Verma L, Macdonald F, Leedham P, McConachie M, Dhanjal S, Hultén M
LSF Research Unit, Regional Genetic Services, Birmingham Heartlands Hospital, UK.
Lancet. 1998 Jul 4;352(9121):9-12. doi: 10.1016/S0140-6736(97)11090-X.
Prenatal diagnosis of chromosomal abnormality requires cytogenetic analysis of amniotic fetal cells. The necessary culture time delays diagnosis, is expensive, and requires substantial scientific expertise. In a masked prospective study, we investigated the feasibility of PCR amplification of chromosome 21 markers for the prenatal diagnosis of Down's syndrome.
The study population consisted of 2167 pregnant women, undergoing amniocentesis for prenatal diagnosis. In this cohort at least 1.5 mL amniotic fluid was available surplus to the requirements for traditional diagnostic methods. DNA was extracted from the surplus amniotic fluid and amplified in fluorescence-based PCR reactions, with three small-tandem-repeat markers located on chromosome 21. The products of the reactions were analysed on a DNA sequencer to identify the presence of two or three copies of chromosome 21.
In 2083 (97.4%) of 2139 samples of amniotic fluid that were not macroscopically blood-stained, two DNA markers gave an informative and correct result, identifying 2053 fetuses as normal and 30 as having trisomy 21 Down's syndrome (as confirmed by cytogenetic analysis). An extra marker was informative in 32 of 41 other clear samples. Thus a total of 99.6% informative results was achieved with these three markers. Macroscopically blood-stained samples (28 [1.3%]) were unsuitable for DNA testing. They gave a typical but non-informative result. There were no false-positive or false-negative results.
The PCR-based DNA diagnostic test has great potential for improved prenatal diagnosis of Down's syndrome, with the advantage that results may be available within a day.
染色体异常的产前诊断需要对羊水胎儿细胞进行细胞遗传学分析。必要的培养时间会延迟诊断，成本高昂，且需要大量专业科学知识。在一项盲法前瞻性研究中，我们调查了通过聚合酶链反应（PCR）扩增21号染色体标记物用于唐氏综合征产前诊断的可行性。
研究人群包括2167名接受羊膜穿刺术进行产前诊断的孕妇。在这个队列中，至少有1.5毫升羊水超出传统诊断方法的需求。从多余的羊水中提取DNA，并在基于荧光的PCR反应中进行扩增，使用位于21号染色体上的三个小串联重复标记物。对反应产物进行DNA测序仪分析，以确定21号染色体是否存在两个或三个拷贝。
在2139份肉眼无血样污染的羊水样本中，有2083份（97.4%）通过两个DNA标记物得到了信息丰富且正确的结果，确定2053名胎儿正常，30名患有21三体唐氏综合征（经细胞遗传学分析证实）。在其他41份清晰样本中的32份中，额外的一个标记物提供了信息。因此，这三个标记物总共获得了99.6%的信息丰富的结果。肉眼有血样污染的样本（28份[1.3%]）不适合进行DNA检测。它们给出了典型但无信息的结果。没有假阳性或假阴性结果。
基于PCR的DNA诊断测试在改善唐氏综合征产前诊断方面具有巨大潜力，其优势在于一天内即可获得结果。
