1. University of Pittsburgh Pittsburgh Pennsylvania USA
2. Children's National Medical Center Washington District of Columbia USA
3. Center for Sickle Cell DiseaseHoward University Washington District of Columbia USA
4. Montfiore Medical Center, Einstein College of Medicine New York New York USA
5. Cincinnati Children's Hospital Medical Center/University of Cincinnati College of Medicine Cincinnati Ohio USA
6. University of Michigan Ann Arbor Michigan USA
7. Mayo Clinic Rochester Minnesota USA
8. University of Illinois at Chicago Chicago Illinois USA