(P-IG-43) Targeted Sequencing Resolves ABO Discrepancy in a Patient with Rare ABO Genotype

Background/Case Studies: Verifying a potential transfusion recipient’s previously documented blood group and serologic records is vital to ensuring safe transfusions. This is typically accomplished by using the previously reported blood group, generally obtained from well-established serologic methods, as a reference for the transfusion process. ABO discrepancies are occasionally encountered but are frequently resolved with routine serologic methods or clinical history. Rarely, the source of an ABO discrepancy remains unexplained after standard clinicoserologic investigations. However, the availability of blood group genotyping tools within transfusion medicine has afforded more sensitive techniques to uncover sources of challenging ABO discrepancies.

Study

Design/Methods: A Hispanic female with a history of upper gastrointestinal bleeds presented to the ED with chest pain and a specimen was submitted for type and screen. Historical ABO typing performed with a commercially available solid phase red cell adherence assay (SPRCA) was available, and routine ABO blood typing was performed on the current specimen using SPRCA and the tube method. DNA sequencing of ABO exon 2,6, and 7 and flanking intron regions were conducted through a regional Immunohematology reference laboratory.

Results/Findings: The historical typing for the patient indicated group B in both forward and reverse typing. Current specimen using SPRCA method showed group B on forward type with 3+ agglutination but group AB for the reverse (i.e., no agglutination observed with reagent A1 and B cells). Current specimen using tube method showed weak reactivity in the forward test with anti-A and a reverse grouping consistent with group B, although the result with the patient's plasma and A1 cells was weak. Targeted sequencing revealed the presence of multiple SNPs consistent with the presence of the following alleles in trans: ABO*AW.09 (c.46A, c.467T, c.1061delC) and ABO*B.01 (c.297G, c.526G, c.657T, c.703A, c.796A, c.803C, c.903A). The patient's predicted phenotype is Group AweaksubgroupB.

Conclusions: While current technologies provide accurate blood group reporting, discrepancies may still occur, especially with weak subgroups. Transfusion services must investigate all discrepancies to avoid incorrect transfusions. The rare AweakB group found in this patient can be falsely typed as B, posing a potential risk for transfusion with plasma-containing products. The patient’s blood type was changed to AB with a restriction to provision only group O red cells. Anti-A1 antibody was added to patient’s profile since the anti-A1 thermal amplitude was not confirmed.

Importance of research: The increasing availability of ABO group genotyping in transfusion medicine has provided new tools to effectively and definitively resolve ABO discrepancies, yielding blood bank laboratory efficiencies and potential benefits for transfusion recipient safety.