Current controversies in prenatal diagnosis 1: should noninvasive DNA testing be the standard screening test for Down syndrome in all pregnant women?

Performance Evaluation of Noninvasive Prenatal Testing in Screening Chromosome Disorders: A Single-Center Observational Study of 15,304 Consecutive Cases in China

Objective

This study was to evaluate the performance of noninvasive prenatal testing (NIPT) in detecting fetal chromosome disorders in pregnant women.

Methods

From October 1st, 2017, to December 31th, 2022, a total of 15,304 plasma cell free DNA-NIPT samples were collected for fetal chromosome disorders screening. The results of NIPT were validated by confirmatory invasive testing or clinical outcome follow-up. Further, NIPT performance between low-risk and high-risk groups, as well as singleton pregnancy and twin pregnancy groups was compared. Besides, analysis of 111 false-positive cases was performed.

Results

Totally, NIPT was performed on 15,086 eligible venous blood samples, of which 179 (1.19%) showed positive NIPT results and 68 were further validated to be true positive samples via confirmatory invasive testing or follow-up of clinical outcomes. For common chromosome aneuploidies, sex chromosome abnormalities (SCA) and other chromosomal aneuploidies, the detection sensitivities of NIPT were all 100%, the specificities were 99.87%, 99.70%, and 99.68% and the positive predictive values (PPVs) were 65.45%, 31.82%, and 10.91%, respectively. No statistically significant variance in detection performance was observed among 2987 high-risk and 12,099 low-risk subjects, as well as singleton and twin pregnancy subjects. The concentration of cell-free fetal DNA of 111 false-positive cases ranged from 5.5% to 33.7%, which was higher than the minimum requirement of NIPT.

Conclusion

With stringent protocol, NIPT shows high sensitivity and specificity for detecting fetal chromosome disorders in a large-scale clinical service, helping improving overall pregnancy management.

Non-invasive prenatal testing for the diagnosis of congenital abnormalities: Insights from a large multicenter study in southern China

Although non-invasive prenatal testing (NIPT) is widely used to detect fetal abnormalities, the results of NIPT vary by population, and data for the screening efficiency of NIPT positive predictive value (PPV) from different populations is limited. Herein, we retrospectively analyzed the NIPT results in a large multicenter study involving 52,855 pregnant women. Depending on gestational age, amniotic fluid or umbilical cord blood was extracted for karyotype and/or chromosome microarray analysis (CMA) in NIPT-positive patients, and the PPV and follow-up data were evaluated to determine its clinical value. Among the 52,855 cases, 754 were NIPT-positive, with a positivity rate of 1.4%. Karyotype analysis and/or CMA confirmed 323 chromosomal abnormalities, with a PPV of 45.1%. PPV for trisomy 21 (T21), trisomy 18 (T18), trisomy 13 (T13), sex chromosomal aneuploidies (SCAs), and copy number variations (CNVs) were 78.9, 35.3, 22.2, 36.9, and 32.9%, respectively. The PPVs for T21, T18, and T13 increased with age, whereas the PPVs for SCAs and CNVs had little correlation with age. The PPV was significantly higher in patients with advanced age and abnormal ultrasound. The NIPT results are affected by population characteristics. NIPT had a high PPV for T21 and a low PPV for T13 and T18, and screening for SCAs and CNVs showed clinical significance in southern China.

Prenatal diagnosis of maternal serum from mothers carrying β-thalassemic fetus

BACKGROUND

This study focuses on the discovery of protein biomarkers from the maternal serum of β-thalassemic trait mothers carrying the normal fetus and β-thalassemic major fetus.

METHODS

Serum samples from β-thalassemic trait mothers carrying major (N = 5) and normal fetuses (N = 5) were studied. The IVS1-5 thalassemia mutation was common among β-thalassemic trait mothers who were carrying a homozygous β-thalassemic fetus (IVS1-5/ IVS1-5 mutation) or a normal fetus (no mutation). We employed two-dimensional gel electrophoresis and mass spectrometry analysis to explore differentially expressed maternal serum proteins from thalassemia carrier couples with the same β-thalassemia mutation. Western blotting was performed for one of the identified proteins to validate our data.

RESULTS

Ten proteins were identified in the maternal serum of β-thalassemic trait mothers carrying the β-thalassemic major fetus and normal fetus. Among these, serotransferrin, haptoglobin, α-1 anti-trypsin, apo-lipoprotein A1, and the fibrinogen-β chain were found to be upregulated in mothers carrying major fetuses and are known to be associated with pregnancy-related disorders. The expression of α-1 anti-trypsin was validated through western blotting.

CONCLUSIONS

Proteins identified in the current study from maternal serum are reported to contribute to hereditary disorders. We suggest that these can serve as putative screening markers for non-invasive prenatal diagnosis in β-thalassemic pregnancies.

[The noninvasive prenatal testing for Down's Syndrome. Retrospective study of 8821 patients]

OBJECTIVE

To demonstrate the decrease in intrauterine invasive procedures through analysis of DNA fetoplacental free circulating in maternal blood: Non Invasive Prenatal Test (NIPT), in Prenatal Diagnosis Center of American Hospital of Paris (AHP).

MATERIALS AND METHODS

Retrospective descriptive study of 8821 patients in Prenatal Diagnosis Center at the AHP between 01/01/2012 and 09/25/2014. The NIPT is available to patients since 1st January 2013.

RESULTS

The number of invasive procedures decreased significantly (P<0.0001) between 2012 (n=1177, i.e. 42 % of the global activity of the Prenatal Diagnosis Center at the AHP in 2012) and 2013 (n=987 or 28.5 %) and between 2013 and 2014 (n=599 or 23.4 %). The NIPT calculated performance statistics are: sensitivity≥99.9 %; specificity=99.8 %; Positive Predictive Value=90.4 %; Negative Predictive Value≥99.9 %; False Positives=3. While the actual screening statistic values are: sensitivity≥95.4 %; specificity=82.5 %; Positive Predictive Value=6.5 %; Negative Predictive Value=99.9 %; False Positives=1197. The NIPT has reduced the number of invasive procedures at the Prenatal Diagnosis Center at the AHP. The NIPT performances are superior to those of the actual screening.

Non-invasive prenatal testing for trisomy 21 based on analysis of cell-free fetal DNA circulating in the maternal plasma

OBJECTIVE

By-the-book implementation of non-invasive prenatal test and clinical validation for trisomy 21.

STUDY DESIGN

Publicly funded prospective study of 225 cases. Women at risk for trisomy 21 > 1/250 based on combined ultrasound and serum markers during first or second trimester were eligible following an informed consent. The technique was established from the available literature and performed on 10 mL of venous blood collected prior to chorionic villus sampling or amniocentesis. Investigators were blinded to the fetal karyotype. Results were expressed in Z-scores of the percentage of each chromosome.

RESULTS

Among 976 eligible cases, 225 were processed: 8 were used for pretesting phase and 23 to build a reference set. One hundred thirty six euploid cases and 47 with trisomy 21 were then run randomly. Eleven cases yielded no result (4.8%). Z-scores were above 3 (7.58+/-2.41) for chromosome 21 in all 47 trisomies and in none of the euploid cases (0.11+/-1.0). Z-scores were within normal range for the other chromosomes in both groups. Using a cut-off of 3, sensitivity and specificity were of 100% 95% CI [94.1, 100] and 100% 95% CI [98, 100], respectively.

CONCLUSION

Non-invasive prenatal test for trisomy 21 is a robust strategy that can be translated from seminal publications. Publicly funded studies should refine its indications and cost-effectiveness in prenatal screening and diagnosis. © 2015 John Wiley & Sons, Ltd.

Women's Experiences of Publicly Funded Non-Invasive Prenatal Testing in Ontario, Canada: Considerations for Health Technology Policy-Making

Non-invasive prenatal testing (NIPT) via fetal DNA in maternal blood has been publicly funded in Ontario, Canada, for high-risk women since 2014. We solicited women's experiences and values related to this new health technology to describe how this test is currently being used in Ontario and to provide information about patient priorities to inform future policy decisions about the use of NIPT. Guided by constructivist grounded theory methodology, we interviewed 38 women who had diverse personal experiences with NIPT. Participants' accounts of their values for decision making about NIPT heavily relied on three mutually modulating factors: timing, accuracy, and risk. The values expressed by women conflict with the way that publicly funded NIPT has typically been implemented in Ontario. We offer recommendations for how NIPT might be integrated into prenatal care pathways in a way more consistent with women's values.