Table 1.

Interpretation of evidence levels used to GRADE CTFPHC recommendations

EVIDENCE LEVEL	DEFINITION
High	We judge evidence to be high quality when we are highly confident that the true effect lies close to that of the estimate of the effect. For example, evidence is judged to be high quality if all of the following apply: there is a range of studies included in the analysis with no serious limitations; there is little variation among studies; and the summary estimate has a narrow CI
Moderate	We judge evidence to be moderate quality when we consider that the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. For example, evidence might be judged to be moderate quality if either of the following applies: there are only a few studies and some have limitations but not serious flaws; or there is some variation among studies or the CI of the summary estimate is wide
Low or very low	We judge evidence to be low or very low quality when the true effect might be substantially different from the estimate of the effect. For example, evidence might be judged as low quality if any of the following applies: the studies have serious flaws; there is important variation among studies; or the CI of the summary estimate is very wide

CTFPHC—Canadian Task Force on Preventive Health Care, GRADE—grading of recommendations, assessment, development, and evaluation.
Adapted from Balshem et al.²²