[1] Emory Univ, Sch Med, Dept Pediat, Off Clin Res, Atlanta, GA 30322 USA
[2] Rho Inc, CSCC CTC Stat Data Management Ctr, Rho Fed Syst Div, Chapel Hill, NC USA
[3] Univ Texas SW, Dallas, TX USA
[4] Childrens Hosp Philadelphia, Philadelphia, PA 19104 USA
[5] St Jude Childrens Res Hosp, Memphis, TN 38105 USA