[1] Childrens Hosp Philadelphia, Craig Dalsimer Div Adolescent Med, Philadelphia, PA 19104 USA
[2] Univ Penn, Sch Med, Dept Pediat, Philadelphia, PA 19104 USA
[3] Childrens Natl Med Ctr, Div Adolescent & Young Adult Med, Washington, DC 20010 USA
[4] George Washington Univ, Sch Med, Dept Pediat, Washington, DC 20052 USA