1. From the Department of Neurology, University of Arizona Health Sciences Center, Tucson (W.M.F.); Laboratory for Clinical Biochemistry Research, Department of Pathology, University of Vermont, Burlington (E.S.C., S.D.N., R.P.T., E.G.B.); Statistics and Epidemiology Research Corporation, Seattle, Wash (L.A.P.); and Department of Medicine (Neurology), University of Texas, San Antonio (R.G.H.).