1. Department of Hematology; St. Jude Children's Research Hospital; Memphis Tennessee
2. Sickle Cell Unit; Tropical Medicine Research Institute (TMRI), University of the West Indies; Kingston Jamaica
3. Instituto De Hematologia Arthur Siqueira Cavalcanti (HEMORIO); Rio De Janeiro Brazil
4. Division of Pediatric Hematology/Oncology and Stem Cell Transplantation; Cohen Children's Medical Center of New York; New Hyde Park New York
5. Wake Forest University School of Medicine; Winston-Salem North Carolina
6. National Heart Lung and Blood Institute; Bethesda Maryland
7. Division of Hematology; Cincinnati Children's Hospital Medical Center; Cincinnati Ohio