Table 1 
Grades of quality of evidence in GRADE [24] 
High = We are very confident that the true effect lies close to that of the estimate of the effect. 

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. 

Low = Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect. 

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. 

Fretheim et al. BMC Medicine 2012 10:33 doi:10.1186/174170151033 