[Molecular blood genotyping in patients with Thalassemia major in Tehran adult thalassemic clinic]

Blood typing by serologic methods after transfusion has limitations due to presence of donor red cells in recipients. Accurate determination of red blood cells [RBCs] antigens is very important in multitransfused patients including beta-thalassemics and sickle cell anemics. So, the aim of this study was to evaluate DNA- based methods as supplement to the hemagglutination technique to determine the red blood cell [RBC] antigen profile of multitransfused patients with beta- thalassemia. DNA was extracted from peripheral blood of 20 apparently normal people and 44 patients including 35 with beta- thalassemia [out of whom 19 had clinical evidence of delayed hemolytic transfusion reaction], 8 with thalassemia intermedia [out of whom 2 had hemolytic reaction], and one with sickle cell thalassemia. RHD/ RHC/ RHc/ RHE/ RHe/ JKA/ JKB/ FYA/ FYB/ KELL1/ KELL2 alleles were determined by PCR and were then compared with the hemagglutination method. Phenotype and genotype results were the same in all controls. The phenotypes and genotypes of 53 blood antigens of 26 patients were incompatible. Most of the discrepancies [19 cases] occurred in the Rh system, and fifteen in the Duffy and Kidd systems. The results show that screening platelet concentrates for bacterial contamination is necessary for blood transfusion centers and hospital blood banks. Blood typing by serologic method was not accurate in this study but genotyping could determine true blood groups in multitransfused patients and help in selection of RBCs without alloimmunized antigens in future transfusion attempts. Specificity, sensitivity, positive and negative predictive values of hemagglutination method for RhD antigen had good values in comparison to the molecular method. This might be due to pre- transfusion determination of RhD for thalassemic patients so as to receive Rh- matched blood units. It seems pre-transfusion blood typing of Rh and Kell antigens, which are the cause of hemolytic reactions, in comparison to the molecular method could be cost effective. In addition, typing of Rh and Kell antigens in some regular blood donors could be helpdul for selecting antigen-negative RBCs for transfusion dependent patients