Bugert Peter, Rink Gabi, Klüter Harald
Institute of Transfusion Medicine and Immunology, Medical Faculty Mannheim, Heidelberg University, German Red Cross Blood Service Baden-Württemberg - Hessen, Mannheim, Germany.
Transfus Med Hemother. 2023 Jan 18;50(4):263-269. doi: 10.1159/000528683. eCollection 2023 Aug.
The molecular diagnosis of the A blood group is based on the exclusion of gene variants causing blood groups A, B, or O. A specific genetic marker for the A blood group is still missing. Recently, long-read ABO sequencing revealed four sequence variations in intron 1 as promising markers for the * allele. Here, we evaluated the diagnostic values of the 4 variants in blood donors with regular and weak A phenotypes and genotypes.
ABO phenotype data (A, B, AB, or O) were taken from the blood donor files. The genotypes (low resolution) were known from a previous study and included the variants c.261delG, c.802G>A, c.803G>C, and c.1061delC. variant alleles (****, *, and *) were identified in weak A donors by sequencing the exons before. For genotyping of the intron 1 variants rs532436, rs1554760445, rs507666, and rs2519093, we applied TaqMan assays with endpoint fluorescence detection according to a standard protocol. Genotypes of the variants were compared with the ABO phenotype and genotype. Evaluation of diagnostic performance included sensitivity, specificity, positive (PPV), and negative predictive value (NPV).
In 1,330 blood donors with regular ABO phenotypes and genotypes, the intron 1 variants were significantly associated with the proposed A blood group. In 15 donors, we found discrepancies to the genotype of at least one of the 4 variants. For the diagnosis of the ABO*A1 allele, the variants showed 98.79-99.48% sensitivity, 99.66-99.81% specificity, 98.80-99.31% PPV, and 99.66-99.86% NPV. Regarding the A phenotype, the diagnostic values were 99.02-99.41% sensitivity, 99.63-99.76% specificity, 99.41-99.61% PPV, and 99.39-99.63% NPV. The * marker allele of all intron 1 variants was also associated with the *, *, and * variants. Samples with *, *, and * variants lacked this association.
The intron 1 variants revealed significant association with the * allele and the A phenotype. However, the intron 1 genotype does not exclude variant alleles causing weak A phenotypes. With the introduction of reliable tag, single nucleotide variants for the A, A, B, and O blood groups and the genotyping instead of phenotyping of the ABO blood group are getting more feasible on a routine basis.
A血型的分子诊断基于排除导致A、B或O血型的基因变异。目前仍缺少A血型的特异性遗传标记。最近，长读长ABO测序揭示了内含子1中的四个序列变异，有望作为A等位基因的标记。在此，我们评估了这4个变异在具有常规和弱A表型及基因型的献血者中的诊断价值。
ABO表型数据（A、B、AB或O）取自献血者档案。之前的一项研究已得知其基因型（低分辨率），包括c.261delG、c.802G>A、c.803G>C和c.1061delC变异。通过之前对弱A献血者的外显子进行测序，鉴定出了变异等位基因（****、和）。对于内含子1变异rs532436、rs1554760445、rs507666和rs2519093的基因分型，我们根据标准方案应用了带有终点荧光检测的TaqMan分析。将变异的基因型与ABO表型和基因型进行比较。诊断性能评估包括敏感性、特异性、阳性预测值（PPV）和阴性预测值（NPV）。
在1330名具有常规ABO表型和基因型的献血者中，内含子1变异与推测的A血型显著相关。在15名献血者中，我们发现至少4个变异之一的基因型存在差异。对于ABOA1等位基因的诊断，这些变异的敏感性为98.79 - 99.48%，特异性为99.66 - 99.81%，PPV为98.80 - 99.31%，NPV为99.66 - 99.86%。对于A表型，诊断价值为敏感性99.02 - 99.41%，特异性99.63 - 99.76%，PPV为99.41 - 99.61%，NPV为99.39 - 99.63%。所有内含子1变异的标记等位基因也与*、和变异相关。具有*、和变异的样本缺乏这种关联。
内含子1变异与*等位基因和A表型显著相关。然而，内含子1基因型并不能排除导致弱A表型的变异等位基因。随着可靠标签的引入，用于A、A、B和O血型的单核苷酸变异以及ABO血型的基因分型而非表型分型在常规操作中变得更加可行。
