Noninvasive prenatal testing for trisomy 21: Challenges for implementation in Australia

Advances in technology can bring great benefits to human health, but their implementation may be influenced by socioeconomic factors, particularly in the field of prenatal screening for Down syndrome. To analyse screening test indications for, and diagnostic yield of, invasive prenatal diagnostic testing (PNDx) according to socioeconomic status. Retrospective analysis of population-based data on PNDx and karyotype results for 2014-2015 in the Australian state of Victoria. Women having PNDx<25weeks due to combined first trimester screening (CFTS), second trimester serum screening (STSS), or noninvasive prenatal testing (NIPT) results were included. PNDx data were analysed by indication and maternal Index of Relative Socio-economic Advantage and Disadvantage (IRSAD), the latter determined by postcode. There were 145206 births in 2014-2015; 1906 women underwent PNDx for the indication of CFTS (70.1%), NIPT (17.8%) or STSS (12.0%). Covariates positively associated with NIPT-indicated PNDx, compared with CFTS-indicated testing, were residence in a region of socioeconomic advantage, metropolitan status and maternal age. Women from the most advantaged regions had higher adjusted odds ratios (aOR) of NIPT-indicated testing compared with women from disadvantaged regions (aOR 5.72, 95% CI: 2.95-11.09). The diagnostic yield of PNDx increased with socioeconomic region, from 14% in the lowest IRSAD quintile to 31.2% in the highest (P<0.0001). Population-based data reveal significant disparities in screening indications for PNDx and hence, in diagnostic yield, according to socioeconomic region. This finding may have ethical and policy implications for prenatal screening in Australia.

Counseling for non-invasive prenatal testing (NIPT): what pregnant women may want to know

Prenatal care has been significantly influenced by the introduction of non-invasive prenatal testing (NIPT) for aneuploidies in 2012. The aim of this study was to describe the current impact of NIPT on prenatal care. We performed a retrospective data analysis including all women with singleton pregnancies who presented for first trimester screening (FTS) between 1 October 2011 and 30 March 2013 and those seeking NIPT. According to the results of FTS the women were categorised into three risk groups: low risk for aneuploidy (<1:300), intermediate risk (1:300-1:50) and high risk (>1:50). They were counselled about the available options for invasive prenatal testing (IPT) and NIPT available at the time of FTS. The nine months before and after the introduction of NIPT were evaluated regarding further testing after FTS. In total, 951 women were included: 505 examinations (group 1) were carried out before NIPT became available, 446 (group 2) thereafter. In group 2, 9.0% (40/446) had NIPT. Here, 60.0% (24/40) had a low risk according to FTS. In group 2 there was an increase of 3.6% of additional prenatal tests after FTS. The greatest increase was noted in the intermediate-risk category (10.7%). The number of invasive prenatal tests decreased by 67.4%. We observed a notable increase in prenatal testing after the implementation of NIPT. NIPT is an additional test for women who need more reassurance. Since the options for pregnant women become more complex and the costs of NIPT are high, prenatal counselling has become more challenging.

AIM: Non -Invasive Prenatal Test is the testing for cell free fetal DNA from maternal blood during pregnancy for Trisomy 21, 18,13 and Monosomy 45XO. The aim of our study is to review our institution’s experience in the use of non-invasive prenatal test for aneuploidy screening METHODS: It is a retrospective study of pregnant women who had undergone non-invasive prenatal test between January 2015 and December 2018 at Fernandez Hospital. A detailed Ultrasonogram is done as a mandatory prerequisite before NIPT to rule out major structural anomalies; pre and post- test counselling was done to all pregnant women who underwent non-invasive prenatal test RESULTS: 322 women who had undergone non-invasive prenatal test were included in the study. 32% of the study population were of advanced maternal age. Low fetal fraction was seen in 2.1% of the study population. An abnormal non -invasive prenatal result (aneuploidy detected or inconclusive result) was reported in 36/322(11%).NIPT had a sensitivity of 100% and specificity of 99.6% in our study. Ever since NIPT has been introduced in our clinical practice the rate of invasive tests performed declined and the number of non-invasive prenatal test performed increased yearly CONCLUSION: NIPT is an excellent method for screening for aneuploidy. There is an increasing uptake of NIPT and a decline in the rate of invasive tests performed. The occurrence of false positive results emphasizes that NIPT is a screening test and not to be considered as a replacement for diagnostic tests.

Non-invasive prenatal testing (NIPT) for trisomies 21, 18, 13 and monosomy X is widely utilized with massively parallel shotgun sequencing (MPSS), digital analysis of selected regions (DANSR), and single nucleotide polymorphism (SNP) analyses being the most widely reported methods. We searched the literature to find all NIPT clinical validation and clinical experience studies between January 2011 and January 2022. Meta-analyses were performed using bivariate random-effects and univariate regression models for estimating summary performance measures across studies. Bivariate meta-regression was performed to explore the influence of testing method and study design. Subgroup and sensitivity analyses evaluated factors that may have led to heterogeneity. Based on 55 validation studies, the detection rate (DR) was significantly higher for retrospective studies, while the false positive rate (FPR) was significantly lower for prospective studies. Comparing the performance of NIPT methods for trisomies 21, 18, and 13 combined, the SNP method had a higher DR and lower FPR than other methods, significantly so for MPSS, though not for DANSR. The performance of the different methods in the 84 clinical experience studies was consistent with validation studies. Clinical positive predictive values of all NIPT methods improved over the last decade. We conclude that all NIPT methods are highly effective for fetal aneuploidy screening, with performance differences across methodologies.

Noninvasive Prenatal Testing for Trisomies 21, 18, and 13, Sex Chromosome Aneuploidies, and Microdeletions in Average-Risk Pregnancies: A Cost-Effectiveness Analysis.

Prenatal screening for fetal Down syndrome has been widely practised in China for many years. In this special issue of BJOG, Tu et al. have published a systematic review on the performance of prenatal screening tests using biochemical and sonographic markers in Chinese women (Tu et al. BJOG 2016). Among the 78 included studies, of which most were from China, the majority (n = 64, 82%) were based on second-trimester biochemical markers. Although the pooled sensitivity and specificity for the second-trimester markers were 0.79 and 0.96, respectively, there were wide variations among individual studies. Most interestingly, 13 of the 64 second-trimester studies had a sensitivity of over 90%. Such an excellent performance has rarely been reported in studies from the non-Chinese population (Alldred et al. Cochrane Database Syst Rev 2012 Jun 13;(6):CD009925). This raised a concern over the quality of individual studies that warranted detailed analysis. In contrast, Li et al. reported in detail how to implement successfully a first-trimester combined screening (FTCS) programme for fetal Down syndrome in a resource-limited area of mainland China (Li et al. BJOG 2016). Despite the resource limitations, the author had followed strictly all the steps that were important for a successful screening programme, namely training and accreditation of staff, generation and use of local data, development of a customised cut-off and continuous quality assurance for both sonographers and biochemical assays. Specifically, the quality assurance steps included the following: (1) all sonographers were accredited by the Fetal Medicine Foundation and re-certified annually; (2) the performance of each sonographer was continuously monitored using a rolling standardised audit quality assurance report; (3) the multiple of the median values of individual biochemical markers were assessed monthly to determine the central tendency and dispersion; and (4) outcome data were followed-up. The above steps allowed early identification of deviation from expected performance for which early intervention could be initiated. Certification and quality assurance of sonographers is a particularly difficult process, requiring the support and cooperation of hospital administrators. It is interesting that in Li et al.'s study the cost of FTCS was quoted to be RMB800. Based on screening performance, noninvasive prenatal testing (NIPT) for fetal Down syndrome by cell-free DNA in maternal plasma is a far better test than FTCS, having a sensitivity and a specificity both above 99%. The cost of NIPT has come down substantially over the past 2 years. In China, NIPT is available in many major cities at a current user price most commonly between RMB2000 and 3000. It should not be long before the cost of NIPT is comparable to that of FTCS. At present, many hospitals in China are developing their own in-house NIPT platforms. This is a suboptimal move because such small hospital-based laboratories will not have enough volume to maintain a meaningful quality assurance programme. It is advisable that these screening programmes are coordinated within a region and centralised in one or a few centres where a strict quality assurance programme could be implemented. Even if NIPT has replaced conventional screening, the concept of ‘quality assurance’ as demonstrated in the study by Li et al. remains the key to the success for all screening programmes. None declared. Completed disclosure of interests form available to view online as supporting information. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Personalized medicine for the embryo and the fetus - Options in modern genetics influence preconception and prenatal choices.

Non invasive prenatal testing (NIPT) for common aneuploidies and beyond

The purpose of this study was to assess the additional contribution of karyotyping compared with genome‐wide non‐invasive prenatal testing (NIPT) for pregnancies at intermediate risk for trisomy 21 (T21), calculated using the maternal serum screening without major structural anomalies detected through sonography. Karyotype results of all pregnancies undergoing invasive prenatal diagnostic testing between January 2013 and March 2022 were obtained from a large hospital‐based laboratory. Pregnancies with no major structural anomalies on ultrasound (including soft markers) and an intermediate risk for T21 on maternal serum screening were included in this study. The additional contribution of karyotyping for abnormal karyotype results was calculated after excluding results that could theoretically be identified with genome‐wide NIPT. Among the 511 pregnancies analyzed, 13 (2.54%) were found to have abnormal karyotype results, 9 (1.76%) of which could theoretically have been detected with genome‐wide NIPT. Within the cohort, 6/263 (2.28%) of women aged 35 years and older, and 3/248 (1.20%) of women younger than 35 years had results that could have been detected with genome‐wide NIPT. After excluding results detectable using genome‐wide NIPT, the additional contribution of karyotyping was found as 4/502 (0.79%) for the entire cohort, 2/257 (0.77%) for women aged 35 years and older, 2/245 (0.81%) for women younger than 35 years. Of the 511 examined pregnancies at intermediate risk for T21 by maternal serum screening, genome‐wide NIPT would have failed to detect 4 of 13 abnormal karyotype results. The findings hold importance in guiding couples' informed decision‐making processes regarding their choice of genetic screening and diagnostic testing in case of intermediate risk for T21.

The value of detailed first-trimester ultrasound in the era of noninvasive prenatal testing

To examine combined first trimester screening (FTS), noninvasive prenatal testing (NIPT) and a two-step policy that combines FTS and NIPT in screening for aneuploidy. Retrospective study involving 21,052 pregnancies where FTS was performed at the Praxis Praenatal.de in Duesseldorf, Germany. In each case, the sum risk of trisomy 21, 18 and 13 was computed. We assumed that NIPT detects 99 %, 98 %, 90 % and 99 % of cases with trisomy 21, 18, 13 and sex chromosomal abnormalities and that the false-positive rate is 0.5 %. The following screening policies were examined: NIPT or FTS with sum risk cut-offs of 1 in 50 and 1 in 250 in all patients or a two-step-policy with FTS in all patients followed by NIPT in the intermediate sum risk group. For the intermediate risk group, sum risk cut-offs of 1 in 50 and 1 in 1000 and 1 in 150 and 1 in 500 were used. There were 127, 34, 13 and 15 pregnancies with trisomy 21, 18, 13 and sex chromosomal abnormalities. 23 fetuses had other chromosomal abnormalities with an increased risk for adverse outcome that are not detectable by NIPT. 20,840 pregnancies were classified as normal as ante- and postnatal examinations did not show any signs of clinically significant chromosomal abnormalities. FTS with a sum risk cut-off of 1 in 50 and 1 in 250 detects 81 % and 91 % for all aneuploidies. NIPT detects 88 % of the respective pregnancies. The 2-step approach with sum risk cut-offs of 1 in 50 and 1 in 1000 detects 94 % of all aneuploidies. With sum risk cut-offs of 1 in 150 and 1 in 500, the detection rate is 93 %. A 2-step policy with FTS for all patients and NIPT in the intermediate risk group results in the highest detection rate of all aneuploidies.

ObjectiveOxidative stress plays a pivotal role in the pathogenesis of Down syndrome (Trisomy 21), as chromosome 21 harbors multiple genes involved in redox homeostasis and antioxidant defense mechanisms. This study aimed to evaluate the roles of transcription factors nuclear factor erythroid 2-related factor 2 (NRF2) and nuclear factor-kappa B (NFKB), along with antioxidant enzymes cystathionine-γ-lyase (CSE) and NAD(P)H dehydrogenase [quinone] 1 (NQO1) in amniotic fluid (AF) and maternal serum (MS) as potential biomarkers for prenatal screening of Down syndrome (DS).MethodsThis prospective case-control study included singleton pregnant women undergoing amniocentesis between 16 and 24 weeks of gestation at Haseki Training and Research Hospital, Istanbul. Participants were divided into two groups: 28 pregnancies with DS confirmed by karyotype analysis (DS group) and 37 pregnancies with normal karyotype results (non-DS group). Amniotic fluid and maternal blood samples were analyzed using enzyme-linked immunosorbent assay (ELISA) kits to measure the levels of selected biomarkers.ResultsNQO1 levels were significantly higher in the DS group compared to the non-DS group in both amniotic fluid (924.84 ± 475.94 vs. 505.62 ± 358.17 ng/ml, p < 0.001) and maternal serum (716.216 ± 242.91 vs. 394.87 ± 344.86 ng/ml, p < 0.001). NRF2 levels were significantly lower in the DS group in both amniotic fluid (3.77 ± 4.20 vs. 6.47 ± 5.53 ng/ml, p = 0.029) and maternal serum (7.54 ± 5.68 vs. 14.46 ± 16.53 ng/ml, p = 0.022).ConclusionThe study highlights the importance of further research to validate the use of these antioxidant enzymes and transcription factors in non-invasive prenatal testing, which may reduce the need for invasive procedures and associated complications.Clinical trial numberNot applicable.

Non-invasive prenatal testing is increasingly available worldwide and stakeholder viewpoints are essential to guide implementation. Here we compare the preferences of women and health professionals from nine different countries towards attributes of non-invasive and invasive prenatal tests for Down syndrome. A discrete choice experiment was used to obtain participants' stated preference for prenatal tests that varied according to four attributes: accuracy, time of test, risk of miscarriage, and type of information. Pregnant women and health professionals were recruited from Canada, Denmark, Iceland, Israel, Italy, the Netherlands, Portugal, Singapore, and the United Kingdom. A total of 2666 women's and 1245 health professionals' questionnaires were included in the analysis. Differences in preferences were seen between women and health professionals within and between countries. Overall, women placed greater emphasis on test safety and comprehensive information than health professionals, who emphasised accuracy and early testing. Differences between women's and health professionals' preferences are marked between countries. Varied approaches to implementation and service delivery are therefore needed and individual countries should develop guidelines appropriate for their own social and screening contexts.

Genome-wide sequencing of maternal plasma cell-free DNA (cfDNA) enables non-invasive prenatal testing (NIPT) of all 24 chromosomes. An expanded NIPT approach can identify rare autosomal trisomies (RATs). However, this is not without interpretative challenges. More evidence is needed to determine pregnancy outcome in cases of RAT detected by NIPT. Between January 2016 and December 2017, a total of 42 924 maternal blood samples were received from Dongguan, Guangdong Province, China, for NIPT as a first-tier screening test as part of a government-funded pilot program. The suggested gestational age for NIPT was 12–22 weeks, and a nuchal translucency or second-trimester ultrasound examination before blood sampling was mandatory. We documented 72 (0.17%) NIPT results positive for RAT, 11 of which were excluded from this study because of loss to follow-up. Trisomy 7 was the most commonly detected RAT, followed equally by trisomies 3 and 16. Pregnancy characteristics, NIPT results and pregnancy outcome are summarized in Table 1. Placental karyotyping confirmed confined placental mosaicism in 54 cases, and the remaining seven had normal placental and maternal lymphocyte karyotype. Nineteen cases opted for amniocentesis, all of which showed normal karyotype; among these, only five (three at risk for trisomy 14 and two at risk for trisomy 15) opted for additional chromosomal microarray analysis, which did not show unbalanced rearrangements or uniparental disomy (UPD) in any case. At follow-up, isolated intrauterine growth restriction (IUGR) was identified in one case of trisomy 16 and one of compound trisomy 7/8. There was no case with a sonographic structural anomaly. All neonates were karyotyped, and none had evidence of true fetal mosaicism. In this study, we found no correlation between NIPT Z-score value and the percentage of abnormal cells observed in the placenta. However, these cell percentages might not represent the true condition of the affected placentas because of biopsy samplingbias. Several genome-wide cfDNA-based NIPT studies have reported RATs in association with a range of pregnancy complications, including miscarriage, true fetal mosaicism and UPD, as well as IUGR1–3. However, our results indicate favorable pregnancy outcome. Ninety-five percent of our cases had an uncomplicated pregnancy. Three reasons might contribute to this discrepancy. First, the a-priori risk in our population may explain the lower incidence of pregnancy complications. Our patients came from the general rather than a high-risk population, as in other studies. As a result, NIPT was positive for RAT in only 0.17% of cases, which is much lower than that (0.43%) in a previous study1. Second, the fact that all NIPT samples were taken only after a pretest ultrasound examination may also explain the relatively favorable outcome, as most of the affected fetuses would have been identified before performing NIPT. Third, the gestational age at NIPT in our study was relatively late, further reducing the incidence of finding an affected pregnancy. We observed a positive predictive value (PPV) of 0 for RATs. Expanding the range of aneuploidies that NIPT targets compounds this problem. Our results showed that RATs are most often mosaic and confined to the placenta. It seems that the risk of adverse pregnancy outcome associated with confined placental mosaicism for RATs is not higher than that in the general population, except for trisomy 164,5. Nevertheless, we found that the PPVs for RATs reflected closely those predicted by placental data. Eighty-eight percent of positive NIPT cases were confirmed by placental investigation. Although the clinical utility of expanding NIPT to include RATs has yet to be demonstrated and, as such, the clinical implementation of this testing is premature in the general population, screening for RATs using NIPT might benefit pregnancy management in some specific situations such as in cases of IUGR with a normal chromosomal microarray analysis result.