Critical Appraisal

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What is critical appraisal?

• …. process of weighing up evidence to see how useful it is in decision making

Why critically appraise?

• Supports sound decision making based on best available evidence

• Helps us determine:– How rigorous a piece of research is– What the results are telling us– How relevant it is to our patient

How to critically appraise?

• Many different tools

• http://www.cebm.net

• http://www.phru.nhs.uk/casp/apprais.htm

• http://www.shef.ac.uk/scharr/ir/netting

But what are the three main things we are looking for?

Three R’s

• Rigour - how good is the study

• Results - what is it actually telling us

• Relevance – is it relevant to our patient

Levels of Evidence

• 1a A systematic review of 2 or more randomised control trials (RCTs)

• 1b an RCT• 2a a cohort study• 2b a case control study• 2c a dramatic uncontrolled experiment• 3 Respected authorities, opinions etc• 4 …someone once told me

Sources of Evidence

• Primary sources– Based on experiments and published

research

• Secondary sources– Systematic reviews– Clinical guidelines– Journals of secondary publication e.g.

Evidence Based Medicine

Getting Started

• Formulate PICO question

• Search appropriate sources

• Obtain article (s)

• Read to suit you!

Statistics

• If in doubt ask a statistician

• Key points to look for– 95% confidence limits used– If p <0.05 then result is statistically significant– Any anomalies discussed– All subjects accounted for even if dropped out

Reading for Critical Appraisal

• Introduction– Logical and knowledgeable

• Aim/research question– Clearly stated

• Methods– Fully described

• Analysis– Appropriate statistics used, all subjects

accounted for

• Conclusions– Justified and valid– Cost/benefits discussed

Can I make a clinical decision based on what I have just read?

Practical Exercise

Appraise the paper given to you and be prepared to share your

comments with the group

Appraising Web Sites

• Authority

• Currency

• No advertisement/sponsorship

• .org, .ac, .gov better than .co.uk/.com

Practical Exercise

In groups comment on the webpages given and be ready to

feedback