[1] George Washington Univ, Sch Med, Childrens Natl Med Ctr, Dept Pediat,Div Adolescent & Young Adult Med, Washington, DC 20052 USA
[2] George Washington Univ, Sch Publ Hlth & Hlth Serv, Dept Epidemiol, Washington, DC 20052 USA
[3] George Washington Univ, Sch Publ Hlth & Hlth Serv, Dept Pediat, Washington, DC 20052 USA