1. From the General Internal Medicine Section, Medical Service, VA Medical Center, San Francisco, Calif (J.A.S.); Division of Clinical Epidemiology, Department of Epidemiology and Biostatistics, University of California–San Francisco (J.A.S., J.F.); and Clinical Biochemistry Branch, Division of Environmental Health Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Ga (J.T.B.).