Code	Quality of evidence	Definition
A	High	We are very confident that the true effect lies close to that of the estimate of the effect. Several high-quality studies with consistent results In special cases: one large, high-quality multi-centre trial
B	Moderate	We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. One high-quality study Several studies with some limitations
C	Low	Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect. One or more studies with severe limitations
D	Very low	We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect. Expert opinion No direct research evidence One or more studies with very severe limitations

Source:GRADE (Grading of Recommendations Assessment, Development and Evaluation) Working Group [Lien] (modified by the EBM Guidelines Editorial Team)