[1] Univ Penn, Sch Med, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[2] Univ Penn, Sch Med, Dept Med, Div Gen Internal Med, Philadelphia, PA 19104 USA
[3] Univ Penn, Sch Med, Leonard Davis Inst, Philadelphia, PA 19104 USA
[4] Univ Penn, Sch Med, Dept Pediat, Craig Dalsimer Program Adolescent Med, Philadelphia, PA 19104 USA
[5] Univ Penn, Sch Med, Dept Med, Craig Dalsimer Program Adolescent Med, Philadelphia, PA 19104 USA
[6] Childrens Hosp Philadelphia, Philadelphia, PA 19104 USA