β-地中海贫血无创产前检测新进展

目前地中海贫血的产前检测技术主要有跨越断裂位点的PCR、PCR结合反向点杂交法、实时荧光定量PCR、基于实时PCR的溶解曲线分析技术、基因芯片、高通量测序技术等。本文综述近年来β-地中海贫血的无创产前检测技术的进展,为后续临床应用提供参考。     

产前筛查——从血清学筛查到无创产前检测

        产前筛查一般指的是对胎儿常见染色体非整倍体的筛查,即21-三体综合征、18-三体综合征、13-三体综合征,不包括其他染色体非整倍体。 浏览更多请关注本刊微信公众号及当期杂志。     

无创产前基因检测在胎儿染色体非整倍体筛查中的应用研究

目的:探讨无创产前基因检测(NIPT)在胎儿染色体非整倍体疾病诊断中的临床应用价值及意义。方法:收集2016年1月至2016年12月在我院行NIPT检测的6030例单活胎孕妇(孕12~32周)外周血标本并提取胎儿游离DNA,进行文库构建后利用高通量测序技术,结合生物学信息分析,推算出胎儿患染色体疾病的风险率。对检测结果提示高风险者建议行羊水或者脐血穿刺及染色体核型分析;对检测结果低风险者进行电话跟踪随访。结果:行NIPT检测的6030例孕妇检出高风险67例,其中21-三体高风险16例,18-三体高风险3例,13-三体高风险5例,性染色体异常高风险34例,其他染色体异常高风险9例。67例高风险孕妇中,10例拒绝进一步产前诊断,余57例均行羊水/脐血穿刺检查,其中确诊胎儿染色体异常34例(21-三体16例,18-三体2例,13-三体2例,性染色体异常12例,其他染色体异常2例);余23例羊水/脐血穿刺结果正常者,继续妊娠。NIPT对21-三体和18-三体的阳性预测值达100.00%和66.67%,但对13-三体、性染色体异常以及其他染色体异常的阳性预测值仅50.00%、42.85%和33.33%。结论:NIPT对21-三体和18-三体的检测符合率较高,但对13-三体、性染色体异常以及其他染色体异常符合率偏低。NIPT是一项筛查技术,测序高风险的孕妇仍需行羊水/脐血穿刺,以保证产前诊断的准确性。     

无创产前基因检测在胎儿性染色体疾病筛查中的应用

目的探讨无创产前基因检测(non-invasive prenatal genetic testing,NIPT)在胎儿性染色体疾病中的临床价值。方法统计深圳市第二人民医院2016年3月至2019年6月行NIPT的16119例单胎孕妇中提示21-三体、18-三体、13-三体、性染色体异常和其他染色体异常的阳性率;对比2016年3月至2019年6月NIPT示“胎儿性染色体异常”与本院染色体核型结果。结果①NIPT对21-三体,18-三体,13-三体,性染色体异常和其他染色体异常筛查的阳性率分别为0.42%(68/16119),0.10%(16/16119),0.07%(11/16119),0.38%(61/16119)和0.22%(36/16119)。②47例“NIPT示胎儿性染色体异常”者中,确诊为性染色体疾病者26例,阳性预测值55.32%。其中,NIPT对胎儿性染色体数目偏多的阳性预测值为91.30%(21/23),对胎儿性染色体数目偏少的阳性预测值20.0%(4/20),对胎儿性染色体数目异常的阳性预测值25.0%(1/4)。结论NIPT可作为胎儿性染色体疾病的筛查方法,但由于其对性染色体偏少和性染色体数目异常的假阳性率较高,检测阳性者仍需要做侵入性产前诊断确诊。     

无创产前检测在高龄孕妇中检测胎儿非整倍体的临床应用

目的:探讨高通量测序(HTS)技术在高龄孕妇胎儿染色体非整倍体筛查中的临床应用。方法:2 090例单胎高龄孕妇行无创产前检测(NIPT),结果异常的孕妇再行羊膜腔穿刺,羊水细胞培养后染色体G320显带核型分析。结果:2 090例样本中,高通量基因测序提示22例胎儿染色体非整倍体高风险,19例孕妇自愿接受羊水产前诊断,其中16例羊水G带核型结果与NIPT测序结果一致,包括12例T21,2例T18,2例性染色体异常,阳性预测值为84.2%(16/19)。结论:对于拒绝接受介入性产前诊断的高龄孕妇,临床可推荐无创的高通量基因测序产前检测技术,进一步降低出生缺陷儿的发生率。     

无创产前检测对临界风险值的检出意义:74例回顾性分析

目的 回顾性分析74例孕妇无创产前检测(non-invasive prenatal testing,NIPT)临界风险值病例的妊娠结局,探讨临界风险值可能的原因以及对妊娠结局的影响.方法 对2017年3月至2020年7月,在中山大学附属第一医院行NIPT的4883例孕妇中,临界风险值T13(3.0＜Z＜4.39);T1...     

无创产前检测进行染色体缺失或重复检测的临床应用价值

目的:探讨无创产前检测(NIPT)进行染色体缺失或重复检测的临床应用价值。方法:对传统产前筛查异常、既往有唐氏儿分娩史及高龄孕妇等3500例孕妇采集外周血,采用Illumina测序技术检测母体血浆胎儿游离DNA(cff DNA),分析胎儿性染色体及除21、13、18号染色体以外的其他常染色体信息,对NIPT阳性的孕妇进行遗传咨询,对其中自愿进行介入性产前诊断的,行染色体核型分析及染色体微阵列分析(CMA)进行验证。结果:3500例接受NIPT的病例中,检出32例常染色体异常(除外21、13、18号),其中有11例接受介入性产前诊断,染色体核型分析及CMA检测分别提示3例异常,符合率27.3%(3/11)。检出45例性染色体异常,其中有23例接受介入性产前诊断,染色体核型分析及CMA检测分别确诊12例异常,符合率52.2%(12/45)。结论:NIPT在预测胎儿性染色体异常及常染色体(除外21、13、18号)异常方面有一定的参考价值,但需要进行染色体核型分析和(或)CMA检测进行验证。     

低胎儿DNA浓度样本重采血行无创产前检测成功的相关因素分析

目的 探讨影响低胎儿DNA浓度样本重采血复测成功的相关因素。方法 回顾性收集2018年1月至2020年12月期间在南京医科大学附属苏州医院做NIPT检测,且首次检测因胎儿DNA浓度低检测失败的单胎孕妇的临床资料,根据重采血复测后是否获得有效结果分为成功组和失败组,分析其母体特征、NIPT检测结果,采用多因素Logistics回归分析影响重采血复测成功的因素。结果 因胎儿DNA浓度低首次NIPT检测失败的的样本157例,重采血复测后有94例(59.87%)样本检测成功获得结果,63例(40.13%)仍因胎儿DNA浓度低检测失败,最终检测失败率0.138%(63/45500)。比较重采血后成功组和失败组样本信息发现：两组样本的重采血孕周和首次检测的胎儿DNA浓度有显著性差异(P<0.05),孕周>19周或首次检测胎儿DNA浓度>3%的样本重采血再检测获得有效NIPT结果的成功率更高。结论 重采血可以降低NIPT检测失败率。重采血孕周和首次检测的胎儿DNA浓度是影响重采复测成功的主要因素。临床医生可以结合这两个参数,给孕妇咨询时选择重采血NIPT检测、其他筛查还是介入性产前...     

基于单体型的杜氏肌营养不良无创产前检测研究

目的:探讨利用先证者辅助单体型分析方法(PAHP)对杜氏肌营养不良(DMD)进行无创产前检测(NIPT)的可行性。方法:招募生育过DMD先证者并再次妊娠的家系17例。对孕妇、孕妇丈夫与先证者外周血基因组DNA(g DNA)样本进行目标序列捕获测序,获得孕妇与致病位点连锁的单体型信息。然后在夫妻双方单体型的辅助下,通过对血浆数据中各个信息可供单核苷酸多态性(SNP)位点分析及统计,推断在DMD基因区域胎儿获得的母源单体型是否与先证者一致。携带与先证者相同单体型的男胎为患胎,女胎为携带者,其余为正常胎。将NIPT结果与DMD基因诊断金标准进行比较,验证其准确性。结果:NIPT结果提示17个家系中9例为男性胎儿,8例为女性胎儿;患胎3例,携带者4例,正常胎10例。该结果与胎儿的DMD基因诊断结果一致,无假阳性与假阴性结果。结论:基于先证者辅助单体型分析方法的NIPT取材方便,能避免宫内介入性操作,同时结果准确,应用于DMD的产前检测具有一定的可行性。     

无创产前检测在胎儿染色体非整倍体筛查中的应用

<正>胎儿染色体非整倍体异常可导致严重的不良妊娠结局及出生缺陷,其产前筛查及诊断是出生缺陷二级预防的重要内容之一。常见严重或致死的胎儿染色体非整倍体有21-三体(唐氏综合征,Down′s Syndrome)、18-三体(爱德华氏综合征,Edwards Syndrome)和13-三体(帕陶氏综合征,Patau Syndrome),其中以21-三体最常见,发病率为0.7‰～1.5‰^[1]。     

Association of non-invasive prenatal testing and chromosomal microarray analysis for prenatal diagnostics

Abstract

The purposes of this study is to examine possibility to use combination of non-invasive prenatal testing (NIPT) and chromosomal microarray analysis (CMA) for prenatal diagnostics and their advantages between combined first-trimester screen with confirmation by karyotyping of CVS or amniocytes. A total of 1968 pregnant women, in this study, have undergone prenatal screening and/or diagnostic tests. NIPT is more suitable and efficient for the detection of aneuploidy. However, this test has limitations for detection deletions/duplications. Use of CMA for confirmation of some NIPT findings or as first test for women with ultrasound abnormalities can detect small imbalances in chromosomes. Combination of NIPT and CMA allows a higher prenatal detection of chromosomal abnormalities.     

Initial experience with non-invasive prenatal testing of cell-free DNA for major chromosomal anomalies in a clinical setting

Objective: To evaluate non-invasive prenatal testing (NIPT) of cell-free DNA (cfDNA) as a screening method for major chromosomal anomalies (CA) in a clinical setting.

Methods: From January to December 2013, Panorama? test or Harmony? prenatal test were offered as advanced NIPT, in addition to first-trimester combined screening in singleton pregnancies.

Results: The cohort included 333 pregnant women with a mean maternal age (MA) of 37 years who underwent testing at a mean gestational age of 14.6 weeks. Eighty-four percent were low-risk pregnancies. Results were provided in 97.3% of patients at a mean reporting time of 12.9 calendar days. Repeat sampling was performed in six cases and results were obtained in five of them. No results were provided in four cases. Four cases of Down syndrome were detected and there was one discordant result of Turner syndrome. We found no statistical differences between commercial tests except in reporting time, fetal fraction and MA. The cfDNA fraction was statistically associated with test type, maternal weight, BMI and log βhCG levels.

Conclusions: NIPT has the potential to be a highly effective screening method for major CA in a clinical setting.     

Clinical utility and cost of non-invasive prenatal testing with cfDNA analysis in high-risk women based on a US population

Abstract

Objective: Evaluate the clinical and economic consequences of fetal trisomy 21 (T21) screening with non-invasive prenatal testing (NIPT) in high-risk pregnant women.

Methods: Using a decision-analytic model, we estimated the number of T21 cases detected, the number of invasive procedures performed, corresponding euploid fetal losses and total costs for three screening strategies: first trimester combined screening (FTS), integrated screening (INT) or NIPT, whereby NIPT was performed in high-risk patients (women 35 years or older or women with a positive conventional screening test). Modeling was based on a 4 million pregnant women cohort in the US.

Results: NIPT, at a base case price of $795, was more clinically effective and less costly (dominant) over both FTS and INT. NIPT detected 4823 T21 cases based on 5330 invasive procedures. FTS detected 3364 T21 cases based on 108?364 procedures and INT detected 3760 cases based on 108?760 procedures. NIPT detected 28% and 43% more T21 cases compared to INT and FTS, respectively, while reducing invasive procedures by >95% and reducing euploid fetal losses by >99%. Total costs were $3786M with FTS, $3919M with INT and $3403M with NIPT.

Conclusions: NIPT leads to improved T21 detection and reduction in euploid fetal loss at lower total healthcare expenditures.     

Causes of aberrant non-invasive prenatal testing for aneuploidy: A systematic review

Non-invasive prenatal testing (NIPT) is performed worldwide to detect common chromosomal aneuploidies. The analysis of cell-free DNA (cfDNA) in maternal blood for NIPT is highly accurate for the detection of the main fetal trisomies: 21,18, and 13. However, false-positive, false-negative, and non-reportable results can occur, and these can have biological causes. Understanding the causes of unexpected NIPT results is essential to enable clinicians and genetic counselors to counsel patients comprehensively and appropriately, both prior to testing as well as after receiving the test results. The classification of non-reportable results from cfDNA analysis is important in order to provide women with precise information. In addition to technical issues, there are biological reasons for discordant results, which can be either fetal or maternal in origin. Contributing fetal factors include insufficient or absent fetal fraction, fetoplacental mosaicism, and the presence of a vanishing twin. In some pregnant women that test positive for NIPT, multiple chromosome aneuploidy has been reported as a result of suspected malignancy, and cancer has been found. False-positive and false-negative results may be the result of placental biology and not a failure in the actual test platform. Explaining the placental origin of cfDNA provides the patient with a clear view of the abilities and limitations of cfDNA-based prenatal screening.     

Questioning the costs and benefits of non-invasive prenatal testing

Abstract

Prenatal testing for Down syndrome through the use of non-invasive prenatal testing (NIPT) has been increasingly implemented in clinical practice and a recent cost analysis suggests that NIPT is cost effective when compared to other screening modalities in high risk populations. However, this anaylsis makes many assumptions regarding uptake of testing and pregnancy termination, which cannot be applied to all populations in the United States. Additionally, this cost analysis, which hinges on fewer Down syndrome births, does not align with the goals of prenatal testing to support autonomous and value consistent decisions. NIPT is an expensive new technology and more careful analysis is needed to determine the impact of NIPT on outcomes and overall healthcare costs.     

Maternal age trends support uptake of non-invasive prenatal testing (NIPT) in the low-risk population

Abstract

Purpose: To examine trends in patients submitting samples for cell-free DNA screening to determine whether they reflect a shift towards NIPT use in the low-risk population.

Methods: A review of demographic information was performed for all specimens submitted to the Ariosa Diagnostics clinical laboratory for the Harmony^® prenatal test between January 1, 2014 and December 30, 2017. The proportions of specimens for patients under 35 years and 35?years and older were compared.

Results: There was a significant increase in the proportion of specimens submitted by patients under 35, from 47.3% in 2014 to 60.3% in 2017 (Chi-square test, p?<?.001).

Conclusions: The proportion of samples submitted to our laboratory by patients under 35?years has significantly increased in the 4-year subset, which represents the demographics of a diverse group of patients from across the globe. This suggests an increase in uptake of NIPT in the low-risk population.     

Clinical,social and ethical issues associated with non-invasive prenatal testing for aneuploidy

Non-invasive prenatal testing (NIPT), based on analysis of cell-free foetal DNA, is rapidly becoming a preferred method to screen for chromosomal aneuploidy with the technology now available in over 90 countries. This review provides an up-to-date discussion of the key clinical, social and ethical implications associated with this revolutionary technology. Stakeholders are positive about a test that is highly accurate, safe, can be perfomed early in pregnancy, identifies affected pregnancies that might otherwise have been missed and reduces the need for invasive testing. Nevertheless, professional societies currently recommend it as an advanced screening test due to the low false positive rate (FPR). Despite the practical and psychological benefits, a number of concerns have been raised which warrant attention. These include the potential for routinisation of testing and subsequent impact on informed decision-making, an “easy” blood test inadvertently contributing to women feeling pressured to take the test, fears NIPT will lead to less tolerance and support for those living with Down syndrome and the heightened expectation of having “perfect babies”. These issues can be addressed to some extent through clinician education, patient information and establishing national and international consensus in the development of comprehensive and regularly updated guidelines. As the number of conditions we are able to test for non-invasively expands it will be increasingly important to ensure pre-test counselling can be delivered effectively supported by knowledgeable healthcare professionals.     

Communicating risk in prenatal genetic testing

Prenatal testing for Down syndrome and neural tube defects has become routine, and testing for other genetic conditions is becoming commonplace. Counseling about these tests involves a discussion of risk information, so pregnant women and their partners can use the information effectively when they make choices about testing. Discussing risk can be challenging, as many individuals, particularly those of lower literacy, have a poor understanding of the numerical concept of risk. Furthermore, whether risk is comprehended accurately or not, it is interpreted by patients in light of their existing knowledge and past experiences. Strategies available to optimize understanding of risk include communication of risk figures as frequencies rather than as probabilities or percentages and explicit discussion of a woman's preconceptions about her risk and about the condition being tested for.