Table CStrength of evidence categories and rules

Strength of Evidence and RulesCriteria
High SOEHigh confidence that the evidence reflects the true effect. Further research is very unlikely to change our confidence in the estimate of effect.
Moderate SOEModerate confidence that the evidence reflects the true effect. Further research may change our confidence in the estimate of effect and may change the estimate.
Low SOELow confidence that the evidence reflects the true effect. Further research is likely to change our confidence in the estimate of effect and is likely to change the estimate.
Insufficient SOEEvidence is either unavailable or does not permit estimation of an effect.
Starting level of strength of RCT evidenceHigh
Starting level of strength of observational evidenceLow, but a single observational study of good quality without confirmation by at least 1 other study of good or fair quality supports an SOE rating of insufficient.
Raise strengthAmong observational studies, raise strength by 1 level if a large effect size is observed, a dose-response association is present, or a plausible confounder could decrease the observed effect. A very large effect size could raise strength by 2 levels.
Reduce strengthReduce strength by 1 level if there is serious concern in an area such as high risk of bias, inconsistent findings, consistency unknown, indirect evidence, imprecise results, or presence of publication bias. Very serious concern in any of these areas could reduce strength by 2 levels.

Abbreviations: RCT = randomized controlled trial; SOE = strength of evidence.

From: Executive Summary

Cover of Local Therapies for Unresectable Primary Hepatocellular Carcinoma
Local Therapies for Unresectable Primary Hepatocellular Carcinoma [Internet].
Comparative Effectiveness Reviews, No. 114.
Belinson S, Yang Y, Chopra R, et al.

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