The RHD (1227 G > A ) DEL ‐associated allele is the most prevalent DEL allele in A ustralian D – blood donors with C + and/or E + phenotypes

Background Red blood cells ( RBCs ) with D antigen levels only detected by anti‐ D adsorption‐elution and an antiglobulin test express a DEL phenotype. For two DEL types, including RHD (1227 G > A ) , immunization of D – recipients has been reported. This study's aim was to measure the prevalence of DEL ‐associated RHD alleles in a cohort of A ustralian D – donors to develop a model to estimate alloimmunization risk. Study Design and Methods D –, C + and/or E + blood donors were screened for RHD exons using quantitative polymerase chain reaction. Donors with RHD signals were DEL phenotyped with MCAD 6 anti‐ D . RHD alleles were characterized via single‐nucleotide polymorphism array or sequencing. Extended DEL phenotyping was performed with an anti‐ D panel. Results Among 2027 donors, 39 carried RHD alleles that have been previously reported to associate with either the DEL or the weak D phenotype. An additional five donors carried previously unreported RHD alleles and exhibited the DEL phenotype: RHD ( IVS 2‐2del A ) , RHD ( IVS 1 + 5 G > C ) , RHD (ex9:del/ CE ) , and RHD (ex8:del/ CE ) represented twice. In total, DEL /weak D –associated RHD alleles were detected in 44 of 2027 donors or 2.17% (95% confidence interval, 1.54%‐2.81%). The RHD (1227 G > A )   DEL allele was the most frequent (n = 16). The risk of transfusing D – females not more than 40 years of age with an RHD (1227 G > A )   DEL RBC unit (when managed as D –) is estimated to be one in 149,109 transfusions (range, 100,680‐294,490). Conclusion DEL /weak D –associated RHD alleles were found in 2.17% of A ustralian D –, C + and/or E + blood donors. This differs from previous E uropean reports in that the clinically significant RHD (1227 G > A )   DEL allele is the most prevalent.