Evaluating the quality of evidence requires judgements about the extent to which one can be confident that an estimate of effect is correct. GRADE provides a systematic and transparent approach to making these judgements for each outcome important to a decision [12]. The judgements are based on the type of study design (randomised trials versus observational studies), the risk of bias (study limitations), the consistency of the results across studies, and the precision of the overall estimate across studies. Based on these considerations for each outcome, the quality of the evidence is rated as high, moderate, low, or very low, using the following definitions: | |
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High | Confident that the true effect lies close to that of the estimate of the effect |
Moderate | 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 | The true effect may be substantially different from the estimate of the effect |
Very low | Very uncertain about the estimate |