Hormonal Contraception and Venous Thromboembolism Risk

Hormonal Contraception and Venous Thromboembolism Risk

To the Editor In observational studies of the association between hormonal contraceptive exposure and the risk of venous thromboembolism (VTE), misclassification of end points will generally tend to move relative risk estimates toward 1, implying underestimation of an increased risk and underestimation of a protective influence. Previous studies have reported a substantial difference in relative risk estimates between studies with and without va…