Red Blood Cell Immunization and Contributing Factors in 685 Thalassemia Patients

Background: An analysis of red blood cell alloimmunization in patients with thalassemia can help to devise specific strategies to decrease the alloimmunization rate. This study explored the frequency and specificity of alloantibodies and autoantibodies against red blood cell (RBC) antigens in patients with thalassemia referring to the Iranian Blood Transfusion Organization (IBTO) Immunohematology Reference Laboratory (IRL) in Tehran. Materials and Methods: This study first examined the laboratory records of 23,113 patients suffering from different diseases referring to IBTO's IRL for pretransfusion testing in the 2008-2015 period. ABO and Rh(D) typing and antibody screening tests were performed for all 23,113 patient records and 685 (2.97%) beta-thalassemia patients with positive pre-transfusion test results (antibody screening and/or DAT) were selected for further investigation. Results: The antibody screening test was positive in 640 out of 685 thalassemic patients (93.4%). DAT was performed for 529 patients, 226 (33%) of which showed positive results. Meanwhile, 161 out of 685 beta-thalassemia patients (23.5%) had positive auto control test results, reflecting the possible presence of allo- and/or autoantibodies. The most common antigen-specific alloantibodies were directed against K and E RBC antigens with a frequency of 25% (Anti-K) and 11.91% (Anti-E), respectively. The development of two antibodies (double antibodies) in one patient was observed in 80 individuals (11.46%). Conclusion: Age, gender, history of pregnancy, and splenectomy were not contributing factors to the antibody presence in the patient population under study. Extended red blood cell phenotyping should be considered as an essential procedure for expected multi-transfused thalassemia patients before blood transfusion. Considering the high frequency of anti-K and anti-E observed in this study, it is recommended that thalassemia patients in Iran are tested through phenotyping of RBC units for K and E antigens before transfusion.