Alloimmunization in β-Thalassemia and Sickle Cell Disease in Middle Eastern Countries: A Systemic Review

Sickle cell disease and β-thalassemia are important health problems in Middle Eastern countries. Transfusion is the cornerstone of the management in these disorders, and red blood cell alloimmunization is among the well-recognized adverse effects associated with it. We reviewed the literature on published studies on alloimmunization prevalence, its associated risk factors, and transfusion policies employed in these countries. Our review included 39 studies on thalassemia (including 9005 patients), and 19 on sickle cell disease (including 3867 patients). The mean alloimmunization prevalence rate in thalassemia was 13.0% (95% CI: 10.0-15.0%), while that in sickle cell disease was 14.0% (95% CI: 10.0 - 19.0%). The distribution of the prevalence rates showed considerable heterogeneity in both diseases. The most frequent alloantibodies detected were anti-K (25.9%), Anti-E (21.8%), and Anti-D (9.2%), with Rhesus and K antibodies comprising 74.2% of all antibodies detected. Some risk factors were significant in several studies, including older age, female sex, older age at first transfusion, number of transfused units, and splenectomy. The prevalence of alloimmunization was significantly higher in retrospective studies compared to cross-sectional ones, in both thalassemia and sickle cell disease (P = 0.04 in each). This review reaffirmed the need to provide ABO+Rhesus + K matched blood to hemoglobinopathy patients in the Middle East, and the need for more research on Rhesus variants in this part of the world.