Prevalence of A2 and A2B Subgroups and Anti-A1 Antibody in Blood Donors in Jazan, Saudi Arabia

Purpose: A(2) and A(2)B are rare phenotypes of the ABO blood group system. Some indivi-duals with A(2) and A(2)B may have anti-A(1) antibodies that may be clinically significant or insignificant. The aim of this study was to determine the frequency of A(2), A(2)B phenotypes and anti-A(1) antibodies in blood donors in Jazan, Saudi Arabia. This study also evaluated the reactivity potential of anti-A(1) antibodies. Materials and Methods: Blood samples collected from 446 blood donors were typed for ABO (cell and serum grouping) and Rh D. Individuals with blood group A and AB were further subtyped by testing with anti-A(1) lectin. In addition to the serum grouping using A(1) red cells, A(2) and A(2)B individuals were screened for the presence of anti-A(1) in their sera against A(1) red cells at 4 degrees C, 22 degrees C and 37 degrees C to determine the thermal amplitude of the reacting anti-A(1) antibody (if present). Results: Among A and AB, A(1) was the commonest phenotype (20.2%, n=90 out of 446) while A(1)B was found to be 1.8% (n=8) among AB phenotype. A(2) and A(2)B were found to be 2.2% (n=10) and 0.9% (n=4), respectively. Only one individual with A(2)B blood type showed cold reactive anti-A(1) antibody, the strength of which was 32. Conclusion: A(2) and A(2)B were the rarest among ABO phenotypes in the studied population. Although rare, anti-A(1) antibody is not so uncommon. Care shall be taken during routine ABO grouping especially in cases of mix-field or weak positive reactions in A and AB phenotypes.