Evidence-based medicine and critical appraisal — formative SAQs

SAQ 1 (10 marks)

You are asked to appraise a randomised controlled trial claiming a new therapy reduces the risk of a serious complication in children. The abstract reports a relative risk reduction of 50 percent. [1]

1. Outline the steps you would take to appraise this trial, in the correct order, before applying its result. (4) [7] [3]
2. Explain why quoting a 50 percent relative risk reduction alone is misleading, and describe how you would present the benefit accurately. (3) [1] [6]
3. Describe how you would decide whether the result applies to your patient and how to move from the evidence to a recommendation. (3) [7] [5]

Model answer

Frame the clinical question in PICO terms, then search the filtered layer first. Judge the internal validity before the results: identify the design, then score the risk of bias with RoB 2, paying attention to randomisation, allocation concealment, blinding, attrition and selective reporting. Only then extract the magnitude and precision of the effect, and check for publication bias if the result comes from a synthesis. [2] [7] [3]

A relative risk reduction quoted alone inflates perceived benefit because it hides the baseline. Present the absolute baseline risk and the absolute risk reduction, give the number needed to treat, and read the confidence interval so the family understands the range compatible with the data. [1] [6]

Assess applicability by comparing the trial population, intervention, comparator, outcomes and setting against the child, and rate the certainty of the body of evidence with GRADE, downgrading for indirectness where the match is poor. Combine that certainty with the balance of benefits and harms and the family's values to set a strong or weak recommendation, and document the reasoning. [7] [4] [5]