Table 4.

Summary of GRADE assessment.

Outcome	Number of participants (n=)	Number of studies (n=)	Estimated effects (MD with 95% CI)	Certainty of the evidence
Migraine frequency at the end of treatment	1567	21	MD: −1.23 (−1.69, −0.76)	⊕⊕○○ Lowa,b
Migraine frequency at the end of follow-up	345	5	MD: −0.96 (−1.70, −0.21)	⊕○○○ Very lowa,b,c
GRADE working group grades of evidence High certainty: we are very confident that the true effect lies close to that of the estimate of the effect Moderate certainty: 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 certainty: our confidence in the effect estimate is limited. The true effect may be substantially different from the estimate of the effect Very low certainty: we have very little confidence in the effect estimate. The true effect is likely to be substantially different from the estimate of the effect Explanation: aHigh risk of bias in blinding may limit the certainty of the results; bhigh heterogeneity may limit the certainty of the results; csmall sample size may limit the certainty of results

Note: CI, confidence interval; MD, mean difference; n, number.