From the Center for Clinical Epidemiology & Biostatistics and the Department of Biostatistics & Epidemiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania (Dr Hennessy, Dr Leonard, Ms Freeman, Dr Metlay, Dr Strom, Dr Bilker); the Center for Education and Research on Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania (Dr Hennessy, Dr Leonard, Ms Freeman, Dr Metlay, Dr Strom, Dr Bilker); the Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania (Dr Metlay, Dr Strom); the Center for Health Equity Research and Promotion, Veterans Affairs Medical Center, Philadelphia, Pennsylvania (Dr Metlay); and the Weis Center for Research, Geisinger Clinic Genomics Core, Danville, Pennsylvania (Dr Chu). Submitted for publica-tion April 13, 2009; revised version accepted June 18, 2009. Address for correspondence: Sean Hennessy, PharmD, PhD, 803 Blockley Hall / 423 Guardian Drive, Philadelphia, Pennsylvania 19104.DOI: 10.1177/0091270009343006