1. Department of Pediatrics, Boston Medical Center, Boston, Massachusetts;
2. School of Medicine, Boston University, Boston, Massachusetts;
3. Data Coordinating Center,
4. Department of Biostatistics, School of Public Health, and
5. Department of Pediatrics, School of Medicine, University of Maryland, Baltimore, Maryland;
6. Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas;
7. Department of Health Management and Policy, Dornfife School of Public Health, Drexel University, Philadelphia, Pennsylvania; and
8. Department of Pediatrics, Hennepin County Medical Center, Minneapolis, Minnesota