Aim: ABO blood group determination is becoming increasingly crucial for guiding donor selection in solid organ transplantation. Emerging studies have revealed the feasibility of ABO-incompatible transplantation (e.g. A2/A2B to B), that significantly expands the donor pool by allowing more flexible allocation. Another factor driving interest in ABO molecular testing is the risk of non-A1 serological misassignment due to inconclusive anti-A1 lectin testing. We address this need by utilizing the design strategy of qPCR HLA assay to develop a new in vitro diagnostic assay combining blood group typing with HLA typing.
Methods: The ABO assay is designed to type the common ABO alleles and to split the main phenotype groups into A1, A2, B, O, A1B, and A2B. The assay consists of total of 25 reactions with 3 reactions specifically targeting A1, 2 targeting A2, 4 targeting B alleles, and 8 targeting O alleles. The A1/A2 separation utilizes the classic site c.1061delC., along with two other sites located in Intron 1. Following latest literatures and recent discoveries in ABO blood group markers, the assay design utilizes sequence polymorphism sites on Intron1, Exon 6 and Exon 7, to resolve serological ambiguities within alleles of A1, A2, B1, and O group.
Results: Verification testing of 40 cell lines and 36 clinical samples showed 100% concordance for both serology and molecular typing. All samples were typed without phenotype ambiguity, with A1, A2, B, O, A1B, and A2B alleles separated.
Conclusion: The unique feature of combined HLA and ABO genotyping in one assay allows for faster turnaround time, lower costs and fewer resources on resolving two genotype results. We believe this development will facilitate faster decision on organ allocation for A2 to B incompatible transplants.
