B subgroup detection in a small hospital transfusion service

Abstract

The ABO blood group system includes phenotypes, or subgroups, that differ in the amount of A and B antigens present on the red blood cells (RBCs). These subgroups also differ in the A, B, or H substances present in secretions (for individuals who have the secretor phenotype). B subgroups are very rare and are less frequently reported than A subgroups. Usually, B subgroups are discovered during serologic testing when there is a discrepancy between RBC and serum grouping results. Subgroups of B are usually identified by a reference laboratory using molecular and adsorption-elution methods. This report details a case of a young, healthy, pregnant woman with a B subgroup detected by a small transfusion service using adsorption-elution methods. Serology and genotyping of the ABO gene was performed at a reference laboratory where the serology was consistent with a B subgroup, but no changes were identified in ABO gene sequencing. It is important to correctly identify B subgroups in donors and recipients to help resolve ABO discrepancies and potentially prevent ABO incompatibility in blood transfusion, thus minimizing transfusion reactions.

A Rare B-Subgroup Causing ABO Discrepancy in Blood Grouping: A Case Report

“…Although the secretor study and more advanced molecular study are available as a better option for the detection of ABO subgroup, the suitability of the adsorption-elution test is demonstrated here which can be used by blood bank laboratories without the confirmatory tests 4 .…”

“…In this present case, we have excluded other causes of discrepant results such as haematogical diseases, extreme age or any transfusion/transplant event. Medication and pregnancy history are also important to rule out causes of discrepancy 1,4 .…”

“…It is better to inform the subgroup individuals about their blood group status and if possible, a special blood group card to be issued explaining their respective donor and recipient status 5,7 . 4,7 . In our patient, packed cell was not transfused, however, fresh frozen plasma and cryoprecipitate were transfused due to coagulopathy and compatible AB plasma was given.…”

“…B subgroup is a rare occurrence, discovered during resolving ABO blood group discrepancy 4 . They are found less frequently than A subgroup 2 .…”

“…The inheritance of B subgroups is considered to be due to mutation in the alleles at the B locus, resulting in the changes in the transferase enzyme activity that add B-sugar to the precursor H antigen 1,5 . The B subgroup is distinguished by decreased quantity of B antigens on RBC and by the presence of B substances in secretions of the secretor individuals 4 . The different phenotypes in B subgroups include B 3 , Bm, Bx and Bel.…”