1 From the Department of Population and Quantitative Health Sciences (W.P.B.), School of Medicine, Case Western Reserve University, Cleveland, OH; and Boston Medical Center (I.S.F.), Boston University, MA. wpb27@case.edu.
2 From the Department of Population and Quantitative Health Sciences (W.P.B.), School of Medicine, Case Western Reserve University, Cleveland, OH; and Boston Medical Center (I.S.F.), Boston University, MA.