Nation‐wide investigation of RHD variants in Thai blood donors: Impact for molecular diagnostics

• Published in: Transfusion (Philadelphia, Pa.) Vol. 61; no. 3; pp. 931 - 938
• Main Authors: Thongbut, Jairak, Laengsri, Vishuda, Raud, Loann, Promwong, Charuporn, I‐Na‐Ayudhya, Chartchalerm, Férec, Claude, Nuchnoi, Pornlada, Fichou, Yann
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-03-2021; Wiley Subscription Services, Inc; Wiley
• Subjects: Alleles; Antigens; Blood; Blood & organ donations; Blood donors; Design; Design optimization; Fluorescence; Gene deletion; Gene frequency; Genotyping; Life Sciences; Nucleotides; Phenotypes; Serology; Thailand
• ISSN: 0041-1132; 1537-2995
• DOI: 10.1111/trf.16242

Background
Knowledge of the molecular determinants driving antigen expression is critical to design, optimize, and implement a genotyping approach on a population‐specific basis. Although RHD gene 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, the RHD gene 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, partial RHD*06.03 was 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 Asian DEL allele 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.