Performance evaluation study of ID RHD XT, a new genotyping assay for the detection of high-prevalence RhD negative and weak D types.

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.