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• Published: 31 January 2022

The fundamentals of critically appraising an article

• Sneha Chotaliya 1  

BDJ Student volume  29 ,  pages 12–13 ( 2022 ) Cite this article

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Sneha Chotaliya

We are often surrounded by an abundance of research and articles, but the quality and validity can vary massively. Not everything will be of a good quality - or even valid. An important part of reading a paper is first assessing the paper. This is a key skill for all healthcare professionals as anything we read can impact or influence our practice. It is also important to stay up to date with the latest research and findings.

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Chambers R, 'Clinical Effectiveness Made Easy', Oxford: Radcliffe Medical Press , 1998

Loney P L, Chambers L W, Bennett K J, Roberts J G and Stratford P W. Critical appraisal of the health research literature: prevalence or incidence of a health problem. Chronic Dis Can 1998; 19 : 170-176.

Brice R. CASP CHECKLISTS - CASP - Critical Appraisal Skills Programme . 2021. Available at: https://casp-uk.net/casp-tools-checklists/ (Accessed 22 July 2021).

White S, Halter M, Hassenkamp A and Mein G. 2021. Critical Appraisal Techniques for Healthcare Literature . St George's, University of London.

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Chotaliya, S. The fundamentals of critically appraising an article. BDJ Student 29 , 12–13 (2022). https://doi.org/10.1038/s41406-021-0275-6

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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

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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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Tools for Critical Appraisal of Studies

“The purpose of critical appraisal is to determine the scientific merit of a research report and its applicability to clinical decision making.” 1 Conducting a critical appraisal of a study is imperative to any well executed evidence review, but the process can be time consuming and difficult. 2 The critical appraisal process requires “a methodological approach coupled with the right tools and skills to match these methods is essential for finding meaningful results.” 3 In short, it is a method of differentiating good research from bad research.

Critical Appraisal by Study Design (featured tools)

• Non-RCTs or Observational Studies
• Diagnostic Accuracy
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• Tool Repository
• AMSTAR 2 The original AMSTAR was developed to assess the risk of bias in systematic reviews that included only randomized controlled trials. AMSTAR 2 was published in 2017 and allows researchers to “identify high quality systematic reviews, including those based on non-randomised studies of healthcare interventions.” 4 more... less... AMSTAR 2 (A MeaSurement Tool to Assess systematic Reviews)
• ROBIS ROBIS is a tool designed specifically to assess the risk of bias in systematic reviews. “The tool is completed in three phases: (1) assess relevance(optional), (2) identify concerns with the review process, and (3) judge risk of bias in the review. Signaling questions are included to help assess specific concerns about potential biases with the review.” 5 more... less... ROBIS (Risk of Bias in Systematic Reviews)
• BMJ Framework for Assessing Systematic Reviews This framework provides a checklist that is used to evaluate the quality of a systematic review.
• CASP Checklist for Systematic Reviews This CASP checklist is not a scoring system, but rather a method of appraising systematic reviews by considering: 1. Are the results of the study valid? 2. What are the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CEBM Systematic Reviews Critical Appraisal Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance, and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• JBI Critical Appraisal Tools, Checklist for Systematic Reviews JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• NHLBI Study Quality Assessment of Systematic Reviews and Meta-Analyses The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. more... less... NHLBI (National Heart, Lung, and Blood Institute)
• RoB 2 RoB 2 “provides a framework for assessing the risk of bias in a single estimate of an intervention effect reported from a randomized trial,” rather than the entire trial. 6 more... less... RoB 2 (revised tool to assess Risk of Bias in randomized trials)
• CASP Randomised Controlled Trials Checklist This CASP checklist considers various aspects of an RCT that require critical appraisal: 1. Is the basic study design valid for a randomized controlled trial? 2. Was the study methodologically sound? 3. What are the results? 4. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CONSORT Statement The CONSORT checklist includes 25 items to determine the quality of randomized controlled trials. “Critical appraisal of the quality of clinical trials is possible only if the design, conduct, and analysis of RCTs are thoroughly and accurately described in the report.” 7 more... less... CONSORT (Consolidated Standards of Reporting Trials)
• NHLBI Study Quality Assessment of Controlled Intervention Studies The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. more... less... NHLBI (National Heart, Lung, and Blood Institute)
• JBI Critical Appraisal Tools Checklist for Randomized Controlled Trials JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• ROBINS-I ROBINS-I is a “tool for evaluating risk of bias in estimates of the comparative effectiveness… of interventions from studies that did not use randomization to allocate units… to comparison groups.” 8 more... less... ROBINS-I (Risk Of Bias in Non-randomized Studies – of Interventions)
• NOS This tool is used primarily to evaluate and appraise case-control or cohort studies. more... less... NOS (Newcastle-Ottawa Scale)
• AXIS Cross-sectional studies are frequently used as an evidence base for diagnostic testing, risk factors for disease, and prevalence studies. “The AXIS tool focuses mainly on the presented [study] methods and results.” 9 more... less... AXIS (Appraisal tool for Cross-Sectional Studies)
• NHLBI Study Quality Assessment Tools for Non-Randomized Studies The NHLBI’s quality assessment tools were designed to assist reviewers in focusing on concepts that are key for critical appraisal of the internal validity of a study. • Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies • Quality Assessment of Case-Control Studies • Quality Assessment Tool for Before-After (Pre-Post) Studies With No Control Group • Quality Assessment Tool for Case Series Studies more... less... NHLBI (National Heart, Lung, and Blood Institute)
• Case Series Studies Quality Appraisal Checklist Developed by the Institute of Health Economics (Canada), the checklist is comprised of 20 questions to assess “the robustness of the evidence of uncontrolled, [case series] studies.” 10
• Methodological Quality and Synthesis of Case Series and Case Reports In this paper, Dr. Murad and colleagues “present a framework for appraisal, synthesis and application of evidence derived from case reports and case series.” 11
• MINORS The MINORS instrument contains 12 items and was developed for evaluating the quality of observational or non-randomized studies. 12 This tool may be of particular interest to researchers who would like to critically appraise surgical studies. more... less... MINORS (Methodological Index for Non-Randomized Studies)
• JBI Critical Appraisal Tools for Non-Randomized Trials JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis. • Checklist for Analytical Cross Sectional Studies • Checklist for Case Control Studies • Checklist for Case Reports • Checklist for Case Series • Checklist for Cohort Studies
• QUADAS-2 The QUADAS-2 tool “is designed to assess the quality of primary diagnostic accuracy studies… [it] consists of 4 key domains that discuss patient selection, index test, reference standard, and flow of patients through the study and timing of the index tests and reference standard.” 13 more... less... QUADAS-2 (a revised tool for the Quality Assessment of Diagnostic Accuracy Studies)
• JBI Critical Appraisal Tools Checklist for Diagnostic Test Accuracy Studies JBI Critical Appraisal Tools help you assess the methodological quality of a study and to determine the extent to which study has addressed the possibility of bias in its design, conduct and analysis.
• STARD 2015 The authors of the standards note that “[e]ssential elements of [diagnostic accuracy] study methods are often poorly described and sometimes completely omitted, making both critical appraisal and replication difficult, if not impossible.”10 The Standards for the Reporting of Diagnostic Accuracy Studies was developed “to help… improve completeness and transparency in reporting of diagnostic accuracy studies.” 14 more... less... STARD 2015 (Standards for the Reporting of Diagnostic Accuracy Studies)
• CASP Diagnostic Study Checklist This CASP checklist considers various aspects of diagnostic test studies including: 1. Are the results of the study valid? 2. What were the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• CEBM Diagnostic Critical Appraisal Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance, and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• SYRCLE’s RoB “[I]mplementation of [SYRCLE’s RoB tool] will facilitate and improve critical appraisal of evidence from animal studies. This may… enhance the efficiency of translating animal research into clinical practice and increase awareness of the necessity of improving the methodological quality of animal studies.” 15 more... less... SYRCLE’s RoB (SYstematic Review Center for Laboratory animal Experimentation’s Risk of Bias)
• ARRIVE 2.0 “The [ARRIVE 2.0] guidelines are a checklist of information to include in a manuscript to ensure that publications [on in vivo animal studies] contain enough information to add to the knowledge base.” 16 more... less... ARRIVE 2.0 (Animal Research: Reporting of In Vivo Experiments)
• Critical Appraisal of Studies Using Laboratory Animal Models This article provides “an approach to critically appraising papers based on the results of laboratory animal experiments,” and discusses various “bias domains” in the literature that critical appraisal can identify. 17
• CEBM Critical Appraisal of Qualitative Studies Sheet The CEBM’s critical appraisal sheets are designed to help you appraise the reliability, importance and applicability of clinical evidence. more... less... CEBM (Centre for Evidence-Based Medicine)
• CASP Qualitative Studies Checklist This CASP checklist considers various aspects of qualitative research studies including: 1. Are the results of the study valid? 2. What were the results? 3. Will the results help locally? more... less... CASP (Critical Appraisal Skills Programme)
• Quality Assessment and Risk of Bias Tool Repository Created by librarians at Duke University, this extensive listing contains over 100 commonly used risk of bias tools that may be sorted by study type.
• Latitudes Network A library of risk of bias tools for use in evidence syntheses that provides selection help and training videos.

References & Recommended Reading

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

2.    Portney LG.  Foundations of clinical research : applications to evidence-based practice.  Fourth edition. ed. Philadelphia: F A Davis; 2020.

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

4.     Singh S.  Critical appraisal skills programme.   Journal of Pharmacology and Pharmacotherapeutics.  2013;4(1):76-77.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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Critical Appraisal Resources for Evidence-Based Nursing Practice

• Levels of Evidence
• Systematic Reviews
• Randomized Controlled Trials
• Quasi-Experimental Studies
• Case-Control Studies

What is a Case-Control Study?

Pro tips: case-control study checklist, articles on case-control study design and methodology.

• Cohort Studies
• Analytical Cross-Sectional Studies
• Qualitative Research

E-Books for Terminology and Definitions

Case-control studies are a type of quantitative research "designed to sample a group of people with and a group of people without the disease or the outcome measure being studied" (Schmidt & Brown, 2019, p. 209).  The cases are individuals with the disease or outcome measure, and the controls are individuals without the disease or outcome measure.  The purpose of a case-control study is to test whether there is an association between an exposure and a disease, condition or outcome measure (Schmidt & Brown, 2019, p. 209). 

Schmidt N. A. & Brown J. M. (2019). Evidence-based practice for nurses: Appraisal and application of research  (4th ed.). Jones & Bartlett Learning. 

Each JBI Checklist provides tips and guidance on what to look for to answer each question.   These tips begin on page 4. 

Below are some additional  Frequently Asked Questions  about the  C ase-Control Studies Checklist  that have been asked by students in previous semesters. 

For more help:  Each JBI Checklist provides detailed guidance on what to look for to answer each question on the checklist.  These explanatory notes begin on page four of each Checklist. Please review these carefully as you conduct critical appraisal using JBI tools. 

Dey, T., Mukherjee, A., & Chakraborty, S. (2020). A practical overview of case-control studies in clinical practice .  Chest ,  158 (1S), S57–S64. https://doi.org/10.1016/j.chest.2020.03.009

Dupépé, E. B., Kicielinski, K. P., Gordon, A. S., & Walters, B. C. (2019). What is a case-control study?   Neurosurgery ,  84 (4), 819–826. https://doi.org/10.1093/neuros/nyy590

Herbert R. (2017). Case-control studies .  Journal of physiotherapy ,  63 (4), 264–266. https://doi.org/10.1016/j.jphys.2017.08.007

Schulz, K. F., & Grimes, D. A. (2002). Case-control studies: Research in reverse .  Lancet ,  359 (9304), 431–434. https://doi.org/10.1016/S0140-6736(02)07605-5

Song, J. W., & Chung, K. C. (2010). Observational studies: Cohort and case-control studies .  Plastic and reconstructive surgery ,  126 (6), 2234–2242. https://doi.org/10.1097/PRS.0b013e3181f44abc

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• Last Updated: Feb 22, 2024 11:26 AM
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Step 3: Critically Appraising Evidence: Case-Control Studies

• PMID: 37657811
• DOI: 10.1891/NN-2022-0037

Critical appraisal of the evidence is the Step 3 in the evidence-based practice (EBP) process. This column, the fourth in a multipart series to describe the critical appraisal process, focuses on the critical appraisal of a case-control study.

Keywords: case; case-control study; control; evidence-based practice; levels of evidence; quantitative evidence.

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