A1 and A2 Sub-Types of Blood Group ‘A’: A Reflection of their Prevalence in North Karnataka Region

Abstract

Introduction: Landsteiner ABO system of blood groups is most important for transfusion medicine and has subtypes of A Antigen, A1 and A2, upon which further groups of A and AB have been classified. Of individuals with A antigen, approximately 20% belong to A2 while rest 80% belong to A1. Anti-A1 Lectin, a cold agglutinin which destroys A1 cells is clinically significant when they react at 37°C, causing transfusion reactions. Aim: To assess the prevalence of A1 and A2 subgroups in the population. Materials and Methods: This was two year retrospective analysis of blood groups of donors coming to the blood bank of Karnataka Institute of Medical Science, Hubli, Karnataka, India. The data of the subgroups A and AB was analysed. Results: 20,864 donors were analysed. Of 5466 (26.20%) of A group, 5406 (98.90%) belonged to A1 subgroup and only 60 (1.10%) belonged to A2 subgroup. Of 1708 donors with blood group AB, 1532 (89.70%) belonged to A1B subgroup and 176 (10.30%) belonged to A2B. It was noted that A2 in AB bloodgroup, as A2B, was more frequent in occurrence than presence of A2 as an A blood group. Rhesus negative frequency in these subgroups was also reported. Conclusion: Having known the prevalence of A1 and A2 subgroups and incorporating them into the ABO grouping system can limit these minor, yet dangerous, transfusion incompatibilities.

Keywords

• a and ab blood groups
• blood donation testing
• donors
• rbc antigen and antibodies