[1] Valparaiso Univ, Coll Nursing & Hlth Profess, Valparaiso, IN 46383 USA
[2] Univ Florida, Coll Med, Dept Pediat, Gainesville, FL USA
[3] Univ N Carolina, Cecil G Sheps Ctr Hlth Serv Res, Chapel Hill, NC USA
[4] Univ Florida, Coll Med, Dept Hlth Outcomes & Policy, Gainesville, FL USA
[5] Univ N Carolina, Dept Hlth Policy & Management, Gillings Sch Global Publ Hlth, Chapel Hill, NC USA
[6] Univ N Carolina, Sch Med, Dept Med, Chapel Hill, NC USA
[7] St Jude Childrens Res Hosp, Dept Epidemiol & Canc Control, 262 Danny Thomas Pl Mail Stop 735, Memphis, TN 38105 USA