The EVAPIL scale, a new tool to assess tolerance of oral contraceptives.

Background: The EVAPIL scale is a self-questionnaire aimed to assess tolerability of oral contraceptives (OC).

Methods: For initial development: a list of questions addressing the more frequent or more unpleasant minor side effects of OC was developed by a group of gynecologists and submitted to several sets of OC users. A final version with 14 questions was issued with scoring rules. For validation, the EVAPIL scale was submitted to 3502 women who were OC users for at least 6 months to evaluate internal consistency and factorial structure. Test-retest reproducibility was studied 30 days apart in 53 other OC users.

Results: Internal consistency was good (Cronbach's alpha .71) without redundant questions. Principal components analysis with Varimax rotation was used to summarise information given by the 14 questions in a smaller number of multivariate dimensions. Dimension 1 explained 22% of the total variance, strongly correlated with all symptoms except oily skin, acne and cycle control. Dimension 2 accounted for 10% of the total variance and was correlated with oily skin and acne. Dimensions 3 and 4 were better correlated with cycle control. Reproducibility was excellent (intraclass correlation 0.88). The EVAPIL scale was found easy to use and took no more than 5 min to complete.

Conclusion: The EVAPIL scale demonstrated interesting psychometric properties to evaluate the tolerability of OCs in OC users. Further research is needed to address sensitivity to change and usefulness in new OC users.