Genotyped RhD+ red cells for D-positive patients with sickle cell disease with conventional RHD and unexpected anti-D

Anti-D can occur in D-positive patients who inherit RHD genetic variants encoding partial D antigen expression, but unexpected anti-D is also found in the plasma of patients with sickle cell disease who have conventional RHD gene(s) and are transfused with units from Black donors. These anti-D are likely stimulated by variant Rh expressed on donor cells; however, patients with anti-D, regardless of cause, are transfused for a lifetime with D-negative (Rh-negative) blood. This results in significant increased use of Rh-negative units, especially for those requiring chronic transfusion, which can strain Rh-negative blood inventories. We tested whether D-positive patients who made anti-D and had conventional RhD by RHD genotyping could safely be returned to D-positive transfusions without anti-D reappearance or compromised red blood cell survival using RHD genotype-matched units from Black donors. Five patients receiving chronic red cell exchange received an increasing number of D-positive units per procedure with a total of 72 D-positive RHD genotyped units transfused, with no anti-D restimulation. Unexpected anti-C and anti-E were identified during the study associated with donors with variant RHCE alleles. RH genotyping of D-positive units for transfusion may improve use and allocation of valuable Black donor units and reduce demand for Rh-negative blood. This trial was registered at www.clinicaltrials.gov as NCT04156906.