[1] Univ Penn, Dept Med, Div Pulm Allergy Crit Care Med, Philadelphia, PA 19104 USA
[2] Boston Univ, Sch Med, Dept Med, Gen Internal Med Sect, Boston, MA 02118 USA
[3] Univ Penn, Grad Sch Educ, Philadelphia, PA 19104 USA
[4] Univ Penn, Dept Family Med & Community Hlth, Philadelphia, PA 19104 USA
[5] Alfred I DuPont Hosp Children, Nemours Ctr Childrens Hlth Media, Wilmington, DE USA
[6] Childrens Hosp, Res Study Coordinator, Boston, MA 02115 USA
[7] Tufts Univ, Sch Med, Dept Publ Hlth & Family Med, Boston, MA 02111 USA
[8] Harvard Univ, Sch Publ Hlth, Dept Soc Human Dev & Hlth, Boston, MA 02115 USA