A distinctive RhD serologic phenotype expressed by p. Glu233Lys RHD alleles DV type 5 and DAU4 in microplate agglutination RhD typing

BACKGROUND: In patients with variant RhD phenotypes, serologic reactions for partial RHD genotypes are indistinguishable from other variants. STUDY DESIGN AND METHODS: In two US transfusion services, patients were typed for RhD by automated microplate RhD typing (Werfen, Norcross, GA) using two directly agglutinating IgM anti-D reagents, MS201 (epitope RhD (epD) 6.1) in Series 4 (Anti-D4) and TH-28 (epD6.4) in Series 5 (Anti-D5). For weak or discrepant RhD typing, we performed a RHD DNA microarray (RHD BeadChip, Werfen, Norcross, GA). For hemi- or homozygous c.697G>A (rs1053359), we obtained c.1136C>T (rs61740966) testing (New York Blood Center) to distinguish DV type 5 (DV.5) from DAU4 (c.1136T). We retrospectively examined previous cases with negative-weak anti-D4 and strong anti-D5 reactions for correlation with either DV.5 or DAU4 genotypes. RESULTS: Eight of 442 patients with weak or discrepant RhD phenotypes (1.8%) had 0-1+ anti-D4, 3-4+ anti-D5 phenotypes. They were the only 8 patients with c.697G>A (correlation p < 0.0001, Fisher's exact test). Two had DV.5 (Hispanic, Armenian), 5 had DAU4 (4 Black, 1 Other), and 1 was not tested for c.1136 (Black). None had anti-D. DISCUSSION: DV.5 and DAU4 alleles express disruptive p.Glu233Lys and are associated with hemolytic anti-D. Microplate RhD typing with decreased IgM anti-D4 reactions did not associate DV.5 and DAU4 with alloimmunization but indicated increased risk of anti-D alloimmunization. Similar epD6.1-weak, epD6.4-strong RhD reactions were observed in 10 DV.5 patients using automated microcolumn typing. Development of anti-D reagents detecting patients with other partial RHD genotypes beyond DVI is desirable.