The Cyprus Institute of Neurology and Genetics, Nicosia, Cyprus.
Prenat Diagn. 2013 Jul;33(7):650-5. doi: 10.1002/pd.4140. Epub 2013 May 28.
The goal of this study is to evaluate the amount of free fetal DNA (ffDNA), total DNA, and 'fetal fraction' found in maternal plasma and whether these influence the enrichment ratios of differentially methylated regions (DMRs) and the correct classification of trisomy 21 using the methylated DNA immunoprecipitation-quantitative polymerase chain reaction (MeDIP-qPCR)-based noninvasive prenatal diagnostic methodology applied in peripheral blood.
Absolute quantification of ffDNA using DYS14 and total DNA using β-globin was applied in 83 maternal plasma samples. The quantification values for all 83 samples were correlated with the enrichment ratios of all seven DMRs and D-values that were obtained from the diagnostic formula of MeDIP-qPCR method.
Our analysis concluded that trisomy 21 samples had significantly higher ffDNA and total DNA levels compared with those of normal samples. Enrichment ratios of the majority of DMRs studied exhibited no association with ffDNA, total DNA, and 'fetal fraction', and only a small portion of DMRs exhibited moderate association. Correlation studies of ffDNA, total DNA, and fetal fraction with the diagnostic D-value showed weak to no association but without affecting the classification of trisomy 21.
Overall, the variability of ffDNA and total DNA among maternal samples does not affect the correct trisomy 21 classification using MeDIP-qPCR methodology applied in peripheral blood.
本研究旨在评估游离胎儿 DNA（ffDNA）、总 DNA 和母体外周血中“胎儿分数”的含量，并探讨这些因素是否会影响应用甲基化 DNA 免疫沉淀-定量聚合酶链反应（MeDIP-qPCR）的非侵入性产前诊断方法检测差异甲基化区域（DMR）的富集比，以及正确诊断 21 三体。
对 83 例母体外周血样本进行 ffDNA 的 DYS14 绝对定量和总 DNA 的β-球蛋白绝对定量。对所有 83 例样本的定量值与所有 7 个 DMR 的富集比以及 MeDIP-qPCR 方法诊断公式的 D 值进行相关性分析。
我们的分析表明，21 三体组的 ffDNA 和总 DNA 水平明显高于正常组。研究的大多数 DMR 的富集比与 ffDNA、总 DNA 和“胎儿分数”无关，只有一小部分 DMR 表现出中度相关性。ffDNA、总 DNA 和胎儿分数与诊断 D 值的相关性研究显示出弱相关或无相关性，但不影响 21 三体的分类。
总的来说，母体外周血中 ffDNA 和总 DNA 的变异性不会影响应用 MeDIP-qPCR 方法对 21 三体的正确诊断。
