[Prospective clinical study on non-invasive prenatal testing for severe thalassemia using tag-labeled targeted...

Objective: To evaluate the clinical performance of a non-invasive prenatal testing (NIPT) approach for fetal severe thalassemia based on tag-labeled targeted capture sequencing combined with a modified Bayesian model (referred to as noninvasive thalassemia testing). Methods: This study was a prospective cohort study involving 452 couples of the Southeast Asian deletion (SEA) type α-thalassemia carriers who were enrolled in Guangdong Women and Children Hospital from June 2018 to July 2021. Maternal peripheral blood was collected at 11-34 gestational weeks. Cell-free fetal DNA (cffDNA) in maternal plasma was analyzed by tag-labeled targeted capture sequencing, and fetal genotypes were inferred using a modified Bayesian algorithm to determine the risk of fetal severe α-thalassemia. The results of invasive prenatal diagnosis were taken as the "gold standard" to evaluate the clinical detection efficacy of this method. Results: Among the 452 pregnant women, 5 cases declined further invasive prenatal diagnosis and 5 cases failed testing due to unsatisfactory sample quality control. The remaining 442 cases were included in the testing performance evaluation. Noninvasive thalassemia testing showed a sensitivity of 97.89%, specificity of 98.56%, positive predictive value of 94.90%, and negative predictive value of 99.42%. Consistency analysis demonstrated that the prediction of severe thalassemia by noninvasive thalassemia testing was highly consistent with invasive prenatal diagnosis (κ=0.954, 95%CI: 0.920-0.988; P<0.001). The noninvasive thalassemia testing results included 2 false-negative and 5 false-positive cases, with an overall concordance rate of 98.42% (435/442) compared with the gold standard. Conclusion: The proposed noninvasive thalassemia testing method achieved good diagnostic performance for severe thalassemia without relying on parental haplotype information, providing a new prenatal testing pathway for couples in high-prevalence thalassemiat regions who are both carriers of the SEA deletion α-thalassemia.