Systematic RHD genotyping in Brazilians reveals a high frequency of partial D in transfused patients serologically...

The discrimination between weak D types and 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 units. The aim of this study was to determine by molecular analysis the type of D variants among Brazilian patients requiring transfusions with serologic weak D phenotypes.

Samples from 87 patients (53 with sickle cell disease, 10 with thalassemia and 24 with myelodysplastic syndrome), serologic typed as weak D by manual tube indirect antiglobulin test or gel test were first RHD genotyped by using the RHD BeadChip Kit (BioArray, Immucor). Sanger sequencing was performed when necessary.

RHD molecular analysis revealed 32 (36.8 %) variant RHD alleles encoding weak D phenotypes and 55 (63.2 %) alleles encoding partial D antigens. RHD variant alleles were present in the homozygous state or as a single RHD allele, one variant RHD allele associated with the RHDΨ allele, or two different variant RHD alleles in compound heterozygosity with each other in 70 patients, 4 patients and 13 patients, respectively. Alloanti-D was found in 9 (16.4 %) cases with RHD alleles predicting a partial D.

The frequency of partial D was higher than weak D types in Brazilian patients serologically typed as weak D, showing the importance to differentiate weak D types and partial D in transfused patients to establish a transfusion policy recommendation.