Alloimmunization in Sickle Cell Anemia and Transfusion of Racially Unmatched Blood

Transfusion therapy for sickle cell anemia is limited by the development of antibodies to foreign red cells. To evaluate the frequency and risk factors associated with such alloimmunization, we determined the transfusion history, red-cell phenotype, and development of alloantibodies in 107 black patients with sickle cell anemia who received transfusions. We compared the results with those from similar studies in 51 black patients with sickle cell disease who had not received transfusions and in 19 nonblack patients who received transfusions for other forms of chronic anemia. We assessed the effect that racial differences might have on the frequency of alloimmunization by comparing the red-cell phenotypes of patients and blood-bank donors (n = 200, 90 percent white). Although they received transfusions less frequently, 30 percent of the patients with sickle cell anemia became alloimmunized, in contrast to 5 percent of the comparison-group patients with other forms of anemia (P