Frequency and characterization of RHD variant alleles in a population of blood donors from southeastern Brazil: Comparison with other populations.

BACKGROUND

The correct determination of D antigen could help to avoid alloimmunization in pregnant women and patients receiving blood transfusions. However, there are limitations in the identification of D variants as the partial and weak D phenotypes make the determination of D antigen a great challenge in the transfusion routine.'

STUDY DESIGN AND METHODS

The molecular characterization of D variants was performed on blood donors from southeastern Brazil with atypical D typing. Furthermore, the serological profile of all RHD variant alleles identified was analyzed using different Anti-D clones. The prevalence of RHD alleles and genotypes found was compared with those described in other countries and in other regions from Brazil.

RESULTS

Atypical serologic D typing occurred in 0.79 % of blood donors. The majority of RHD variant alleles (88 %) were first characterized by multiplex PCR and PCR-SSP as RHDweak partial 4 (47 %), followed by RHDweak D type 3 (29.9 %), RHDweak D type 2 (3.9 %) and RHDweak D type 1 (3.1 %). Genomic DNA sequencing characterized the RHDweak partial 4 variants found in RHDDAR1.2 (weak 4.2.2) (22 %), RHDDAR3 (weak 4.0.1) (2.4 %), RHDDAR3.1 (weak 4.0) (22 %) and RHDDAR4 (weak 4.1) (0.8 %). RHD variant alleles associated with partial D, such as, RHDDAU-4 (1.6 %), RHDDAU-5 (2.4 %), RHDDAU-6 (1.6 %), RHD* DIII type 8 (1.6 %), RHDDVII (3.9 %) and RHD DMH (0.8 %) were also observed.

CONCLUSION

The prevalence of RHD variant alleles observed in this cohort differ from those found in other populations, including Brazilians from other regions. RHD allele distribution in specific regions should be considered for implementation of algorithms and genotyping strategies aiming at a more effective and safe transfusion.