Nanopore third-generation sequencing for the diagnosis of rare hemoglobinopathies in Southern China

Thalassemia, a genetically inherited hemoglobinopathy, represents a significant global health challenge with profound socioeconomic implications, particularly in endemic regions. The emergence of third-generation sequencing (TGS) technologies has revolutionized thalassemia research and diagnostic paradigms, offering unprecedented capabilities for comprehensive genetic characterization. Between 2021 and 2024, we conducted a comprehensive analysis of 536 clinically suspected thalassemia cases from southern China, conventional diagnostic methods and Nanopore TGS were performed simultaneously. Among the 536 subjects analyzed, TGS identified 332 cases harboring either common or rare variants, which included 160 cases with rare thalassemia variants, 50 cases with abnormal hemoglobin variants, and 122 cases carrying common α- or β-thalassemia mutations. --THAI and HKαα emerging as the most prevalent variants among rare thalassemia, followed by Chinese (Aγδβ)0 and α-Fusion gene. The predominant abnormal hemoglobin was Hb New York (HBB:c.341 T > A). We used TGS and discovered three rare variants that have not been identified by conventional diagnostic methods for thalassemia, the variants included two cases of α-globin chain 32.8 kb deletions and one case of β-globin chain 3.5 kb deletion. Hb G-Ferrara (HBB:c.174 C > A) and Hb Ethiopia (HBA2:c.421 T > C) were firstly identified in the Chinese population. Moreover, two novel α-globin variants: NC_000016.10:g.176260-176930del and HBA1:c.386 T > C were discovered in this study. This study expands the genetic landscape of hemoglobinopathies in Southern China by characterizing a comprehensive spectrum of rare variants. Our findings demonstrate the superior diagnostic capability of TGS in identifying rare thalassemia genotypes, suggesting its potential as a first-line molecular diagnostic tool for comprehensive hemoglobinopathy screening.