Identification of partial D can be of clinical importance because carriers of partial D antigen may develop anti-D when transfused with D-positive red blood cell (RBC) units. Anti-D can also result from altered Rh epitopes on donor RBCs in transfused patients carrying conventional D antigens.

The aim of this study was to evaluate the risk of anti-D production in SCD patients with partial D and with conventional D transfused with D+ RBCs. We also accessed the clinical significance and the persistence of the alloantibody produced.

A retrospective study was performed in 79 D+ patients genotyped for RHD who received at least three D+ RBC units. All patients had complete serological and molecular analyses. Number of D+ RBC transfusions, anti-D identification and anti-D persistence were also recorded. A lookback on the donors and transfusions for those patients including laboratory and clinical findings was performed. Donors whose RBCs were transfused for these patients suspected of having variants were recruited for further analysis. Laboratory and clinical findings were also used to evaluate the clinical significance of the alloantibodies produced.

: Partial D phenotypes were found in 25/79 (31.6%) of these patients and included: DAR, DAU0, DAU3, DIVa, DIIIa, DVa, Weak partial D 4.0. Eight (32%) patients produced anti-D: 1 DAR, 1 DAU3, 1 DIVa, 1 DIIIa, 1 DVa, 3 DAU0. Laboratory and clinical evidence of a delayed hemolytic transfusion or decreased survival of transfused RBCs were associated with five anti-D produced in patients with partial D (DAR, DAU3, DIVa, DIIIa, DVa). Anti-D produced by the patients with partial D DAU0 were not clinically significant and patients with weak partial D 4.0 did not develop anti-D even with more exposures of D+ RBC units than those with the other partial D types. Unexpected anti-D was also found in 5/54 (9.3%) patients with conventional D type as a result of D+ RBC transfusions from donors with altered Rh epitopes. Anti-D was more persistent in patients with partial D DAR, DAU3, DIVa, DIIIa, DVa compared to those with DAU0 and conventional D.

Patients with partial D are more likely to develop clinically significant and more persistent anti-D than patients with conventional D and therefore may benefit from prophylactic D- RBC units or RHD genotype-matched transfusions. Our results also suggest that patients with partial D DAU0 do not develop clinically significant anti-D and patients with weak partial D 4.0 are not at risk of developing anti-D.