Combined Hormonal Contraceptives

29 Nov
Kaiser Permanente

Image by Chris Fritz via Flickr

Birth control pill
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Does new generation of contraceptive pills present a risk of Cardiovascular disease ?

Aiming to assess the security of third generation contraceptive pills, two major health care insurers in the US (Kaiser Permanente and Medicaid) have putted in common their huge reimbursement data base. Using only computerized extractions, they designed a study involving thousands of women aged from 14 to 55 years. They used the method named retrospective cohort. They constructed an a posteriori numeric cohort of female enrollees and followed it backward for arterial thrombosis, acute myocardial infarction, stroke and deep venous thrombosis endpoints. Comparators were the first generation contraceptive pills. Data came from the ICD9 coded diagnoses attached to hospital bills and pharmaceutical reimbursements. Quality of the results depends heavily on the liability of the way the data base is implemented routinely. The method leads to samples whose sizes are very high. Big is beautiful because differences are always statistically significant. But does it mean that such differences are clinically significant? Furthermore, the authors didn’t evoke the better clinical tolerance of third generation contraceptive pills. The big size of samples obtained with large data base extractions always leads to findings of significant differences. Balanced medical decision must take into account clinical aspects and not only statistical significance.

The full text of the study is accessible here.

The study is authored by the FDA office of surveillance and epidemiology, the Kaiser Permanente division of research (northern and southern California), the Vanderbilt University division of general paediatrics in Nashville and  the University of Washington School of public health.


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