critical appraisal of research definition

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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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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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• Review Article
• Published: 20 January 2009

How to critically appraise an article

• Jane M Young 1 &
• Michael J Solomon 2  

Nature Clinical Practice Gastroenterology & Hepatology volume  6 ,  pages 82–91 ( 2009 ) Cite this article

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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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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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Critical Appraisal of Research Articles: Home

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Online Resources

Need additional resources for critical appraisal? 

• Centre for Evidence Based Medicine
• Joanna Briggs Institute 
• Critical Appraisals Skills Programme (CASP) 

Which study design answers which questions best?

Etiology, Causation, Harm

Cohort study > Case control > Case Series > Cross sectional study

  Diagnostic Testing

Prospective, blind comparison to the gold standard

  Prognosis

Cohort study > Case control > Case series

Therapy, Prevention

Randomized Controlled Trial (RCT) > Cohort > Case Control

What is Critical Appraisal?

"Critical appraisal is the process of systematically examining research evidence to assess its validity, results, and relevance before using it to inform a decision."

Hill, A. Spittlehouse, C. What is Critical Appraisal? What is...? series . Retrieved from http://www.whatisseries.co.uk/whatis/pdfs/What_is_crit_appr.pdf

Types of Studies

Please see our tutorial, Study Design 101 .

Randomized Controlled Trial (RCT)

A clinical trial involving one or more new treatments and at least one control treatment with specified outcome measures for evaluating the intervention.  The treatment may be a drug, device, or procedure. Controls are either placebo or an active treatment that is currently considered the "gold standard".  If patients are randomized via mathmatical techniques then the trial is designated as a randomized controlled trial.

Cohort Study

In cohort studies, groups of individuals, who are initially free of disease, are classified according to exposure or non-exposure to a risk factor and followed over time to determine the incidence of an outcome of interest.  In a prospective cohort study, the exposure information for the study subjects is collected at the start of the study and the new cases of disease are identified from that point on.  In a retrospective cohort study, the exposure status was measured in the past and disease identification has already begun. 

Case-control Study

Studies that start by identifying persons with and without a disease of interest (cases and controls, respectively) and then look back in time to find differences in exposure to risk factors. 

Cross-sectional Study

Studies in which the presence or absence of disease or other health-related variables are determined in each member of a population at one particular time. 

Meta-analysis

A quantitative method of combining the results of independent studies, which are drawn from the published literature, and synthesizing summaries and conclusions.

Systematic Review

A review which endeavors to consider all published and unpublished material on a specific question.  Studies that are judged methodologically sound are then combined quantitatively or qualitatively depending on their similarity.

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Critically Appraised Topics

CATs are critical summaries of a research article.  They are concise, standardized, and provide an appraisal of the research.

If a CAT already exists for an article, it can be read quickly and the clinical bottom line can be put to use as the clinician sees fit.  If a CAT does not exist, the CAT format provides a template to appraise the article of interest.

Critical appraisal is the process of carefully and systematically assessing the outcome of scientific research (evidence) to judge its trustworthiness, value and relevance in a particular context. Critical appraisal looks at the way a study is conducted and examines factors such as internal validity, generalizability and relevance.

  Some initial appraisal questions you could ask are:

• Is the evidence from a known, reputable source?
• Has the evidence been evaluated in any way? If so, how and by whom?
• How up-to-date is the evidence?

 Second, you look at the study itself and ask the following general appraisal questions:

• Is the methodology used appropriate for the researchers question? Is the aim clear?
• How was the outcome measured? Is that a reliable way to measure? How large was the sample size? Does the sample accurately reflect the population?
• Can the results be replicated?
• Have exclusions or limitations been listed?
• What implications does the study have for your practice? Is it relevant, logical?
• Can the results be applied to your organization/purpose?
• Centre for Evidence Based Medicine - Critical Appraisal Tools
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CASP Checklists 

CASP Case Control Checklist

CASP Clinical Protection Rule Checklist

CASP Cohort Study Checklist

CASP Diagnostic Checklist

CASP Economic Evaluation Checklist

CASP Qualitative Study Checklist

CASP Randomized Controlled Trial (RCT) Checklist

CASP Systematic Review Checklist

Appraisal: Validity vs. Reliability & Calculators

Appraisal is the third step in the Evidence Based Medicine process. It requires that the evidence found be evaluated for its validity and clinical usefulness. 

What is validity?

• Internal validity is the extent to which the experiment demonstrated a cause-effect relationship between the independent and dependent variables.
• External validity is the extent to which one may safely generalize from the sample studied to the defined target population and to other populations.

What is reliability?

Reliability is the extent to which the results of the experiment are replicable.  The research methodology should be described in detail so that the experiment could be repeated with similar results.

Statistical Calculators for Appraisal

• Diagnostic Test Calculator
• Risk Reduction Calculator
• Diagnostic Test - calculates the Sensitivity, Specificity, PPV, NPV, LR+, and LR-
• Prospective Study - calculates the Relative Risk (RR), Absolute Relative Risk (ARR), and Number Needed to Treat (NNT)
• Case-control Study - calculates the Odds Ratio (OR)
• Randomized Control Trial (RCT) - calculates the Relative Risk Reduction (RRR), ARR, and NNT
• Chi-Square Calculator
• Likelihood Ratio (LR) Calculations - The LR is used to assess how good a diagnostic test is and to help in selecting an appropriate diagnostic test(s) or sequence of tests. They have advantages over sensitivity and specificity because they are less likely to change with the prevalence of the disorder, they can be calculated for several levels of the symptom/sign or test, they can be used to combine the results of multiple diagnostic test and the can be used to calculate post-test probability for a target disorder.
• Odds Ratio - In statistics, the odds ratio (usually abbreviated "OR") is one of three main ways to quantify how strongly the presence or absence of property A is associated with the presence or absence of property B in a given population.
• Odds Ratio to NNT Converter - To convert odds ratios to NNTs, enter a number that is > 1 or < 1 in the odds ratio textbox and a number that is not equal to 0 or 1 for the Patient's Expected Event Rate (PEER). After entering the numbers, click "Calculate" to convert the odds ratio to NNT.
• One Factor ANOVA
• Relative Risk Calculator - In statistics and epidemiology, relative risk or risk ratio (RR) is the ratio of the probability of an event occurring (for example, developing a disease, being injured) in an exposed group to the probability of the event occurring in a comparison, non-exposed group.
• Two Factor ANOVA
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Critical Appraisal: Assessing the Quality of Studies

• First Online: 05 August 2020

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• Niall McCrae   ORCID: orcid.org/0000-0001-9776-7694 4  

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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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What is critical appraisal?

We critically appraise information constantly, formally or informally, to determine if something is going to be valuable for our purpose and whether we trust the content it provides.

In the context of a literature search, critical appraisal is the process of systematically evaluating and assessing the research you have found in order to determine its quality and validity. It is essential to evidence-based practice.

More formally, critical appraisal is a systematic evaluation of research papers in order to answer the following questions:

• Does this study address a clearly focused question?
• Did the study use valid methods to address this question?
• Are there factors, based on the study type, that might have confounded its results?
• Are the valid results of this study important?
• What are the confines of what can be concluded from the study?
• Are these valid, important, though possibly limited, results applicable to my own research?

What is quality and how do you assess it?

In research we commissioned in 2018, researchers told us that they define ‘high quality evidence’ by factors such as:

• Publication in a journal they consider reputable or with a high Impact Factor.
• The peer review process, coordinated by publishers and carried out by other researchers.
• Research institutions and authors who undertake quality research, and with whom they are familiar.

In other words, researchers use their own experience and expertise to assess quality.

However, students and early career researchers are unlikely to have built up that level of experience, and no matter how experienced a researcher is, there are certain times (for instance, when conducting a systematic review) when they will need to take a very close look at the validity of research articles.

There are checklists available to help with critical appraisal.  The checklists outline the key questions to ask for a specific study design.  Examples can be found in the  Critical Appraisal  section of this guide, and the Further Resources section.  

You may also find it beneficial to discuss issues such as quality and reputation with:

• Your principal investigator (PI)
• Your supervisor or other senior colleagues
• Journal clubs. These are sometimes held by faculty or within organisations to encourage researchers to work together to discover and critically appraise information.
• Topic-specific working groups

The more you practice critical appraisal, the quicker and more confident you will become at it.

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Critical Appraisal Questionnaires

Critical appraisal is the process of carefully and systematically assessing the outcome of scientific research (evidence) to judge its trustworthiness, value and relevance in a particular context. Critical appraisal looks at the way a study is conducted and examines factors such as internal validity, generalizability and relevance.

Some initial appraisal questions you could ask are:

• Is the evidence from a known, reputable source?
• Has the evidence been evaluated in any way? If so, how and by whom?
• How up-to-date is the evidence?

Second, you could look at the study itself and ask the following general appraisal questions:

• How was the outcome measured?
• Is that a reliable way to measure?
• How large was the effect size?
• What implications does the study have for your practice? Is it relevant?
• Can the results be applied to your organization?

Questionnaires

If you would like to critically appraise a study, we strongly recommend using the app we have developed for iOS and Android:  CAT Manager App

You could also consider using the following appraisal questionnaires (checklists) for specific study designs, but we do not recommend this. 

Appraisal of a meta-analysis or systematic review

Appraisal of a controlled study, appraisal of a cohort or panel study, appraisal of a case control study, appraisal of a cross-sectional study (survey), appraisal of a qualitative study, appraisal of a case study.

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Critical Appraisal : What is critical appraisal?

What is critical appraisal.

• Where to start
• Education and childhood studies
• Occupational Therapy
• Physiotherapy
• Interpreting statistics
• Further reading and resources

About this guide

This guide is designed to help students (mainly in Health Sciences, but there are checklist tools for Business and Education students) to understand the purpose and process of critical appraisal, and different methods and frameworks that can be used in different contexts.

Critical appraisal is an essential step in any evidence based process and it is defined by CASP as "t he process of assessing and interpreting evidence by systematically considering its validity , results and relevance ".

The hierarchy of evidence pyramid below provides a means to visualise the levels of evidence as well as the amount of evidence available. Systematic reviews and meta-analyses are the highest level of evidence therefore they are at the top of the pyramid but they are also the least common because they are based on the studies below them.  Moving down the pyramid, the amount of studies increases but the level of evidence decreases. The use of the hierarchy of evidence pyramid is not enough to determine the quality of research because study types can vary in quality whether it is a systematic review or a case study therefore critical appraisal skills are required to evaluate all types of evidence regardless of their level. It is important to apply your own critical appraisal skills when you evaluate research studies to decide if they merit being considered or used as reliable sources of information. Some studies have found that many research findings in published articles may in fact be false  ( Ioannidis, 2005 ).  In the worst cases, some researchers may commit research fraud to acquire research grants  ( Harvey, 2020 ).

Image: Weill Cornell Medicine (2024) Adapted from DiCenso A, Bayley L, Haynes R.B. (2009) 'ACP Journal Club. Editorial: Accessing preappraised evidence: fine-tuning the 5S model into a 6S model'. Annals of Internal Medicine , 151(6), JC3. Available at: https://med.cornell.libguides.com/

Critical appraisal involves using a set of systematic techniques that enable you to evaluate the quality of published research including the research methodology, potential bias, strengths and weaknesses and, ultimately, its trustworthiness. It is often the case that even peer-reviewed research can have methodological flaws, incorrectly interpret data, draw incorrect conclusions or exaggerate findings. A uthors' affiliations, funding sources, study design flaws, sample size and potential bias are only some of the factors that can lead you to include poor quality research in your own work if not addressed through critical appraisal.

Critical appraisal often involves the  use of checklists to guide you to look out for specific areas in the appraisal process. Checklists vary according to types of research or study designs you are evaluating.

It is important therefore that you possess a good knowledge of research methods in your field of study and a good basic understanding of statistics where statistical analysis is involved.

Please see read  What is critical appraisal?   and see the resources on this page for further information on critical appraisal.

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Critical appraisal (CA) is an essential step in validating evidence based medicine (EBM), and the internet is a powerful tool to improve your understanding of CA.

The Public Health Resource Unit's website ( www.phru.nhs.uk/casp/appraisa.htm ) provides useful and easy checklists. You select the article that you wish to make the critical appraisal for, decide the type of study, and then download the relevant checklist. By answering the questions in the checklist, you will reach a conclusion about the usefulness of the article. In addition, there are non-virtual workshops that you may subscribe to, but these may lack the benefit of convenience offered by online learning.

The University of Birmingham offers a simple and useful presentation about critical appraisal ( www.bham.ac.uk/arif/casp/caspslides_files/frame.htm ), which provides a clear idea about CA. If CA is new to you this might be an ideal source and may also be used in departmental teaching.

In the Centre for Evidence-Based Medicine in Oxford ( www.cebm.net/cats.asp ) the Critically Appraised Topics Program, “CAT”, is a simple software program that helps clinicians to summarise the evidence. The program can be used to save any CA you have done on a previous occasion. When you access the site, if, for example, there is debate about some research that you have already appraised, you will be able to use the program as proof that you have done so.

The University of Sheffield's website ( www.shef.ac.uk/scharr/ir/units/critapp/index.htm ) gives further options in offering you guidance in how to appraise websites, how to present CA, and also links to other web resources including many from the BMJ .

The University of Alberta, Canada's website ( www.med.ualberta.ca/ebm ) gives free statistical analysis software for power and sample size, which is essential for the value of a study. EBM calculations are also available, plus checklists of a similar format to those found on the Public Health Resource Unit's website.

Finally, if you are registered with the Journal of the American Medical Association ( JAMA ), ( http://ugi.usersguides.org/usersguides/hg/hh_logon.asp? ) you will have access to the User Guide to Medical Literature. This is a good text about CA made available online, and is unlikely to leave any of your questions unanswered. Access is also allowed to fellows, members, and registered trainees of the Royal College of Obstetricians and Gynaecologists (RCOG) ( www.rcog.org.uk ). To gain access you must go to the secure site, then to information services, straight to E journals, look for the JAMA shortcut, and then obtain a user-name and password.

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• About RCS England

• Dissecting the literature: the importance of critical appraisal

08 Dec 2017

Kirsty Morrison

This post was updated  in 2023.

Critical appraisal is the process of carefully and systematically examining research to judge its trustworthiness, and its value and relevance in a particular context.

Amanda Burls, What is Critical Appraisal?

Why is critical appraisal needed?

Literature searches using databases like Medline or EMBASE often result in an overwhelming volume of results which can vary in quality. Similarly, those who browse medical literature for the purposes of CPD or in response to a clinical query will know that there are vast amounts of content available. Critical appraisal helps to reduce the burden and allow you to focus on articles that are relevant to the research question, and that can reliably support or refute its claims with high-quality evidence, or identify high-level research relevant to your practice.

Critical appraisal allows us to:

• reduce information overload by eliminating irrelevant or weak studies
• identify the most relevant papers
• distinguish evidence from opinion, assumptions, misreporting, and belief
• assess the validity of the study
• assess the usefulness and clinical applicability of the study
• recognise any potential for bias.

Critical appraisal helps to separate what is significant from what is not. One way we use critical appraisal in the Library is to prioritise the most clinically relevant content for our Current Awareness Updates .

How to critically appraise a paper

There are some general rules to help you, including a range of checklists highlighted at the end of this blog. Some key questions to consider when critically appraising a paper:

• Is the study question relevant to my field?
• Does the study add anything new to the evidence in my field?
• What type of research question is being asked? A well-developed research question usually identifies three components: the group or population of patients, the studied parameter (e.g. a therapy or clinical intervention) and outcomes of interest.
• Was the study design appropriate for the research question? You can learn more about different study types and the hierarchy of evidence here .
• Did the methodology address important potential sources of bias? Bias can be attributed to chance (e.g. random error) or to the study methods (systematic bias).
• Was the study performed according to the original protocol? Deviations from the planned protocol can affect the validity or relevance of a study, e.g. a decrease in the studied population over the course of a randomised controlled trial .
• Does the study test a stated hypothesis? Is there a clear statement of what the investigators expect the study to find which can be tested, and confirmed or refuted.
• Were the statistical analyses performed correctly? The approach to dealing with missing data, and the statistical techniques that have been applied should be specified. Original data should be presented clearly so that readers can check the statistical accuracy of the paper.
• Do the data justify the conclusions? Watch out for definite conclusions based on statistically insignificant results, generalised findings from a small sample size, and statistically significant associations being misinterpreted to imply a cause and effect.
• Are there any conflicts of interest? Who has funded the study and can we trust their objectivity? Do the authors have any potential conflicts of interest, and have these been declared?

And an important consideration for surgeons:

• Will the results help me manage my patients?

At the end of the appraisal process you should have a better appreciation of how strong the evidence is, and ultimately whether or not you should apply it to your patients.

Further resources:

• How to Read a Paper by Trisha Greenhalgh
• The Doctor’s Guide to Critical Appraisal by Narinder Kaur Gosall
• CASP checklists
• CEBM Critical Appraisal Tools
• Critical Appraisal: a checklist
• Critical Appraisal of a Journal Article (PDF)
• Introduction to...Critical appraisal of literature
• Reporting guidelines for the main study types

Kirsty Morrison, Information Specialist

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• Library Blog

• Last edited on January 21, 2024

Critical Appraisal and Statistics

Table of contents, random error vs. systematic error (bias), the research question, inclusion/exclusion criteria, study design, randomization, cross-sectional, case-control, case-non-case, national registers, network meta-analyses, cheat sheet, effect sizes (cohen's d), poor statistical methodologies, results section, results: means, results: risk, relative risk (rr), relative risk reduction (rrr), absolute risk reduction (arr), number needed to treat (nnt), odds ratio (or), hazard ratios (hr), linear regression, confidence intervals (ci), bradford-hill criteria, placebo effect, evidence-based medicine, replication crisis, scientific misconduct.

Critical Appraisal is the process of carefully and systematically assessing the outcome of scientific research (evidence) to judge its trustworthiness, value, and relevance in a particular clinical context. When critically appraising a research study, you want to think about and comment on:

• How solid is the rationale for the research question?
• How important is the research question?
• What is the potential impact of answering it? (clinically, research, health policies, etc…)
• Can I trust the results of this research?

Having a systematic approach to critically appraising a piece of research can be helpful. Below is a guide.

Before You Begin... Read This Section First

Errors and biases.

Random error is an error in a study that occurs due to pure random chance. For example, if the inherent prevalence of depression is 4%, and we do a study with sample size of 100 examining the prevalence of depression, the study could by pure random chance have 0 people with people depression even though the prevalence is 4%. Increasing the sample size decreases the likelihood of random errors occuring, because increases your power to detect findings.

Systematic error is also known as bias . This is an error in the design, conduct, or analysis of a study that results in a mistaken estimate of a treatment's or exposure's effect on the risk or outcome of a disease. These errors can distort the results of a study in a particular direction (e.g. - favouring a medication treatment, or not favouring a treatment).

The Eternal Challenge in Medical Research

Systematic errors (i.e. - biases) can threaten the validity of a study. There are two types of validity:

• External Validity : How generalizable are the findings of the study to the patient you see in front of you
• Internal Validity : Is the study actually measuring and investigating what it set out to do in the study?

There are many types of biases, and some of them are listed out in the table below. Researchers also use more comprehensive tools to measure and assess for bias. The most commonly used tool is the Cochrane Risk of Bias Tool . The components of the Cochrane Risk of Bias Tool is not described here.

Examples of Biases

More Reading:

• O’Sullivan, J. W., Banerjee, A., Heneghan, C., & Pluddemann, A. (2018). Verification bias. BMJ evidence-based medicine.
• Residual Confounding, Confounding by Indication, & Reverse Causality

A research question that leads to a research study is often quite general, but the answer that we get from a published research study is actually extremely specific. As an example, as a researcher, I might want to know if a new SSRI is more effective than older SSRIs. This seems like an easy question to answer, but the reality is much more complicated. When looking at the results of a study, you want to think how specific or generalizable are the findings?

Study Population

Ask yourself, what is the target population in the research question? Then ask yourself, does the study sample itself actually represent this target population? Sometimes, the study sample will be systematically different from the target population and this can reduce the external validity/generalizability of the findings (also known as sampling bias). After this, you should look at the inclusion and exclusion criteria for the participants:

• Diagnoses and medical conditions
• Medications
• Demographics
• Clinical Characteristics
• Geographic Characteristics
• Temporal Characteristics
• High likelihood of being lost to follow-up
• Inability to provide good data
• High risk of side effects
• Any characteristic that has possibility of confounding the outcomes

Different study designs have different limitations. Having an understanding of each type of common study design is an important part of critically appraising a study. The most common study designs in psychiatric research are experimental designs, such as randomized controlled trials, and observational studies, including: cross-sectional, cohort, and case-control.

Comparison of Common Study Types

Randomization Controlled Trials

Randomized Control Trials (RCTs) allows us to do a true experiment to test a hypothesis. Randomization with sufficient sample sizes, that both measurable and unmeasurable variables are even distributed across the treatment and non-treatment groups. It also ensures that reasons for assignment to treatment or no treatment are not biased (avoids selection bias).

• Check if randomization (of measured factors) was achieved – look at the demographics table (Table 1) to see if both groups seem similar. (However, just because the p value is > 0.05 does not mean randomization was successful)
• The researcher who allocates participants to treatment groups (avoids selection bias)
• Patients in the study (avoids desirability bias)
• Care providers (avoids subconsciously managing patients differently)
• Assessors (avoids measurement bias)

Blinding is of course not always possible (e.g. - an active medication may have a very obvious side effect that a placebo doesn't have, making it very obvious to the participant if they are on a placebo or not). One needs to understand potential impact of the breaking of the blind in these studies. Some studies may therefore implement active placebos rather than inert placebos, to counter this potential bias. [1]

What Are the Limitations of RCTs?

Why do we even need a control/placebo group anyways.

• Regression to the mean : on repeated measurements over time, extreme values or symptoms tend to move closer to the mean (i.e. - people tend to get better over time, especially in psychiatric disorders such as depression and anxiety).
• Hawthorne Effect : participants have a tendency to improve based on being in clinical trial, because they are aware they are being observed.
• Desirability Bias :patient/rater wanting to show that treatment works

The presence of a placebo or control group can adequately account for these confounding factors.

More Reading

• Slate Star Codex: The Control Group Is Out Of Control
• Mataix-Cols, D., & Andersson, E. Ten Practical Recommendations for Improving Blinding Integrity and Reporting in Psychotherapy Trials. JAMA Psychiatry.
• Stroup, T. S., & Geddes, J. R. (2008). Randomized controlled trials for schizophrenia: study designs targeted to distinct goals. Schizophrenia bulletin, 34(2), 266
• Bland, J. M., & Altman, D. G. (1994). Regression towards the mean. BMJ: British Medical Journal, 308(6942), 1499.
• Hengartner, M. P. (2019). Is there a genuine placebo effect in acute depression treatments? A reassessment of regression to the mean and spontaneous remission. BMJ evidence-based medicine, bmjebm-2019.
• Perlis, R. H., Ostacher, M., Fava, M., Nierenberg, A. A., Sachs, G. S., & Rosenbaum, J. F. (2010). Assuring that double-blind is blind. American Journal of Psychiatry, 167(3), 250-252.
• Moncrieff, J., Wessely, S., & Hardy, R. (1998). Active placebos versus antidepressants for depression. Cochrane Database of Systematic Reviews, (3).

Why are clinical studies so obsessed with randomization and randomized control trials (RCTs) ? Randomization allows us to balance out not just both known biases and factors, but more importantly, unknown biases and risk factors. Randomization saves us from the arduous process of needing to account for every single possible bias or factor in a study. For example, in a study looking at the effectiveness of an antidepressant versus a placebo, a possible bias that might affect the result could be might be gender or other medication use (something you can measure). Of course, you try to skip randomization, and try to divide the groups equally amongst gender and medication use by yourself. However, unmeasurable factors (like family support, resiliency, genetics) might also affect a participant's response to medications.

Randomization is Hard

The beauty of a properly done randomization is you can eliminate (or come close to eliminating) all the unknown factors. This way, you can be sure that the outcomes of your study are not affected by these factors since randomization should equally distribute all known and unknown factors amongst all treatment groups. Randomization is most effective when sample sizes are large. When studies have small sample sizes, they are called underpowered studies, which makes it hard to ensure the sample has been adequately randomized.

Observational Studies

• Thiese, M. S. (2014). Observational and interventional study design types; an overview. Biochemia medica: Biochemia medica, 24(2), 199-210.
• Song, J. W., & Chung, K. C. (2010). Observational studies: cohort and case-control studies. Plastic and reconstructive surgery, 126(6), 2234.
• Brazauskas, R., & Logan, B. R. (2016). Observational studies: matching or regression?. Biology of Blood and Marrow Transplantation, 22(3), 557-563.
• Tanaka, S. et al. (2015). Methodological issues in observational studies and non-randomized controlled trials in oncology in the era of big data. Japanese journal of clinical oncology, 45(4), 323-327.

Observational Studies are studies where researchers observe the effect of a risk factor, medical test, treatment or other intervention without trying to change who is or is not exposed to it. Thus these studies do not have randomization and do not have control groups. Observational studies come in several flavours, including cross-sectional, cohort, and case-control studies.

• e.g. - Point prevalence: at one specific point in time
• e.g. - Period prevalence: within 1 month period, within 12 month period
• You cannot infer causality from cross-sectional studies, only associations
• There is a risk for sampling Bias because you have no control over who is being measured at this specific point in time
• Faresjö, T., & Faresjö, Å. (2010). To match or not to match in epidemiological studies—same outcome but less power. International journal of environmental research and public health, 7(1), 325-332.

Case-control studies (also known as retrospective studies) are studies where there are “cases” that already have the outcome data (e.g. - completed suicide, diagnosis of depression, diagnosis of dementia), and “controls” that do not have the outcome (hence the name case-control). Rather than watch for disease or outcome development, case-control studies look for and compare the prevalence of risk factors that lead to the outcome happening. For example, a research might look at antidepressant use, and whether that affects the outcome they already know (e.g. - cases of completed suicides)

• Case-control studies are always retrospective (looking into the past!)
• Rather than watch for outcome (i.e. - disease development), compare prevalence of risk factors
• “Cases” have the outcome (i.e. - completed suicide, dementia diagnosis, depression diagnosis); “controls” do not
• Since you already have selected a predetermined number of people with and without the disease, you cannot calculate a relative risk (RR). However, you can calculate an odds ratio (OR).
• This is the only way to study rare diseases, since you already know how many cases there are!
• It is inexpensive because it invariably uses pre-existing data
• You want to make sure that cases are not “atypical” presentations of a disease
• To mitigate this: try to include all cases that are a representative sample of the population
• You need to make sure that the outcome cases are relatively similar to controls other than on the exposure. Otherwise, the controls might never even have been exposed to the risk factor or have very little chance of developing the outcome!
• To mitigate this: Select controls from same population as cases, match cases and controls on key variables, and have multiple control groups
• The outcome cases more likely to remember an exposure than the controls (e.g. - asbestos and lung cancer)
• To mitigate this: use records kept from before the outcome occurred, and in some cases, the keep exact hypothesis concealed from the case (i.e. - person) being studied
• Faillie, J. L. (2017). Case-non case studies: principles, methods, bias and interpretation. Therapie, 73(3), 247-255.
• Reeves, B. C. (2019). Appraising descriptive and analytic findings of large cohort studies. CMAJ, 191(30), E828-E829.

A cohort study (also known as a prospective study) follows a group of subjects over time .

• It is the only way to describe incidence (incidence = number of new cases /time )
• It is a little better for inferring causality, but can take a long follow up time, and you need a large sample size
• Unlike a case-control study, you can also calculate a relative risk (RR) of a given outcome (i.e. - you can compares outcome between 2 groups who differ on a certain risk factor)
• Usually you have an exposure or a risk factor (e.g. - antidepressant) plus an outcome (e.g. - dementia)
• e.g. - those who take antidepressants might have more severe depression than those who do not
• e.g. - depression might be a confounding factor for dementia
• When looking at cohort studies, it is important to pay attention to the demographics table (“Table 1”), and look for selection bias and important confounding factors. Also try to think of other factors that might not have been measured in the study. This is an important issue with retrospective studies (relative to RCTs), since researchers do not have control over what was measured!

Key Difference Between Cohort and Case-Control Studies

• In cohort studies , the participant's groups are classified according to their exposure status (whether or not they have the risk/exposure factor). Cohort studies follow an exposure over time and looks to see whether it will cause disease. You can calculate a relative risk (RR).
• In case-control studies , the different groups are identified according to their already known health outcomes (whether or not they have the disease ). You already know who has what disease, and are now travelling back in time to find out what risk factors may have played a role. You can only calculate an odds ratio (OR), and cannot calculate an RR from a cohort study.
• Sedgwick, P. (2014). What is an open label trial?. BMJ: British Medical Journal (Online), 348.
• Leucht, S., & Davis, J. M. (2018). Enthusiasm and Skepticism About Using National Registers to Analyze Psychotropic Drug Outcomes. JAMA psychiatry.

Systematic Reviews and Meta-Analyses

• Berlin, J. A., & Golub, R. M. (2014). Meta-analysis as evidence: building a better pyramid. Jama, 312(6), 603-606.
• Barnard, N. D. et al. (2017). The Misuse of Meta-analysis in Nutrition Research. JAMA.
• Efthimiou, O. (2018). Practical guide to the meta-analysis of rare events. Evidence-based mental health, 21(2), 72-76.
• Ioannidis, J. P. (2016). The mass production of redundant, misleading, and conflicted systematic reviews and meta‐analyses. The Milbank Quarterly, 94(3), 485-514.

Systematic Reviews (SR) and Meta-Analyses (MA) synthesize all the available evidence in the scientific literature to answer a specific research question. Systematic reviews describes outcomes of each study individually (always look for a forest plot in the paper). The meta-analysis is an extension of a systematic review that uses complex statistics to combine outcomes (if outcomes of different studies are similar enough). In most meta-analyses, there are usually strict criteria for study inclusion that usually weeds out flawed research study. However, this is not always the case! Poor study selection can often result in flawed meta-analysis findings (garbage in = garbage out)! It is also important to watch for publication bias (i.e. - certain articles might be favoured over others).

• Stein, M. B., & Norman, S. B. (2019). When does meta-analysis of a network not work?: Fishing for answers. JAMA psychiatry, 76(9), 885-886.
• Bayes for Clinicians Who Need to Know but Don’t Like Math

Statistical Tests

Statistical Significance

• McShane, B. B., & Gal, D. (2017). Rejoinder: Statistical significance and the dichotomization of evidence. Journal of the American Statistical Association, 112(519), 904-908.
• Abandon Statistical Significance
• FiveThirtyEight: Hack Your Way To Scientific Glory
• Ioannidis, J. P. (2018). The proposal to lower p value thresholds to. 005. Jama, 319(14), 1429-1430
• FiveThirtyEight: Not Even Scientists Can Easily Explain P-values
• Altman, D. G., & Bland, J. M. (1995). Statistics notes: Absence of evidence is not evidence of absence. Bmj, 311(7003), 485.

Manipulating the Alpha Level Cannot Cure Significance Testing

• Interpreting Cohen's d Effect Size: An Interactive Visualization
• This is what you will often see in an RCT to illustrate the magnitude of an effect
• Can just mean a difference between means, or it can be standardized (e.g. Cohen’s d = difference between means/SD)
• Often described as small, medium or large
• For Cohen’s d: 0.2 is small, 0.5 is med, > 0.8 is large
• SlateStarCodex: Two Dark Side Statistics Papers

Depending on the design of the study, the results section will look very different. However, all studies should:

• Describe the sample (prevalence, incidence, and a “Table 1” of demographics)
• Show the relationships between factors (e.g. - treatment and outcome, risk factor and outcome)
• Tell you how large was a treatment effect (if looking at this)

Results may first compare the mean (average) between a treatment or non-treatment group:

• T-test, F-test (ANOVA): if p<0.05, then there is a significant difference
• See this in your “Table 1s” and in primary analysis of RCT outcomes
• If making multiple comparisons (tests) then you increase the chance that there will, by chance, be a significant result that is a false positive (Type I error), you can adjust for this using the Bonferroni correction .

Results can be expressed in a number of ways, including:

• Relative Risk
• Relative Risk Reduction
• Number Needed To Treat (NNT)
• Number Needed to Harm (NNH)

How Might The Results Be Misleading?

• If you calculate the relative risk reduction (RRR), it is 25% (1 ÷ 4 = 0.25)
• If however, you calculate the absolute risk reduction (ARR), it is only 0.1% (1 ÷ 1000 = 0.001)!!
• A drug company might be inclined publish the relative risk and relative risk reduction to make the benefits look great (Wow! We can advertise a 25% reduction in deaths!). On the flip aside, they might want to market side effects by expressing it in absolute risks instead (to make it seem much less). So you might read an article that Drug A will lower the risk of deaths by 25% (over-selling the drug) and the risks of developing side effects is very small (under-estimating the side effects).
• One should always express the risk in absolute and avoid percentages. So if the absolute risk reduction with this new drug is 0.1%, it means you need to treat 1,000 people with the drug to prevent 1 death. Does not sound as great as a drug that “reduces mortality by 25%”, now does it? Always get the ABSOLUTE !

</WRAP>

Measuring Treatment Effect

Relative Risk (RR) is a ratio of the probability of an outcome in an exposed group compared to the probability of an outcome in an unexposed group

• Dichotomous variables can offer relative risk calculations of an event happening (i.e. - risk in group 1 relative to risk in group 2)
• RR is used for cohort studies, and randomized control trials
• RR tells us how strongly related 2 factors are but says nothing about the magnitude of the risk.
• If RR = 1, then both groups have equal risk

Interpreting Relative Risk (RR)

Relative risk reduction (RRR) measures how much the risk is reduced in the experimental group compared to a control group. For example, if 50% of the control group died and 25% of the treated group died, the treatment would have a relative risk reduction of 0.5 or 50% (the rate of death in the treated group is half of that in the control group).

Absolute Risk Reduction (ARR) is the absolute difference in outcome rates between the control and treatment groups (i.e. - CER - EER). Since ARR does not involve an explicit comparison to the control group like RRR, it does not confound the effect size of the treatment/intervention with the baseline risk.

Number Needed to Treat (NNT) is another way to express the absolute risk reduction (ARR). NNT answers the question “How many people do you need to treat to get one person to remission, or to prevent one bad outcome?” To compare, a RR and RRR value might appear impressive, but it does not tell you how many patients would you actually need to treat before seeing a benefit. The NNT is one of the most intuitive statistics to help answer this question. In general a NNT between 2-4 means there is an excellent benefit (e.g. - antibiotics for infection), NNT between 5-7 is associated with a meaningful health benefit (e.g. - antidepressants), while NNT >10 is at most associated with a small net health benefit (e.g. - using statins to prevent heart attacks). [4]

• Andrade, C. (2015). Understanding relative risk, odds ratio, and related terms: as simple as it can get. The Journal of clinical psychiatry, 76(7), 0-0.
• Bland, J. M., & Altman, D. G. (2000). The odds ratio. Bmj, 320(7247), 1468.
• Odds Ratio = odds that a case is exposed/odds that a case is not exposed
• Used for case-control studies because there is no way to compute the risk of the outcome (i.e. - because you started with the outcome already)
• Very frequently used because it is the output of a logistic regression
• Note that as a rule of thumb, if the outcome occurs in less than 10% of the unexposed population, the OR provides a reasonable approximation of the RR.
• If OR = 1, then equal odds for both exposed and non-exposed groups (lower bound is 0)

Interpreting Odds Ratio (OR)

• = a/(a + b) ÷ c/(c + d)
• = 2/(2 + 248) ÷ 3/(3 + 747)
• = (a ÷ c) ÷ (b ÷ d)
• = (a × d) ÷ (b × c)
• = (2 × 747) ÷ (3 × 248)
• OR = 2.0080645161 = 2.01

Note that even though RR and OR both = 2, they do not mean the same thing!

• An OR = 1.2 = there is a 20% increase in the odds of an outcome (not risk) with a given exposure
• This can also be stated that there is a doubling of the odds of the outcome (e.g. - high pesticides exposure are 2 times as likely to have lukemia)
• Note, this is not the same as saying a doubling of the risk (i.e. - RR = 2.0)
• An OR = 0.2 means there is am 80% decrease in the odds of an outcome with a given exposure
• Covariate Selection
• Censoring in Time-to-Event Analysis
• Tutorial about Hazard Ratios

In psychiatry, studies may typically look at the time to relapse for an event (e.g. - time until a depressive episode relapse). There are several “buzz words” that may be used:

• Univariate analysis means there are Kaplan-Meier Curves
• Multivariable analyses most commonly use Cox proportional hazard modelling
• Censoring allows for analysis of data when the outcome [dependent variable] has not yet occurred for some patients in the study
• e.g. - a 5-year study looking a diagnosis of dementia, but not all participants have dementia by the end of the 5-year study
• [chance of an event occurring in the treatment arm]/[chance of an event occurring in the control arm], or
• [risk of outcome in one group]/[risk of outcome in another group]… occurring over a given interval of time

Linear regression generates a beta, which is the slope of a line

• Beta = 0 means no relationship (horizontal line)
• Beta > 0 means positive relationship
• Beta < 0 means negative relationship
• Range of values within which the true mean of the population is expected to fall, with a specified probability.
• CI for sample mean = x ± Z(SE)
• The 95% CI (α = 0.05) is often used
• As sample size increases, CI narrows
• For the 95% CI, Z = 1.96
• For the 99% CI, Z = 2.58

Interpreting Confidence Intervals (CI)

Most studies only demonstrate an association (e.g. - antidepressant use in pregnancy associated with an increased rate of preterm birth). How can we decide whether association is, in fact, causation? (e.g. -Does anti-depressant use in pregnancy actually cause preterm birth?). The Bradford Hill criteria, otherwise known as Hill's criteria for causation, are a group of nine principles that can be useful in establishing epidemiologic evidence of a causal relationship between a presumed cause and an observed effect

• Researcher controls assignment of subjects and exposure
• Strength of Association : what is the size of relative risk or odds ratio (remember, RR or OR = 1 means no association)
• Consistency : same estimates of risk between different studies
• Gradient : increasing the exposure results in increasing rate of the occurrence
• Biological and Clinical Plausibility : judgement as to plausibility based on clinical experience and known evidence
• Specificity : when an exposure factor is known to associated only with the outcome of interest and when outcome not caused by or associated with other risk factors (e.g. - thalidomide)
• Coherence : also called “triangulation”: when the evidence from disparate types of studies “hang together”
• Temporality : realistic timing of outcome based on exposure
• Analogy : similar associations or causal relationships found in other relevant areas of epidemiology

Other Issues

• Ioannidis, J. P. (2016). Evidence-based medicine has been hijacked: a report to David Sackett. Journal of clinical epidemiology, 73, 82-86.
• Jureidini, J., & McHenry, L. B. (2022). The illusion of evidence based medicine. bmj, 376.
• Greenhalgh, T., Howick, J., & Maskrey, N. (2014). Evidence based medicine: a movement in crisis?. Bmj, 348.
• Isaacs, D., & Fitzgerald, D. (1999). Seven alternatives to evidence based medicine. Bmj, 319(7225), 1618.
• Braithwaite, R. S. (2020). EBM’s six dangerous words. JAMA, 323(17), 1676-1677.

Evidence-Based Medicine (EBM) typically will depend on the use of statistical and critical appraisal approaches. However, there are also inherent limitations and potential issues with the way EBM is applied in current medical research.

• Oza, A. (2023). Reproducibility trial: 246 biologists get different results from same data sets. Nature, 622(7984), 677-678.
• Bishop, D. (2019). Rein in the four horsemen of irreproducibility. Nature, 568(7753)
• Nature: Replication failures in psychology not due to differences in study populations
• Eric J. Topol, John P. A. Ioannidis. Ioannidis: Most Research Is Flawed; Let's Fix It - Medscape - Jun 25, 2018
• Sox, H. C., & Rennie, D. (2006). Research misconduct, retraction, and cleansing the medical literature: lessons from the Poehlman case. Annals of Internal Medicine, 144(8), 609-613.
• Substack: Stop and Think - If only critical appraisal was this good for *all* studies
• Rational Psychiatry: How To Read a Paper (Thomas Reilly )

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 a harder job 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 having an understanding of 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.  
• “ Clinical evidence made easy ” contains several chapters on different study designs and also includes critical appraisal tools. (3)  
• “ 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. (4)  
• 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. Harris M, Jackson D, Taylor G. Clinical evidence made easy. Oxfordshire, England: Scion Publishing; 2014.

4. 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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Critical Appraisal of Clinical Research

Affiliations.

• 1 Professor, Department of Orthodontics, King Saud bin Abdul Aziz University for Health Sciences-College of Dentistry, Riyadh, Kingdom of Saudi Arabia.
• 2 Associate Professor, Department of Oral and Maxillofacial Surgery, Al Farabi Dental College, Riyadh, KSA.
• PMID: 28658805
• PMCID: PMC5483707
• DOI: 10.7860/JCDR/2017/26047.9942

Evidence-based practice is the integration of individual clinical expertise with the best available external clinical evidence from systematic research and patient's values and expectations into the decision making process for patient care. It is a fundamental skill to be able to identify and appraise the best available evidence in order to integrate it with your own clinical experience and patients values. The aim of this article is to provide a robust and simple process for assessing the credibility of articles and their value to your clinical practice.

Keywords: Evidence-based practice; Method assessment; Research design.

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Factors affecting the critical appraisal of research articles in Evidence‐Based practices by advanced practice nurses: A descriptive qualitative study

Ai tomotaki.

1 Faculty of Nursing, School of Medicine, Tokai University, Isehara‐shi Kanagawa, Japan

Ikuko Sakai

2 Department of Nursing Systems Management, Graduate School of Nursing, Chiba University, Chiba‐shi Chiba, Japan

Hiroki Fukahori

3 Faculty of Nursing and Medical Care, Keio University, Fujisawa‐shi Kanagawa, Japan

Yasunobu Tsuda

4 St. Marianna University Hospital, Kawasaki‐shi Kanagawa, Japan

Akemi Okumura‐Hiroshige

5 Department of Nursing Science, Faculty of Health Sciences, Tokyo Metropolitan University, Arakawa‐ku Tokyo, Japan

Associated Data

The data that support the findings of this study are available from the corresponding author upon reasonable request.

To describe factors affecting critical appraisal of research articles in evidence‐based practice by certified nurse specialists who were advanced practice nurses in Japan.

A descriptive qualitative study.

Fourteen certified nurse specialists with master's degree were included by a snowball sampling to maximize the variety of specialty fields for advanced practice nurses in Japan. Individual semi‐structured interviews were conducted between November 2016 and March 2017. Interview guides included the experience of evidence‐based practice and learning about critical appraisal.

The following four aspects were identified as factors affecting the critical appraisal of research articles in evidence‐based practices—individual beliefs and attitude, learning status, organizational readiness and availability of research evidence. Each factor included both positive and negative aspects for critical appraisal in evidence‐based practice.

Patient or Public Contribution

If advanced practice nurses acquire knowledge/skills of critical appraisal, they would be able to select more appropriate care. This will increase to improve the health‐related outcome for patients or populations.

1. INTRODUCTION

Evidence‐based medicine has been defined as the integration of best research evidence, clinical expertise, and the patient's unique values and circumstances (Straus et al.,  2019 ). The process is based on the following five steps: ask, acquire, appraise, apply and assess. This definition has been adopted in various medical fields, and evidence‐based practice (EBP) is one of the core competencies for clinical nurses and the foundations of nursing and healthcare (Melnyk et al.,  2018 ).

Generally, clinical nurses have recognized the importance of EBP. However, the self‐evaluations have revealed a low frequency of engagement (Melnyk et al.,  2018 ; Saunders & Vehviläinen‐Julkunen,  2016 ; Tomotaki et al.,  2020 ). The previous studies reported that nurses lack knowledge and skills in statistics and research design (Hines et al.,  2021 ; Saunders & Vehviläinen‐Julkunen,  2016 ) and there is little time to do “appraise” in the five steps of EBP (Tomotaki et al.,  2020 ). A critical appraisal of research articles evaluates and discusses the validity of the study design and methodology, effect size and precision, and applicability to one's own clinical setting (Straus et al.,  2019 ). Lack of knowledge and skills in these research activities is a barrier to doing EBP for many clinical nurses, which indicate the importance of strengthening education, especially about critical appraisal in EBP.

The curriculum to enhance EBP should include both clinical practice and research and such education is provided in graduate school for advanced practice nurses (APNs). An APN is a generalist or specialized nurse who has acquired, through additional graduate education with a master's or doctoral degree (International Council of Nurses,  2022 ). They are especially expected to take on the role of enhancing EBP (Institute of Medicine of the National Academies,  2011 ). APNs' competencies for EBP are higher than other clinical nurses (Melnyk et al.,  2018 ), but the frequency was low. In Japan, certified nurse specialists (CNSs) with master's degree are recognized as APNs and will be expected as leaders in enhancing EBP (Subcommittee on Nursing Science, Committee on Health/Human Life Science, Science Council of Japan,  2011 ). The CNS system was the first certification system adopted in Japan for training APNs at the graduate level.

1.1. Background

EBP education is provided in continuous education for professionals, including in undergraduate and graduate schools, and on‐the‐job training (OJT) as clinical practitioners. Examples of OJT for EBP include participating in an EBP implementation project or journal clubs (Häggman‐Laitila et al.,  2016 ). Through activity in a journal club, clinical practitioners have an opportunity to reflect on their own professional practice and can increase their confidence in daily practice when their clinical experience links to research findings (Beck et al.,  2020 ). Such journal clubs, and EBP rounds, are incorporated into the EBP implementation strategy model termed Advancing Research and Clinical Practice Through Close Collaboration Model (Melnyk & Fineout‐Overholt,  2018 ).

Many previous studies of EBP education include programs for critical appraisal (Albarqouni et al.,  2018 ). However, effective EBP education has not yet been established (Lehane et al.,  2019 ). It requires to strengthen design and develop interventions considering principles (e.g. motivations, barriers) that are particular to the learner, including the interaction between the characteristics of EBP learners and the development of EBP competencies. This might mean that traditional empirical studies are limited in establishing effective educational interventions. Further research, using qualitative or mixed method study, is needed to clarify the mechanism and conditions under which educational interventions work effectively.

EBP is a part of point‐of‐care; it needs to be described that how APNs overcome or effort for improving knowledge and skills of clinical appraisal in the context of not only academic settings but also clinical settings. As to the healthcare professionals who graduated from a master's program, Hole et al. (Hole et al.,  2016 ) reported that they perceived higher skill/knowledge on a personal level, but organizational factors were essential for them to use their skills; individual competence and organizational factors are interdependent. However, it remains unclear what the barriers and facilitators of critical appraisal of research articles have in the EBP process. In addition, a previous study showed that nurses perceive research education as essential and nurses sometime express negative feelings about research (Hines et al.,  2021 ), but this study was not focused on APNs. Thus, to examine the process of acquiring critical appraisal skills, it must investigate APNs who have learned and engaged in critical appraisal in EBP.

2. THE STUDY

To describe factors affecting critical appraisal of research articles in EBP by APNs in Japan.

2.2. Methods

2.2.1. design.

This was a qualitative descriptive study using summative content analysis (Hsieh & Shannon,  2005 ). To derive the barriers and facilitators to the critical appraisal of EBP, individual face‐to‐face interviews were conducted between November 2016 and March 2017. Quantitative data about the participants' background were gathered. An instrument for evaluating EBP was used to describe APNs' perception of EBP quantitatively. The study was reported according with the consolidated criteria for reporting qualitative research (COREQ) checklist (Tong et al.,  2007 ).

2.2.2. Sample/participants

Inclusion criteria were (a) CNSs with master's degree certifying them as an APN by the Japan Nursing Association ( https://www.nurse.or.jp/jna/english/nursing/education.html ), (b) engaging in clinical care for patients, including nurse educator in clinical settings, and (c) previous experience in EBP, or is planning and interested in EBP. The hospital's Director of Nursing and academic faculty members were excluded. Participants were recruited by investigators involved in this study using the snowball sampling approach via e‐mail. A purposive sampling was adopted to acquire samples with various CNSs' specialty fields. The sample size for this study was planned as 20 CNSs. However, recruitment of CNSs from some specialties could not be achieved. Therefore, the number of participants was lower than planned. Of the 16 CNSs screened for this study, two were excluded due to conflicting schedules.

2.3. Data collection

2.3.1. interview data.

A semi‐structured interview was conducted using an interview guide (Appendix  S1 ). Our main question studied critical appraisal of the evidence and quantitative research literature used as a reference in own EBP. To focus on the EBP context, the following items were included the: (a) EBP activities that the participants have been involved in or are planning to involve in; (b) factors for success and challenge in EBP activities; and (c) literature used to reference EBP and the critical appraisals of quantitative research. Each interview was conducted by one investigator (AT), who was a faculty member in a nursing university with a master's degree in health science and a licence as a registered nurse. Interviews were conducted at a location selected by the participant or in a quiet place selected by the investigator. Each participant was only interviewed one time for approximately 1 h. All interviews were audio‐recorded, and the transcriptions were written in Japanese.

2.3.2. Demographics data

Participants' characteristics were collected by self‐reported questionnaires. Demographics included gender, years of clinical experience as a nurse, years certified as a CNS, CNS specialty field, workspace (university hospital, public hospitals, non‐hospital facilities or department of research in hospital), and position (staff nurse, charge nurse, full‐time member of a cross‐functional team, researcher). EBP readiness was assessed using the Japanese version of the Evidence‐Based Practice Questionnaire (EBPQ‐J) (Tomotaki et al.,  2018 ). The EBPQ‐J is an 18‐item scale with four subscales (practice, attitude, knowledge/skills about research and knowledge/skills about practice) assessed with 7‐Likert scale, with scores ranging from 1 to 7. The higher scores mean that the respondent is doing EBP more frequently, has a more positive attitude and perceives that they have the knowledge and skills for EBP. For the “Habit of reading article,” participants were asked how many research articles were read per month, including full‐text and abstract. This quantitative data were collected to describe the participants' characteristics.

2.4. Data analysis

Participants' demographics were calculated by descriptive statistics. EBPQ‐J scores were calculated as the total scores of all items and each subscale.

A descriptive qualitative analysis using summative content analysis was used to analyse interview data (Hsieh & Shannon,  2005 ). AT conducted all the interviews, reviewed all transcriptions, and coded all the data. After text in relation to EBP initiatives was identified and extracted for this study, codes, sub‐categories, categories and factors were labelled. Microsoft Word and Excel were used to manage data.

2.5. Rigour

In the initial process of the interview data analysis, one case was analysed by the principal investigator, AT, who did not have experience in conducting qualitative research, and four cases were analysed under the supervision of AO, HF and YT (AO, HF, YT and IS were the researchers for the qualitative research, and HF, YT and IS were the researchers for EBP), and these cases underwent member checking by the participants in this interview. Finally, IS reviewed the transcriptions and pre‐coded and analysed the codes, sub‐categories, categories and factors. The other investigators (YT, AO and HF) reviewed them as supervisors. The final factors, categories, sub‐categories and quotes in this article were translated from Japanese into English. Examples of qualitative data are shown in italic font.

3.1. Participants' demographics

Fourteen CNSs in nine specialties were finally enrolled (Table  1 ). Most of the participants had 10–14 years of clinical experience as a clinical nurse. Almost all participants worked as a staff nurse in a university or public hospital. Six participants were currently enrolled in or had completed their doctoral courses in a university. The total EBPQ‐J score ranged from 48 to 99, and the scores of practice and knowledge/skills about research were lower than the scores of attitude and knowledge/skills of practice on each subscale. Almost half of participants read five or more research articles per month.

Participants' demographics

Abbreviations: CNS, certified nurse specialists; EBPQ‐J: Evidence‐Based Practice Questionnaire‐Japanese version; Min: Minimum value; Max: Maximum value.

3.2. Factors influencing critical appraisal of EBP

Four factors were extracted from the data: individual beliefs and attitude, learning status, organizational readiness, and availability of research evidence, which comprised 12 categories (Table  2 ).

Categorization matrix

Abbreviations: CNS, Certified nurse specialist; EBP, Evidence‐based Practice; n , Number of participants.

3.3. Factor 1: Individual beliefs and attitude

“Individual beliefs and attitude” refers to the CNSs' positive beliefs and attitude towards EBP and critical appraisal. Participants had daily activities connected to EBP, with both positive beliefs about and conflicts with EBP.

Daily activities connected to EBP were in various situations: challenges in their own clinical practice, issues in their organization, consultation with others and insights from research articles.

It is often used in the literature when there is a care method or policy in place that makes it difficult to choose what to do with the patient. (ID‐9)

I am in charge of education at my workplace, and I do a needs assessment at my workplace, and I found that the staff had a very high need for a study session on a care of A. (ID‐2)

I am in a leadership position (in my work zone) and provide care together with other nurses, and the care differs depending on the person (patient). What? We talked about whether it makes sense. (ID‐3)

An academic article in 2013 reported that the authors could use a device A with patients, and in 2014, they reported that they could do this much with it. I thought that was interesting (if I could use it in own clinical practice). (ID‐8)

These daily activities were supported by their positive beliefs—that they had own roles or responsibilities to practice EBP or had experienced the need for research evidence in clinical practice. As a CNS, they were expected to act as a change agent or a core member in an EBP project, or they had perceived that EBP is the responsibility of medical professionals. They also used research evidence as a basis for decision‐making or confirmed research evidence to compensate for their own lack of knowledge.

I thought that I could do the best and improve the quality of my work in the best environment if I had a base in practice and gradually gained knowledge in research. I knew it had to be CNS. (ID‐8)

I've experienced to stumble in practice that would have been better if there was evidence. (ID‐5)

The conflicts in EBP included integration with patient's individuality and difficulties in application. For example, they experienced hesitation in applying care to individuals by making it a rule, and difficulty in applying it in a way that suited the facility.

In short, even if guidelines and such are published quickly, everyone thinks that it is rather difficult to apply them in a way that fits the needs and methods of their own facility. (ID‐14)

3.4. Factor 2: Learning status

Learning status included the participants' self‐assessment of their competency in critical appraisal of research articles and learning experiences of it in the current and past. The experience also included learning about research methodology.

The participants self‐evaluated their own knowledge/skills in quantitative research and research utilization in clinical practice, including difficulty in examining research methodology and statistics, and language barriers (i.e. papers written in English). One participant expressed uncertainty in reading articles correctly without others' help.

I still can't understand a quantitative research paper. It's too difficult. (ID‐6)

The participants used various opportunities for learning critical appraisal, including participation into a journal club hosted by doctors in a hospital, case study conferences with CNSs and certified nurses, autonomous study groups, educational research programs and admission to doctoral programs. Self‐learning included reading English while using a dictionary and books on research design and statistics.

There are a lot of things I don't understand in the medical research articles (when I participate in a journal club by medical doctors), but I can learn about statistical data analysis. Even if I don't know anything about medical topics, I can learn about critical appraisal of the article. If I don't touch those things, I'll forget them. (ID‐9)

The participants had previous coursework experience and had received their supervisor's teaching in the CNS programs. However, almost all participants perceived their past learning environment to be insufficient, citing a lack of academic support and curriculum in the CNS program. They said that there were few opportunities to learn about quantitative research, the faculty member's specialty was qualitative research, and the research they conducted in the CNS program was qualitative or case studies.

I think one of the strengths of CNS is that when they want to do EBP, they know how to get to EBP. We're trained in how to find resources. (ID‐1)

When I got to the CNS course, there was no course on research utilization or anything like that. I thought, ‘Is this okay?’ I thought, ‘Is this right?’ (ID‐4)

3.5. Factor 3: Organizational readiness

Organizational readiness refers to the other staff and healthcare professionals' attitudes and organizational culture for EBP activities related to critical appraisal. The factors were identified as cooperative, difficult or not ready.

First, “cooperative” organizational readiness included that the participants' organization had a cooperative structure, positive climate and understanding persons for EBP. The CNSs cooperated with the Quality Improvement Center, cross‐departmental activities and collaborate with the Epidemiology Center in EBP. In a positive climate, other staff and professionals were willing to look into questions and were open to good practices and research evidence. Understanding persons included nurses, doctors, nurses from other hospitals and supervisors and managers.

We have a culture here where we can introduce  staffs to the evidence that's out there and say, ‘This is something that's been proven to be good, so let's do it.’ (ID‐14)

We now have a group consisted of certified nurse specialists and certified nurses, and once a month we have a case study meeting where we introduce our own cases to the staff adding a scientific perspective. (ID‐9)

Second, “difficult” organizational readiness presented a situation in which EBP is less of a priority. Three examples of such situations were as follows: difficulty in getting cooperation, inadequate readiness and unutilized learning opportunities. Difficulty in obtaining cooperation was created by the workload (balance with routine work, after‐hours work) and feasibility (difficulty in reorganizing conventional methods). Inadequate readiness included research evidence and attitudes towards understanding patients and knowledge skills in clinical practice. Lastly, even though learning opportunities were available, they were not being utilized because someone was not motivated or could not afford to participate in a voluntary study group.

When it comes to incorporating something new and different, it's difficult to find a way to link it with existing things… We can't make major changes to what you're already working on. (ID‐2)

We are very busy (in clinical practice). We have to deal with what is right in front of us, and that's how we get swept away. (ID‐13)

Third, “not ready” organizational readiness indicates less emphasis on research evidence or an unconcerned and insufficient learning environment. For example, some nurses were reluctant to accept research evidence reported outside of Japan, resisted being asked for evidence, felt as if their way of doing things is being denied, followed conventional policies, emphasize hearsay or adopted the opinion of the person with the most say. Unconcerned attitude means that someone is not interested in “reviewing care,” which is the start of EBP. Additionally, some may not be interested in the need for evidence to support their practice, or nursing managers require only minimal care to nurses and such care does not include EBP. An insufficient learning environment included a lack of clinical nurses to support EBP and collaboration with nursing universities.

I thought nurses were just adjusting an intravenous drip as the doctor told you to. … I wonder if the nurses I work with have the same sense of urgency that I do (such as it's not good if they don't have the evidence to back up their practice.) (ID‐5)

3.6. Factor 4: Availability of research evidence

Availability of research evidence refers includes ease of search and availability, richness of the research evidence and not reading enough before and during the process of obtaining research evidence.

Ease of search and availability included ease of reading full‐text articles (e.g. subscribing to open access articles and browsing services of full‐text articles for domestic literature), ease of searching (e.g. the facility subscribes to a fee‐based database) and procedures for copy services (e.g. the need to go to the library for the procedures). The richness of research evidence included whether there was secondary literature (e.g. Cochrane review or clinical guidelines) and issues of research (no literature published that met own objectives, low quality of research) were mentioned.

In Japan, there are many cases where we can't read the text, when the title of an article catches our attention. So, we have to go to the library and request it. Then, after reading the text, I find that it was something different. It's a lot of work. (ID‐8)

4. DISCUSSION

This study identified factors affecting the critical appraisal of research articles in EBP from experiences and perceptions of CNSs who were APNs in Japan. Four factors (individual beliefs and attitude, organizational readiness, learning status and availability of research evidence) were identified as both enhancing and inhibiting critical appraisal in EBP. For example, many participants recognized that they were not sufficiently skilled or good at critical appraisal of research articles. These negative aspects about research and statistics generally are barriers to EBP activities (Kajermo et al.,  2010 ), in other words, it means that the APNs in this study could identify what is lacking to enhance critical appraisal in EBP. This finding would support the previous studies that the barriers to research utilization or EBP are not necessarily related to practice, attitudes and knowledge and skills for EBP (Brown et al.,  2010 ). In addition, this study highlights that the CNSs perceived both positive and negative factors simultaneously, even though they were engaged or interested in critical appraisal in EBP.

The CNSs who participated in this study had positive beliefs about EBP and a positive attitude towards critical appraisal, which is similar to previous studies of clinical nurses with postgraduate degrees (Karlsson et al.,  2019 ). Although EBP activity was associated with a positive attitude towards EBP (Squires et al.,  2011 ), clinical nurses do not necessarily practice EBP. APNs' stronger motivation to engage in EBP might be influenced by individual recognition of the need to review current care to give optimal patient care in addition to positive beliefs and attitude.

The factor of organizational readiness derived from this study was similar to the implementation and dissemination of evidence‐based intervention (Damschroder et al.,  2022 ) and knowledge uptake and sustainability (Grinspun et al.,  2022 ). The step of critical appraisal of research evidence in EBP requires discussion about the generalizability and applicability of research evidence to patients in one's own clinical setting. Since the process of applying research evidence is usually decided by a multidisciplinary team or departments, this result would be reasonable. Additionally, physicians are one of the proponents for EBP, and a previous study reported that nurse practitioners recognized a collaboration with doctors for EBP implementation (Clarke et al.,  2021 ). There are few CNSs in Japan and only one or a few CNSs are often assigned per facility; the lack of human resources for EBP in the organization might affect CNSs' activity of critical appraisal. For example, one of the barriers to EBP is a lack of teamwork and organizational support for implementing evidence‐based guidelines (McArthur et al.,  2021 ). The current study showed that such teamwork and organizational support are required not only for the implementation phase of evidence but also for critical appraisal of the evidence. The findings of this study are useful for countries and organizations applying the EBP implementation strategy model developed in EBP‐leading countries (Melnyk et al.,  2018 ).

Additionally, an environment in which individuals can continue to learn after obtaining their CNS certification must be provided. The current findings show that improvement of knowledge skills of critical appraisal in EBP needs to be an organizational activity, rather than relying on individual efforts. Such organizational activities to empower EBP for APNs include, for example, running of journal clubs in each institution and expanding contracts for available bibliographies and academic articles. At the same time, a positive climate for EBP is particularly necessary for nurse managers, staff nurses and other medical staffs (Hines et al.,  2021 ).

When planning an EBP education program focused on critical appraisal, educators and researchers could use the four factors derived from this study to review their program and the evaluation. A further study is expected to evaluate the relationship between CNSs' EBP activities and the four factors identified in this study by using quantitative research or a mixed methods model. Additionally, it has been suggested that EBP education needs to be taught in the context of clinical practice rather than just for conducting research (Straus et al.,  2019 ). Education about critical appraisals should be established with the focus on EBP as continuous education for professionals at each phase of EBP including undergraduate, graduate and post‐graduate.

4.1. Limitations

First, the findings may not reach saturation in this study due to fewer participants than planned. Second, the results of our study might have been affected by sampling bias since the recruitment of the participants considered only CNSs' specialty fields. For example, almost all the participants were urban residents. It is estimated to have influenced their learning environment or performance of critical appraisal in EBP. Third, the definition of EBP might have been perceived differently for each CNS, and lead to different findings. Finally, our findings would not be generalizable to CNSs who were uninterested in or not confident in EBP and critical appraisal.

5. CONCLUSION

As factors affecting critical appraisal in EBP by CNSs who were APNs in Japan, 4 factors comprising 12 categories were extracted from the obtained data. These factors included both positive and negative aspects for critical appraisal in EBP and comprised an internal factor, learning status, organizational context and acquiring literature. APNs are expected to be role models for staff nurses to integrate research evidence into practice. Continuous critical appraisal will result in obtaining the best available research for the EBP team. Therefore, a richer learning environment for critical appraisal of EBP is required for APNs.

AUTHOR CONTRIBUTIONS

AT, YT and HF participated in the study design. AT collected the clinical data and data analysis was conducted by AT and IS. All investigators interpreted the row data and results. AT wrote and revised the draft and subsequent manuscripts. All investigators reviewed the draft manuscripts and approved the final manuscript.

FUNDING INFORMATION

This study was supported by JSPS KAKENHI (grant number JP16H07464 and JP 18 K17452).

CONFLICT OF INTEREST

The authors have no conflicts of interest directly relevant to the content of this article.

ETHICS STATEMENT

This study was approved by the relevant ethical review board of the National Center for Global and Health and Medicine in Japan (approval no. NCGM‐G‐002093‐00). We followed the Ethical Guidelines for Medical Research Involving Human Subjects in Japan. The investigator explained this study to the participants in writing and orally, and consent was obtained from participants before starting the interview.

Supporting information

Appendix S1

ACKNOWLEDGEMENTS

The authors thank all participants of this study and Enago ( www.enago.jp ) for the English language review.

Tomotaki, A. , Sakai, I. , Fukahori, H. , Tsuda, Y. , & Okumura‐Hiroshige, A. (2023). Factors affecting the critical appraisal of research articles in Evidence‐Based practices by advanced practice nurses: A descriptive qualitative study . Nursing Open , 10 , 3719–3727. 10.1002/nop2.1628 [ PMC free article ] [ PubMed ] [ CrossRef ] [ Google Scholar ]

Clinical trial registration number: No.

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