Prevalence of A 2 and A 2 B Subgroups and Anti-A 1 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 individuals 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°C, 22°C and 37°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.
Competing Interests: The authors report no conflicts of interest in this work.
(© 2020 Saboor et al.)