1. From the Department of Pediatrics, Virginia Commonwealth University School of Medicine, Richmond, Virginia;
2. Pediatric Research in Office Settings, American Academy of Pediatrics, Elk Grove Village, Illinois;
3. Department of Pediatrics, University of Vermont College of Medicine, Burlington, Vermont;
4. Department of Statistics, University of Chicago, Chicago, Illinois; and
5. School of Public Health, Department of Maternal and Child Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.