Prevalence of Blood Group A2 among Group A and Ab Donors who Visit the Southern Area Blood Centre

ABSTRACT

Introduction: The ABO blood group antigens are major antigens whose discovery paved way for the performance of safe blood transfusions and transplantations. Subgroups of the ABO antigens were discovered few years after ABO antigens discovery. A1 and A2 are the two principal subgroups of A, both of which are produced by different enzymes. Anti-A1 antibody appears as an atypical cold agglutinin in the sera of some individuals with A2 or A2B who lack the corresponding antigen. One to eight percent of group A2 individuals and 22-35% of group A2B individuals develop anti-A1 in their serum which can cause discrepancies in ABO blood typing leading to haemolytic transfusion reactions. Knowing the proportion and distribution of blood group A2 will be helpful in preventing Haemolytic Disease of the Newborn (HDN) and also help in safe blood transfusion. Knowledge of antigen A2 frequency will also improve the profile of ABO blood groups among Ghanaians. 

Aim: The aim of this study was to determine the prevalence of antigen A2 among group A and AB blood donors visiting the Southern Area Blood Centre (SABC), Accra. 

Methods: This study was carried out at all the sites operated by the SABC. It was a cross sectional study that included all blood donors who passed the pre-donation screening. Approximately 2mls of their donated blood was used for the study. Using the tube method, forward and reverse ABO blood grouping was done with their cells and serum using anti-A, anti-B monoclonal reagents. Blood group A and AB were selected and used against Anti-A1 reagent (Dolichos lectin) for blood group A2 screening. Commercially prepared A1 and A2 red cells were used against the serum of the group A samples which served as controls. Data obtained was analyzed using SPSS version 22.

Results: A total of one thousand, one hundred and forty (1,140) participants (all Ghanaians) who were made up of 942 (82.6%) males and 198 (17.4%) females were screened for the study. The ABO blood group distribution observed was; O(51.3%), A1(16.8%), A2(4.4%), B(23.5%), A1B(1.7%), A2B (2.2%). The prevalence of antigen A2 among the study participants was 6.6%. Among participants with antigen A (groups A and AB individuals), 74% were A1 whiles 26% were A2. Among group A individuals, 20.66% were A2 whiles 79.34% were A1. The prevalence of antigen A2 among group A2B individuals was 55%. Only one individual with blood group A2 had developed anti-A1 antibody.

Conclusion: The prevalence of blood group A2 among group A and AB individuals in the Ghanaian population is similar to that obtained from studies in several West African countries. However, unlike many African countries, antigen A2 is the most prevalent A antigen among AB individuals in Ghana. Anti-A1, which causes discrepancies in blood typing leading to transfusion reactions in group A2 and A2B individuals, was hardly seen among Ghanaians with antigen A2 hence screening for anti-A1 may not be necessary among Ghanaian donors.