Critical appraisal is the process of carefully and systematically examining research to judge its credibility, its value and its relevance in a specific context.
The aim of critical appraisal is to understand the strengths, weaknesses, and potential for bias in clinical research before it is applied to a patient. Validity, applicability, and clinical importance should be considered during critical appraisal to ensure that research evidence is used reliably and efficiently and that false conclusions are not drawn.
Why do we need to critically appraise the literature?
Critical appraisal is necessary to:
The selection and appraisal process includes:
A valid piece of research truly measures what it sets out to measure.
To give valid results, a piece of research needs to:
How do we critically appraise the literature?
The following questions may be asked to appraise the validity of research:
1. What is the research question? Are the objectives of the study clearly stated? Why was this research necessary?
2. Is the research original or important? Does the study have new findings? Is a treatment outcome clinically relevant?
3. Does the research question consider the following:
4. Did the authors use the relevant type of study for the research question?
5. Did the study design minimise the risk of bias in its methodology, reporting and patient selection? Did the study use best practice design such as a randomised controlled trial or a systematic review? Blinding of patients and outcome assessors, randomization, concealment, intention-to-treat analysis, similarity of patients for known prognostic factors, and completeness of follow-up are indicators of validity.
6. Was the study designed in line with the original protocol? Is the focus of the report in keeping with the study objectives? Were changes made to the inclusion or exclusion criteria?
7. Has the study's hypothesis been tested?
8. Is the analysis of the data accurate? What level of uncertainty surrounds any results?
9. Are the conclusions based on the data and analysis? Do the authors draw conclusions that are supported by the data? Have the authors discussed other work that both supports and contradicts their findings? Have the authors identified any limitations to their study?
10. Does the study contribute to the understanding of the problem being investigated? What are the strengths and limitations of the study? Are the findings of the study useful for clinical practice? Do the risks of a treatment or diagnostic procedure outweigh the potential benefits?
Remember that while general principles apply, critical appraisal may be a little different for each type of study.
The following is a selection of useful resources that assess the quality of both quantitative and qualitative studies: