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Critical appraisal made easy for the MRCGP

Candidates' critical appraisal skills are crucial for success, so it's vital to perfect them, says Dr Nigel Giam

Candidates' critical appraisal skills are crucial for success, so it's vital to perfect them, says Dr Nigel Giam

With the last few sittings of the current MRCGP fast approaching, registrars attempting the exam would be wise to read up on critical appraisal early. Examiners state that it is critical appraisal that differentiates stronger and weaker candidates.

Critical appraisal is a skill and one that requires much practice. In Paper One, there will probably be two to three questions on critical appraisal, a mixture of qualitative and quantitative questions. Candidates are never expected to appraise a whole research paper, they are asked to concentrate on particular aspects.

Questions on qualitative studies tend to concentrate on methodology and sampling, whereas those on quantitative studies focus on results and data interpretation.

When faced with a bulk of text or a table of numbers in the exam, take a logical and structured approach to critical appraisal.

The ABCDE critical appraisal framework

You can use a simple framework to identify the relevant elements of sampling, methodology and data interpretation, as well as to appraise other aspects of a paper.

A) AIM Was this well defined? Worthwhile? Appropriate? At the end of the paper, was the aim truly tested by the method?

B) BACKGROUND INFORMATION In a good paper, background information to the paper may allude to some of the strengths and weaknesses of the study.

C) SETTING Was the study UK based? In primary or secondary care? If in primary care, what type of practice took part? How far can the study be generalised to the GP population?

C) SAMPLE How were the study participants selected? Is there selection bias? Have the authors been explicit and justified their inclusion and exclusion criteria?

Random selection – this is used generally to obtain an average viewpoint or result that is representative of the population from which the sample was taken. This is often seen in quantitative studies where one is concerned with the average outcome from a treatment/intervention group versus a control group.

Purposeful/selective sampling – this is used when viewpoints from a particular population are sought and is most often seen in qualitative studies.

C) CONTROLS Controls are most often used in quantitative studies when interventional outcomes are being studied. If controls were used, look for how they were selected and if they are matched to the treatment group for all relevant factors.

D) DESIGN Look at the design as a whole. Is this a qualitative or quantitative study? Is it retrospective or prospective? Cross sectional? Case Controlled? Cohort? Always ask if the design is appropriate to the aim.

D) DATA Look to see how data was collected and analysed. In qualitative studies, were questionnaires piloted? Was observer or interviewer error commented on? Were different tools used to gather data? In quantitative studies, was data measurement validated and was it reliable? Are statistics employed and if so what is the statistical and clinical significance of the results?

D) DROP OUT Look for key tables. Do figures add up? Is data missing? Is this accounted for? Does drop-out or non-response affect results? Is intention to treat analysis employed?

E) EVALUATION Are conclusions made in the discussion justified by the results?Ask yourself whether the results are:

– valid – how close the study findings are to the 'truth'

– reliable: how reproducible the findings are

– generalisable: how relevant and transferable the results are to another practice population

– clinically significant –clinically relevant –clinically applicable

From this framework, one can identify from the outset that there are a multitude of factors to look for when critically appraising a paper. When asked to comment on sampling or methodology, try to remain objective and look for evident strengths and weaknesses. Remember that sampling comes under the umbrella of methodology, so try to remain focused when asked to comment on sampling and methodology respectively.

Justification is key, so do not throw in terms like validity or reliability without demonstrating what you mean by this.

As with the other modules of this exam, practice makes perfect, but knowing the ground rules will certainly help.

Nigel Giam is an MRCGP course director for the London Faculties RCGP and a GP in private practice in London

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