Background and objectives: Routine serologic D typing does not distinguish between weak D subtypes and partial D phenotypes. The goal of this study was to validate the performance of the ID RHD XT genotyping assay.
Material and methods: Previously serotyped samples for D antigen (n = 1000; 16% weak D serotyped donors) were analysed. The reference methods used for comparison were licensed serology tests for D antigen phenotype, and bidirectional sequencing (BDS) for weak D type confirmation and HPA-1 phenotype prediction. Discrepancies were solved with BDS and BLOODchip® Reference.
Results: There were no system failure, a 100% call rate and no inconclusive results. ID RHD XT correctly called all (88/88) weak D types 1, 2 and 3. Review of other 87 apparent discrepancies identified a small number of serology errors and showed that ID RHD XT correctly signalled the presence of other RHD variants which were further confirmed by BDS and BLOODchip® Reference. The predicted HPA-1 phenotype by ID RHD XT was 100% concordant with BDS.
Conclusion: ID RHD XT genotype predictions for high-prevalence RhD negative and weak D types 1, 2 and 3 as well as for HPA-1a/HPA-1b antigens were accurate, which is of clinical significance in guiding transfusion needs.
Keywords: HPA-1; ID RHD XT; RHD; blood group genotyping; sensitivity; specificity.
© 2018 International Society of Blood Transfusion.