1. From the Clinical Trials Scientific Research Group, Division of Epidemiology and Clinical Applications, National Heart, Lung, and Blood Institute, Bethesda, Md (H.A.C., D.L.D., M.J.D.); the Division of Cardiology, Georgetown University Medical Center, Washington, DC (H.A.C., D.L.D.); and the Department of Biostatistics, University of North Carolina, Chapel Hill (C.E.D., Y.L.S.).