Table 6– Quality of evidence and strength of recommendations
Quality of evidenceHighEvidence includes well-designed, well-conducted randomised trials or meta-analyses of randomised trials, without risk of bias, indirectness, imprecision, inconsistency or publication bias. Alternatively, the evidence may include well-designed, well-conducted observational studies with either a very large effect or at least two of the following: a large effect, dose–response gradient, and/or reverse confounding.
ModerateEvidence includes randomised trials or meta-analyses of randomised trials downgraded because of a serious risk of bias, indirectness, imprecision, inconsistency or publication bias. Alternatively, the evidence may include well-designed, well-conducted observational studies upgraded because of a large effect, dose–response gradient or reverse confounding.
LowEvidence includes well-designed, well-conducted observational studies, or randomised trials or meta-analyses of randomised trials downgraded two levels because of very serious risk of bias, indirectness, imprecision, inconsistency or publication bias.
Very lowEvidence consists of case reports, case series or unsystematic clinical observations (i.e. clinical experience or expert opinion).
Strength of recommendationsStrongThe committee feels certain that the benefits of the intervention substantially outweigh its risks, burdens and costs.
WeakThe committee believes, but is uncertain, that the benefits of the intervention substantially outweigh its risks, burdens and costs.