kidney disease and diabetes mellitus: A narrative review. https://pubmed.ncbi.nlm.nih.gov/29201367/  Dickerson, S. S., Connors, L. M., Fayad, A., & Dean, G. E. (2014). Sleep-wake disturbances in cancer patients: narrative review of literature focusing on improving quality of life outcomes.  https://pubmed.ncbi.nlm.nih.gov/25050080/ Systematic Reviews and Other Evidence Synthesis Types Guide Systematic review and other evidence synthesis types. Types of Evidence Synthesis Evidence Synthesis Comparison Are You Ready to Conduct an Evidence Synthesis? UT Southwestern Evidence Synthesis Services Task 1 - Find Articles Task 2 - Formulate Question Task 3 - Select Reporting Guideline Task 4 - Write and Register Protocol Evidence Synthesis - Search (Task 5) Screen and Appraise (Tasks 6 – 11) Synthesize (Tasks 12 – 15) Write Up Review (Task 16) Systematic Review or Meta-Analysis Integrative Review Narrative/Literature Review Rapid Review Scoping Review Umbrella Review Request UT Southwestern Library Evidence Synthesis/Systematic Review Services The UT Southwestern Librarians provide two levels of Evidence Synthesis/Systematic Review (ES/SR) support. Level 1 – Education (No Cost) A librarian will provide training about the systematic review process. Use the Training Request Form . Level 2 – Librarian As ES/SR Team Member and Co-Author (Fee-Based) The librarian is an active contributor. UT Southwestern faculty UT Southwestern residents or fellows UT Southwestern Medical Center and University Hospitals clinicians Begin by completing the Evidence Synthesis/Systematic Review Request Form . For more information on the fees ($1,250 per PICO or equivalent question), see the "Costs" section in the form. If a Librarian joins the ES/SR Team, the ES/SR Team will complete the Evidence Synthesis/Systematic Review Library Services Agreement . Contact LibAsk Schedule an appointment with UT Southwestern librarians. In 2021, the Library completed a comprehensive update of its Systematic Review Guide.  As the breadth of methodologies and types of complex searches we support has evolved, the new Systematic Review and Evidence Synthesis Types Guide includes content from the Systematic Review Guide as well as new content of other types of evidence synthesis.   For the purpose of this guide, the terms "evidence synthesis" and “knowledge synthesis” are used interchangeably and encompass a broad group of review families, including but not limited to systematic review, meta-analysis, integrative review, rapid review, scoping review and umbrella review. The left column displays the Table of Contents.  Depending on your familiarity, you can either methodically review the Guide in its entirety or go directly to one (or more) specific chapter(s) for a quick review. The tabs along the top within each chapter include more material and are organized to help users find information efficiently. Next: What Is Evidence Synthesis? >> Last Updated: Sep 24, 2024 12:06 PM URL: https://utsouthwestern.libguides.com/sres Library Guides Literature Reviews Getting Started Literature Reviews: Getting Started What is a literature review. A literature review is an overview of the available research for a specific scholarly topic. Literature reviews summarize existing research to answer a review question, provide context for new research, or identify important gaps in the existing body of literature. An incredible amount of academic literature is published each year; by some estimates nearly three million articles . Sorting through and reviewing that literature can be complicated, so this Research Guide provides a structured approach to make the process more manageable. THIS GUIDE IS AN OVERVIEW OF THE LITERATURE REVIEW PROCESS: Getting Started (asking a research question | defining scope) Choosing a Type of Review Searching the Literature Organizing the Literature Writing the Literature Review (analyzing | synthesizing) A  literature search  is a systematic search of the scholarly sources in a particular discipline. A  literature review   is the analysis, critical evaluation and synthesis of the results of that search. During this process you will move from a review  of  the literature to a review  for   your research.   Your synthesis of the literature is your unique contribution to research. WHO IS THIS RESEARCH GUIDE FOR? — those new to reviewing the literature — those that need a refresher or a deeper understanding of writing literature reviews You may need to do a literature review as a part of a course assignment, a capstone project, a master's thesis, a dissertation, or as part of a journal article. No matter the context, a literature review is an essential part of the research process.  Literature Review Process Purpose of a Literature Review What is the purpose of a literature review. A literature review is typically performed for a specific reason. Even when assigned as an assignment, the goal of the literature review will be one or more of the following: To communicate a project's novelty by identifying a research gap An overview of research issues , methodologies or results relevant to field To explore the  volume and types of available studies To establish familiarity with current research before carrying out a new project To resolve conflicts amongst contradictory previous studies Reviewing the literature helps you understand a research topic and develop your own perspective. A LITERATURE REVIEW IS NOT : An annotated bibliography – which is a list of annotated citations to books, articles and documents that includes a brief description and evaluation for each entry A literary review – which is a critical discussion of the merits and weaknesses of a literary work A book review – which is a critical discussion of the merits and weaknesses of a particular book Attribution Thanks to Librarian Jamie Niehof at the University of Michigan for providing permission to reuse and remix this Literature Reviews guide. Workshop Materials Materials from OSU Literature Review Workshop Last Updated: Sep 23, 2024 11:11 AM URL: https://info.library.okstate.edu/literaturereviews Online Study Skills Hub: Literature Review Where do I start? What is Gen AI? Academic Integrity and Plagiarism Using Gen AI in assessment Using AI for feedback on your assessment Using prompts & generating feedback Using Gen AI for revision Finding Information with AI Key terminology Critical Thinking & Writing Editing & Proofreading Essay Planning: Structuring your work Dissertations & Theses Reflective Writing Lab Reports Report Writing Annotated Bibliography Literature Review Exam Preparation Exam Checklist Useful Links Finding Books & eBooks Finding Resources Step by Step Guide Logging in to Online Resources Request an Item Understanding Resource Lists Using eBooks Presentation Skills Reading & Note Taking Referencing: How & Why You Should do it This link opens in a new window Resit Toolkit Statistics & SPSS This link opens in a new window Time Management Skills Understanding Feedback A literature review is a critical summary of existing research on a particular topic, typically included in university assignments like dissertations, essays, or research projects. Its main purpose is to give an overview of what has already been studied, allowing you to identify key theories, methods, and findings related to your research question. It helps you understand the current state of knowledge, as well as any gaps or areas of debate in the field. By reviewing the literature, you can position your own work in the context of existing studies, demonstrating how it builds on or challenges previous research. In a literature review, you evaluate and synthesise the sources, rather than just listing them. This means comparing and contrasting different authors’ viewpoints, highlighting trends or patterns, and critically assessing the strengths and weaknesses of their arguments. A well-done literature review shows that you have a solid grasp of your topic and have engaged deeply with the relevant scholarship. It also provides a foundation for your own research, helping to justify your study’s aims and methods. << Previous: Annotated Bibliography Next: Exam Preparation & Revision >> Last Updated: Sep 23, 2024 9:51 AM URL: https://library.roehampton.ac.uk/studyskills An official website of the United States government The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site. The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely. Publications Account settings My Bibliography Collections Citation manager Save citation to file Email citation, add to collections. Create a new collection Add to an existing collection Add to My Bibliography Your saved search, create a file for external citation management software, your rss feed. Search in PubMed Search in NLM Catalog Add to Search Unusual Presentation of Propionic Acidemia Mimicking Botulism in an Infant: A Case Report and Literature Review Affiliations. 1 Orthopedic Surgery, Wayne State University School of Medicine, Detroit, USA. 2 Pediatrics, Wayne State University School of Medicine, Detroit, USA. 3 Neurology, Henry Ford Health System, Detroit, USA. PMID: 39280525 PMCID: PMC11398609 DOI: 10.7759/cureus.66870 Propionic acidemia (PA) is a rare metabolic disorder stemming from genetic mutations, often causing hyperammonemia, acidosis, and basal ganglia issues. Its symptoms range from vomiting to neurological abnormalities, with severe cases presenting in neonates. Neurological complications including stroke-like episodes are common, requiring immediate attention. An eight-month-old boy with PA presented to the emergency department with respiratory distress, cough, and lethargy. Initial evaluation showed acidemia and elevated ammonia levels. He tested positive for rhinovirus and was diagnosed with acute viral bronchiolitis. While his respiratory symptoms improved, he developed neurological deficits, including hypotonia and weakness. Neurology consultations explored possible diagnoses such as botulism or acute inflammatory demyelinating polyneuropathy (AIDP). Imaging revealed basal ganglia abnormalities consistent with PA progression. Due to aspiration risk, he was transferred to the pediatric intensive care unit for supportive care. Despite unremarkable lumbar puncture and MRI results, new metabolic brain changes were noted, particularly in the basal ganglia. He was managed for weakness and feeding difficulties due to a metabolic stroke. After adjusting nutritional support and discussing long-term feeding options, he was discharged on day 29 with a nasogastric tube due to his inability to meet caloric goals orally. Neurological complications in PA, such as basal ganglia abnormalities and stroke-like episodes, are well-documented. Our case illustrates how an acute respiratory illness can obscure underlying neurological deficits, leading to delayed diagnosis. Symptoms resembling other conditions, such as descending hypotonia in our case, broaden the differential diagnosis to include botulism toxicity and AIDP. This report demonstrates the variety of clinical features patients with PA can present with and the importance of working up a metabolic crisis in addition to conditions with overlapping symptoms. Keywords: basal ganglia; botulin toxin; botulinum; descending paralysis; infant; mri; neurology; pediatrics; propionic acidemia. Copyright © 2024, Boland et al. PubMed Disclaimer Conflict of interest statement Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work. Figure 1. Diffusion-weighted image MRI showing bilateral… Figure 1. Diffusion-weighted image MRI showing bilateral symmetric areas of diffusion restriction mainly involving the… Figure 2. Apparent diffusion coefficient MRI showing… Figure 2. Apparent diffusion coefficient MRI showing bilateral symmetric areas of diffusion restriction mainly involving… Figure 3. Fluid-attenuated inversion recovery MRI showing… Figure 3. Fluid-attenuated inversion recovery MRI showing bilateral symmetric areas of diffusion restriction mainly involving… Figure 4. Propionyl-CoA metabolism. Neuropathological report of propionic acidemia. Cao LX, Hu WZ, Dong W, et al. Neuropathology. 2023;43:143–150. - PubMed Evaluation and management of patients with propionic acidemia undergoing liver transplantation: a comprehensive review. Barshes NR, Vanatta JM, Patel AJ, Carter BA, O'Mahony CA, Karpen SJ, Goss JA. Pediatr Transplant. 2006;10:773–781. - PubMed Spontaneous rapid resolution of acute basal ganglia changes in an untreated infant with propionic acidemia: a clue to pathogenesis? Broomfield A, Gunny R, Prabhakar P, Grunewald S. Neuropediatrics. 2010;41:256–260. - PubMed Propionic acidemia associated with visual hallucinations. Shuaib T, Al-Hashmi N, Ghaziuddin M, et al. J Child Neurol. 2012;27:799–803. - PubMed Bodamer OA. UpToDate. Philadelphia, PA: Wolters Kluwer; 2024. Organic acidemias: an overview and specific defects. Publication types Search in MeSH Related information Linkout - more resources, full text sources. PubMed Central Citation Manager NCBI Literature Resources MeSH PMC Bookshelf Disclaimer The PubMed wordmark and PubMed logo are registered trademarks of the U.S. Department of Health and Human Services (HHS). Unauthorized use of these marks is strictly prohibited. Advertisement Accelerating FLAIR imaging via deep learning reconstruction: potential for evaluating white matter hyperintensities Original Article Open access Published: 24 September 2024 Cite this article You have full access to this open access article Noriko Nishioka   ORCID: orcid.org/0000-0001-9954-3838 1 , 2 , Yukie Shimizu   ORCID: orcid.org/0000-0002-6070-3766 1 , 2 , Yukio Kaneko 3 , Toru Shirai 3 , Atsuro Suzuki 3 , Tomoki Amemiya 3 , Hisaaki Ochi 3 , Yoshitaka Bito 2 , 4 , Masahiro Takizawa 4 , Yohei Ikebe 1 , 5 , Hiroyuki Kameda 1 , 6 , Taisuke Harada 1 , 2 , Noriyuki Fujima 1 , 2 & Kohsuke Kudo 1 , 2 , 5 , 7   To evaluate deep learning-reconstructed (DLR)–fluid-attenuated inversion recovery (FLAIR) images generated from undersampled data, compare them with fully sampled and rapidly acquired FLAIR images, and assess their potential for white matter hyperintensity evaluation. Materials and methods We examined 30 patients with white matter hyperintensities, obtaining fully sampled FLAIR images (standard FLAIR, std-FLAIR). We created accelerated FLAIR (acc-FLAIR) images using one-third of the fully sampled data and applied deep learning to generate DLR–FLAIR images. Three neuroradiologists assessed the quality (amount of noise and gray/white matter contrast) in all three image types. The reproducibility of hyperintensities was evaluated by comparing a subset of 100 hyperintensities in acc-FLAIR and DLR–FLAIR images with those in the std-FLAIR images. Quantitatively, similarities and errors of the entire image and the focused regions on white matter hyperintensities in acc-FLAIR and DLR–FLAIR images were measured against std-FLAIR images using structural similarity index measure (SSIM), regional SSIM, normalized root mean square error (NRMSE), and regional NRMSE values. All three neuroradiologists evaluated DLR–FLAIR as having significantly less noise and higher image quality scores compared with std-FLAIR and acc-FLAIR ( p  < 0.001). All three neuroradiologists assigned significantly higher frontal lobe gray/white matter visibility scores for DLR–FLAIR than for acc-FLAIR ( p  < 0.001); two neuroradiologists attributed significantly higher scores for DLR–FLAIR than for std-FLAIR ( p  < 0.05). Regarding white matter hyperintensities, all three neuroradiologists significantly preferred DLR–FLAIR ( p  < 0.0001). DLR–FLAIR exhibited higher similarity to std-FLAIR in terms of visibility of the hyperintensities, with 97% of the hyperintensities rated as nearly identical or equivalent. Quantitatively, DLR–FLAIR demonstrated significantly higher SSIM and regional SSIM values than acc-FLAIR, with significantly lower NRMSE and regional NRMSE values ( p  < 0.0001). Conclusions DLR–FLAIR can reduce scan time and generate images of similar quality to std-FLAIR in patients with white matter hyperintensities. Therefore, DLR–FLAIR may serve as an effective method in traditional magnetic resonance imaging protocols. Explore related subjects Medical Imaging Avoid common mistakes on your manuscript. Introduction Magnetic resonance imaging (MRI) is widely used in medical diagnostics and currently serves as the gold standard for investigating most central nervous system disorders. Owing to its exceptional ability to suppress cerebrospinal fluid signals, fluid-attenuated inversion recovery (FLAIR) imaging is considered one of the most valuable imaging sequences for white matter hyperintensity evaluation, and thus is routinely employed in clinical practice [ 1 , 2 ]. However, FLAIR imaging, which employs an inversion recovery technique for water signal suppression, inherently results in a lower signal-to-noise ratio, thereby lengthening acquisition time and rendering the sequence more susceptible to subject motion; this may increase noise and artifacts, potentially compromising diagnostic accuracy [ 3 ]. Recent advancements in rapid imaging techniques have highlighted their clinical benefits, including reduced scan time and enhanced image quality. Notably, shorter examination time is preferred to maximize patient compliance. Various acceleration techniques have been developed to address the limitations of traditional FLAIR imaging. Parallel imaging (PI) methods, such as sensitivity encoding, offer the advantage of faster image acquisition using phased-array coils to facilitate image reconstruction with fewer data points [ 4 , 5 ]. Similarly, compressed sensing has emerged as a promising approach for accelerating MRI acquisition by exploiting sparsity in image representations and employing iterative reconstruction algorithms [ 6 , 7 , 8 ]. Despite these advancements, challenges remain, including signal-to-noise ratio losses associated with high acceleration factors (AFs) in PI techniques and the computational intensity of iterative compressed sensing algorithms, especially for high-resolution images [ 9 , 10 ]. To address these challenges, various deep learning-based MRI reconstruction methods have been developed with the expectation of enhancing image quality and reducing scan time [ 11 ]. Recently, deep learning-based reconstruction methods have demonstrated rapid development across various fields of radiology [ 12 , 13 , 14 , 15 ], including brain MRI [ 16 , 17 ], with a growing focus on adapting FLAIR sequence [ 18 , 19 , 20 , 21 ]. With the progress in research in this area, it is important to verify the high quality of deep learning-generated images and evaluate their clinical applicability. In particular, for FLAIR images, which are used in white matter hyperintensity assessment, it is necessary to validate whether images generated by deep learning accurately depict both normal structures and white matter hyperintensities. However, studies on the verification of deep learning-reconstructed FLAIR (DLR–FLAIR) images for accurately rendering both normal structures and white matter hyperintensities are limited. The aim of this study was to evaluate whether DLR–FLAIR images obtained rapidly using undersampled data can substitute fully sampled images in clinical settings. By focusing on images and white matter hyperintensities, we qualitatively and quantitatively compared three types of images: fully sampled FLAIR, rapidly acquired FLAIR, and rapidly acquired DLR–FLAIR images. Our institutional review board approved this retrospective, single-center study, and the need for written informed consent was waived owing to the retrospective nature of the study. Patient data Patient data were collected exclusively at our institution. The study cohort comprised individuals who met the following criteria: (a) previously underwent FLAIR MRI revealing multiple white matter hyperintensities, (b) underwent follow-up MRI between July 2022 and October 2022, (c) were imaged using a specific MRI device capable of storing raw data used for this investigation, and (d) had successful acquisition of raw FLAIR data. MRI image acquisition All patients were scanned using a 3-T MRI scanner with a 32-channel head coil (FUJIFILM Healthcare Corporation, Tokyo, Japan). The acquisition parameters for two-dimensional (2D) axial FLAIR were as follows: repetition time 12,000 ms, echo time 118.8 ms, inversion time 2770 ms, flip angle 90 \(^\circ\) , field of view 240 × 240 mm, reconstructed matrix 512 × 512 (acquired matrix 320 × 376), slice thickness 5 mm, and slice gap 1.5 mm. The scan time of fully sampled data was 4 min 37 s. The image obtained using this fully sampled method was referred to as the standard FLAIR (std-FLAIR) image. We retrospectively reconstructed 3 \(\times\) accelerated images (i.e., images obtained by applying AF = 3) using one-third of the fully sampled raw k-space data. MATLAB (version 2022a, MathWorks Inc., Natick, MA, USA) was used for the reconstruction. Intel Core i9-7900X CPU (Intel Inc., CA, USA) was used, with a memory of 32 GB. Images with a 3 \(\times\) AF were generated by first performing a Fourier transform on the fully sampled complex image of each channel to generate a k-space signal. This signal was then reduced by performing equidistant under-sampling in the phase encoding direction, sampling every third line. The 3 \(\times\) accelerated image was generated from the reduced k-space signal using a conventional reconstruction method (sensitivity encoding) or iterative reconstruction. An image equivalent to that obtained via 3 \(\times\) acceleration was designated as an accelerated FLAIR (acc-FLAIR) image. To estimate the anticipated scan time for 3 \(\times\) acc-FLAIR, the time required for full sampling was divided by the AF (AF = 3). Deep learning-based reconstruction PI produces spatially non-uniform noise when the AF is high. To reduce non-uniform noise, we developed a method that combines iterative reconstruction with soft-thresholding and deep-learning-based denoising, with details published in the literature [ 22 ]. Our iterative reconstruction method was based on projections onto convex sets (POCS) [ 23 ]. In the POCS method, noise amplification depended on the sensitivity distribution, and spatial noise non-uniformity was generated. Wavelet-based soft-thresholding was added to the POCS method to reduce noise amplification. After spatial noise nonuniformity was reduced via wavelet-based soft-thresholding, spatial noise uniformity was reduced via deep learning-based denoising. Deep learning-based denoising combines a super-resolution convolutional neural network [ 24 ] with a residual network [ 25 ]. Super-resolution convolutional neural network comprises three layers, and each layer performs convolution, bias, and rectified linear unit operations. The kernel size was 9 × 9 for the first layer and 5 × 5 for the second and third layers. The first, second, and third layers had 64, 32, and 1 channels, respectively. Training was performed using reference image/noisy image pairs [ 22 ]. We applied deep learning-based reconstruction to the 3 \(\times\) acc-FLAIR images and designated the resulting images as DLR–FLAIR images. Qualitative analysis (reader study) Image quality evaluation. As part of the qualitative assessment, three board-certified neuroradiologists with 14, 10, and 9 years of experience in radiology, respectively, visually evaluated the std-FLAIR, acc-FLAIR, and DLR–FLAIR images of all patients. All FLAIR images were anonymized and randomly displayed. The images were independently and blindly evaluated by the three neuroradiologists using a dedicated viewer (VOX-BASE Browser/View; J-Mac System, Sapporo, Japan). To assess the image quality, two aspects were emphasized: (i) the amount of noise and (ii) the visibility of the gray/white matter contrast in the frontal lobes. Each aspect was rated on a 4-point scale. The amount of noise was evaluated as follows: the image contained excessive noise, and thus was unsuitable for diagnosis (1 point); noise was present, potentially impacting the diagnostic interpretation (2 points); noise was minimal, posing little to no effect on diagnosis (3 points); and almost no noise was evident, providing minimal diagnostic limitations (4 points). The visibility of gray/white matter contrast in the frontal lobes was assessed as follows: obscure (1 point), partially obscure (2 points), mostly visible (3 points), and fully visible (4 points). White matter hyperintensity identification Two radiologists with 15 and 17 years of experience, distinct from the three evaluators, selected 100 white matter hyperintensities, each measuring 3–10 mm in diameter. These hyperintensities were identified from the std-FLAIR images of 30 patients. Each patient had at least one hyperintensity, with a preference for those situated at the level of the centrum semiovale. The 100 hyperintensities were randomly displayed using combinations of std-FLAIR and either acc-FLAIR or DLR–FLAIR images. The same three board-certified neuroradiologists who assessed the image quality evaluated hyperintensity visibility in acc-FLAIR and DLR–FLAIR images compared with that in std-FLAIR images. The boundaries of hyperintensities were rated on a 4-point scale as follows: unclear and different from std-FLAIR (1 point), partially different (2 points), nearly identical (3 points), and equivalent (4 points). Quantitative analysis Image quality. The structural similarity index measure (SSIM) and normalized root mean square error (NRMSE) were calculated as pixel-based quantitative measures across the full image set, encompassing the entire brain. SSIM values (ranging from 0 to 1) indicate the percentage deviation of the acc-FLAIR and DLR–FLAIR images from the std-FLAIR image, with higher values denoting greater similarity to std-FLAIR image [ 26 ]. The NRMSE, a normalized variant of the root mean square error, offers a scale where lower values suggest less error, and thus closer resemblance between the acc-FLAIR or DLR–FLAIR and the std-FLAIR baseline image. In addition, regions of 25 × 25 pixels containing 100 extracted white matter hyperintensities were harvested from each image at precisely the same coordinate axis. For the 100 white matter hyperintensities, the SSIM and NRMSE values in the region of 25 × 25 pixels (regional SSIM and regional NRMSE) for acc-FLAIR and DLR–FLAIR images were computed and compared with those for the std-FLAIR image. MATLAB (The MathWorks Inc.) was used for the quantitative analysis. Statistical analysis The neuroradiologist-assigned image quality assessment scores for std-FLAIR, acc-FLAIR, and DLR–FLAIR were evaluated for statistical significance using the Wilcoxon signed-rank test. Bonferroni-corrected p values were employed, with statistical significance defined as a p value < 0.05. Results are discussed based on these corrected p values. The neuroradiologist-assigned white matter hyperintensity identification and quantitative (SSIM, NRMSE, regional SSIM, and regional NRMSE) scores for acc-FLAIR and DLR–FLAIR images were evaluated for statistical significance using the Wilcoxon signed-rank test. Statistical significance was defined as a p value < 0.05. For qualitative assessment, the intraclass correlation coefficient (ICC) (2,1) was employed to evaluate inter-rater reliability among the evaluators (neuroradiologists) with values falling into the following categories: < 0.50 (poor), 0.50–0.75 (moderate), 0.75–0.90 (good), > 0.90 (excellent) [ 27 ]. The Wilcoxon signed-rank test was performed using JMP Software (version 16.1.0; SAS Institute Inc., Cary, NC, USA), and the ICC (2,1) was calculated using the Bell Curve for Excel (Social Survey Research Information Co., Tokyo). All p values reported in this study have been Bonferroni-corrected. A flowchart of patient inclusion and exclusion is provided in Fig.  1 . Forty patients met the inclusion criteria. However, 10 patients were excluded because of body motion-induced artifacts. Subsequently, data from 30 patients were included in the final analysis. Of the 30 patients, 12 were men and 18 were women. The age of the study cohort was 54.8 ± 13.7 years (mean ± standard deviation). Flowchart of patient inclusion and exclusion MRI was performed in the 30 patients for the following conditions: moyamoya disease ( n  = 8), cerebral aneurysm ( n  = 5), multiple sclerosis ( n  = 3), arterial dissection ( n  = 2), and one case each of white matter lesions, acquired immunodeficiency syndrome, postoperative treatment of vascular malformation, hypertension, headache, post-internal carotid artery stent placement, brainstem lesion, cavernous sinus syndrome, chronic pain, hypothalamic lesion, cerebellar arteriovenous malformation, and treatment after vestibular schwannoma. The 100 white matter hyperintensities selected for this study included those reflecting the pathologies of the aforementioned conditions, as well as ischemic changes and old infarcts, which are considered to be less directly related to the primary underlying pathologies. Estimated image acquisition time The calculated scan times for acc-FLAIR and DLR–FLAIR were approximately 1 min and 32 s, respectively. Figure  2 shows the image quality an hyperintensity identification scores assigned by the three neuroradiologists to std-FLAIR, acc-FLAIR, and DLR–FLAIR. Figure  3 presents the entire representative FLAIR images from these three reconstruction methods. Figure  4 displays an enlarged and partially cropped section of the same three reconstruction methods. Scores assigned by the three neuroradiologists for each image type. a Amount of noise. b Visibility of gray/white matter contrast in the frontal lobes. c White matter hyperintensity identification. * p  < 0.001, ** p  < 0.05, *** p  < 0.0001. FLAIR fluid-attenuated inversion recovery, acc accelerated, DLR deep learning-reconstructed, std standard Entire representative FLAIR images from three reconstruction methods Enlarged and partially cropped sections of three reconstruction methods. a In acc-FLAIR imaging, there is a noticeable amount of noise in the central area, resulting in an overall grainy image. In contrast, std-FLAIR and DLR–FLAIR imaging have less noise, with DLR–FLAIR displaying less noise compared with std-FLAIR. b In acc-FLAIR imaging, the central area shows excessive noise, which obscures the gray/white matter contrast in certain areas. Conversely, DLR–FLAIR imaging, by removing noise, achieves a gray/white matter contrast comparable to that of std-FLAIR imaging. c In acc-FLAIR imaging, the white matter hyperintensity appears slightly larger due to the noise blurring its edge (arrow). DLR–FLAIR imaging shows hyperintensity edges that are equivalent to those in std-FLAIR imaging. FLAIR fluid-attenuated inversion recovery, acc accelerated, DLR deep learning-reconstructed, std standard Regarding image quality based on noise level evaluation, the scores assigned by the three neuroradiologists were as follows (mean ± standard deviation): Reader 1 assigned scores of 2.87 ± 0.50, 1.43 ± 0.50, and 3.67 ± 0.47; Reader 2 assigned scores of 2.93 ± 0.51, 1.63 ± 0.71, and 3.93 ± 0.25; Reader 3 assigned scores of 3.47 ± 0.50, 2.17 ± 0.37, and 4.00 ± 0.00, for std-FLAIR, acc-FLAIR, and DLR–FLAIR, respectively. All three neuroradiologists significantly favored std-FLAIR and DLR–FLAIR over acc-FLAIR ( p  < 0.001). Moreover, they assigned significantly higher scores for DLR–FLAIR than for std-FLAIR ( p  < 0.001). Concerning the image quality based on the assessment of the visibility of gray/white matter contrast in the frontal lobe, the scores assigned were as follows (mean ± standard deviation): Reader 1 assigned scores of 2.93 ± 0.51, 1.63 ± 0.55, and 3.30 ± 0.53; Reader 2 assigned scores of 3.00 ± 0.63, 1.67 ± 0.60, and 3.43 ± 0.62; Reader 3 assigned scores of 3.63 ± 0.48, 2.63 ± 0.71, and 3.83 ± 0.37, for std-FLAIR, acc-FLAIR, and DLR–FLAIR, respectively. All three neuroradiologists assigned significantly higher scores for std-FLAIR and DLR–FLAIR than for acc-FLAIR ( p  < 0.001). In the comparison between std-FLAIR and DLR–FLAIR, two neuroradiologists (Reader 1 and Reader 2) assigned significantly higher scores for DLR–FLAIR ( p  < 0.05). One neuroradiologist (Reader 3) tended to assign higher scores for DLR–FLAIR images, although the difference from other scores was not statistically significant ( p  = 0.0942). Concerning white matter hyperintensity evaluation, hyperintensity appearance resemblances of acc-FLAIR and DLR–FLAIR images were compared with those of std-FLAIR images. The scores assigned by the three neuroradiologists for acc-FLAIR vs. DLR–FLAIR images were as follows (mean ± standard deviation): Readers 1, 2, and 3 assigned scores of 2.27 ± 0.69 vs. 3.76 ± 0.47, 2.30 ± 0.69 vs. 3.63 ± 0.63, and 3.02 ± 0.80 vs. 3.76 ± 0.51, respectively. All three neuroradiologists significantly favored DLR–FLAIR images by assigning higher scores ( p  < 0.0001 for all comparisons), indicating that the hyperintensities depicted by DLR–FLAIR were more similar to those depicted by std-FLAIR. The distribution of the scores assigned by the three neuroradiologists for the 100 white matter hyperintensities is shown in Fig.  5 . Notably, 52% of the hyperintensities depicted by acc-FLAIR images and 97% of those depicted by DLR–FLAIR images were rated 3 (nearly identical to std-FLAIR images) and 4 (equivalent to std-FLAIR images) points, respectively. Figure  6 shows a hyperintensity that appeared differently in acc-FLAIR and DLR–FLAIR compared to std-FLAIR. This hyperintensity was rated as "hyperintensity boundary visibility was different from that in std-FLAIR and unclear (1 point)" by all evaluators for acc-FLAIR, and it was scored 1 point by both Reader 2 and Reader 3 for DLR–FLAIR. The ICC (2,1) for inter-rater reliability is summarized in Table  1 . Although the inter-rater reliability was good between Readers 1 and 2 (0.776–0.798), it was poor to moderate between Readers 1 and 3 as well as between Readers 2 and 3 (0.462–0.761). Distribution of neuroradiologist scores for white matter hyperintensities in acc-FLAIR and DLR–FLAIR images relative to those in std-FLAIR images. In acc-FLAIR imaging, neuroradiologists attributed 1 or 2 points for 48% of the white matter hyperintensities. This suggests that nearly half of the hyperintensities in acc-FLAIR images differed in appearance from those in std-FLAIR images. In contrast, in DLR–FLAIR imaging, neuroradiologists assigned 3 or 4 points for 97% of the hyperintensities, implying that the hyperintensity depiction in DLR–FLAIR imaging is comparable to that seen in std-FLAIR. FLAIR, fluid-attenuated inversion recovery; acc, accelerated; DLR, deep learning-reconstructed; std, standard Hyperintensity that appeared differently in acc-FLAIR and DLR–FLAIR compared to std-FLAIR. In the acc-FLAIR image, the hyperintensity shows more noise and appears differently in shape compared to std-FLAIR image. In the DLR–FLAIR image, while the noise is removed, the hyperintensity shape still differs from that in the std-FLAIR image. This hyperintensity was scored 1 by all neuroradiologists for acc-FLAIR and by two neuroradiologists for DLR–FLAIR A quantitative comparison of the overall image quality of acc-FLAIR and DLR–FLAIR image qualities against that of std-FLAIR as a benchmark showed significantly higher SSIM values for DLR–FLAIR images (0.964 ± 0.0077) than for acc-FLAIR images (0.919 ± 0.0136), suggesting a closer resemblance between DLR–FLAIR and std-FLAIR images. Furthermore, DLR–FLAIR images exhibited a significantly lower NRMSE value (0.0131 ± 0.0018) than acc-FLAIR images (0.0178 ± 0.0026), indicating reduced deviation from std-FLAIR images. Regarding white matter hyperintensity analysis, DLR–FLAIR images showed significantly higher regional SSIM (0.99992 ± 0.00003) and significantly lower regional NRMSE values (0.0637 ± 0.0180) than acc-FLAIR images (0.99978 ± 0.00009 and 0.0948 ± 0.0292, respectively) (Table  2 ). In this study, we qualitatively and quantitatively evaluated three types of images: std-FLAIR, acc-FLAIR, and DLR–FLAIR. In the qualitative assessment, DLR–FLAIR images exhibited the lowest noise levels and best visibility of gray/white matter contrast in the frontal lobe. Conversely, acc-FLAIR images demonstrated the highest noise levels and poorest contrast visibility. Furthermore, 97% of white matter hyperintensities in DLR–FLAIR images were rated 3 (nearly identical to std-FLAIR images) or 4 (equivalent to std-FLAIR images) points, indicating that DLR–FLAIR closely matches std-FLAIR in white matter hyperintensity depiction. In the quantitative evaluation, DLR–FLAIR showed significantly higher SSIM and lower NRMSE values compared to acc-FLAIR. However, regional SSIM values for white matter hyperintensity areas were similarly high for both DLR–FLAIR and acc-FLAIR, despite the clear visual differences. This suggests that SSIM values may not always align with human perception. Overall, this study demonstrates that deep learning-based reconstruction technology significantly improves the visual quality of FLAIR images obtained from undersampled data. This advancement can potentially be applied in clinical settings, enhancing the efficiency and quality of FLAIR imaging. The efficacy of deep learning-based noise reduction in brain MRI has been previously reported. Kidoh et al. demonstrated that applying a denoising approach with DLR–FLAIR sequences imaged with a reduced number of image acquisitions can yield an image quality equivalent to or better than that obtained with a higher number of image acquisitions, while also reducing the scan time [ 18 ]. Tajima et al. reported that by adapting a denoising approach with deep learning reconstruction technology to 1.5-T brain MRI images, including FLAIR sequences, they achieved an image quality nearly equivalent to or surpassing that of 3.0-T brain images [ 19 ]. However, these studies were conducted on healthy individuals, and thus the image quality was not examined in terms of hyperintensity visibility. Yamamoto et al. reported potential image quality improvements, lesion identification enhancement, and scan time diminution after the application of noise reduction via deep learning-based reconstruction to accelerated three-dimensional (3D) FLAIR MRI images of patients with multiple sclerosis [ 21 ]. Estler et al. demonstrated that accelerated DLR–FLAIR sequences (scan time 1 min 39 s) improved image quality and diagnostic reliability while reducing examination time by 38% compared with std-FLAIR sequences (scan time 2 min 40 s) in the assessment of brain metastases [ 20 ]. In this study, we did not focus on specific diseases but rather on white matter hyperintensities present in patients with diverse underlying conditions. The DLR–FLAIR images generated from undersampled data depict these hyperintensities similar to those in std-FLAIR images. This suggests that DLR–FLAIR has the potential to accelerate FLAIR imaging and be widely adopted in clinical practice. Yamamoto et al. and Estler et al. applied deep learning reconstruction to data obtained through prospective k-space undersampling. In contrast, our study employed retrospective reconstruction. Prospective undersampling reduces the data during the imaging process itself, while retrospective undersampling applies this reduction after full data acquisition. There are distinct differences between prospective and retrospective undersampling, especially in subjects with minor to severe motion or low SNR. While we excluded cases with motion artifacts, some differences compared to studies using prospective undersampling might still arise. Our study has a few limitations. First, the small sample size of 30 patients underscores the need for future research with larger sample sizes to validate our findings, as the limited number may not fully represent the diverse array of clinical presentations. Second, our analysis was limited to 2D-FLAIR imaging, and thus did not explore the potential of artificial intelligence (AI)-based denoising techniques in other MRI sequences (such as T2- and T1-weighted imaging) or 3D imaging modalities (such as 3D-FLAIR imaging). Further research should extend AI-based denoising application to a broader sequence spectrum to evaluate its overall utility and effectiveness. Third, the under-sampling rate in this study was limited to 3 × AF. Future studies should consider applying deep learning reconstruction techniques to images with higher under-sampling rates to determine their effectiveness with even less data. Furthermore, various sampling patterns should also be considered in future research to assess their potential benefits. Fourth, our study evaluated only the overall image quality and the visibility of white matter hyperintensities, without assessing the detection capability of these hyperintensities. Future research should apply deep learning reconstruction to images with higher under-sampling rates and evaluate its effectiveness in detecting white matter hyperintensities. Finally, the AI-based denoising method employed in our study was specific to MRI systems from a single manufacturer, raising questions regarding its transferability to devices from other manufacturers. Future studies should assess the performance of this technique across various MRI platforms to ensure its adaptability and wider clinical applicability. 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Download references Acknowledgements Not applicable. This work was supported by JSPS KAKENHI (Grant number: JP22K15837). Author information Authors and affiliations. Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Japan Noriko Nishioka, Yukie Shimizu, Yohei Ikebe, Hiroyuki Kameda, Taisuke Harada, Noriyuki Fujima & Kohsuke Kudo Department of Diagnostic Imaging, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Japan Noriko Nishioka, Yukie Shimizu, Yoshitaka Bito, Taisuke Harada, Noriyuki Fujima & Kohsuke Kudo Medical Systems Research & Development Center, FUJIFILM Corporation, Tokyo, Japan Yukio Kaneko, Toru Shirai, Atsuro Suzuki, Tomoki Amemiya & Hisaaki Ochi FUJIFILM Healthcare Corporation, Tokyo, Japan Yoshitaka Bito & Masahiro Takizawa Center for Cause of Death Investigation, Faculty of Medicine, Hokkaido University, Sapporo, Japan Yohei Ikebe & Kohsuke Kudo Faculty of Dental Medicine, Department of Radiology, Hokkaido University, Sapporo, Japan Hiroyuki Kameda Division of Medical AI Education and Research, Hokkaido University Graduate School of Medicine, Sapporo, Japan Kohsuke Kudo You can also search for this author in PubMed   Google Scholar Corresponding author Correspondence to Yukie Shimizu . Ethics declarations Competing interest. The authors of this manuscript declare relationships with the following companies: Yukio Kaneko, Toru Shirai, Atsuro Suzuki, Tomoki Amemiya, and Hisaaki Ochi are currently employed by the FUJIFILM Corporation. Yoshitaka Bito was employed by FUJIFILM Healthcare Corporation. Masahiro Takizawa is employed by FUJIFILM Healthcare Corporation. Kohsuke Kudo received funding from FUJIFILM Healthcare Corporation for this research. Ethical statement The Institutional Review Board (IRB) of our hospital approved this retrospective study (ID: 019–0192), and the requirement for informed consent was waived. This study was conducted in accordance with the ethical standards of the IRB as well as the tenets of the 1964 Helsinki Declaration and its later amendments. Consent for publication Additional information, publisher's note. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Rights and permissions This article is published under an open access license. Please check the 'Copyright Information' section either on this page or in the PDF for details of this license and what re-use is permitted. If your intended use exceeds what is permitted by the license or if you are unable to locate the licence and re-use information, please contact the Rights and Permissions team . About this article Nishioka, N., Shimizu, Y., Kaneko, Y. et al. Accelerating FLAIR imaging via deep learning reconstruction: potential for evaluating white matter hyperintensities. Jpn J Radiol (2024). https://doi.org/10.1007/s11604-024-01666-5 Download citation Received : 28 May 2024 Accepted : 16 September 2024 Published : 24 September 2024 DOI : https://doi.org/10.1007/s11604-024-01666-5 Share this article Anyone you share the following link with will be able to read this content: Sorry, a shareable link is not currently available for this article. Provided by the Springer Nature SharedIt content-sharing initiative Deep learning reconstruction White matter hyperintensity Accelerated image Find a journal Publish with us Track your research 364 COMMENTS Types of Literature Review 1. Narrative Literature Review. A narrative literature review, also known as a traditional literature review, involves analyzing and summarizing existing literature without adhering to a structured methodology. It typically provides a descriptive overview of key concepts, theories, and relevant findings of the research topic. Research Guides: Systematic Reviews: Types of Literature Reviews Rapid review. Assessment of what is already known about a policy or practice issue, by using systematic review methods to search and critically appraise existing research. Completeness of searching determined by time constraints. Time-limited formal quality assessment. Typically narrative and tabular. Literature Review: Types of literature reviews Narrative or traditional literature reviews. Critically Appraised Topic (CAT) Scoping reviews. Systematic literature reviews. Annotated bibliographies. These are not the only types of reviews of literature that can be conducted. Often the term "review" and "literature" can be confusing and used in the wrong context. 14 Types Of Literature Review 4 Major Types Of Literature Review. The four major types include, Narrative Review, Systematic Review, Meta-Analysis, and Scoping Review. These are known as the major ones because they're like the "go-to" methods for researchers in academic and research circles. Think of them as the classic tools in the researcher's toolbox. Types of reviews Types of reviews and examples. Definition: "A term used to describe a conventional overview of the literature, particularly when contrasted with a systematic review (Booth et al., 2012, p. 265). Characteristics: Example: Mitchell, L. E., & Zajchowski, C. A. (2022). The history of air quality in Utah: A narrative review. Types of Reviews This site explores different review methodologies such as, systematic, scoping, realist, narrative, state of the art, meta-ethnography, critical, and integrative reviews. The LITR-EX site has a health professions education focus, but the advice and information is widely applicable. Types of Reviews. Review the table to peruse review types and ... Types of Reviews and Their Differences There are many types of literature reviews. The purposes of a literature review will vary, and the sources used in one will depend on the discipline and the review's topic. Literature reviews may have differences that include: Purpose: The reason or objective of the review. One review may be to see how much has been published on a topic (a ... Types of Literature Reviews Listed below are definitions of types of literature reviews: Argumentative Review. This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Literature Review Types, Taxonomies Narrative (Literature) Review - Broad, generic term - Refers to an examination and general synthesis of the research literature, often with a wide scope; completeness and comprehensiveness may vary. Does not follow an established protocol. ... Literature Review Types/Typologies, Taxonomies. Grant, M. J., and A. Booth. "A Typology of Reviews: An ... How to Write a Literature Review Examples of literature reviews. Step 1 - Search for relevant literature. Step 2 - Evaluate and select sources. Step 3 - Identify themes, debates, and gaps. Step 4 - Outline your literature review's structure. Step 5 - Write your literature review. Literature Review: The What, Why and How-to Guide What kinds of literature reviews are written? Narrative review: The purpose of this type of review is to describe the current state of the research on a specific topic/research and to offer a critical analysis of the literature reviewed. Studies are grouped by research/theoretical categories, and themes and trends, strengths and weakness, and gaps are identified. Methodological Approaches to Literature Review This chapter discusses the methodological approaches to conducting a literature review and offers an overview of different types of reviews. There are various types of reviews, including narrative reviews, scoping reviews, and systematic reviews with reporting strategies such as meta-analysis and meta-synthesis. Types of Literature Reviews A literature review summarizes and synthesizes material on a research topic. It provides a summary of previous research and provides context for the material presented in your thesis. The literature review is your opportunity to show what you understand about your topic area, and distinguish previous research from the work you are doing. Research Guides: Literature Reviews: Choosing a Type of Review LITERATURE REVIEW. Often used as a generic term to describe any type of review. More precise definition: Published materials that provide an examination of published literature. Can cover wide range of subjects at various levels of comprehensiveness. Identifies gaps in research, explains importance of topic, hypothesizes future work, etc. How to Conduct a Literature Review: Types of Literature Reviews Literature reviews are pervasive throughout various academic disciplines, and thus you can adopt various approaches to effectively organize and write your literature review. The University of Southern California created a summarized list of the various types of literature reviews, reprinted here: Argumentative Review Types of Literature Review The choice of a specific type depends on your research approach and design. The following types of literature review are the most popular in business studies: Narrative literature review, also referred to as traditional literature review, critiques literature and summarizes the body of a literature. Narrative review also draws conclusions about ... Which review is that? A guide to review types This quick reference tool provides information on a wide range of literature review types that are available for research synthesis for publication and research purposes. Graphic and guide based on on the work of Sutton et al., (2019) on 'Review Families'. Types of Literature Reviews Quantities of literature and overall quality/direction of effect of literature. Scoping review: Preliminary assessment of potential size and scope of available research literature. Aims to identify nature and extent of research evidence (usually including ongoing research). Completeness of searching determined by time/scope constraints. Chapter 9 Methods for Literature Reviews 9.3. Types of Review Articles and Brief Illustrations. EHealth researchers have at their disposal a number of approaches and methods for making sense out of existing literature, all with the purpose of casting current research findings into historical contexts or explaining contradictions that might exist among a set of primary research studies conducted on a particular topic. 5. The Literature Review A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories.A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that ... Types of Reviews There are many types of reviews --- narrative reviews, scoping reviews, systematic reviews, integrative reviews, umbrella reviews, rapid reviews and others --- and it's not always straightforward to choose which type of review to conduct.These Review Navigator tools (see below) ask a series of questions to guide you through the various kinds of reviews and to help you determine the best choice ... Systematic Reviews: Methods & Resources Gold-standard guideline on how to perform and write-up a systematic review and/or meta-analysis of the outcomes reported in multiple clinical trials of therapeutic interventions. AHRQ's Methods Guide for Effectiveness and Comparative Effectiveness Reviews. Synthesis without meta-analysis (SWiM) in systematic reviews. Literature review as a research methodology: An overview and guidelines This is why the literature review as a research method is more relevant than ever. Traditional literature reviews often lack thoroughness and rigor and are conducted ad hoc, rather than following a specific methodology. Therefore, questions can be raised about the quality and trustworthiness of these types of reviews. Evidence Syntheses (Scoping, systematic, & other types of reviews) A typology of reviews: an analysis of 14 review types and associated methodologies. Health Info Libr J. 2009 Jun;26(2):91-108. Defines 14 types of reviews and provides a helpful summary table on pp. 94-95. Sutton A, Clowes M, Preston L, Booth A. Meeting the review family: exploring review types and associated information retrieval requirements. Systematic Reviews and Other Evidence Synthesis Types Guide In 2021, the Library completed a comprehensive update of its Systematic Review Guide. As the breadth of methodologies and types of complex searches we support has evolved, the new Systematic Review and Evidence Synthesis Types Guide includes content from the Systematic Review Guide as well as new content of other types of evidence synthesis. Getting Started A literature review is an overview of the available research for a specific scholarly topic. Literature reviews summarize existing research to answer a review question, provide context for new research, or identify important gaps in the existing body of literature.. An incredible amount of academic literature is published each year; by some estimates nearly three million articles. Library Home: Online Study Skills Hub: Literature Review Literature Review. A literature review is a critical summary of existing research on a particular topic, typically included in university assignments like dissertations, essays, or research projects. Its main purpose is to give an overview of what has already been studied, allowing you to identify key theories, methods, and findings related to your research question. Unusual Presentation of Propionic Acidemia Mimicking Botulism in an Unusual Presentation of Propionic Acidemia Mimicking Botulism in an Infant: A Case Report and Literature Review Cureus. 2024 Aug 14;16(8):e66870. doi: 10.7759/cureus.66870. eCollection 2024 Aug. Authors Allison C Boland 1 ... Publication types Case Reports ... Accelerating FLAIR imaging via deep learning reconstruction ... Purpose To evaluate deep learning-reconstructed (DLR)-fluid-attenuated inversion recovery (FLAIR) images generated from undersampled data, compare them with fully sampled and rapidly acquired FLAIR images, and assess their potential for white matter hyperintensity evaluation. Materials and methods We examined 30 patients with white matter hyperintensities, obtaining fully sampled FLAIR ... essay homework paper phd review speech study thesis