[1] Tufts Med Ctr, Dept Pediat, 800 Washington St 854, Boston, MA 02111 USA
[2] Univ Calif Los Angeles, Dept Pediat, RAND Corp, RAND Hlth, Los Angeles, CA 90024 USA
[3] Univ Calif Los Angeles, Dept Hlth Policy & Management, RAND Corp, RAND Hlth, Los Angeles, CA USA
[4] Univ Calif Los Angeles, Mattel Childrens Hosp, Childrens Discovery & Innovat Inst, Los Angeles, CA USA
[5] Mayo Clin, Dept Pediat & Adolescent Med, Rochester, MN USA