1. Departments of Pediatrics, Medicine and Pathology, Anschutz Medical Center, University of Colorado Denver, Aurora, Colorado.
2. Department of Pediatrics, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil.
3. Westat, Rockville, Maryland.
4. Departamento de Medicina da Universidade Federal de Sao Carlos, Sao Carlos, Brazil.
5. Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland.