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.