RHD variants in F landers, B elgium

Background D antigen variants may be grouped into partial D , weak D , and DEL types. Cumulative phenotype frequencies of these D variants may approach 1% in certain E uropean regions. Unambiguous and quick identification of D variants is of immediate clinical relevance, with implications for transfusion strategy. Study Design and Methods A total of 628 samples with ambiguous serologic results from different immunohematology laboratories throughout the F landers region, B elgium, were genotyped using a commercially available weak D typing approach. After exclusion of detectable weak D types, molecular RHD exon scanning was performed for the remaining samples, and RHD sequencing was performed in two particular cases. Results Of all samples investigated, 424 (67.5%) were positive for weak D T ype 1, 2, or 3, and 22 cases (3.5%) typed weak D T ype 4.0/4.1/4.3, 4.2, 5, 11, 15, or 17. Another 49 (7.8%) samples were partial D variants, with a major proportion being category DVI types (n = 27). One RHD ( S103P ) sample was identified as high‐grade partial D , with DIII ‐like phenotype and anti‐ D and anti‐ C immunization. Additionally, a novel DVI T ype 3 ( A399T ) variant was found. Of the remaining 133 samples mainly tested because of ambiguous serologic D typing results due to recent transfusion, 32 (5.1%) were negative for RHD , and 101 (16.1%) were indistinguishable from wild‐type RHD and not investigated further. Conclusion Despite the enormous diversity of RHD alleles, first‐line weak D genotyping was remarkably informative, allowing for rapid classification of most samples with conspicuous RhD phenotype in F landers. The clinical implications are discussed.