Sequential combined test, second trimester maternal serum markers, and circulating fetal cells to select women for invasive prenatal diagnosis

A new contingent screening strategy increased detection rate of trisomy 21 in the first trimester

BACKGROUND

Although the traditional contingent screening strategy is effective, there are still undetected low-risk trisomy 21. This study aims to define appropriate cut-off values of serum biochemical markers at low-risk and develop a strategy for sequential prenatal testing associated with first-trimester screening to increase the detection rate of trisomy 21.

METHODS

This was a 9-year retrospective analysis of singleton pregnant women who underwent serum biochemical screening or combined first-trimester screening (CFTS) in the first trimester. For the low-risk group, the cut-off values of the serum biochemical markers were adjusted to determine the appropriate detection efficiency. Gravidas with abnormal serum biochemical markers at low-risk were advised to undergo further non-invasive prenatal screening (NIPS), whereas others continued with routine prenatal care.

RESULTS

When cut-off values of free beta subunit of human chorionic gonadotropin (free β-hCG) multiples of the median (MoM) or pregnancy-associated plasma protein A (PAPP-A) MoM were defined with ≥ 2.75 or ≤ 0.5, 7.72% (2,194/28,405) in the serum biochemical screening group and 12.36% (4,005/32,403) in CFTS group could be detected as abnormal results for further NIPS. Finally, 55.56% (5/9) and 85.71% (6/7) of trisomy 21 cases with false-negative results were detected, and the overall detection rate for trisomy 21 was improved by 10.64% (5/47) and 12.77% (6/47), respectively.

CONCLUSIONS

The new contingent screening strategy can increase the detection rate of trisomy 21 compared with the traditional contingent screening strategy.

Isolation and Enrichment of Circulating Fetal Cells for NIPD: An Overview

Prenatal diagnosis plays a crucial role in clinical genetics. Non-invasive prenatal diagnosis using fetal cells circulating in maternal peripheral blood has become the goal of prenatal diagnosis, to obtain complete fetal genetic information and avoid risks to mother and fetus. The development of high-efficiency separation technologies is necessary to obtain the scarce fetal cells from the maternal circulation. Over the years, multiple approaches have been applied, including choice of the ideal cell targets, different cell recovering technologies, and refined cell isolation yield procedures. In order to provide a useful tool and to give insights about limitations and advantages of the technologies available today, we review the genetic research on the creation and validation of non-invasive prenatal diagnostic testing protocols based on the rare and labile circulating fetal cells during pregnancy.

Application of intelligent algorithms in Down syndrome screening during second trimester pregnancy

BACKGROUND

Down syndrome (DS) is one of the most common chromosomal aneuploidy diseases. Prenatal screening and diagnostic tests can aid the early diagnosis, appropriate management of these fetuses, and give parents an informed choice about whether or not to terminate a pregnancy. In recent years, investigations have been conducted to achieve a high detection rate (DR) and reduce the false positive rate (FPR). Hospitals have accumulated large numbers of screened cases. However, artificial intelligence methods are rarely used in the risk assessment of prenatal screening for DS.

AIM

To use a support vector machine algorithm, classification and regression tree algorithm, and AdaBoost algorithm in machine learning for modeling and analysis of prenatal DS screening.

METHODS

The dataset was from the Center for Prenatal Diagnosis at the First Hospital of Jilin University. We designed and developed intelligent algorithms based on the synthetic minority over-sampling technique (SMOTE)-Tomek and adaptive synthetic sampling over-sampling techniques to preprocess the dataset of prenatal screening information. The machine learning model was then established. Finally, the feasibility of artificial intelligence algorithms in DS screening evaluation is discussed.

RESULTS

The database contained 31 DS diagnosed cases, accounting for 0.03% of all patients. The dataset showed a large difference between the numbers of DS affected and non-affected cases. A combination of over-sampling and under-sampling techniques can greatly increase the performance of the algorithm at processing non-balanced datasets. As the number of iterations increases, the combination of the classification and regression tree algorithm and the SMOTE-Tomek over-sampling technique can obtain a high DR while keeping the FPR to a minimum.

CONCLUSION

The support vector machine algorithm and the classification and regression tree algorithm achieved good results on the DS screening dataset. When the T21 risk cutoff value was set to 270, machine learning methods had a higher DR and a lower FPR than statistical methods.

Overview and recent developments in cell-based noninvasive prenatal testing

Investigators have long been interested in the natural phenomenon of fetal and placental cell trafficking into the maternal circulation. The scarcity of these circulating cells makes their detection and isolation technically challenging. However, as a DNA source of fetal origin not mixed with maternal DNA, they have the potential of considerable benefit over circulating cell-free DNA-based noninvasive prenatal genetic testing (NIPT). Endocervical trophoblasts, which are less rare but more challenging to recover are also being investigated as an approach for cell-based NIPT. We review published studies from around the world describing both forms of cell-based NIPT and highlight the different approaches' advantages and drawbacks. We also offer guidance for developing a sound cell-based NIPT protocol.

Applications of noninvasive prenatal testing in vanishing twin syndrome pregnancies after treatment of assisted reproductive technology in a single center

OBJECTIVE

The objective of the study is to assess the clinical application of noninvasive prenatal testing (NIPT) for VTS pregnancies after the treatment of assisted reproductive technology (ART).

METHOD

This was a retrospective study on VTS pregnancies through ART treatment. Participants underwent NIPT at 11 to 13 weeks gestation by sequencing. Resampling was recommended for both positive and testing failure cases. For NIPT positive results, participants were advised to have invasive testing. Clinical outcomes were obtained by telephone interview.

RESULTS

In total of 579 cases, testing failure rates after first sampling and resampling were 7.6% and 1.4%, respectively. Twelve positive results were reported by NIPT. But only one true positive was confirmed, giving a PPV of 8%. A total of 576 cases completed the follow-up (including 533 NIPT negative, 12 positive, and 31 testing failure) and three cases lost follow-up. Among the 536 cases with NIPT negative results, 504 (94.0%) resulted in live-birth and 29 (5.4%) resulted in miscarriage or stillbirths. No false-negative result was reported.

CONCLUSION

NIPT has the potential to be used in prenatal screening for VTS pregnancies. For the pregnant women who obtained positive and testing failure results, resampling after 15 weeks of gestation is recommended.

A Retrospective Analysis Of Different Contingent Screening Models For Fetal Down Syndrome In Southwestern China

To discuss combinations of traditional screening and noninvasive prenatal screening (NIPS) and to compare which traditional screening is the most suitable first-line screening approach to NIPS, pregnant women were recruited in this retrospective observational study. Pregnant women underwent one of four traditional screening tests. The 9 contingent models were combined by high risk cut-offs of 1:50, 1:100, 1:270 and intermediate risk cut-offs of 1:1000, 1:1500, 1:2000. We analyzed cost and performance of various screening models with contingent screening of different risk cut-offs. Compared with other screening tests, combined first-trimester screening (CFTS) had the lowest proportion of high risk (≥1:270) with the highest detection rate (DR) (78.79%) and the lowest proportion of intermediate risk (1:271~1:1000). When intermediate risk was 1:51 ~1:1500, CFTS as first-line screening had the lowest cost with DR of 93.94%. Other screening tests as the first-line screening with intermediate risk of 1:51~1:1000 had the lowest cost, there DR were 90.91%, 84.62%, 91.67%, respectively. Our study demonstrated if only one traditional screening was allowed to screen pregnant women, CFTS was recommended as the first choice. According to local health and economic conditions, adopting appropriate traditional screening with suitable cut-offs as first-line screening will contributed to a cost-effective screening model.

Novel perspectives in fetal biomarker implementation for the noninvasive prenatal testing

Noninvasive prenatal testing (NIPT) utilizes cell-free fetal DNA (cffDNA) present in maternal peripheral blood to detect chromosomal abnormalities. The detection of 21-trisomy, 18-trisomy, and 13-trisomy in the fetus has become a common screening method during pregnancy and has been widely applied in routine clinical testing because of its analytical and clinical validity. Currently, noninvasive prenatal testing involving copy number variations (CNVs) and other frequent single-gene disorders is being widely studied, and it plays an important and indispensable role in prenatal detection. The multiple approaches that have been reported and validated by various laboratories have different merits and limitations. Their clinical validity, utility, and application vary with different diseases. This review summarizes the principles, methods, advantages, and limitations of noninvasive prenatal testing for the detection of aneuploidy, CNVs and single-gene disorders. Before implementation of NIPT into clinical practice, a list of criteria that the application must meet is crucial. Essential parameters such as clinical sensitivity, clinical specificity, positive predictive value (PPV) and negative predictive value (NPV) are required to properly evaluate the clinical validity and utility of NIPT. We then discuss and analyze these clinical parameters and clinical application guidelines, providing physicians and scientists with feasible strategies and the latest research information.

Non-invasive prenatal screening: A 20-year experience in Italy

Over the past two decades, there has been a rapid evolution in prenatal screening for fetal chromosome abnormalities. Initially, testing was focused on the identification of affected pregnancies in either the first, or, the second trimester (e.g. the Combined test or the triple test). This was replaced by sequential modalities (e.g. contingent screening) that have enhanced detection while reducing the need for invasive testing. More recently, the introduction of technologies based on cell-free DNA (cfDNA) in maternal plasma and enrichment of fetal cells in maternal circulation have further refined the concept of sequential screening. In this review, we document our experience with serum and ultrasound-based contingent screening where we were able to achieve a detection rate of 96.8%, a false-positive rate of 2.8% and an odds of being affected given a positive result of 1:11. We also describe our initial experience with a novel sequential protocol that includes the analysis of fetal cells in maternal blood. Methods for enrichment for fetal cells cfDNA and cfDNA technologies offer the possibility of greater sensitivity and specificity as well as expansion in the scope of genetic disorders detectable. As costs decline, these technologies will become increasingly used as primary screening tools. In the meantime, sequential use offers a practical approach to maximizing the benefits of prenatal testing.