Application of targeted sequencing in the molecular diagnosis of thalassemia in Southern China

Thalassemia is a relatively common monogenic inherited blood disorder in southern China. This study aims to evaluate the additional diagnostic yield of targeted sequencing for thalassemia gene compared to traditional mainstream methods, providing evidence to support clinical decision-making and application. A total of 449 specimens with the negative common thalassemia test result were randomly selected for next-generation sequencing(NGS) testing. For rare thalassemia genotypes and abnormal hemoglobin variants detected by NGS, hematological information such as mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and hemoglobin electrophoresis was summarized and statistically analyzed. Through targeted sequencing for thalassemia, an additional 42 cases of rare thalassemia genotypes and 10 cases of abnormal hemoglobin variants were detected in the traditional test-negative groups (Neg_70 and Neg_80). Compared with traditional gene testing, the overall additional positive rate for NGS was 9.35% (42/449). In the traditional test-positive group (Pos_80), 2 cases of abnormal hemoglobin variants were identified, with an additional positive rate of 0.88% (2/226). The most frequently detected rare genotypes were the α-thalassemia variant -^THAI and the δβ-thalassemia variant Chinese(^Gγ + (^Aγδβ)⁰), found in 20 and 7 cases, respectively. Additionally, a novel heterozygous variant of the HBA2 gene was identified: NM_000517.6:c.16delG. NGS demonstrates superior detection efficacy and higher detection rates in individuals with low mean corpuscular volume, particularly in those with severe microcytic hypochromic anemia. It effectively identifies rare mutations and reduces the misdiagnosis rate of thalassemia.