1. Department of Biostatistics and Epidemiology, Hudson College of Public Health, University of Oklahoma Health Sciences Center, Oklahoma City (A.W.).
2. Thrombosis and Atherosclerosis Research Institute, Hamilton, Ontario, Canada (J.I.W.).
3. Department of Medicine (J.I.W.), McMaster University, Hamilton, Ontario, Canada.
4. Department of Biochemistry and Biomedical Sciences (J.I.W.), McMaster University, Hamilton, Ontario, Canada.