Detection of a rare subgroup of A phenotype while resolving ABO discrepancy

Abstract

Weaker subgroups of ABO blood group system give rise to discrepancies between forward and reverse grouping and cause diagnostic difficulties in routine blood banking. Weaker subgroups of A blood group that have been reported so far include A3, Aend, Ax, Am, Ay, and Ael. We report a case of a 54-year-old patient whose red cells showed a discrepancy between cell and serum grouping on initial testing. Serological investigation included absorption elution tests and saliva testing after performing initial blood grouping. Molecular genotyping of the ABO gene was performed by DNA sequencing of exons 6 and 7 of the ABO gene. The serological characteristics of the patient's red cells were similar to Ax subtype. The patient was a secretor and only H substance was present in the saliva. Serum did not show the presence of anti-A1. Molecular genotyping confirmed the ABO status as Aw06/O13. The weak A phenotype identified in the propositus had serological characteristics similar to Ax and showed the ABO genotype Aw06/O13. Although Aw06 allele has been previously reported in the Indian population, this is the first study to report O13 allele in the Indian population.

A case report of occult weak 'A' subgroup: An important message for renal transplant physicians

“…Weaker variants of A and B arise due to inheritance and expression of variant alleles at the ABO locus and are mostly identified using hemagglutination-based methods. [ 7 ] Hence, accurate ABO typing is vital for a successful organ transplantation and should be confirmed with additional studies when initial blood grouping shows a discrepancy. Detailed workup on blood groups can help identify weaker subgroups of A and B or rare Bombay and para-Bombay phenotypes so that appropriate desensitization protocols can be followed.…”

Significant of Molecular Genotyping Over Serological Phenotyping Techniques in Determination of Blood Group Systems among Multiple Transfused Patients and Blood Donors to Prevent Alloimmunization: A Review Article

“…A typing result that differs from the historical record often results in time-consuming analyses. Since the bases of many of the weak subgroups of A and B are associated with altered transferase genes, PCR-based assays can be used to define the transferase gene and thus the ABO group (Nair et al, 2019). Similarly with the D antigen of the Rh blood group system, a proportion of blood donors that historically have been typed as D-negative are now reclassified as D-positive, due to monoclonal reagents that detect small and specific parts of the D antigen.…”

Patient with a rare weaker subgroup-A exhibiting ABO discrepancy: a case report

“…In subgroup A3, Am and Ay secretor individuals, A and H substances can be detected in the saliva by a saliva test 4 . In the adsorption-elution test, adsorption is done using polyclonal anti-A and anti-A,B derived from Group-B and Group-O individuals, respectively, followed by elution of bound antibody and subsequently testing the elute against A 1 or B reagent red cells 7,11 . Serum glycosyltransferase study is a useful method to differentiate weaker subgroups where it may show the presence of A-transferase enzyme in A3, Am and Ax, but absence in Aend and Ael 4,7 .…”

“…The weaker ABO subgroups pose a challenge for immunohaematology practice in the blood bank. The weaker subgroups may have the chance to be wrongly grouped as group O due to the use of variable techniques and reagents, which can lead to a haemolytic transfusion reaction 4,11 . Although the subgroups are rare, they are usually discovered during resolving discrepancies between the forward and reverse group results 12 .…”