The Validation of Whole β-Globin Gene Sequencing for Detecting β-Thalassemia Mutations Found in Thailand Using Next-Generation Sequencing (NGS)

Beta-thalassemia is an inherited disorder prevalent in Thailand and Southeast Asia. Several molecular techniques for identifying β-thalassemia mutations have been reported. Next-generation sequencing (NGS) is a type of effective molecular testing with high throughput and accuracy. Hence, this study aims to evaluate a novel barcode-tagged NGS approach based on a short-read assay. A total of 258 samples with 54 different β-thalassemia genotypes related to 32 mutations were gathered and evaluated. A library was constructed with the BTSeq^TM kit and sequencing was performed on the Illumina NGS machine. The validation results showed 98.45% concordance with conventional genotypes. Less discordant results (1.55%) were limited to insertional mutations and included one case of each of the following: <i>HBB</i>:c.27dupG, <i>HBB</i>:c.85dupC, <i>HBB</i>:c.216dupT, and <i>HBB</i>:c.440_441dupAC. Five single-nucleotide polymorphisms that derived from the NGS results were also analyzed in terms of allele frequency and revealed significant differences between the wild types and other β-genotypes. Furthermore, this paper is the first to describe rare single-nucleotide polymorphisms including IVS II-109 (C/T), IVS II-258 (G/A), IVS II-613 (T-C), and IVS II-806 (G/C). Interestingly, the C allele of IVS II-806 was found to have 100% linkage with two cases of Hb Tak. The haplotype and phylogenetic analysis was also constructed based on variants and revealed three clusters in the Hb variants, which represented their evolution and genetic background. Finally, NGS with the barcode-tagged method has a high throughput, which is suitable for large population screening. Its cost effectiveness and less complicated process promote its application in further works.