Uncertainty in Identification of Blood Group A Subtypes by Agglutination Test

Abstract

Identification of the blood group A subtypes, i.e. A₁, A₂, and A₁-A₂ intermediate (Aint), by agglutination test, particularly in AB red cells, is ambiguous. The expressions of A subtypes in red blood cells are the consequences of diverse formations of the A substances by the action of three types of blood group N-acetyl-galactosaminyl-transferases controlled by A₁, A₂, and Aint genes. Therefore, the A subtypes are more directly identified by examining the kinetic characters of A-enzymes existing in plasma. Several Black AB subjects classified as non-A₁ by the agglutination test were identified as A₁B and AintB on the enzyme basis. A subject serologically classified as A₁ had A₂-enzyme in her plasma, i.e. she is genetically A₂O or A₂A₂. The present and previous studies indicate that red cell A₂ status is occasionally expressed as a result of the combination of Aint and B, and of A₁ and superactive B. The imbalance between A₁/A₂ and A₁B/ A₂B observed in some Black populations could be attributed to high frequencies of the Aint and B. sup. genes in Blacks.

Distribution of Blood Groups in the East African Somali Population

“…However, although present, it was not al ways possible to decide whether a sample belonged to Ain, subgroup [see also Yoshida et al, 1985], Suspected Ajnt were in cluded with Ai in the frequency calcula tions.…”

A intermediate (Aint) subgroup with warm anti-A1 antibody: A case report

“…A subgroups like A 2 or others may have anti-A 1 antibody reactive at 37°C and should receive either O group or same group packed red cells but not A 1 red cells [1]. Yoshida et al showed in a study that an individual can be even A int B group and plasma enzyme determination is better than routine serological methods in determination of A 1 , A 2 , or A int subtypes [9,10].…”