Genetics Laboratories, Guy's and St. Thomas' NHS Foundation Trust, London, UK.
Nonacus Ltd., Birmingham Research Park, Birmingham, UK.
Br J Haematol. 2020 Jul;190(1):119-124. doi: 10.1111/bjh.16529. Epub 2020 Feb 25.
Sickle cell disease (SCD) is the most common genetic haematological disorder. The availability of non-invasive prenatal diagnosis (NIPD) is predicted to increase uptake of prenatal diagnosis for SCD, as it has no perceived procedure-related miscarriage risk. We report the development of a targeted massively parallel sequencing (MPS) assay for the NIPD of fetal SCD using fetal cell-free (cf)DNA from maternal plasma, with no requirement for paternal or proband samples. In all, 64 plasma samples from pregnant women were analysed: 42 from SCD carriers, 15 from women with homozygous (Hb SS) SCD and seven from women with compound heterozygous (Hb SC) SCD. Our assay incorporated a relative mutation dosage assay for maternal carriers and a wild type allele detection assay for affected women (Hb SS/Hb SC). Selective analysis of only smaller cfDNA fragments and modifications to DNA fragment hybridisation capture improved diagnostic accuracy. Clinical sensitivity was 100% and clinical specificity was 100%. One sample with a fetal fraction of <4% was correctly called as 'unaffected', but with a discordant genotype (Hb AA rather than Hb AS). Six samples gave inconclusive results, of which two had a fetal fraction of <4%. This study demonstrates that NIPD for SCD is approaching clinical utility.
镰状细胞病（SCD）是最常见的遗传性血液疾病。预计非侵入性产前诊断（NIPD）的可用性将增加 SCD 的产前诊断率，因为它没有被认为与程序相关的流产风险。我们报告了一种使用母体血浆中的胎儿游离（cf）DNA 进行胎儿 SCD 的靶向大规模平行测序（MPS）检测方法的开发，无需父亲或先证者样本。总共分析了 64 份孕妇血浆样本：42 份来自 SCD 携带者，15 份来自纯合子（Hb SS）SCD 妇女，7 份来自复合杂合子（Hb SC）SCD 妇女。我们的检测方法包括母体携带者的相对突变剂量检测和受影响妇女（Hb SS/Hb SC）的野生型等位基因检测。仅选择性分析较小的 cfDNA 片段和 DNA 片段杂交捕获的修饰可提高诊断准确性。临床灵敏度为 100%，临床特异性为 100%。一个胎儿分数<4%的样本被正确地称为“正常”，但基因型不一致（Hb AA 而不是 Hb AS）。六个样本给出了不确定的结果，其中两个样本的胎儿分数<4%。这项研究表明，SCD 的 NIPD 已接近临床应用。
