Third-generation sequencing identified a novel complex variant in a patient with rare alpha-thalassemia.

BACKGROUND: Thalassemias represent some of the most common monogenic diseases worldwide and are caused by variations in human hemoglobin genes which disrupt the balance of synthesis between the alpha and beta globin chains. Thalassemia gene detection technology is the gold standard to achieve accurate detection of thalassemia, but in clinical practice, most of the tests are only for common genotypes, which can easily lead to missing or misdiagnosis of rare thalassemia genotypes. CASE PRESENTATION: We present the case of an 18-year-old Chinese female with abnormal values of routine hematological indices who was admitted for genetic screening for thalassemia. Genomic DNA was extracted and used for the genetic assays. Gap polymerase chain reaction and agarose gel electrophoresis were performed to detect HBA gene deletions, while PCR-reverse dot blot hybridization was used to detect point mutations in the HBA and HBB genes. Next-generation sequencing and third-generation sequencing (TGS) were used to identify known and potentially novel genotypes of thalassemia. We identified a novel complex variant αHb WestmeadαHb Westmeadαanti3.7/-α3.7 in a patient with rare alpha-thalassemia. CONCLUSIONS: Our study identified a novel complex variant that expands the thalassemia gene variants spectrum. Meanwhile, the study suggests that TGS could effectively improve the specificity of thalassemia gene detection, and has promising potential for the discovery of novel thalassemia genotypes, which could also improve the accuracy of genetic counseling. Couples who are thalassemia carriers have the opportunity to reduce their risk of having a child with thalassemia.

Screening for thalassemia carriers among the Han population of childbearing age in Southwestern of China.

Purpose: Thalassemia is a severe hereditary blood disorder that poses a significant threat to human health and leads to mortality and disability. It is one of the most prevalent monogenic diseases worldwide. The aim of this study was to analyze the molecular epidemiological data of individuals of childbearing age from the Han ethnic group with thalassemia in Southwest China and to explore the application of next-generation sequencing (NGS) technology in screening thalassemia carriers. Methods: The participants were Han males and females of childbearing age who sought medical advice at the West China Second University Hospital, Sichuan University from June 2022 to June 2023. We detected α- and ß-thalassemia mutations using full-length capture of the thalassemia genes and NGS technology. Results: In a cohort of 1,093 participants, 130 thalassemia carriers were identified, with an overall detection rate of 11.89% (130/1,093). Among these, 0.91% (10/1,093) had mutations that could not be detected using traditional PCR techniques. The proportions of carriers with α-, ß-, and α-complexed ß-thalassemia gene mutations were 7.68% (84/1,093), 3.93% (43/1,093), and 0.27% (3/1,093), respectively. We identified a novel HBA2 c.166del variant that has not been previously reported. Conclusion: Using NGS technology, we found that the mutation-carrying rate of thalassemia genes was 11.89% in the Han population of childbearing age in Southwest China. Compared with the results of traditional PCR techniques, NGS detected an additional 0.91% (10/1,093) rare genetic variants. NGS technology should be utilized as the primary screening method for thalassemia carriers among Han nationality people of childbearing age in Southwest China.

A Retrospective Analysis Of Different Contingent Screening Models For Fetal Down Syndrome In Southwestern China.

To discuss combinations of traditional screening and noninvasive prenatal screening (NIPS) and to compare which traditional screening is the most suitable first-line screening approach to NIPS, pregnant women were recruited in this retrospective observational study. Pregnant women underwent one of four traditional screening tests. The 9 contingent models were combined by high risk cut-offs of 1:50, 1:100, 1:270 and intermediate risk cut-offs of 1:1000, 1:1500, 1:2000. We analyzed cost and performance of various screening models with contingent screening of different risk cut-offs. Compared with other screening tests, combined first-trimester screening (CFTS) had the lowest proportion of high risk (≥1:270) with the highest detection rate (DR) (78.79%) and the lowest proportion of intermediate risk (1:271~1:1000). When intermediate risk was 1:51 ~1:1500, CFTS as first-line screening had the lowest cost with DR of 93.94%. Other screening tests as the first-line screening with intermediate risk of 1:51~1:1000 had the lowest cost, there DR were 90.91%, 84.62%, 91.67%, respectively. Our study demonstrated if only one traditional screening was allowed to screen pregnant women, CFTS was recommended as the first choice. According to local health and economic conditions, adopting appropriate traditional screening with suitable cut-offs as first-line screening will contributed to a cost-effective screening model.