The need for routine detection of the Asian-type DEL allele in individuals with weak or partial D phenotypes from East and Southeast Asian populations.

Background and objectives: Among the rare serologically D-negative (D-) individuals in Asia, those carrying the Asian-type DEL allele (RHD*DEL1) can be safely managed as D+ individuals during transfusion and pregnancy. Recently, some individuals carrying RHD*DEL1, who exhibit serologically weak/partial D phenotypes rather than the serologically D- phenotype, have also been described. Whether anti-D alloimmunization can occur among them was explored.

Materials and methods: A retrospective study was carried out in 143 Chinese pregnant women identified as serologically weak/partial D phenotypes. The RHD*DEL1 allele was detected using the high-resolution melting method. Then, RHD genotyping was determined mainly by Sanger sequencing. D epitope expression was detected with the anti-D panel (D-Screen) by haemagglutination and adsorption/elution tests.

Results: RHD*DEL1 allele carriers were identified in 42.0% (60/143) of weak/partial D women. The single genotypes (mainly RHD*DEL1/01N.01 or RHD*DEL1/DEL1, n = 52) and the compound heterozygous genotypes (RHD*DEL1/weak or partial D allele, n = 8) were detected. A complete repertoire of D epitopes was shown in six weak/partial D women who simultaneously carried the RHD*DEL1 allele. Alloanti-D was not observed among any carriers (0/60). In the remaining 78 weak/partial D samples available but not carrying RHD*DEL1, 24 types of RHD variant alleles, including six novel alleles, were detected.

Conclusion: The RHD*DEL1 allele occurred often in the Chinese individuals with weak/partial D phenotypes who showed a lack of anti-D alloimmunization. Routine Asian-type DEL genotyping is recommended both in serologically D- and weak D/partial D individuals with East and Southeast Asian ancestry to consider Asian-type DEL carriers as D+ individuals during transfusion and pregnancy.