TABLE 1

Definition of Grade of Evidence for Primary Studies and Systematic Reviews

Quality	Definition
High	Further research is unlikely to change confidence in estimate of effect of intervention. No serious limitations were noted.
Moderate	Further research is likely to have important impact on confidence in estimate of effect of intervention and may change estimate. Few serious limitations were noted.
Low	Further research is very likely to have important impact on confidence in estimate of effect of intervention and is likely to change estimate. Typically, more than 2 serious limitations were noted.
Unclear	Any estimate of effect is uncertain. Evidence is either lacking or was not described well enough to allow critical appraisal or make any estimate.