Critical appraisal: how to do it
Posted on 17th May 2013 by Geethu Parvathy
I got to grips with critical appraisal for the first time after dealing with Students 4 Best Evidence. In India, evidence-based medicine is not included much in our curriculum, although we know the basics of epidemiology. In fact, critical appraisal has been added as a topic to many medical school and university curricula. But is still not a part of curriculum in India.
As you all know, evidence-based medicine refers to the judicious and explicit use of current best evidence in patient care.
The 5 steps in EBM are:
- Making an answerable question from an uncertain clinical problem.
This includes questioning, study designs etc.
- Search for the evidence
- Critical appraisal
- Application of results in practice
- Evaluation of new practice
Critical appraisal is a systemic assessment and interpretation of evidence, it can be a study or an article, by considering its validity, results, trustworthiness and relevance to an individual’s work.
Why do we need to critically appraise a study?
There have been many times in which unjustified scientific or medical claims have been published in journals and newspapers, without proper evidence or data or significant study results, but may attain public attention, the so called “bad science”.
Critical appraisal is essential to combat information overload and to identify papers that are clinically relevant. It is also a part of continuing professional development [CPD]. It also helps in identifying the influence of bias in a study.
How to critically appraise a study?
Methods of critically appraising various studies are different depending upon the study design. For different study questions we need different study designs. The best design for studies evaluating the effectiveness of an intervention or treatment, is a randomized controlled trial. Others include descriptive studies, quantitative studies like case-control and cohort studies, systematic reviews and meta-analysis. For each type of study, different checklists for assessing them. Commonly used checklists are:
- SIGN50: A guideline developer’s handbook: http://www.sign.ac.uk/assets/sign50_2011.pdf
- CASP: https://casp-uk.net/casp-tools-checklists/
Whenever you read any research paper, be it a systematic review, randomized control trial, economic evaluation or other study design – it is important to remember that there are three broad things to consider: validity, results and relevance. It is always necessary to consider the following questions.
● has the research been conducted in such a way as to minimise bias?
● if so, what does the study show?
● what do the results mean for the particular patient or context in which a decision is being made?
 Horsley T, Hyde C, Santesso N, Parkes J, Milne R, Stewart R: Teaching critical appraisal skills in healthcare settings, The Cochrane Library 2011, Issue 11.[cited on 15 May 2013]
 Amanda Burls: What is critical appraisal? 2009. London, Hayward Group second edition [cited on 15th May 2013]
 UCL library available online at: http://www.ucl.ac.uk/ich/support-services/library/services_and_facilities/training/critical-appraisal_material/critical-appraisal
 Anon. Appraising the evidence [Internet]. Oxford: Critical Appraisal Skills Programme (CASP); 26 May 2008 [cited 17 May 2013]. Available from: https://casp-uk.net/casp-tools-checklists/