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Critical appraisal is the process of systematically analysing research to assess methods, validity and usefulness.


The key questions in critical appraisal are:

  • Why was the study done?

    A clearly focused question should address population, intervention and outcomes.

  • What type of study was done?

    The study design must match the question asked. Intervention questions are best answered with randomised controlled trials.

  • What are the study characteristics?

    Use the PICO question format to help you answer this question.

  • What was done to address bias?

    a) Was the assignment of patients to treatments randomised?

    b) Were patients, health workers and study personnel ‘blind’ to treatment allocation?

    c) Were all of the patients who entered the trial properly accounted for at its conclusion? Look for follow-up tables and whether patients were analysed in the groups to which they were randomised.

    d) Were the groups similar at the start of the study?

    e) Aside from the experimental intervention, were the groups treated equally? 

  • What are the results and are the results valid?

    a) Are the outcome measures relevant?

    b) How large was the treatment effect?

    c) How precise was the estimate of the treatment effect? Look for confidence limits and p values.

  • What conclusions can you make?

    a) Can the results be applied to my patients? Were all clinically important outcomes considered? Are the benefits worth the harms and costs?

    b) Are the results relevant to my situation? Patient population / similar definitions/protocols / health system similarities