GRADE Working Group: Grades of evidence are important in understanding results especially those derived from meta-analyses.
High quality: Very confident that the true effect lies close to that of the estimate of the effect
Moderate quality: 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
Low quality: Confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect
Very low quality: Very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect