[1] Duke Univ, Med Ctr, Dept Pediat, Durham, NC 27710 USA
[2] Washington Univ, Dept Pediat, 660 S Euclid Ave,Campus Box 8208, St Louis, MO 63110 USA
[3] Duke Univ, Med Ctr, Dept Med, Durham, NC 27710 USA
[4] Duke Canc Inst, Durham, NC USA
[5] Duke Univ, Sch Med, Dept Populat Hlth Sci, Durham, NC USA