[1] Bayero Univ, Aminu Kano Teaching Hosp, Dept Med, Kano, Nigeria
[2] Bayero Univ, Aminu Kano Teaching Hosp, Dept Haematol & Blood Transfus, Kano, Nigeria
[3] Rodeghier Consultants, Chicago, IL USA
[4] Vanderbilt Univ, Sch Med, Dept Pediat, Nashville, TN 37212 USA
[5] Vanderbilt Univ, Sch Med, Vanderbilt & Meharry Sickle Cell Dis Ctr Excellen, Nashville, TN 37212 USA