Risk Factors for Red Cell Alloimmunisation in Multi-Transfused Patients in a Referral Hospital, North-Eastern India

Introduction: The formation of red cell (RBC) alloantibody in a transfused patient can complicate transfusion therapy and limit the availability of compatible blood for future transfusions. It has a significant negative impact on laboratory and institutional resources. Therefore, identification of patients associated with increased risk of RBC-alloimmunisation is important so as to prioritize the provision of prophylactic extended antigen matched red cell units for those patients. Methods: Our study was conducted for a period of one and half year to determine the prevalence of RBC alloimmunisation and associated risk factors for its development in multi-transfused patients who received 2 units of packed red cells and/or whole blood. Red cell alloimmunisation was analysed based on the factors i. e. number of units transfused, age of 1st transfusion, disease of transfusion, gender of transfusion and alloantigen specificities. Laboratory tests performed in all study cases were ABO blood group, Rh (D) type, and antibody screen (AS). Direct antiglobulin test (DAT) and antibody identification were carried out when antibody screen was positive. Results: Twelve cases (7.45 %) of the study population (n=161) were RBC-immunised, of which RBC alloimmunisation were identified in 9 patients (5.59 %). Our study could not identify the specificity of antibody in 3 patients of DAT positive cases and labelled them as �unidentified� (1.86 %). RBC alloimmunisation were more (10.81 %, 4/37) among the patients who had transfused 16 units. There was an association of RBC alloimmunisation and transfusion count. A higher risk of alloimmunisation was also observed (10.53 %, 4/38) when 1st transfusions were between 16-30 years of age when compared with the younger and older age groups. The prevalence for RBC alloimmunisation among different diseases/conditions were 14.29 % in thalassaemia (n=21), 9.09 % in aplastic anaemia (n=11), 7.14 % in chronic kidney disease (n=28), 4.35 % in trauma (n=23), none were alloimmunised in malignancy and 2.56 % in other conditions/diseases (acute bleeding/blood loss from different causes/anaemia of chronic diseases etc. ). Females were more alloimmunised (6.59 %) than males (4.29). The distribution of alloantigen specificities were anti-E=4, anti-c=2, anti-D=1, anti-K=1, one each for anti-M and anti-JKa and unidentified=3. Among the ten (10) identified alloantibodies, maximum (70 %) were directed against Rhesus group of antigens. Conclusion: Based on our observations measures to reduce red cell alloimmunisation may include early initiation of transfusion (2 years), avoidance of 1st transfusion therapy in young adults (16-30 years) and restricted transfusion regime in female gender and disease (s) with increased alloimmunisation risk or transfusion of RBC units that are antigen-matched for the commonly occurring antibodies to RBC antigens such as Rhesus a Kell antigens.