BACKGROUND:

Epidemiologic studies have identified Factor V Leiden as the most common cause of heritable thrombophilia, a prothrombotic mutation associated with a 5 to 7-fold increase in the risk of venous thromboembolism (VTE). In pre-menopausal women, the use of oral contraceptives is associated with a 4-fold increase in VTE risk, and the joint effects of oral contraceptive use and Factor V Leiden carriership increase the VTE risk of by a factor of 35. Recently, the results of several observational studies and randomized clinical trials suggest that in post-menopausal women, the use of hormone replacement therapy is associated with a 3-fold increase in VTE risk. Whether post-menopausal women with prothrombotic mutations experience a similar 20-fold increase in risk when they take post-menopausal hormones remains unknown.

DESIGN NARRATIVE:

In this case-control study, post-menopausal women with a first episode of objectively confirmed venous thromboembolism, and population-based controls were identified and recruited from the GHC enrollment files. Controls were frequency matched to the cases on age and calendar-year. Data collection included a review of ambulatory medical record and a telephone interview. The GHC computerized pharmacy database was used to assess exposure to hormone replacement therapy. A venous blood specimen was obtained from consenting subjects, processed into aliquots of white cells, plasma, and red cells, and stored at 70 degrees C prior to laboratory analysis. DNA was extracted from white cells, and molecular genotyping assays were conducted to assess carriership of prothrombotic mutations.