RHD 1227 A and hybrid Rhesus box analysis in Thai RhD+ and RhD- blood donors: Prevalence, RHD zygosity, and molecular screening

Background and objectives DEL (D-elute) red blood cells (RBCs) are typed as D- by routine serological methods, as they carry a very weak form of D variant. Asia type DEL (c.1227 G>A) is the most prevalent DEL allele in East Asian populations that can lead to alloimmunization in D negative transfusion recipients. This study aimed to screen D+ and D- Thai blood donors for the Asia type DEL and its zygosity. Materials and methods Blood samples of 723 D+ , and 191 D- Thai blood donors were collected. D antigen was typed by the routine serological method and adsorption-elution test to screen DEL phenotype. The hybrid Rhesus box, RHD 1227 G, RHD 1227 A and RHD exon 4 were analyzed with polymerase chain reaction using sequence specific primers, PCR-SSP. Results Among 191 D- blood donors, 52 (27.2%) RHD 1227 A allele carriers were detected, and 39 out of these 52 (75.0%) were positive for the hybrid Rhesus box (i.e. hemizygous RHD 1227 A). The remaining carriers were RHD 1227 A homozygous. RHD zygosity analysis in Thai D+ blood donors showed that only 4% (29/723) had a Dd genotype (hemizygous RHD 1227 G). Five (0.69%) blood donors were detected with RHD 1227 A alleles among 723 D+ blood donors. They were all G/A heterozygous at the RHD 1227 site. Conclusion This study indicates that the high prevalence of RHD 1227 A allele among serologically apparent D- blood donors in Thais. Furthermore, the screening of hybrid Rhesus box, RHD 1227 A combined with RHD exon 4 is useful for analyses of Asia type DEL and its zygosity.