1. Department of Epidemiology; University of Washington; Seattle WA USA
2. Group Health Research Institute; Group Health Cooperative; Seattle WA USA
3. Seattle Epidemiologic Research and Information Center; Veterans Affairs Office of Research and Development; Seattle WA USA
4. Division of Angiology and Haemostasis; Geneva University Hospitals and Faculty of Medicine; Geneva Switzerland
5. Department of Medicine; University of Washington; Seattle WA USA
6. Department of Biostatistics; University of Washington; Seattle WA USA
7. Departments of Clinical Epidemiology and of Thrombosis and Haemostasis; Leiden University Medical Center; Leiden the Netherlands
8. Department of Pharmacy; University of Washington; Seattle WA USA
9. Department of Health Services; University of Washington; Seattle WA USA