GRADE is the international standard for rating certainty. We walk through all five downgrade and three upgrade domains with practical examples.
GRADE (Grading of Recommendations Assessment, Development and Evaluation) is a systematic approach for rating the certainty of evidence in systematic reviews and clinical guidelines. It is used in Cochrane Reviews, WHO guidelines, and most major clinical practice guidelines worldwide.
High: We are very confident that the true effect lies close to the estimate of the effect.
Moderate: We are moderately confident in the effect estimate. The true effect is likely to be close to the estimate, but there is a possibility that it is substantially different.
Low: Our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate.
Very Low: We have very little confidence in the effect estimate. The true effect is likely to be substantially different from the estimate.
1. Risk of bias. Methodological limitations in the included studies — randomisation, blinding, selective reporting.
2. Inconsistency. Unexplained heterogeneity across studies. High I² with no clear explanation warrants downgrading.
3. Indirectness. The evidence does not directly answer the research question — different population, intervention, comparator, or outcome.
4. Imprecision. Wide confidence intervals that cross the threshold for clinical significance. Driven by small sample sizes or few events.
5. Publication bias. Systematic underreporting of negative or null results. Assessed via funnel plot asymmetry and Egger's test.
Observational studies start at Low certainty but can be upgraded for: large magnitude of effect, dose-response gradient, or effect of plausible confounding.
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