Synopsis
Frame answerable questions, find and appraise relevant evidence, integrate effect certainty with patient values and context, and verify whether the resulting decision achieves its intended outcome.
- Translate uncertainty into a structured question with population, intervention or exposure, comparator, outcomes, setting and relevant time horizon.
- Search for the highest-level current evidence that can answer that question, then check that its included studies and dates match the decision.
- Appraise validity by bias domain rather than awarding a study a single quality label based only on design name.
Reasoning priorities
Define what evidence would be relevant before searching.
Specify population, intervention or exposure, comparator, outcomes, time and setting; omitting harms or patient-important outcomes biases the question itself.
Worked reasoning
Inputs: a review estimates RR 0.75 for a harmful event over five years; applicable baseline risk is 20%; evidence certainty is moderate and treatment adds a 3% absolute risk of a troublesome adverse effect.
- Calculate treated event risk under a constant relative effect: 0.20 multiplied by 0.75 equals 0.15, or 15% over five years.
- Calculate absolute benefit: 20% minus 15% equals 5 percentage points, equivalent to about 50 fewer harmful events per 1,000 treated over five years.
- Place benefit beside harm: about 30 additional troublesome adverse effects per 1,000, while noting that the outcomes differ in severity and cannot be netted arithmetically without patient values.
- Explain moderate certainty as a real possibility that the effect estimate could change, then discuss burden, alternatives and how much the patient values avoiding each outcome.
- Agree an individual plan and review point rather than presenting RR 0.75 alone as the decision.
- Verify arithmetic with NNT for benefit: one divided by 0.05 equals 20 over five years; 1,000 divided by 20 gives 50 events prevented, matching the absolute calculation.