Impact of antigenic exposures and role of molecular blood grouping in enhancing transfusion safety in chronically transfused thalassemics

BACKGROUND: Red cell alloimmunization is an acknowledged complication of blood transfusion. Current transfusion practices for thalassemia do not cater to this risk. Serological phenotyping is usually not reliable in these cases unless performed before the first transfusion. Under such circumstances, molecular blood grouping is an effective alternative. AIM: To perform molecular blood group genotyping in chronically transfused thalassemia patients and assess the risk of antigenic exposure and incidence of alloimmunization with current transfusion protocols. MATERIALS AND METHODS: Molecular blood group genotyping was performed for 47 chronically transfused thalassemia patients. Their 1-year transfusion records were retrieved to assess the antigenic exposure and the frequency thereof. RESULTS: Of 47 patients, 6 were already alloimmunized (3 with anti-E and 3 with anti-K) and were receiving the corresponding antigen negative units. We observed that random selection of ABO and Rh D matched units resulted in 57.7% ±8.26% chance of Rh and Kell phenotype matching also. Forty-four patients had received one or more antigenic exposures at least once. The 6 already alloimmunized patients were further exposed to antigens other than the ones they were immunized to. During the study period, only one patient developed an alloantibody, anti-E with exposure to antigens C (92%) and/or E (32%) at each transfusion. CONCLUSION: Several factors apart from mere antigen exposure may influence the development of alloimmunization as most of our patients received antigenic exposures but not alloimmunized. Our data provide an impetus for future large-scale studies to understand the development of alloimmunization in such patients.