Non-invasive prenatal diagnosis of beta-thalassemia by semiconductor sequencing: a feasibility study in the sardinian population

beta-Thalassemia is the most common autosomal recessive single-gene disorder in Sardinia, where approximately 10.3% of the population is a carrier. Prenatal diagnosis is carried out at 12 weeks of gestation via villocentesis and is commonly aimed at ascertaining the presence or absence of the HBB variant c.118C > T, which is the most common in Sardinia. In this study, we describe for the first time the application of semiconductor sequencing to the non-invasive prenatal diagnosis of beta-thalassemia in 37 couples at risk for this variant. In particular, by using a haplotyping-based approach with a hidden Markov model (HMM) and a dedicated pipeline, the two parental haplotypes most likely inherited by the foetus could be established in 30 out of 37 cffDNA samples. Specifically, the paternally inherited haplotype was correctly determined in all 30 of the samples, while the maternal haplotype was incorrectly predicted in six of the 30 genotyped samples. The lack of informative SNPs hampered the inference of both parental haplotypes in the remaining seven samples. As shown in previous studies, we have confirmed that the haplotyping-based approach represents a valuable resource, as it improves the detection of both parental haplotypes inherited by the foetus. In general, our results are encouraging, as we have proven that NIPD is also feasible in couples who are at risk for a monogenic disorder and share the same variant.