1. Division of Intramural Population Health Research (E.F.S., S.L.M., Z.C., G.M.B.L.), Eunice Kennedy Shriver National Institute of Child Health and Human Development, Rockville, Maryland 20852
2. Department of Biotechnical and Clinical Laboratory Sciences (R.W.B.), University at Buffalo, State University of New York at Buffalo, Buffalo, New York 14214
3. Rollins School of Public Health (D.B.B.), Emory University, Atlanta, Georgia 30322