|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.
|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.
|C||Low||Our confidence in the effect estimate is limited: The true effect may
be substantially different from the estimate of the effect.
|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.
Source: GRADE (Grading of Recommendations Assessment, Development and Evaluation) Working Group «http://www.gradeworkinggroup.org»1 (modified by the EBM Guidelines Editorial Team)