Evidence-based medicine and critical appraisal — branching viva

Opening (candidate)

I would treat this as a structured critical appraisal rather than a result handover. First I would frame the question in PICO terms, then judge the internal validity with RoB 2 before reading the results, then extract the absolute effect and its confidence interval, and finally assess applicability to the patient and rate the certainty with GRADE. [2] [7]

Branch A — Definition and the order of appraisal

Examiner: Why must you judge validity before the results? [3]

Candidate: A biased or confounded estimate is wrong no matter how large, precise, or statistically significant it appears, so validity always comes first. I would score the risk of bias with RoB 2, focusing on randomisation, allocation concealment, blinding, attrition, and selective reporting, and only then read the magnitude and precision of the effect. [3] [6]

Branch B — Magnitude and precision

Examiner: The abstract quotes a 50 percent relative risk reduction. How do you convey this to a family? [1]

Candidate: A relative figure quoted alone inflates perceived benefit, so I would state the absolute baseline risk and the absolute risk reduction, give the number needed to treat, and read the confidence interval. Where the interval crosses unity in a subgroup, I would say plainly that the result there is compatible with both benefit and harm. [1] [6]

Branch C — Certainty and recommendation

Examiner: How do you move from this single trial to a recommendation? [4]

Candidate: I would place the trial in the totality of the evidence and rate the certainty with GRADE, starting from the design and moving down for risk of bias, inconsistency, indirectness, imprecision, or publication bias. I would then combine that certainty with the balance of benefits and harms and the family's values to set a strong or weak recommendation. [4] [5]

Branch D — Applicability

Examiner: The trial was done in adults. Your patient is a four-year-old. Your approach? [7]

Candidate: I would assess applicability by comparing the population, intervention, comparator, outcomes, and setting against the child, and rate the evidence down for indirectness under GRADE where the match is poor. I would present the residual uncertainty honestly and let the family share the decision in full knowledge of it. [7] [5]

Branch E — Failure mode

Examiner: A colleague tells the family the treatment is 'proven and risk-free'. [6]

Candidate: I would avoid contradicting my colleague harshly in front of the family, but I would not leave the overclaim uncorrected. I would acknowledge the reassurance, introduce the balanced benefit-and-harm picture with the absolute numbers and the confidence interval, and align the team afterwards so the family hears one defensible message. [6] [7]

Close

Confirm understanding with teach-back, leave a written summary of the appraised evidence and its certainty, name the next contact, and document the question, the evidence, the certainty rating, the shared decision, and the plan to reassess. [5] [7]