Associate Professor / HLA Laboratory Director SUNY Upstate Medical University Syracuse, New York
Aim: ABO genotyping, in the context of transplantation, is a laboratory developed test that enables the evaluation of ABO blood group in cases where serologic testing may be ambiguous or not feasible. Despite the increasing interest, and the regulatory requirement for proficiency testing (PT) assessment, there is currently no graded external PT program for ABO genotyping. Here, we summarize the results of the ungraded ABO genotyping challenges offered by the American Society for Histocompatibility and Immunogenetics (ASHI) PT Committee and Southwest Immunodiagnostics (SWI) in preparation for establishing the first graded PT survey for ABO genotyping in the US.
Methods: Data including ABO genotype, subtype (when applicable), phenotype, method and vendor were extracted from Excel spreadsheets used to collect the results from participants in the 2023-2024 ungraded challenges. Consensus was determined for the reported ABO phenotype, based on the genotyping results. In addition, we assessed the feasibility of utilizing the ASHI PT HLA Typing (HT) survey for ABO genotyping in terms of ABO blood group diversity.
Results: The number of laboratories participating in the ASHI and SWI ABO genotyping challenges in 2023-2024 ranged between 7 and 15 laboratories per challenge. All laboratories participating in the SWI challenge reported their results by Real-Time PCR. Laboratories participating in the ASHI challenge reported results by Real-Time PCR/Sequence-specific primer (n=13), Sanger sequencing (n=1) and Next-generation sequencing (n=6). Forty specimens were tested, exhibiting a good variety of blood groups (14 O, 11 A1, 3 A2, 1 A1B, 4 A2B, 7 B). Thirty-seven of the 40 specimens (92.5%) produced 100% consensus for ABO phenotype among participating laboratories. Three specimens had <100% consensus, one with 93% consensus (one laboratory reported A instead of B), one with 85% consensus (2 laboratories reported A instead of A1), and one with 80% consensus (3 laboratories reported A instead of A1).
Conclusion: The results of the ungraded PT challenges show excellent concordance between laboratories and sufficient ABO type diversity. Therefore, we conclude that the HT survey can be used to test for ABO molecular genotyping as a graded survey.
