Table 9 The effect of considering imprecision when judging quality of evidence

Imprecision

Menstruation in girls is another potential prognostic factor investigated in the pediatric headache literature. Wang and colleagues [22], the only study in our review that investigated this factor, sought to explore the prognostic value of menses in girls on migraine persistence in two follow-up annual surveys with a sample of 449 junior high school students with migraine. In their study, 134 out of 449 participants reported persistent migraine for all 3 years. Multiple logistic regression was used to explore the association between 14 potential prognostic factors (including menses in girls) and migraine persistence. This analysis has sufficient statistical power. No significant association between menses and persistent migraine was found; however, no effect size or confidence interval values were provided, so conclusions regarding the level of imprecision of the estimated effect of the menses remain unclear. Consequently, we considered the level of imprecision as unclear.