Aim: Thalassaemia is a good candidate disease for control by preventive genetic programmes in developing countries. Accurate population frequency data are needed for planning the control of thalassaemia in the high risk Guangdong Province of southern China. Methods: In total, 13 397 consecutive samples from five geographical areas of Guangdong Province were analysed for both haematological and molecular parameters.Results: There was a high prevalence of carriers of a thalassaemia (8.53%), b thalassaemia (2.54%), and both a and b thalassaemia (0.26%). Overall, 11.07% of the population in this area were heterozygous carriers of a and b thalassaemia. The mutation spectrum of a and b thalassaemia and its constitution were fully described in this area. This study reports the true prevalence of silent a thalassaemia in the southern China population for the first time. In addition, two novel mutations that give rise to a thalassaemia, one deletion resulting in b thalassaemia, and a rare deletion (22 THAI allele) previously unreported in mainland China were detected. The frequency of the most common mutation, the Southeast Asian type of deletion (22 SEA , accounting for 48.54% of all a thalassaemias) was similar to the total of two a + thalassaemia deletions (2a 3.7 and 2a 4.2 , accounting for 47.49% of a thalassaemia). Conclusion: Both a and b thalassaemia are widely distributed in Guangdong Province of China. The knowledge gained in this study will enable the projected number of pregnancies at risk to be estimated and a screening strategy for control of thalassaemia to be designed in this area.

BackgroundConventional prenatal screening tests, such as maternal serum tests and ultrasound scan, have limited resolution and accuracy.MethodsWe developed an advanced noninvasive prenatal diagnosis method based on massively parallel sequencing. The Noninvasive Fetal Trisomy (NIFTY) test, combines an optimized Student’s t-test with a locally weighted polynomial regression and binary hypotheses. We applied the NIFTY test to 903 pregnancies and compared the diagnostic results with those of full karyotyping.Results16 of 16 trisomy 21, 12 of 12 trisomy 18, two of two trisomy 13, three of four 45, X, one of one XYY and two of two XXY abnormalities were correctly identified. But one false positive case of trisomy 18 and one false negative case of 45, X were observed. The test performed with 100% sensitivity and 99.9% specificity for autosomal aneuploidies and 85.7% sensitivity and 99.9% specificity for sex chromosomal aneuploidies. Compared with three previously reported z-score approaches with/without GC-bias removal and with internal control, the NIFTY test was more accurate and robust for the detection of both autosomal and sex chromosomal aneuploidies in fetuses.ConclusionOur study demonstrates a powerful and reliable methodology for noninvasive prenatal diagnosis.

Accurate and up-to-date data on the frequency of haemoglobinopathies among the populations of Guangxi Zhuang Autonomous Region, where haemoglobinopathies are most endemic in China, are required. In our study, a total of 5789 samples obtained from members of the Han, Zhang, and Yao ethnic groups in six geographical areas of Guangxi Province were analysed systematically in terms of both haematological and molecular parameters. The results presented that the total heterozygote frequency of thalassaemias and other haemoglobinopathies was 24.51%, of which 17.55% was due to alpha-thalassaemia, 6.43% to beta-thalassaemia, 0.38% to structural haemoglobin variants, and 0.16% to delta-thalassaemia. The mutational spectrum among the local population for each type of disorder was described, including the first report on the true prevalence of three silent alpha thalassemia defects, -alpha(3.7)/(4.78%), -alpha(4.2)/(1.61%) and Hb Westmead (alpha(WS)alpha/) (1.57%) and of delta-thalassemia resulting from five novel and two rare mutations never before identified in Chinese individuals. Comparison of the frequencies of alpha-globin mutations among the ethnic groups showed that there was a statistically significant difference between the Han (15.71%) and Zhuang (20.12%), and between the Han (15.71%) and Yao (20.84%) ethnic groups. In addition, we have performed the first extensive study of haematological parameters of the Hb Westmead mutation using a group of Chinese subjects with compound heterozygosity for this variant and an alpha-thalassaemia deletion. The knowledge gained in this study will enable us to estimate the health burden in this high-risk population and to elucidate the various genetic alterations that underlie haemoglobinopathies.

Key Points The prevalence of KLF1 mutations is significantly higher in a thalassemia endemic region of China than in a nonendemic region. KLF1 mutations ameliorate the clinical and hematologic features of β-thalassemia.

Hemoglobinopathies are among the most common autosomal-recessive disorders worldwide. A comprehensive next-generation sequencing (NGS) test would greatly facilitate screening and diagnosis of these disorders. An NGS panel targeting the coding regions of hemoglobin genes and four modifier genes was designed. We validated the assay by using 2522 subjects affected with hemoglobinopathies and applied it to carrier testing in a cohort of 10,111 couples who were also screened through traditional methods. In the clinical genotyping analysis of 1182 β-thalassemia subjects, we identified a group of additional variants that can be used for accurate diagnosis. In the molecular screening analysis of the 10,111 couples, we detected 4180 individuals in total who carried 4840 mutant alleles, and identified 186 couples at risk of having affected offspring. 12.1% of the pathogenic or likely pathogenic variants identified by our NGS assay, which were undetectable by traditional methods. Compared with the traditional methods, our assay identified an additional at-risk 35 couples. We describe a comprehensive NGS-based test that offers advantages over the traditional screening/molecular testing methods. To our knowledge, this is among the first large-scale population study to systematically evaluate the application of an NGS technique in carrier screening and molecular diagnosis of hemoglobinopathies.

Expanded carrier screening (ECS) has been demonstrated to increase the detection rate of carriers compared with traditional tests. The aim of this study was to assess the potential value of ECS for clinical application in Southern China, a region with high prevalence of thalassemia and with diverse ethnic groups, and to provide a reference for future implementations in areas with similar population characteristics. A total of 10,476 prenatal/preconception couples from 34 self-reported ethnic groups were simultaneously tested and analyzed anonymously for 11 Mendelian disorders using targeted next-generation sequencing. Overall, 27.49% of individuals without self-reported family history of disorders were found to be carriers of at least 1 of the 11 conditions, and the carrier frequency varied greatly between ethnic groups, ranging from 4.15% to 81.35%. Furthermore, 255 couples (2.43%) were identified as carrier couples at an elevated risk having an affected baby, sixty-five of which would not have been identified through the existing screening strategy, which only detects thalassemia. The modeled risk of fetuses being affected by any of the selected disorders was 531 per 100,000 (95% CI, 497–567 per 100,000). Our data demonstrate the feasibility of ECS, and provide evidence that ECS is a promising alternative to traditional one-condition screening strategies. The lessons learned from this experience should be applicable for other countries or regions with diverse ethnic groups.

The increasing number of disease-causing mutations demands a simple, direct, and cost-effective diagnostic genotyping technique capable of detecting multiple mutations. This study validated the efficacy of a novel melting curve analysis-based genotyping assay (MeltPro HBB assay) for 24 ␤-thalassemia mutations in the Chinese population. The diagnostic potential of this assay was evaluated in 1022 pretyped genomic DNA samples, including 909 clinical cases of ␤-thalassemia minor or major, using a double-blind analysis in a multicenter validation study. Reproducibility of the assay was 100%, and the limit of detection was 10 pg per reaction. All 24 ␤-thalassemia mutations were accurately genotyped, and ␤-thalassemia genotypes were correctly determined in all 1022 samples, yielding overall sensitivity and specificity of 100%. The concordance rate was 99.4% between this assay and the reference method. It was concluded that the MeltPro HBB assay is useful for reliable genotyping of multiple ␤-thalassemia mutations in clinical settings and may have potential as a versatile method for rapid genotyping of known mutations because of its high throughput, accuracy, ease of use, and low cost.

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