Initiative for rare donor registry for A2/A2B subgroups with Rh phenotyping: A first of its kind

Aims: Aim of this study is to create donor registry of A2/A2B subgroup blood donors with Rh and Kell phenotype, to provide transfusion to multi-transfused A2/A2B subgroup patients and to prevent adverse transfusion reaction due to immunological stimulation by pre-existing anti-A1 antibodies having enhanced titer and thermal amplitude. Prevalence of A2/A2B subgroup in Indian population is rare with highest prevalence of “e” antigen among the five Rh antigens, phenotyped serologically, and “E” antigen being the lowest in prevalence. Anti-A1 antibodies appear as cold agglutinins in A2/A2B individuals and can be clinically significant when reactive at 37 °C, causing hemolysis of A1 RBCs. Methods: A retrospective data analysis was done in a tertiary care hospital-based blood center at capital city of India from January 2016 to December 2020. All donors were subjected to ABO Rh grouping, Rh and Kell phenotyping by solid phase method. Tube technique was used to distinguish A2/A2B by agglutination reaction with anti-A1 lectin. Results: Total 40,051 donors were analyzed during study period, of which, A and AB groups constituted 21.26% and 9.01% respectively; out of these, only 0.47% belonged to A2 subgroup while A2B subgroup was more frequent (1.06%). The rarest Rh phenotypes found were R1Rz, r”r, r’r” in A2/A2B blood donors. Conclusion: There is a need to create rare donor registry for A2/A2B subgroups and clinically significant blood group antigens and share at various levels. This is a first small step to create a rare donor registry of A2/A2B subgroups with Rh and Kell phenotype, to provide transfusion to A2/A2B patients to prevent adverse transfusion reaction due to immunological stimulation by pre-existing anti-A1 antibodies having enhanced titer and thermal amplitude and to ensure improved quality of transfusion therapy.