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A guide to critical appraisal of evidence

Fineout-Overholt, Ellen PhD, RN, FNAP, FAAN

Ellen Fineout-Overholt is the Mary Coulter Dowdy Distinguished Professor of Nursing at the University of Texas at Tyler School of Nursing, Tyler, Tex.

The author has disclosed no financial relationships related to this article.

Critical appraisal is the assessment of research studies' worth to clinical practice. Critical appraisal—the heart of evidence-based practice—involves four phases: rapid critical appraisal, evaluation, synthesis, and recommendation. This article reviews each phase and provides examples, tips, and caveats to help evidence appraisers successfully determine what is known about a clinical issue. Patient outcomes are improved when clinicians apply a body of evidence to daily practice.

How do nurses assess the quality of clinical research? This article outlines a stepwise approach to critical appraisal of research studies' worth to clinical practice: rapid critical appraisal, evaluation, synthesis, and recommendation. When critical care nurses apply a body of valid, reliable, and applicable evidence to daily practice, patient outcomes are improved.

Critical care nurses can best explain the reasoning for their clinical actions when they understand the worth of the research supporting their practices. In c ritical appraisal , clinicians assess the worth of research studies to clinical practice. Given that achieving improved patient outcomes is the reason patients enter the healthcare system, nurses must be confident their care techniques will reliably achieve best outcomes.

Nurses must verify that the information supporting their clinical care is valid, reliable, and applicable. Validity of research refers to the quality of research methods used, or how good of a job researchers did conducting a study. Reliability of research means similar outcomes can be achieved when the care techniques of a study are replicated by clinicians. Applicability of research means it was conducted in a similar sample to the patients for whom the findings will be applied. These three criteria determine a study's worth in clinical practice.

Appraising the worth of research requires a standardized approach. This approach applies to both quantitative research (research that deals with counting things and comparing those counts) and qualitative research (research that describes experiences and perceptions). The word critique has a negative connotation. In the past, some clinicians were taught that studies with flaws should be discarded. Today, it is important to consider all valid and reliable research informative to what we understand as best practice. Therefore, the author developed the critical appraisal methodology that enables clinicians to determine quickly which evidence is worth keeping and which must be discarded because of poor validity, reliability, or applicability.

Evidence-based practice process

The evidence-based practice (EBP) process is a seven-step problem-solving approach that begins with data gathering (see Seven steps to EBP ). During daily practice, clinicians gather data supporting inquiry into a particular clinical issue (Step 0). The description is then framed as an answerable question (Step 1) using the PICOT question format ( P opulation of interest; I ssue of interest or intervention; C omparison to the intervention; desired O utcome; and T ime for the outcome to be achieved). 1 Consistently using the PICOT format helps ensure that all elements of the clinical issue are covered. Next, clinicians conduct a systematic search to gather data answering the PICOT question (Step 2). Using the PICOT framework, clinicians can systematically search multiple databases to find available studies to help determine the best practice to achieve the desired outcome for their patients. When the systematic search is completed, the work of critical appraisal begins (Step 3). The known group of valid and reliable studies that answers the PICOT question is called the body of evidence and is the foundation for the best practice implementation (Step 4). Next, clinicians evaluate integration of best evidence with clinical expertise and patient preferences and values to determine if the outcomes in the studies are realized in practice (Step 5). Because healthcare is a community of practice, it is important that experiences with evidence implementation be shared, whether the outcome is what was expected or not. This enables critical care nurses concerned with similar care issues to better understand what has been successful and what has not (Step 6).

Critical appraisal of evidence

The first phase of critical appraisal, rapid critical appraisal, begins with determining which studies will be kept in the body of evidence. All valid, reliable, and applicable studies on the topic should be included. This is accomplished using design-specific checklists with key markers of good research. When clinicians determine a study is one they want to keep (a “keeper” study) and that it belongs in the body of evidence, they move on to phase 2, evaluation. 2

In the evaluation phase, the keeper studies are put together in a table so that they can be compared as a body of evidence, rather than individual studies. This phase of critical appraisal helps clinicians identify what is already known about a clinical issue. In the third phase, synthesis, certain data that provide a snapshot of a particular aspect of the clinical issue are pulled out of the evaluation table to showcase what is known. These snapshots of information underpin clinicians' decision-making and lead to phase 4, recommendation. A recommendation is a specific statement based on the body of evidence indicating what should be done—best practice. Critical appraisal is not complete without a specific recommendation. Each of the phases is explained in more detail below.

Phase 1: Rapid critical appraisal . Rapid critical appraisal involves using two tools that help clinicians determine if a research study is worthy of keeping in the body of evidence. The first tool, General Appraisal Overview for All Studies (GAO), covers the basics of all research studies (see Elements of the General Appraisal Overview for All Studies ). Sometimes, clinicians find gaps in knowledge about certain elements of research studies (for example, sampling or statistics) and need to review some content. Conducting an internet search for resources that explain how to read a research paper, such as an instructional video or step-by-step guide, can be helpful. Finding basic definitions of research methods often helps resolve identified gaps.

To accomplish the GAO, it is best to begin with finding out why the study was conducted and how it answers the PICOT question (for example, does it provide information critical care nurses want to know from the literature). If the study purpose helps answer the PICOT question, then the type of study design is evaluated. The study design is compared with the hierarchy of evidence for the type of PICOT question. The higher the design falls within the hierarchy or levels of evidence, the more confidence nurses can have in its finding, if the study was conducted well. 3,4 Next, find out what the researchers wanted to learn from their study. These are called the research questions or hypotheses. Research questions are just what they imply; insufficient information from theories or the literature are available to guide an educated guess, so a question is asked. Hypotheses are reasonable expectations guided by understanding from theory and other research that predicts what will be found when the research is conducted. The research questions or hypotheses provide the purpose of the study.

Next, the sample size is evaluated. Expectations of sample size are present for every study design. As an example, consider as a rule that quantitative study designs operate best when there is a sample size large enough to establish that relationships do not exist by chance. In general, the more participants in a study, the more confidence in the findings. Qualitative designs operate best with fewer people in the sample because these designs represent a deeper dive into the understanding or experience of each person in the study. 5 It is always important to describe the sample, as clinicians need to know if the study sample resembles their patients. It is equally important to identify the major variables in the study and how they are defined because this helps clinicians best understand what the study is about.

The final step in the GAO is to consider the analyses that answer the study research questions or confirm the study hypothesis. This is another opportunity for clinicians to learn, as learning about statistics in healthcare education has traditionally focused on conducting statistical tests as opposed to interpreting statistical tests. Understanding what the statistics indicate about the study findings is an imperative of critical appraisal of quantitative evidence.

The second tool is one of the variety of rapid critical appraisal checklists that speak to validity, reliability, and applicability of specific study designs, which are available at varying locations (see Critical appraisal resources ). When choosing a checklist to implement with a group of critical care nurses, it is important to verify that the checklist is complete and simple to use. Be sure to check that the checklist has answers to three key questions. The first question is: Are the results of the study valid? Related subquestions should help nurses discern if certain markers of good research design are present within the study. For example, identifying that study participants were randomly assigned to study groups is an essential marker of good research for a randomized controlled trial. Checking these essential markers helps clinicians quickly review a study to check off these important requirements. Clinical judgment is required when the study lacks any of the identified quality markers. Clinicians must discern whether the absence of any of the essential markers negates the usefulness of the study findings. 6-9

The second question is: What are the study results? This is answered by reviewing whether the study found what it was expecting to and if those findings were meaningful to clinical practice. Basic knowledge of how to interpret statistics is important for understanding quantitative studies, and basic knowledge of qualitative analysis greatly facilitates understanding those results. 6-9

The third question is: Are the results applicable to my patients? Answering this question involves consideration of the feasibility of implementing the study findings into the clinicians' environment as well as any contraindication within the clinicians' patient populations. Consider issues such as organizational politics, financial feasibility, and patient preferences. 6-9

When these questions have been answered, clinicians must decide about whether to keep the particular study in the body of evidence. Once the final group of keeper studies is identified, clinicians are ready to move into the phase of critical appraisal. 6-9

Phase 2: Evaluation . The goal of evaluation is to determine how studies within the body of evidence agree or disagree by identifying common patterns of information across studies. For example, an evaluator may compare whether the same intervention is used or if the outcomes are measured in the same way across all studies. A useful tool to help clinicians accomplish this is an evaluation table. This table serves two purposes: first, it enables clinicians to extract data from the studies and place the information in one table for easy comparison with other studies; and second, it eliminates the need for further searching through piles of periodicals for the information. (See Bonus Content: Evaluation table headings .) Although the information for each of the columns may not be what clinicians consider as part of their daily work, the information is important for them to understand about the body of evidence so that they can explain the patterns of agreement or disagreement they identify across studies. Further, the in-depth understanding of the body of evidence from the evaluation table helps with discussing the relevant clinical issue to facilitate best practice. Their discussion comes from a place of knowledge and experience, which affords the most confidence. The patterns and in-depth understanding are what lead to the synthesis phase of critical appraisal.

The key to a successful evaluation table is simplicity. Entering data into the table in a simple, consistent manner offers more opportunity for comparing studies. 6-9 For example, using abbreviations versus complete sentences in all columns except the final one allows for ease of comparison. An example might be the dependent variable of depression defined as “feelings of severe despondency and dejection” in one study and as “feeling sad and lonely” in another study. 10 Because these are two different definitions, they need to be different dependent variables. Clinicians must use their clinical judgment to discern that these different dependent variables require different names and abbreviations and how these further their comparison across studies.

Sample and theoretical or conceptual underpinnings are important to understanding how studies compare. Similar samples and settings across studies increase agreement. Several studies with the same conceptual framework increase the likelihood of common independent variables and dependent variables. The findings of a study are dependent on the analyses conducted. That is why an analysis column is dedicated to recording the kind of analysis used (for example, the name of the statistical analyses for quantitative studies). Only statistics that help answer the clinical question belong in this column. The findings column must have a result for each of the analyses listed; however, in the actual results, not in words. For example, a clinician lists a t -test as a statistic in the analysis column, so a t -value should reflect whether the groups are different as well as probability ( P -value or confidence interval) that reflects statistical significance. The explanation for these results would go in the last column that describes worth of the research to practice. This column is much more flexible and contains other information such as the level of evidence, the studies' strengths and limitations, any caveats about the methodology, or other aspects of the study that would be helpful to its use in practice. The final piece of information in this column is a recommendation for how this study would be used in practice. Each of the studies in the body of evidence that addresses the clinical question is placed in one evaluation table to facilitate the ease of comparing across the studies. This comparison sets the stage for synthesis.

Phase 3: Synthesis . In the synthesis phase, clinicians pull out key information from the evaluation table to produce a snapshot of the body of evidence. A table also is used here to feature what is known and help all those viewing the synthesis table to come to the same conclusion. A hypothetical example table included here demonstrates that a music therapy intervention is effective in reducing the outcome of oxygen saturation (SaO 2 ) in six of the eight studies in the body of evidence that evaluated that outcome (see Sample synthesis table: Impact on outcomes ). Simply using arrows to indicate effect offers readers a collective view of the agreement across studies that prompts action. Action may be to change practice, affirm current practice, or conduct research to strengthen the body of evidence by collaborating with nurse scientists.

When synthesizing evidence, there are at least two recommended synthesis tables, including the level-of-evidence table and the impact-on-outcomes table for quantitative questions, such as therapy or relevant themes table for “meaning” questions about human experience. (See Bonus Content: Level of evidence for intervention studies: Synthesis of type .) The sample synthesis table also demonstrates that a final column labeled synthesis indicates agreement across the studies. Of the three outcomes, the most reliable for clinicians to see with music therapy is SaO 2 , with positive results in six out of eight studies. The second most reliable outcome would be reducing increased respiratory rate (RR). Parental engagement has the least support as a reliable outcome, with only two of five studies showing positive results. Synthesis tables make the recommendation clear to all those who are involved in caring for that patient population. Although the two synthesis tables mentioned are a great start, the evidence may require more synthesis tables to adequately explain what is known. These tables are the foundation that supports clinically meaningful recommendations.

Phase 4: Recommendation . Recommendations are definitive statements based on what is known from the body of evidence. For example, with an intervention question, clinicians should be able to discern from the evidence if they will reliably get the desired outcome when they deliver the intervention as it was in the studies. In the sample synthesis table, the recommendation would be to implement the music therapy intervention across all settings with the population, and measure SaO 2 and RR, with the expectation that both would be optimally improved with the intervention. When the synthesis demonstrates that studies consistently verify an outcome occurs as a result of an intervention, however that intervention is not currently practiced, care is not best practice. Therefore, a firm recommendation to deliver the intervention and measure the appropriate outcomes must be made, which concludes critical appraisal of the evidence.

A recommendation that is off limits is conducting more research, as this is not the focus of clinicians' critical appraisal. In the case of insufficient evidence to make a recommendation for practice change, the recommendation would be to continue current practice and monitor outcomes and processes until there are more reliable studies to be added to the body of evidence. Researchers who use the critical appraisal process may indeed identify gaps in knowledge, research methods, or analyses, for example, that they then recommend studies that would fill in the identified gaps. In this way, clinicians and nurse scientists work together to build relevant, efficient bodies of evidence that guide clinical practice.

Evidence into action

Critical appraisal helps clinicians understand the literature so they can implement it. Critical care nurses have a professional and ethical responsibility to make sure their care is based on a solid foundation of available evidence that is carefully appraised using the phases outlined here. Critical appraisal allows for decision-making based on evidence that demonstrates reliable outcomes. Any other approach to the literature is likely haphazard and may lead to misguided care and unreliable outcomes. 11 Evidence translated into practice should have the desired outcomes and their measurement defined from the body of evidence. It is also imperative that all critical care nurses carefully monitor care delivery outcomes to establish that best outcomes are sustained. With the EBP paradigm as the basis for decision-making and the EBP process as the basis for addressing clinical issues, critical care nurses can improve patient, provider, and system outcomes by providing best care.

Seven steps to EBP

Step 0–A spirit of inquiry to notice internal data that indicate an opportunity for positive change.

Step 1– Ask a clinical question using the PICOT question format.

Step 2–Conduct a systematic search to find out what is already known about a clinical issue.

Step 3–Conduct a critical appraisal (rapid critical appraisal, evaluation, synthesis, and recommendation).

Step 4–Implement best practices by blending external evidence with clinician expertise and patient preferences and values.

Step 5–Evaluate evidence implementation to see if study outcomes happened in practice and if the implementation went well.

Step 6–Share project results, good or bad, with others in healthcare.

Adapted from: Steps of the evidence-based practice (EBP) process leading to high-quality healthcare and best patient outcomes. © Melnyk & Fineout-Overholt, 2017. Used with permission.

Critical appraisal resources

• The Joanna Briggs Institute http://joannabriggs.org/research/critical-appraisal-tools.html
• Critical Appraisal Skills Programme (CASP) www.casp-uk.net/casp-tools-checklists
• Center for Evidence-Based Medicine www.cebm.net/critical-appraisal
• Melnyk BM, Fineout-Overholt E. Evidence-Based Practice in Nursing and Healthcare: A Guide to Best Practice . 3rd ed. Philadelphia, PA: Wolters Kluwer; 2015.

A full set of critical appraisal checklists are available in the appendices.

Bonus content!

This article includes supplementary online-exclusive material. Visit the online version of this article at www.nursingcriticalcare.com to access this content.

critical appraisal; decision-making; evaluation of research; evidence-based practice; synthesis

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Critical Appraisal: Assessing the Quality of Studies

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There is great variation in the type and quality of research evidence. Having completed your search and assembled your studies, the next step is to critically appraise the studies to ascertain their quality. Ultimately you will be making a judgement about the overall evidence, but that comes later. You will see throughout this chapter that we make a clear differentiation between the individual studies and what we call the body of evidence , which is all of the studies and anything else that we use to answer the question or to make a recommendation. This chapter deals with only the first of these—the individual studies. Critical appraisal, like everything else in systematic literature reviewing, is a scientific exercise that requires individual judgement, and we describe some tools to help you.

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Purssell, E., McCrae, N. (2020). Critical Appraisal: Assessing the Quality of Studies. In: How to Perform a Systematic Literature Review. Springer, Cham. https://doi.org/10.1007/978-3-030-49672-2_6

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Some reviews require a critical appraisal for each study that makes it through the screening process. This involves a risk of bias assessment and/or a quality assessment. The goal of these reviews is not just to find all of the studies, but to determine their methodological rigor, and therefore, their credibility.

"Critical appraisal is the balanced assessment of a piece of research, looking for its strengths and weaknesses and them coming to a balanced judgement about its trustworthiness and its suitability for use in a particular context." 1

It's important to consider the impact that poorly designed studies could have on your findings and to rule out inaccurate or biased work.

Selection of a valid critical appraisal tool, testing the tool with several of the selected studies, and involving two or more reviewers in the appraisal are good practices to follow.

1. Purssell E, McCrae N. How to Perform a Systematic Literature Review: A Guide for Healthcare Researchers, Practitioners and Students. 1st ed. Springer ;  2020.

Evaluation Tools

• The Appraisal of Guidelines for Research & Evaluation Instrument (AGREE II) The Appraisal of Guidelines for Research & Evaluation Instrument (AGREE II) was developed to address the issue of variability in the quality of practice guidelines.
• Centre for Evidence-Based Medicine (CEBM). Critical Appraisal Tools "contains useful tools and downloads for the critical appraisal of different types of medical evidence. Example appraisal sheets are provided together with several helpful examples."
• Critical Appraisal Skills Programme (CASP) Checklists Critical Appraisal checklists for many different study types
• Critical Review Form for Qualitative Studies Version 2, developed out of McMaster University
• Development of a critical appraisal tool to assess the quality of cross-sectional studies (AXIS) Downes MJ, Brennan ML, Williams HC, et al. Development of a critical appraisal tool to assess the quality of cross-sectional studies (AXIS). BMJ Open 2016;6:e011458. doi:10.1136/bmjopen-2016-011458
• Downs & Black Checklist for Assessing Studies Downs, S. H., & Black, N. (1998). The Feasibility of Creating a Checklist for the Assessment of the Methodological Quality Both of Randomised and Non-Randomised Studies of Health Care Interventions. Journal of Epidemiology and Community Health (1979-), 52(6), 377–384.
• GRADE The Grading of Recommendations Assessment, Development and Evaluation (GRADE) working group "has developed a common, sensible and transparent approach to grading quality (or certainty) of evidence and strength of recommendations."
• Grade Handbook Full handbook on the GRADE method for grading quality of evidence.
• MAGIC (Making GRADE the Irresistible choice) Clear succinct guidance in how to use GRADE
• Joanna Briggs Institute. Critical Appraisal Tools "JBI’s critical appraisal tools assist in assessing the trustworthiness, relevance and results of published papers." Includes checklists for 13 types of articles.
• Latitudes Network This is a searchable library of validity assessment tools for use in evidence syntheses. This website also provides access to training on the process of validity assessment.
• Mixed Methods Appraisal Tool A tool that can be used to appraise a mix of studies that are included in a systematic review - qualitative research, RCTs, non-randomized studies, quantitative studies, mixed methods studies.
• RoB 2 Tool Higgins JPT, Sterne JAC, Savović J, Page MJ, Hróbjartsson A, Boutron I, Reeves B, Eldridge S. A revised tool for assessing risk of bias in randomized trials In: Chandler J, McKenzie J, Boutron I, Welch V (editors). Cochrane Methods. Cochrane Database of Systematic Reviews 2016, Issue 10 (Suppl 1). dx.doi.org/10.1002/14651858.CD201601.
• ROBINS-I Risk of Bias for non-randomized (observational) studies or cohorts of interventions Sterne J A, Hernán M A, Reeves B C, Savović J, Berkman N D, Viswanathan M et al. ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions BMJ 2016; 355 :i4919 doi:10.1136/bmj.i4919
• Scottish Intercollegiate Guidelines Network. Critical Appraisal Notes and Checklists "Methodological assessment of studies selected as potential sources of evidence is based on a number of criteria that focus on those aspects of the study design that research has shown to have a significant effect on the risk of bias in the results reported and conclusions drawn. These criteria differ between study types, and a range of checklists is used to bring a degree of consistency to the assessment process."
• The TREND Statement (CDC) Des Jarlais DC, Lyles C, Crepaz N, and the TREND Group. Improving the reporting quality of nonrandomized evaluations of behavioral and public health interventions: The TREND statement. Am J Public Health. 2004;94:361-366.
• Assembling the Pieces of a Systematic Reviews, Chapter 8: Evaluating: Study Selection and Critical Appraisal.
• How to Perform a Systematic Literature Review, Chapter: Critical Appraisal: Assessing the Quality of Studies.

Other library guides

• Duke University Medical Center Library. Systematic Reviews: Assess for Quality and Bias
• UNC Health Sciences Library. Systematic Reviews: Assess Quality of Included Studies
• Last Updated: Sep 6, 2024 12:39 PM
• URL: https://guides.lib.utexas.edu/systematicreviews

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Critical appraisal is a systematic process used to identify the strengths and weaknesses of a research article in order to assess the usefulness and validity of research findings. The most important components of a critical appraisal are an evaluation of the appropriateness of the study design for the research question and a careful assessment of the key methodological features of this design. Other factors that also should be considered include the suitability of the statistical methods used and their subsequent interpretation, potential conflicts of interest and the relevance of the research to one's own practice. This Review presents a 10-step guide to critical appraisal that aims to assist clinicians to identify the most relevant high-quality studies available to guide their clinical practice.

Critical appraisal is a systematic process used to identify the strengths and weaknesses of a research article

Critical appraisal provides a basis for decisions on whether to use the results of a study in clinical practice

Different study designs are prone to various sources of systematic bias

Design-specific, critical-appraisal checklists are useful tools to help assess study quality

Assessments of other factors, including the importance of the research question, the appropriateness of statistical analysis, the legitimacy of conclusions and potential conflicts of interest are an important part of the critical appraisal process

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Making sense of the literature: an introduction to critical appraisal for the primary care practitioner

How to appraise the literature: basic principles for the busy clinician - part 2: systematic reviews and meta-analyses

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JM Young is an Associate Professor of Public Health and the Executive Director of the Surgical Outcomes Research Centre at the University of Sydney and Sydney South-West Area Health Service, Sydney,

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MJ Solomon is Head of the Surgical Outcomes Research Centre and Director of Colorectal Research at the University of Sydney and Sydney South-West Area Health Service, Sydney, Australia.,

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Young, J., Solomon, M. How to critically appraise an article. Nat Rev Gastroenterol Hepatol 6 , 82–91 (2009). https://doi.org/10.1038/ncpgasthep1331

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Received : 10 August 2008

Accepted : 03 November 2008

Published : 20 January 2009

Issue Date : February 2009

DOI : https://doi.org/10.1038/ncpgasthep1331

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What is Critical Appraisal?

Critical Appraisal is the process of carefully and systematically examining research to judge its trustworthiness, and its value and relevance in a particular context. It is an essential skill for evidence-based medicine because it allows people to find and use research evidence reliably and efficiently. All of us would like to enjoy the best possible health we can. To achieve this, we need reliable information about what might harm or help us when we make healthcare decisions.

Why is Critical Appraisal important?

Critical appraisal skills are important as they enable you to assess systematically the trustworthiness, relevance and results of published papers. Where an article is published, or who wrote it should not be an indication of its trustworthiness and relevance.

Randomised Controlled Trials (RCTs): An experiment that randomises participants into two groups: one that receives the treatment and another that serves as the control. RCTs are often used in healthcare to test the efficacy of different treatments.

Learn more about how to critically appraise an RCT.

Systematic Reviews : A thorough and structured analysis of all relevant studies on a particular research question. These are often used in evidence-based practice to evaluate the effects of health and social interventions.

Discover what systematic reviews are, and why they are important .

Cohort Studies : This is an observational study where two or more groups (cohorts) of individuals are followed over time and their outcomes are compared. It's used often in medical research to investigate the potential causes of disease.

Learn more about cohort studies .

Case-Control Studies : This is an observational study where two groups differing in outcome are identified and compared on the basis of some supposed causal attribute. These are often used in epidemiological research.

Check out this article to better understand what a case-control study is in research .

Cross-Sectional Studies : An observational study that examines the relationship between health outcomes and other variables of interest in a defined population at a single point in time. They're useful for determining prevalence and risk factors.

Discover what a cross-sectonal study is and when to use one .

Qualitative Research : An in-depth analysis of a phenomenon based on unstructured data, such as interviews, observations, or written material. It's often used to gain insights into behaviours, value systems, attitudes, motivations, or culture.

This guide will help you increase your knowledge of qualitative research .

Economic Evaluation : A comparison of two or more alternatives in terms of their costs and consequences. Often used in healthcare decision making to maximise efficiency and equity.

Diagnostic Studies : Evaluates the performance of a diagnostic test in predicting the presence or absence of a disease. It is commonly used to validate the accuracy and utility of a new diagnostic procedure.

Case Series : Describes characteristics of a group of patients with a particular disease or who have undergone a specific procedure. Used in clinical medicine to present preliminary observations.

Case Studies : Detailed examination of a single individual or group. Common in psychology and social sciences, this can provide in-depth understanding of complex phenomena in their real-life context.

Aren’t we already doing it?

To some extent, the answer to this question is “yes”. Evidence-based journals can give us reliable, relevant summaries of recent research; guidelines, protocols, and pathways can synthesise the best evidence and present it in the context of a clinical problem. However, we still need to be able to assess research quality to be able to adapt what we read to what we do.

There are still significant gaps in access to evidence.

The main issues we need to address are:

Health and Social Care provision must be based on sound decisions.

In order to make well-informed and sensible choices, we need evidence that is rigorous in methodology and robust in findings.

What types of questions does a critical appraisal encourage you to ask?

• What is the main objective of the research?
• Who conducted the research and are they reputable?
• How was the research funded? Are there any potential conflicts of interest?
• How was the study designed?
• Was the sample size large enough to provide accurate results?
• Were the participants or subjects selected appropriately?
• What data collection methods were used and were they reliable and valid?
• Was the data analysed accurately and rigorously?
• Were the results and conclusions drawn directly from the data or were there assumptions made?
• Can the findings be generalised to the broader population?
• How does this research contribute to existing knowledge in this field?
• Were ethical standards maintained throughout the study?
• Were any potential biases accounted for in the design, data collection or data analysis?
• Have the researchers made suggestions for future research based on their findings?
• Are the findings of the research replicable?
• Are there any implications for policy or practice based on the research findings?
• Were all aspects of the research clearly explained and detailed?

How do you critically appraise a paper?

Critically appraising a paper involves examining the quality, validity, and relevance of a published work to identify its strengths and weaknesses.

This allows the reader to judge its trustworthiness and applicability to their area of work or research. Below are general steps for critically appraising a paper:

Decide how trustworthy a piece of research is (Validity)

• Determine what the research is telling us (Results)
• Weigh up how useful the research will be in your context (Relevance)

You need to understand the research question, do a methodology evaluation, analyse the results, check the conclusion and review the implications and limitations.

That's just a quick summary but we provide a range of in-depth  training courses  and  workshops  to help you improve your knowledge around how to successfully perform critical appraisals so book onto one today or contact us for more information.

Is Critical Appraisal In Research Different To Front-Line Usage In Nursing, Etc?

Critical appraisal in research is different from front-line usage in nursing.

Critical appraisal in research involves a careful analysis of a study's methodology, results, and conclusions to assess the quality and validity of the study. This helps researchers to determine if the study's findings are robust, reliable and applicable in their own research context. It requires a specific set of skills including understanding of research methodology, statistics, and evidence-based practices.

Front-line usage in nursing refers to the direct application of evidence-based practice and research findings in patient care settings. Nurses need to appraise the evidence critically too but their focus is on the direct implications of the research on patient care and health outcomes. The skills required here would be the ability to understand the clinical implications of research findings, communicate these effectively to patients, and incorporate these into their practice.

Both require critical appraisal but the purpose, context, and skills involved are different. Critical appraisal in research is more about evaluating research for validity and reliability whereas front-line usage in nursing is about effectively applying valid and reliable research findings to improve patient care.

How do you know if you're performing critical appraisals correctly?

Thorough Understanding : You've thoroughly read and understood the research, its aims, methodology, and conclusions. You should also be aware of the limitations or potential bias in the research.

Using a Framework or Checklist : Various frameworks exist for critically appraising research (including CASP’s own!). Using these can provide structure and make sure all key points are considered. By keeping a record of your appraisal you will be able to show your reasoning behind whether you’ve implemented a decision based on research.

Identifying Research Methods : Recognising the research design, methods used, sample size, and how data was collected and analysed are crucial in assessing the research's validity and reliability.

Checking Results and Conclusions : Check if the conclusions drawn from the research are justified by the results and data provided, and if any biases could have influenced these conclusions.

Relevance and applicability : Determine if the research's results and conclusions can be applied to other situations, particularly those relevant to your context or question.

Updating Skills : Continually updating your skills in research methods and statistical analysis will improve your confidence and ability in critically appraising research.

Finally, getting feedback from colleagues or mentors on your critical appraisals can also provide a good check on how well you're doing. They can provide an additional perspective and catch anything you might have missed. If possible, we would always recommend doing appraisals in small groups or pairs, working together is always helpful for another perspective, or if you can – join and take part in a journal club.

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Risk of Bias of Individual Studies

““Assessment of risk of bias is a key step that informs many other steps and decisions made in conducting systematic reviews. It plays an important role in the final assessment of the strength of the evidence.” 1  

Risk of Bias by Study Design (featured tools)

• Systematic Reviews
• Non-RCTs or Observational Studies
• Diagnostic Accuracy
• Animal Studies
• Qualitative Research
• Tool Repository
• AMSTAR 2 The original AMSTAR was developed to assess the risk of bias in systematic reviews that included only randomized controlled trials. AMSTAR 2 was published in 2017 and allows researchers to identify high quality systematic reviews, including those based on non-randomised studies of healthcare interventions. more... less... AMSTAR 2 (A MeaSurement Tool to Assess systematic Reviews)
• ROBIS ROBIS is a tool designed specifically to assess the risk of bias in systematic reviews. The tool is completed in three phases: (1) assess relevance(optional), (2) identify concerns with the review process, and (3) judge risk of bias in the review. Signaling questions are included to help assess specific concerns about potential biases with the review. more... less... ROBIS (Risk of Bias in Systematic Reviews)
• BMJ Framework for Assessing Systematic Reviews This framework provides a checklist that is used to evaluate the quality of a systematic review.
• CASP Checklist for Systematic Reviews This CASP checklist is not a scoring system, but rather a method of appraising systematic reviews by considering: 1. Are the results of the study valid? 2. What are the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CEBM Systematic Reviews Critical Appraisal Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance, and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• JBI Critical Appraisal Tools, Checklist for Systematic Reviews JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• NHLBI Study Quality Assessment of Systematic Reviews and Meta-Analyses The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. more... less... NHLBI (National Heart, Lung, and Blood Institute)
• RoB 2 RoB 2 provides a framework for assessing the risk of bias in a single estimate of an intervention effect reported from a randomized trial, rather than the entire trial. more... less... RoB 2 (revised tool to assess Risk of Bias in randomized trials)
• CASP Randomised Controlled Trials Checklist This CASP checklist considers various aspects of an RCT that require critical appraisal: 1. Is the basic study design valid for a randomized controlled trial? 2. Was the study methodologically sound? 3. What are the results? 4. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CONSORT Statement The CONSORT checklist includes 25 items to determine the quality of randomized controlled trials. Critical appraisal of the quality of clinical trials is possible only if the design, conduct, and analysis of RCTs are thoroughly and accurately described in the report. more... less... CONSORT (Consolidated Standards of Reporting Trials)
• NHLBI Study Quality Assessment of Controlled Intervention Studies The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. more... less... NHLBI (National Heart, Lung, and Blood Institute)
• JBI Critical Appraisal Tools Checklist for Randomized Controlled Trials JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• ROBINS-I ROBINS-I is a tool for evaluating risk of bias in estimates of the comparative effectiveness… of interventions from studies that did not use randomization to allocate units to comparison groups. more... less... ROBINS-I (Risk Of Bias in Non-randomized Studies – of Interventions)
• NOS This tool is used primarily to evaluate and appraise case-control or cohort studies. more... less... NOS (Newcastle-Ottawa Scale)
• AXIS Cross-sectional studies are frequently used as an evidence base for diagnostic testing, risk factors for disease, and prevalence studies. The AXIS tool focuses mainly on the presented study methods and results. more... less... AXIS (Appraisal tool for Cross-Sectional Studies)
• NHLBI Study Quality Assessment Tools for Non-Randomized Studies The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. • Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies • Quality Assessment of Case-Control Studies • Quality Assessment Tool for Before-After (Pre-Post) Studies With No Control Group • Quality Assessment Tool for Case Series Studies more... less... NHLBI (National Heart, Lung, and Blood Institute)
• Case Series Studies Quality Appraisal Checklist Developed by the Institute of Health Economics (Canada), the checklist is comprised of 20 questions to assess the robustness of the evidence of uncontrolled case series studies.
• Methodological Quality and Synthesis of Case Series and Case Reports In this paper, Dr. Murad and colleagues present a framework for appraisal, synthesis and application of evidence derived from case reports and case series.
• MINORS The MINORS instrument contains 12 items and was developed for evaluating the quality of observational or non-randomized studies. This tool may be of particular interest to researchers who would like to critically appraise surgical studies. more... less... MINORS (Methodological Index for Non-Randomized Studies)
• JBI Critical Appraisal Tools for Non-Randomized Trials JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis. • Checklist for Analytical Cross Sectional Studies • Checklist for Case Control Studies • Checklist for Case Reports • Checklist for Case Series • Checklist for Cohort Studies
• QUADAS-2 The QUADAS-2 tool is designed to assess the quality of primary diagnostic accuracy studies it consists of 4 key domains that discuss patient selection, index test, reference standard, and flow of patients through the study and timing of the index tests and reference standard. more... less... QUADAS-2 (a revised tool for the Quality Assessment of Diagnostic Accuracy Studies)
• JBI Critical Appraisal Tools Checklist for Diagnostic Test Accuracy Studies JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• STARD 2015 The authors of the standards note that essential elements of diagnostic accuracy study methods are often poorly described and sometimes completely omitted, making both critical appraisal and replication difficult, if not impossible. The Standards for the Reporting of Diagnostic Accuracy Studies was developed to help improve completeness and transparency in reporting of diagnostic accuracy studies. more... less... STARD 2015 (Standards for the Reporting of Diagnostic Accuracy Studies)
• CASP Diagnostic Study Checklist This CASP checklist considers various aspects of diagnostic test studies including: 1. Are the results of the study valid? 2. What were the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CEBM Diagnostic Critical Appraisal Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance, and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• SYRCLE’s RoB Implementation of SYRCLE’s RoB tool will facilitate and improve critical appraisal of evidence from animal studies. This may enhance the efficiency of translating animal research into clinical practice and increase awareness of the necessity of improving the methodological quality of animal studies. more... less... SYRCLE’s RoB (SYstematic Review Center for Laboratory animal Experimentation’s Risk of Bias)
• ARRIVE 2.0 The ARRIVE 2.0 guidelines are a checklist of information to include in a manuscript to ensure that publications on in vivo animal studies contain enough information to add to the knowledge base. more... less... ARRIVE 2.0 (Animal Research: Reporting of In Vivo Experiments)
• Critical Appraisal of Studies Using Laboratory Animal Models This article provides an approach to critically appraising papers based on the results of laboratory animal experiments, and discusses various bias domains in the literature that critical appraisal can identify.
• CEBM Critical Appraisal of Qualitative Studies Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• CASP Qualitative Studies Checklist This CASP checklist considers various aspects of qualitative research studies including: 1. Are the results of the study valid? 2. What were the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• Quality Assessment and Risk of Bias Tool Repository Created by librarians at Duke University, this extensive listing contains over 100 commonly used risk of bias tools that may be sorted by study type.
• Latitudes Network A library of risk of bias tools for use in evidence syntheses that provides selection help and training videos.

References & Recommended Reading

1.    Viswanathan, M., Patnode, C. D., Berkman, N. D., Bass, E. B., Chang, S., Hartling, L., ... & Kane, R. L. (2018). Recommendations for assessing the risk of bias in systematic reviews of health-care interventions .  Journal of clinical epidemiology ,  97 , 26-34.

2.     Kolaski, K., Logan, L. R., & Ioannidis, J. P. (2024). Guidance to best tools and practices for systematic reviews .  British Journal of Pharmacology ,  181 (1), 180-210

3.     Fowkes FG, Fulton PM.  Critical appraisal of published research: introductory guidelines.   BMJ (Clinical research ed).  1991;302(6785):1136-1140.

4.     Shea BJ, Reeves BC, Wells G, et al.  AMSTAR 2: a critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both.   BMJ (Clinical research ed).  2017;358:j4008.

5..     Whiting P, Savovic J, Higgins JPT, et al.  ROBIS: A new tool to assess risk of bias in systematic reviews was developed.   Journal of clinical epidemiology.  2016;69:225-234.

6.     Sterne JAC, Savovic J, Page MJ, et al.  RoB 2: a revised tool for assessing risk of bias in randomised trials.  BMJ (Clinical research ed).  2019;366:l4898.

7.     Moher D, Hopewell S, Schulz KF, et al.  CONSORT 2010 Explanation and Elaboration: Updated guidelines for reporting parallel group randomised trials.  Journal of clinical epidemiology.  2010;63(8):e1-37.

8..    Sterne JA, Hernan MA, Reeves BC, et al.  ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions.  BMJ (Clinical research ed).  2016;355:i4919.

9.    Downes MJ, Brennan ML, Williams HC, Dean RS.  Development of a critical appraisal tool to assess the quality of cross-sectional studies (AXIS).   BMJ open.  2016;6(12):e011458.

10.   Guo B, Moga C, Harstall C, Schopflocher D.  A principal component analysis is conducted for a case series quality appraisal checklist.   Journal of clinical epidemiology.  2016;69:199-207.e192.

11.   Murad MH, Sultan S, Haffar S, Bazerbachi F.  Methodological quality and synthesis of case series and case reports.  BMJ evidence-based medicine.  2018;23(2):60-63.

12.   Slim K, Nini E, Forestier D, Kwiatkowski F, Panis Y, Chipponi J.  Methodological index for non-randomized studies (MINORS): development and validation of a new instrument.   ANZ journal of surgery.  2003;73(9):712-716.

13.   Whiting PF, Rutjes AWS, Westwood ME, et al.  QUADAS-2: a revised tool for the quality assessment of diagnostic accuracy studies.   Annals of internal medicine.  2011;155(8):529-536.

14.   Bossuyt PM, Reitsma JB, Bruns DE, et al.  STARD 2015: an updated list of essential items for reporting diagnostic accuracy studies.   BMJ (Clinical research ed).  2015;351:h5527.

15.   Hooijmans CR, Rovers MM, de Vries RBM, Leenaars M, Ritskes-Hoitinga M, Langendam MW.  SYRCLE's risk of bias tool for animal studies.   BMC medical research methodology.  2014;14:43.

16.   Percie du Sert N, Ahluwalia A, Alam S, et al.  Reporting animal research: Explanation and elaboration for the ARRIVE guidelines 2.0.  PLoS biology.  2020;18(7):e3000411.

17.   O'Connor AM, Sargeant JM.  Critical appraisal of studies using laboratory animal models.   ILAR journal.  2014;55(3):405-417.

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Medicine: A Brief Guide to Critical Appraisal

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Have you ever seen a news piece about a scientific breakthrough and wondered how accurate the reporting is? Or wondered about the research behind the headlines? This is the beginning of critical appraisal: thinking critically about what you see and hear, and asking questions to determine how much of a 'breakthrough' something really is.

The article " Is this study legit? 5 questions to ask when reading news stories of medical research " is a succinct introduction to the sorts of questions you should ask in these situations, but there's more than that when it comes to critical appraisal. Read on to learn more about this practical and crucial aspect of evidence-based practice.

What is Critical Appraisal?

Critical appraisal forms part of the process of evidence-based practice. “ Evidence-based practice across the health professions ” outlines the fives steps of this process. Critical appraisal is step three:

• Ask a question
• Access the information
• Appraise the articles found
• Apply the information

Critical appraisal is the examination of evidence to determine applicability to clinical practice. It considers (1) :

• Are the results of the study believable?
• Was the study methodologically sound?  
• What is the clinical importance of the study’s results?
• Are the findings sufficiently important? That is, are they practice-changing?  
• Are the results of the study applicable to your patient?
• Is your patient comparable to the population in the study?

Why Critically Appraise?

If practitioners hope to ‘stand on the shoulders of giants’, practicing in a manner that is responsive to the discoveries of the research community, then it makes sense for the responsible, critically thinking practitioner to consider the reliability, influence, and relevance of the evidence presented to them.

While critical thinking is valuable, it is also important to avoid treading too much into cynicism; in the words of Hoffman et al. (1):

… keep in mind that no research is perfect and that it is important not to be overly critical of research articles. An article just needs to be good enough to assist you to make a clinical decision.

How do I Critically Appraise?

Evidence-based practice is intended to be practical . To enable this, critical appraisal checklists have been developed to guide practitioners through the process in an efficient yet comprehensive manner.

Critical appraisal checklists guide the reader through the appraisal process by prompting the reader to ask certain questions of the paper they are appraising. There are many different critical appraisal checklists but the best apply certain questions based on what type of study the paper is describing. This allows for a more nuanced and appropriate appraisal. Wherever possible, choose the appraisal tool that best fits the study you are appraising.

Like many things in life, repetition builds confidence and the more you apply critical appraisal tools (like checklists) to the literature the more the process will become second nature for you and the more effective you will be.

How do I Identify Study Types?

Identifying the study type described in the paper is sometimes harder than it should be. Helpful papers spell out the study type in the title or abstract, but not all papers are helpful in this way. As such, the critical appraiser may need to do a little work to identify what type of study they are about to critique. Again, experience builds confidence, but understanding the typical features of common study types certainly helps.

To assist with this, the Library has produced a guide to study designs in health research .

The following selected references will help also with understanding study types but there are also other resources in the Library’s collection and freely available online:

• The “ How to read a paper ” article series from The BMJ is a well-known source for establishing an understanding of the features of different study types; this series was subsequently adapted into a book (“ How to read a paper: the basics of evidence-based medicine ”) which offers more depth and currency than that found in the articles. (2)  
• Chapter two of “ Evidence-based practice across the health professions ” briefly outlines some study types and their application; subsequent chapters go into more detail about different study types depending on what type of question they are exploring (intervention, diagnosis, prognosis, qualitative) along with systematic reviews.  
• “ Translational research and clinical practice: basic tools for medical decision making and self-learning ” unpacks the components of a paper, explaining their purpose along with key features of different study designs. (3)  
• The BMJ website contains the contents of the fourth edition of the book “ Epidemiology for the uninitiated ”. This eBook contains chapters exploring ecological studies, longitudinal studies, case-control and cross-sectional studies, and experimental studies.

Reporting Guidelines

In order to encourage consistency and quality, authors of reports on research should follow reporting guidelines when writing their papers. The EQUATOR Network is a good source of reporting guidelines for the main study types.

While these guidelines aren't critical appraisal tools as such, they can assist by prompting you to consider whether the reporting of the research is missing important elements.

Once you've identified the study type at hand, visit EQUATOR to find the associated reporting guidelines and ask yourself: does this paper meet the guideline for its study type?

Which Checklist Should I Use?

Determining which checklist to use ultimately comes down to finding an appraisal tool that:

• Fits best with the study you are appraising
• Is reliable, well-known or otherwise validated
• You understand and are comfortable using

Below are some sources of critical appraisal tools. These have been selected as they are known to be widely accepted, easily applicable, and relevant to appraisal of a typical journal article. You may find another tool that you prefer, which is acceptable as long as it is defensible:

• CASP (Critical Appraisal Skills Programme)
• JBI (Joanna Briggs Institute)
• CEBM (Centre for Evidence-Based Medicine)
• SIGN (Scottish Intercollegiate Guidelines Network)
• STROBE (Strengthing the Reporting of Observational Studies in Epidemiology)
• BMJ Best Practice

The information on this page has been compiled by the Medical Librarian. Please contact the Library's Health Team ( [email protected] ) for further assistance.

Reference list

1. Hoffmann T, Bennett S, Del Mar C. Evidence-based practice across the health professions. 2nd ed. Chatswood, N.S.W., Australia: Elsevier Churchill Livingston; 2013.

2. Greenhalgh T. How to read a paper: the basics of evidence-based medicine. 5th ed. Chichester, West Sussex: Wiley; 2014.

3.  Aronoff SC. Translational research and clinical practice: basic tools for medical decision making and self-learning. New York: Oxford University Press; 2011.

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• v.30(2); Jul-Dec 2009

Critical appraisal skills are essential to informed decision-making

Rahul mhaskar.

1 Center for Evidence-based Medicine and Health Outcomes Research, USA

3 Clinical and Translational Science Institute, University of South Florida, College of Medicine, Tampa, Florida, USA

Patricia Emmanuel

5 Department of Internal Medicine, University of South Florida, College of Medicine, Tampa, Florida, USA

Shobha Mishra

4 Department of Preventive and Social Medicine, Government Medical College, Vadodara, India,

Sangita Patel

Eknath naik, ambuj kumar.

2 Department of Health Outcomes and Behavior, Moffitt Cancer Center, USA

Whenever a trial is conducted, there are three possible explanations for the results: a) findings are correct (truth), b) represents random variation (chance) or c) they are influenced by systematic error (bias). Random error is deviation from the ‘truth’ and happens due to play of chance (e.g. trials with small sample, etc.). Systematic distortion of the estimated intervention effect away from the ‘truth’ can also be caused by inadequacies in the design, conduct or analysis of a trial. Several studies have shown that bias can obscure up to 60% of the real effect of a healthcare intervention. A mounting body of empirical evidence shows that ‘biased results from poorly designed and reported trials can mislead decision making in healthcare at all levels’. Poorly conducted and reported RCTs seriously compromise the integrity of the research process especially when biased results receive false credibility. Therefore, critical appraisal of the quality of clinical research is central to informed decision-making in healthcare. Critical appraisal is the process of carefully and systematically examining research evidence to judge its trustworthiness, its value and relevance in a particular context. It allows clinicians to use research evidence reliably and efficiently. Critical appraisal is intended to enhance the healthcare professional's skill to determine whether the research evidence is true (free of bias) and relevant to their patients.

INTRODUCTION

A five-year-old male child presents with dry and scaly skin on his cheeks and was brought to the pediatric out-patient clinic by his parents. After initial evaluation, the young patient was diagnosed with atopic dermatitis. During the initial consultation, a junior resident mentions that a topical formulation of tacrolimus, an immunosuppressant currently marketed for the prevention of rejection after solid organ transplant, is a potential therapeutic agent for atopic dermatitis. Nevertheless, the senior resident wants to know the evidence related to the safety and efficacy of topical tacrolimus in treating younger patients with atopic dermatitis. The junior resident enthusiastically performs an electronic search of the literature and finds a randomized controlled trial (RCT) conducted to determine the safety and efficacy of tacrolimus ointment in pediatric patients with moderate-to-severe atopic dermatitis.[ 1 ] The junior resident also mentions that since this is an RCT, it should be considered reliable as it stands at a higher level in the hierarchy of the evidence pyramid [ Figure 1 ]. However, the question now arises that because the trial claims to be a RCT, are the results from this study reliable, and whether the results are applicable to the young patient in question here?

Evidence pyramid showing the hierarchy of evidence.[ 13 ]

THE NEED FOR CRITICAL APPRAISAL

Whenever a trial is conducted, there are three possible explanations for the results: a) findings are correct (truth), b) represents random variation (chance) or c) they are influenced by systematic error (bias). Random error is deviation from the ‘truth’ and happens due to play of chance (e.g. trials with small sample, etc.). Systematic distortion of the estimated intervention effect away from the ‘truth’ can also be caused by inadequacies in the design, conduct or analysis of a trial. Several studies have shown that bias can obscure up to 60% of the real effect of a healthcare intervention. A mounting body of empirical evidence shows that ‘biased results from poorly designed and reported trials can mislead decision-making in healthcare at all levels’.[ 2 ] Poorly conducted and reported RCTs seriously compromise the integrity of the research process especially when biased results receive false credibility. Therefore, critical appraisal of the quality of clinical research is central to informed decision-making in healthcare.

Critical appraisal is the process of systematically examining research evidence to judge its trustworthiness, its value and relevance in a particular context. It allows clinicians to use research evidence reliably and efficiently.[ 3 ] Critical appraisal is intended to enhance the healthcare professional's skill to determine whether the research evidence is true (free of bias) and relevant to their patients. In this paper, we focus on the evaluation of an article (RCT) on a treatment intervention. The same framework would be applicable to preventive interventions as well.

Three essential questions need to be asked when dealing with an article on therapeutic intervention.[ 4 ]

• Are the results valid? Do the findings of this study represent the truth? That is, do the results provide an unbiased estimate of the treatment effect, or have they been clouded by bias leading to false conclusions?
• How precise are the results? If the results are unbiased, they need further examination in terms of precision. The precision would be better in larger studies compared with smaller studies.
• Are the results applicable to my patient? What are the patient populations, disease and treatments (including comparators) under investigation? What are the benefits and risks associated with the treatment? Do the benefits outweigh the harms?

Is there a clearly stated aim and research question? Ideally, a well-designed RCT should follow the acronym of PICOTS, which stands for patient, intervention, control, outcome, timing and setting, to formulate the research question. Is there a sound and understandable explanation of the population being studied (inclusion and exclusion criteria)? Is there an overview of which interventions are being compared? Are the outcomes being measured clearly stated with a rationale as to why these outcomes were selected for the study?

Randomization aims to balance the groups for known and unknown prognostic factors by allocating patients to two groups by chance alone. The aim is to minimize the probabilities of treatment differences attributed to chance and to maximize the attribution to treatment effects. Therefore, it is important that the intervention and control groups are similar in all aspects apart from receiving the treatment being tested. Otherwise, we cannot be sure that any difference in outcome at the end is not due to pre-existing disparity. If one group has a significantly different average age or social class make-up, this might be an explanation of why that group did better or worse. The best method to create two groups that are similar in all important respects is by deciding entirely by chance, into which group a patient will be assigned.[ 5 ] This is achieved by random assignment of patients to the groups. In true randomization, all patients have the same chance as each other of being placed into any of the groups.[ 4 , 5 ] Allocation concealment ensures that those assessing eligibility and assigning subjects to groups do not have knowledge of the allocation sequence. In order to ensure adequate allocation concealment, centralized computer randomization is ideal and is often used in multicenter RCTs. The successful randomization process will result in similar groups. It is important to note that randomization will not always produce groups balanced for known prognostic factors. A large sample size will potentially reduce the likelihood of placing individuals with better prognoses in one group.[ 4 , 6 ]

Participants in a RCT are considered lost to follow-up when their status or outcomes are not known at the end of the study. Dropouts might happen due to several natural reasons (e.g. participant relocation). It is assumed that such dropouts will not necessarily be a substantial number. However, when the dropout rate is large (e.g. >10%), it is a reason for concern. Often the reason that patients are lost to follow up relates to a systematic difference in their prognosis compared with patients who continue with a study until the end (e.g., patients lost to follow-up may have more adverse events or worse outcomes than those who continue). Therefore, the loss of many participants may threaten internal validity of the trial. Furthermore, if loss to follow-up and drop outs is different between two study groups, it may result in missing data that can disrupt the balance in groups created by randomization.

The abovementioned questions should be adequate for screening purposes of the manuscript to help make a decision whether to continue assessing the article further. That is, if the answers to the first three questions are negative, it is not worth evaluating the findings, as the results from this study would not be considered reliable to be used in decision-making.

The readers of the paper should be attentive as to whether authors of the study adequately describe the data collection that was employed in the study. These should be clearly described and justified. All outcome measures should be referenced and their validity reviewed. If data was self-reported by patients, it would need to be verified in some way for maximum credibility.

Were the methods of analysis appropriate, clearly described and justified? Analysis should relate to the original aims and research questions. Choice of statistical analyses should be explained with a clear rationale. Any unconventional tests should be justified with references to validation studies.

An important issue to consider in the analysis of a RCT is whether the analysis was performed according to the intention to treat (ITT) principle. According to this principle, all patients are analyzed in the same treatment arm regardless of whether they received the treatment or not. Intention to treat (ITT) analysis is important because it preserves the benefit of randomization. If certain patients in either arm dropped out, were non-compliant or had adverse events are not considered in the analysis, it is similar to allowing patients to select their treatment and the purpose of randomization is rendered futile.

Alternatively, a ‘per-protocol’ or ‘on treatment’ analysis includes only patients who have sufficiently complied with the trial's protocol. Compliance covers exposure to treatment, availability of measurements and absence of major protocol violations and is necessary to measure the treatment-related harm (TRH) outcomes. Adhering to ITT analysis for assessment of TRH leads to biased estimates.[ 7 , 8 ] In summary, analysis of benefits associated with treatments should be performed using the ITT principle and associated risks according to per protocol.

The findings should answer the primary research question(s). Each outcome measure should be analyzed and its results presented with comparisons between the groups. Other issues of analysis include the magnitude of the effect, which can be measured by relative and absolute risk differences, odds ratios and numbers needed to treat. The significance of any differences between the groups should be discussed, with p-values given to indicate statistical significance (< 0.05 being the common threshold for significance). The confidence intervals should be presented to demonstrate the degree of precision of the results. Was the sub-group analyses preplanned or derived post hoc (derived from a fishing expedition after data collection)? For example, in the RCT mentioned in the clinical scenario, tacrolimus in children aged 6 to 17 years suffering from atopic dermatitis had a statistically significant difference compared with vehicle group for the outcome of Physician's Global Evaluation of clinical response.[ 1 ] It is important to note that the study was adequately powered to address the primary question only. It would be incorrect if the investigators decided to address the issue of efficacy according to age groups (e.g. subgroup of 6 to 8 years old versus 9 to 17) or any other subgroups if it was not decided a priori. That is, subgroup analysis could be justified for hypothesis generation but not hypothesis testing. The validity of subgroup–treatment effects can only be tested by reproducing the results in future trials. Rarely are trials powered to detect subgroup effects. There is often a high false negative rate for tests of subgroup-treatment effect interaction when a true interaction exists.[ 9 ]

The authors should include the descriptive analysis of the data (mean, median, standard deviation, frequencies etc.) and not just the results of statistical tests used. Most often, results are presented as dichotomous outcomes (yes or no). Consider a study in which 25% (0.25) of the control group died and 20% (0.20) of the treatment group died. The results can be expressed in many ways as shown in Table 1 .[ 10 ]

Essential terminologies and their interpretations

How will the results help me work with my patients/clients? Can the results be applied to the local population of my practice and clients? How similar is the study sample to your own clients? Are there any key differences that you would need to consider for your own practice?

In the case of our five-year-old with atopic dermatitis, even if the trial was performed flawlessly with positive results, if the population studied was not similar then the evidence is not applicable. An example of this would be if the study was performed in patients with severe atopic disease who had failed all other regimens but our patient was naïve to any therapy. If the population was a different age range or ethnicity, it could also impact relevance.

Other important considerations are whether you have the necessary skills or resources to deliver the intervention. Were all the important outcomes considered? Has the research covered the most important outcomes for your patients? If key outcomes were overlooked, do you need further evidence before changing your practice? Are the benefits of the intervention worth the harms and the costs? If the study does not answer this question, you will need to use your own judgment, taking into account your patients, all the stakeholders, yourself and your colleagues.

Absolute Risk Reduction (ARR) = risk of the outcome in the control group – risk of the outcome in the treatment group.

In our example, the ARR = 0.25 – 0.20 = 0.05 or 5%. Absolute Risk Reduction (ARR) indicates the decrease in risk of a given outcome in patients with the treatment in relation to risk of that outcome in individuals not receiving the treatment.

An ARR of ‘0’ suggests that there is no difference between the two groups indicating that treatment had no effect.

Relative Risk Reduction (RRR) = absolute risk reduction / risk of the outcome in the control group.

In our example, the RRR = 0.05/0.25 = 0.20 or 20%. Relative Risk Reduction (RRR) indicates the reduction in the rate of the outcome in the treatment group relative to that in the control group.

Number Needed to Treat (NNT) = 1 / ARR.

In our example, the NNT = 1/ 0.05 = 20. Number Needed to Treat (NNT) is the number of patients needs to be treated in order to prevent one additional bad outcome.

In conclusion, the reporting of RCT can be plagued with numerous quality control issues. Consolidated Standards of Reporting Trials group (CONSORT) has developed various initiatives to improve the issues arising from inadequate reporting of RCTs. The main products of CONSORT are the CONSORT statement[ 11 ] and CONSORT harms statement,[ 12 ] which are an evidence-based, minimum set of recommendations for reporting RCTs. These offer a standard way for authors to prepare reports of trial findings, facilitating their complete and transparent reporting and aiding their critical interpretation.[ 11 ] In essence there is a need to assess the quality of evidence; and, if adequate, establish the range of true treatment effect. Then, consider whether results are generalizable to the patient at hand, and whether the measured outcomes are relevant and important. Finally, carefully review the patient's risk of TRH and related treatment benefit – risk ratio.[ 6 ] We believe that methodologically assessing the strength of evidence and using it to guide treatment of each patient will certainly improve health outcomes.

Additional material

A critical appraisal worksheet (with permission from http://www.cebm.net/index.aspx?o=1157 ) is provided in the appendix section of the manuscript. We encourage the readers to assess the manuscript mentioned in the clinical scenario[ 1 ] and critically appraise it using the worksheet (see appendix ).

ACKNOWLEDGEMENT

This paper was supported in part by the Fogarty International Center/USNIH: Grant # 1D43TW006793-01A2-AITRP.

Source of Support: Fogarty International Center/USNIH: Grant #1D43TW006793-01A2-AITRP.

Conflict of Interest: None declared.

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hi are there any international destinations by train from novgorod?

Very easy to answer: no

how about st petersburg? how long and how much?

I can by tickets to helsinki from novgorod at the station?

There is no direct train from Novgorod to any destination abroad - i.e. you need to change a train (and, most likely, train station - in St.Petersburg or Moscow).

so how much would it cost to get from novgorod to st petersburg?

ticket for Novgorod - St.Petersburg train costs about 700 rubles - a $21.

This topic has been closed to new posts due to inactivity.

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