Vishuda Laengsri

Background: Knowledge of the molecular determinants driving antigen expression is critical to design, optimize, and implement a genotyping approach on a population‐specific basis. AlthoughRHDgene variability has been extensively reported in Caucasians, Africans, and East‐Asians, it remains to be explored in Southeast Asia. Thus the molecular basis of non‐D+ blood donors was investigated in Thailand.Study Design and Methods: First, 1176 blood samples exhibiting an inconclusive or negative result by automated serological testing were collected in the 12 Regional Blood Centres of the Thai Red Cross located throughout Thailand. Second, theRHDgene was analyzed in all samples by 1) quantitative multiplex PCR of short fluorescent fragments, and 2) direct sequencing, when necessary, for identifying structural variants and single nucleotide variants, respectively.Results: Additional serological typing yielded 51 and 1125 samples with weak/partial D and D‐negative (D‐) phenotype, respectively. In the first subset, partialRHD*06.03was the most common variant allele (allele frequency: 18.6%). In the second subset, the whole deletion of the gene is largely the most frequent (allele frequency: 84.9%), followed by the AsianDELallele found in 15.6% of the samples. Eight novel alleles with various mutational mechanisms were identified.Conclusion: We report, for the first time at the national level, the molecular basis of weak/partial D and serologically D‐ phenotypes in Thai blood donors. The design and implementation of a dedicated diagnostic strategy in blood donors and patients are the very next steps for optimizing the management and supply of RBC units in Thailand.