Frequency of the 'Asia type' DEL with weak D phenotype in chinese.

Background: DEL individuals account for 9-30% of serological RhD negative population in east Asia and majority of them carrying the RHD*DEL1 allele are referred to as 'Asia type' DEL individuals. There is a lack of data on the molecular basis for 'Asia type' DELs with weak RhD phenotype. Therefore, the aim of this study is to unveil 'Asia type' DELs by elucidating the genetic background and analyzing the serological results.

Methods: With a microplate typing protocol, RhD characterization was performed in samples from one million blood donors collected at Chengdu blood center during the period from 2019 to 2022. RhD confirmatory test was performed by direct antiglobulin test and indirect antiglobulin test with five anti-D reagents to detect RhD variants. Molecular characterization of samples categorized as RhD variants was studied by using direct genomic DNA sequencing and RHD zygosity analysis, followed by adsorption and elution tests conduced for samples carrying RHD*DEL1 allele to confirm the presence of RhD antigens on the red cells.

Results: We reported here 21 RhD variant samples were detected by micro-column gel agglutination assay with IgG anti-D antibodies. Moreover, the agglutination reaction was stronger with IgG anti-D reagents in micro-column gel card than with IgM/IgG blended anti-D antibodies. Each of the 21 samples carried the RHD*DEL1 allele, which indicated that they were 'Asia type' DEL. Of the 21 'Asia type' DEL samples, 9 samples were detected to be RHD+/ RHD + homozygotes, whereas the other 12 samples were RHD+/RHD- hemizygotes. Among the samples phenotyped for RhCE, seven were CCee and four were Ccee.

Conclusions: In this study, DEL samples carrying RHD*DEL1 showed weak RhD phenotype with some anti-D reagents in RhD confirmatory test, which suggest that a serology strategy using several anti-D reagents may be helpful to detect this 'Asia type' DEL. Further studies are needed to elucidate whether the 'Asia type' DELs with weak RhD phenotype have stronger antigenicity and could cause serious transfusion reaction.