Cell-free DNA screening and sex chromosome aneuploidies

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.

DNA corona on nanoparticles leads to an enhanced immunostimulatory effect with implications for autoimmune diseases

Autoimmune and inflammatory diseases are highly complex, limiting treatment and the development of new therapies. Recent work has shown that cell-free DNA bound to biological microparticles is linked to systemic lupus erythematosus, a prototypic autoimmune disease. However, the heterogeneity and technical challenges associated with the study of biological particles have hindered a mechanistic understanding of their role. Our goal was to develop a well-controlled DNA-particle model system to understand how DNA-particle complexes affect cells. We first characterized the adsorption of DNA on the surface of polystyrene nanoparticles (200 nm and 2 µm) using transmission electron microscopy, dynamic light scattering, and colorimetric DNA concentration assays. We found that DNA adsorbed on the surface of nanoparticles was resistant to degradation by DNase 1. Macrophage cells incubated with the DNA-nanoparticle complexes had increased production of pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). We probed two intracellular DNA sensing pathways, toll-like receptor 9 (TLR9) and cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING), to determine how cells sense the DNA-nanoparticle complexes. We found that the cGAS-STING pathway is the primary route for the interaction between DNA-nanoparticles and macrophages. These studies provide a molecular and cellular-level understanding of DNA-nanoparticle-macrophage interactions. In addition, this work provides the mechanistic information necessary for future in vivo experiments to elucidate the role of DNA-particle interactions in autoimmune diseases, providing a unique experimental framework to develop novel therapeutic approaches.

Relationships among maternal monosomy X mosaicism, maternal trisomy, and discordant sex chromosome aneuploidies

OBJECTIVE

To explore the impact of maternal factors on the false-positive fetal sex chromosome aneuploidies (SCAs) results obtained through noninvasive prenatal screening (NIPS).

METHODS

We retrospectively analyzed pregnant women with high-risk SCAs as revealed using NIPS between January 2017 and December 2022. Clinical data such as results of invasive prenatal diagnoses, copy number variation sequencing (CNV-seq) and pregnancy outcomes were analysed.

RESULTS

Overall, 177 (0.6 %) women with SCA-positive results were collected from 27,941 patients who had undergone NIPS. Among them, 110 (62.2 %) pregnant women chose prenatal diagnosis and 39 (35.5 %) cases were confirmed. For the women with monosomy X false-positive results from the NIPS, 53.1 % (17/32) were found to be maternal mosaicism monosomy X. In cases with 47, XXX false-positive results, 60 % (6/10) of them were maternal 47,XXX (5 cases) or maternal mosaicism 47,XXX (1 case). One (1/6, 16.7 %) case of maternal mosaicism monosomy X was detected in the false positive results of 47, XXY/47, XYY revealed. The incidence rate of maternal sex chromosome abnormalities was positively correlated with the Z-score of ChrX. When the Z-score of ChrX ≥ 15, more than 50 % of pregnant women were found to be maternal sex chromosome abnormalities, and when Z-score ≥ 30, the incidence rate was as high as 100 %.

CONCLUSIONS

Maternal monosomy X mosaicism and trisomy X respectively played an important role in the discordance of 45, X and 47, XXX revealed by NIPS. CNV-seq was recommended for the pregnant women at risk of maternal sex chromosome abnormalities, which could help clinicians to provide more accurate and efficient advice during genetic counseling and to guide appropriate prenatal diagnosis strategy for the next pregnancy.

Chorionic Villous Testing Versus Amniocentesis After Abnormal Noninvasive Prenatal Testing

In the setting of a normal first-trimester ultrasound, an amniocentesis may be a better option than chorionic villous sampling for invasive diagnostic testing after a cell-free DNA high risk for trisomy 13, given the high rates of confined placental mosaicism. In unaffected fetuses, other evaluations should be considered depending on the cell-free DNA results, including maternal karyotyping for monosomy X, uniparental disomy testing for chromosomes with imprinted genes, serial growth scans for trisomy 16, and a workup for maternal malignancy for multiple aneuploidies or autosomal monosomy.

Noninvasive prenatal screening (NIPS) results for participants of the eXtraordinarY babies study: Screening, counseling, diagnosis, and discordance

Sex chromosome aneuploidies (SCAs), including 47,XXY, 47,XXX, 47,XYY, and supernumerary variants, occur collectively in approximately one of 500 live births. Clinical phenotypes are highly variable resulting in previous ascertainment rates estimated to be only 10%-25% during a lifetime. Historically, prenatal SCA diagnoses were incidental findings, accounting for ≤10% of cases, with the majority of diagnoses occurring postnatally during evaluations for neurodevelopmental, medical, or infertility concerns. The initiation of noninvasive prenatal screening (NIPS) in 2012 and adoption into standardized obstetric care provides a unique opportunity to significantly increase prenatal ascertainment of SCAs. However, the impact NIPS has had on ascertainment of SCAs is understudied, particularly for those who may defer diagnostic testing until after birth. This study evaluates the timing of diagnostic testing following positive NIPS in 152 infants with SCAs and potential factors influencing this decision. Eighty-seven (57%) elected to defer diagnostic testing after a positive NIPS until birth, and 8% (7/87) of those confirmed after birth were found to have discordant results on postnatal diagnostic testing, most of which would have influenced genetic counseling.

Ethical issues associated with prenatal screening using non-invasive prenatal testing for sex chromosome aneuploidy

Prenatal screening for sex chromosome aneuploidies (SCAs) is increasingly available through expanded non-invasive prenatal testing (NIPT). NIPT for SCAs raises complex ethical issues for clinical providers, prospective parents and future children. This paper discusses the ethical issues that arise around NIPT for SCAs and current guidelines and protocols for management. The first section outlines current practice and the limitations of NIPT for SCAs. It then outlines key guidelines before discussing the ethical issues raised by this use of NIPT. We conclude that while screening for SCAs should be made available for people seeking to use NIPT, its implementation requires careful consideration of what, when and how information is provided to users.

Cell-free DNA screening positive for monosomy X: clinical evaluation and management of suspected maternal or fetal Turner syndrome

Initially provided as an alternative to evaluation of serum analytes and nuchal translucency for the assessment of pregnancies at high risk of trisomy 21, cell-free DNA screening for fetal aneuploidy, also referred to as noninvasive prenatal screening, can now also screen for fetal sex chromosome anomalies such as monosomy X as early as 9 to 10 weeks of gestation. Early identification of Turner syndrome, a sex chromosome anomaly resulting from the complete or partial absence of the second X chromosome, allows medical interventions such as optimizing obstetrical outcomes, hormone replacement therapy, fertility preservation and support, and improved neurocognitive outcomes. However, cell-free DNA screening for sex chromosome anomalies and monosomy X in particular is associated with high false-positive rates and low positive predictive value. A cell-free DNA result positive for monosomy X may represent fetal Turner syndrome, maternal Turner syndrome, or confined placental mosaicism. A positive screen for monosomy X with discordant results of diagnostic fetal karyotype presents unique interpretation and management challenges because of potential implications for previously unrecognized maternal Turner syndrome. The current international consensus clinical practice guidelines for the care of individuals with Turner syndrome throughout the lifespan do not specifically address management of individuals with a cell-free DNA screen positive for monosomy X. This study aimed to provide context and expert-driven recommendations for maternal and/or fetal evaluation and management when cell-free DNA screening is positive for monosomy X. We highlight unique challenges of cell-free DNA screening that is incidentally positive for monosomy X, present recommendations for determining if the result is a true-positive, and discuss when diagnosis of Turner syndrome is applicable to the fetus vs the mother. Whereas we defer the subsequent management of confirmed Turner syndrome to the clinical practice guidelines, we highlight unique considerations for individuals initially identified through cell-free DNA screening.

Genome-Wide Cell-Free DNA Test for Fetal Chromosomal Abnormalities and Variants: Unrestricted Versus Restricted Reporting

This study aimed to compare the screening performance of genome-wide cfDNA testing for chromosomal abnormalities between two periods where additional findings were reported and not reported. Data were obtained from consecutive pregnant women with a singleton pregnancy at ≥10 weeks who requested cfDNA testing during 2015–2019. The performance of screening of the cfDNA test was determined by calculating the concordance rate, detection rate, and false-positive rate. Data from 3981 women were included. The no-result rates were similar between the two reporting periods (2.04% vs. 2.08%). Concordance rates for trisomy 21 and 18 were 100% and 100%, respectively. There were two cases tested high risk for trisomy 13, with a concordance rate of 0%. In total, 12 cases were high risk for any sex chromosome aneuploidy with an overall concordance of 75%, and 15 cases tested high risk for any rare autosomal trisomy, with a 13.3% concordance rate. The detection rates for trisomy 21 and 18 were 100% and 100%, respectively. For any SCA, the detection rate was 90%. For the two reporting periods, the combined false-positive rates were 0.93% and 0.17%, which were significantly different (p = 0.002). Restricting the reporting of additional findings from genome-wide cfDNA analysis has reduced the false-positive rate but without a reduction in the no-result rate.

Prenatal Detection and Evaluation of Differences of Sex Development: A Qualitative Interview Study of Parental Perspectives and Unmet Needs

Objectives

Prenatal diagnoses of differences of sex development (DSD) are increasing due to availability of cell‐free DNA screening (cell‐free DNA screening (cfDNA)). This study explores first‐hand experiences of parents whose children had prenatal findings of DSD.

Methods

Eligible parents were identified through chart review at a pediatric center and interviewed about their prenatal evaluation, decision making, informational sources, and support systems. Interviews were coded using a combined inductive and deductive thematic analysis. Parents also completed quantitative measures of decisional regret.

Results

Seventeen parents (13 mothers; 4 fathers) of 13 children (with 7 DSD diagnoses) were recruited. Four children had discordance between sex predicted by cfDNA versus prenatal ultrasound, and 2 had non‐binary appearing (atypical) genitalia on prenatal ultrasound. Of these 6, 3 were not offered additional prenatal testing or counseling.

Most parents described tension between obtaining support through disclosure of their child's diagnosis and preserving their child's autonomy/privacy, highlighting the need for mental health support.

Conclusion

This is the first study to gather qualitative data from parents whose children had prenatal findings of DSD. We identified multiple targets for intervention to improve care for patients with DSD across the lifespan, including improvements in clinician education, pre‐ and post‐test counseling, and patient education materials.

What's already known about this topic? What does this study add?

Prenatal detection of potential differences of sex development (DSD) is increasing as the availability of non‐invasive prenatal screening increases.

Algorithms have been developed for the diagnostic evaluation, but little is known about the psychosocial implications of that process.

This study focuses on the first‐hand experiences of families whose children had prenatal findings of a potential DSD, to identify existing sources of support and information, and areas for future improvement.

Droplet Digital PCR for Non-Invasive Prenatal Detection of Fetal Single-Gene Point Mutations in Maternal Plasma

Non-invasive prenatal testing (NIPT) is based on the detection and characterization of circulating cell-free fetal DNA (ccffDNA) in maternal plasma and aims to identify genetic abnormalities. At present, commercial NIPT kits can detect only aneuploidies, small deletions and insertions and some paternally inherited single-gene point mutations causing genetic diseases, but not maternally inherited ones. In this work, we have developed two NIPT assays, based on the innovative and sensitive droplet digital PCR (ddPCR) technology, to identify the two most common β thalassemia mutations in the Mediterranean area (β⁺IVSI-110 and β⁰39), maternally and/or paternally inherited, by fetal genotyping. The assays were optimized in terms of amplification efficiency and hybridization specificity, using mixtures of two genomic DNAs with different genotypes and percentages to simulate fetal and maternal circulating cell-free DNA (ccfDNA) at various gestational weeks. The two ddPCR assays were then applied to determine the fetal genotype from 52 maternal plasma samples at different gestational ages. The diagnostic outcomes were confirmed for all the samples by DNA sequencing. In the case of mutations inherited from the mother or from both parents, a precise dosage of normal and mutated alleles was required to determine the fetal genotype. In particular, we identified two diagnostic ranges for allelic ratio values statistically distinct and not overlapping, allowing correct fetal genotype determinations for almost all the analyzed samples. In conclusion, we have developed a simple and sensitive diagnostic tool, based on ddPCR, for the NIPT of β⁺IVSI-110 and β⁰39 mutations paternally and, for the first time, maternally inherited, a tool, which may be applied to other single point mutations causing monogenic diseases.

Cell-Free DNA Screening for Sex Chromosome Abnormalities and Pregnancy Outcomes, 2018-2020: A Retrospective Analysis

To evaluate the efficacy of non-invasive prenatal screening (NIPT) for detecting fetal sex chromosome abnormalities, a total of 639 women carrying sex chromosome abnormalities were selected from 222,107 pregnant women who participated in free NIPT from April 2018 to December 2020. The clinical data, prenatal diagnosis results, and follow-up pregnancy outcomes of participants were collected. The positive predictive value (PPV) was used to analyze the performance of NIPT. Around 235 cases were confirmed with sex chromosome abnormalities, including 229 cases with sex chromosome aneuploidy (45, X (n = 37), 47, XXX (n = 37), 47, XXY (n = 110), 47, XYY (n = 42)) and 6 cases with structural abnormalities. The total incidence rate was 0.11% (235/222,107). The PPV of NIPT was 45.37% (235/518). NIPT accuracy for detecting sex chromosome polysomes was higher than that for sex chromosome monomers. The termination of pregnancy rate for fetal diagnosis of 45, X, and 47, XXY was higher than that of 47, XXX, and 47, XYY. The detection rate of fetal sex chromosome abnormalities was higher in 2018–2020 than in 2010–2012 (χ² = 69.708, P < 2.2 × 10⁻¹⁶), indicating that NIPT is greatly efficient to detect fetal sex chromosome abnormalities.

Decision-making for prenatal genetic screening: how will pregnant women navigate a growing number of aneuploidy and carrier screening options?

BACKGROUND

Prenatal genetic screens, including carrier screening (CS) and aneuploidy screening (AS), comprise an important component of reproductive healthcare delivery. Clinical practice guidelines emphasize the importance of informed decision-making and patient's preferences regarding the use of these screens. Yet, it is unclear how to achieve this ideal as prenatal genetic screening options rapidly become more complex and increasingly available to patients. With increased complexity and availability of reproductive testing options, decision-support strategies are critical to prepare patients to consider AS and/or CS.

METHODS

A self-administered survey evaluated knowledge and decision-making preferences for expanded carrier (CS) and aneuploidy (AS) prenatal screening. The survey was administered to participants before their first prenatal visit to assess baseline decision-making needs and preference at the initiation of prenatal care. Analysis was approached as a descriptive process.

RESULTS

Participants had similar familiarity with the concepts associated with AS compared to CS; mean knowledge scores for CS was 0.59 [possible range 0.00 to 1.00] and 0.55 for AS. Participants reported preferences to learn about a range of conditions, including those with severe or mild impact, childhood-onset, and adult-onset. Decision-making preference with respect to learning about the associated disease phenotypes for the contained on AS and CS panel shifted with the complexity of the panel, with a greater preference to learn about conditions post-test compared pre-test education as panels increased from 5 to 100 conditions.

CONCLUSION

Patients' baseline knowledge of prenatal genetic screens coupled with evolving decision-making preferences presents challenges for the delivery of prenatal genetic screens. This calls for the development and implementation of innovative approaches to support pregnant patients' decision-making commensurate with advances in prenatal genomics.

Efficiency of Noninvasive Prenatal Testing for Sex Chromosome Aneuploidies

OBJECTIVE

This study was designed to investigate the efficiency of noninvasive prenatal testing (NIPT) for screening fetal sex chromosome aneuploidies (SCAs) through sequencing of cell-free DNA in maternal plasma.

METHODS

This is a retrospective study on the positive NIPT results for SCAs collected from our hospital between January 2012 and December 2018. Samples with positive NIPT results for SCAs were then confirmed by prenatal or postnatal karyotyping analysis.

RESULTS

After cytogenetic analysis, abnormal karyotypes were confirmed in 104 cases and the overall positive predictive value (PPV) of NIPT for SCAs was 43.40% (102/235). The most frequently detected karyotypes included 47,XXY (n = 42), 47,XXX (n = 20), 47,XYY (n = 16), and 45,X (n = 2). Meanwhile, 10 cases were confirmed with mosaic karyotype 45,X/46,XX and 14 cases with numerical or structural chromosome abnormalities, including a double trisomy 48,XXX,+18. Cytogenetic results from the other 131 cases showed normal XX or XY, which were discordant with NIPT results. Upon analysis of parental karyotypes, 29 (12.34%) showed false positivity in NIPT results that were caused by maternal sex chromosome abnormalities.

CONCLUSION

NIPT is an effective screening tool for SCA with a PPV of 43.40%. Maternal karyotype abnormalities occurred in 12.34% of the cases with abnormal NIPT. Diagnostic testing of the fetus and the mother are recommended.

Fetal sex discordance

Fetal sex discordance is an entity that is becoming more frequent due to the expansion of the cfDNA for prenatal diagnosis. Its incidence can be estimated in 1/1500-2000 pregnancies, a frequency as high as that of some common chromosomopathies. The causes of this phenomenon are multiple and diverse, ranging from laboratory errors to important pathologies such as disorders of sexual differentiation. The management of a case of fetal sex discordance must be structured, starting with the review of the clinical history and the tests performed, and may require the performance of invasive tests to reach a diagnosis. Prevention through adequate pretest counseling and ultrasound confirmation can help to reduce its incidence.

An assessment of the analytical performance of non-invasive prenatal testing (NIPT) in detecting sex chromosome aneuploidies: 34,717-patient sample in a single prenatal diagnosis Centre in China

OBJECTIVE

The present study aimed to evaluate the efficacy of a non-invasive prenatal test (NIPT) in the detection of the sex chromosome aneuploidies (SCAs) at our prenatal diagnosis centre.

METHODS

Among a cohort of 34,717 pregnancies, maternal plasma samples from our prenatal diagnosis centre were subject to analysis of SCAs using NIPT detection. Pregnant women with NIPT positive results of SCAs were recommended to undergo an invasive prenatal diagnosis (i.e. karyotyping and fluorescence in situ hybridization) to validate the prediction value of NIPT.

RESULTS

From 34,717 clinical pregnancies, 229 (0.66%) pregnancies were identified with SCAs. Of these, 78 (34.1%) cases were positive for 45,X and 151 (65.9%) cases comprised a sex chromosome trisomy. Of the 229 positive NIPT results, 193 (84.3%) cases had accepted an invasive diagnosis involving karyotyping analysis of the amniotic fluid, which confirmed 67 cases (34.7%) as true positive, as well as 126 cases (65.3%) as false positive. The positive predictive values were 23.07%, 50%, 36% and 27.27% respectively. The remaining 36 (15.7%) cases declined a prenatal diagnosis. The termination rates of 45,X, 47,XXY, 47,XXX and 47,XYY were 20.5%,46%,12.9% and 11.5% respectively.

CONCLUSIONS

NIPT demonstrated a lower accuracy in predicting monosomy X than sex chromosome trisomies. After invasive testing, the fetal chromosome with 45,X and 47,XXY were terminated more often than those with 47,XXX, 47,XYY. Because NIPT is a screening test, false positive/negative cases exist, and pre- and post-test counselling is essential for informing patients about the benefits and limitations of the test. Confirmatory testing of abnormal results is recommended prenatally or after birth, and the importance of confirmatory testing and benefits of early diagnosis should be addressed.

Noninvasive prenatal screening for fetal sex chromosome aneuploidies

INTRODUCTION

Sex chromosome aneuploidies (SCAs) are among the most common chromosome abnormalities observed in humans. Manifestations include low fertility, infertility, delayed language development, and dysfunction in motor development. Noninvasive prenatal screening (NIPS) based on cell-free fetal DNA from the peripheral blood of pregnant women is increasingly used for the screening of fetal chromosome abnormalities, including screening for fetal gender and fetal sex chromosome aneuploidy. A systematic review of the literature about NIPS for SCAs is needed.

AREAS COVERED

This review evaluated a vast array of published studies focusing on the clinical significance, detection methods, performance of NIPS for SCAs, and the management of positive SCA results following screening with the aim of facilitating a comprehensive and systematic understanding of NIPS for SCAs.

EXPERT COMMENTARY

Looking forward, NIPS is expected to become the primary screening test for common aneuploidies as well as other chromosome abnormalities, including some micro-deletions and micro-duplications, with the potential to transition from a screening test to a prenatal diagnosis method. Ultimately, the goal is to provide a safe and accurate method for increasing early diagnosis to improve long-term outcomes for the SCA patients and families by well- informed health care providers.

Prenatal Genetic Diagnosis of a Sex Chromosome Aneuploidy: Parent Experiences

Sex chromosome aneuploidies (SCAs) occur in 1 in every 400 births. SCAs are highly variable and have uncertain prognoses, complicating the delivery of prenatal cell-free DNA (cfDNA) results or diagnosis following amniocentesis or chorionic villus sampling. Using a mixed-methods approach, we explored the experiences of parents receiving a prenatal diagnosis of a fetus with SCA. Responses to open-ended questions were qualitatively analyzed. Of the 323 parents who completed the survey, 122 received a prenatal diagnosis and answered at least one open-ended question. Most parents did not recall being informed that cfDNA screening or amniocentesis could reveal the presence of a SCA prior to testing and described feeling unprepared for a positive result. Variation was found between parents who were delivered a diagnosis by a genetic professional versus other clinical specialties. Many parents expressed that the diagnosis was delivered in a way that emphasized the negative attributes of the SCA and that they were provided limited support materials. Parents who received a prenatal diagnosis of a SCA expressed a desire for more supportive delivery of prenatal diagnosis that focuses on parental education and nuanced discussion of potential phenotypes. Genetic counselors should be aware of the range of parental experiences when receiving a SCA diagnosis from non-genetic providers. Prenatal SCA diagnoses are predicted to increase as prenatal cfDNA screening becomes more widely used. Collaborations for greater provider education and comprehensive materials on SCAs are essential to facilitate the delivery of SCA diagnoses and improve parent understanding and support.

Confirmation rate of cell free DNA screening for sex chromosomal abnormalities according to the method of confirmatory testing

OBJECTIVE

To examine the positive predictive value (PPV) of cfDNA screening for sex chromosome aneuploidies (SCA) in a large series of over 90 000 patients.

METHODS

Retrospective study based on samples that were sent to Cenata, a private laboratory which uses the Harmony Prenatal Test. The SCA high-risk results were stratified according to the method of diagnostic testing and according to karyotype result.

RESULTS

The study population consisted of 144 cases. The CfDNA test indicated monosomy X, XXX, XXY, and XYY in 62, 37, 40, and 5 cases, respectively. The overall PPV was 38.9% (30.9-47.4), 29.0% (18.2-42.9) for monosomy X, 29.7% (15.9-47.9) for 47,XXX, 57.5% (40.9-73.0) for 47,XXY, and 80.0% (28.4-99.5) for 47,XYY). A total of 112 (77.8%) women with a high-risk result for SCAs opted for prenatal karyotyping. In this group, there were significant differences in the PPV if the karyotype was assessed by amniocentesis or by CVS: 29.5% vs 50.0%. This significant difference was driven by the monosomy X result which shows a significantly higher PPV in CVS (54.6% (23.4-83.3) vs 17.1% (6.6-33.6)). For the other SCAs, the differences were not significant.

CONCLUSION

PPV of an abnormal cfDNA test for SCAs is low, particularly for monosomy X. The confirmation rate depends on the type of confirmatory test.

Discordant fetal sex on NIPT and ultrasound

Prenatal diagnosis of sex discordance is a relatively new phenomenon. Prior to cell-free DNA testing, the diagnosis of a disorder of sexual differentiation was serendipitous, either through identification of ambiguous genitalia at the midtrimester morphology ultrasound or discovery of genotype-phenotype discordance in cases where preimplantation genetic diagnosis or invasive prenatal testing had occurred. The widespread integration of cfDNA testing into modern antenatal screening has made sex chromosome assessment possible from 10 weeks of gestation, and discordant fetal sex is now more commonly diagnosed prenatally, with a prevalence of approximately 1 in 1500-2000 pregnancies. Early detection of phenotype-genotype sex discordance is important as it may indicate an underlying genetic, chromosomal or biochemical condition and it also allows for time-critical postnatal treatment. The aim of this article is to review cfDNA and ultrasound diagnosis of fetal sex, identify possible causes of phenotype-genotype discordance and provide a systematic approach for clinicians when counseling and managing couples in this circumstance.

Family experiences and attitudes about receiving the diagnosis of sex chromosome aneuploidy in a child

The most common sex chromosome aneuploidies (SCA) (47, XXY; 47, XYY; 47, XXX) frequently result in a milder phenotype than autosomal aneuploidies. Nevertheless, these conditions are highly variable and more symptomatic phenotypes may require significant clinical involvement, including specialty care. While historically most individuals with mild phenotypes remained undiagnosed during their lifetime, the increasing use of genetic testing in clinical care has increased the prenatal and postnatal diagnosis of SCAs. These genetic tests are frequently ordered by nongenetic providers who are also responsible for delivering the diagnosis. We surveyed parents of children (n = 308) to evaluate their experience of receiving a diagnosis and their support needs. The majority (73.3%) received the diagnosis from a nongenetic medical provider. Following a prenatal diagnosis parents reported experiencing depression, anxiety, and less optimism than those receiving a postnatal diagnosis. Few parents reported receiving materials explaining their child's condition that they found to be up-to-date, accurate, and unbiased. The frequently negative reported experiences of parents at time of diagnosis suggests more educational opportunities should be provided for nongenetic providers in order to become more informed about these conditions and communicate the diagnosis in a way parents experience as supportive.

Cell-free DNA screening for sex chromosome aneuploidies by non-invasive prenatal testing in maternal plasma

BACKGROUND

Non-invasive prenatal testing (NIPT) has been confirmed as the most accurate screening test for trisomies 21, 18, and 13. However, reports on NIPT performance in sex chromosome aneuploidies (SCA) based on real clinical data are still limited.

METHODS

High-throughput massively parallel genomic sequencing (MPS) technique was used to screen for fetal SCAs as part of the research to determine the potential value of NIPT in detecting fetal SCAs in the second trimester. A number of 12,243 consecutive cases from a single center were included in this study.

RESULTS

The positive predictive value (PPV) of NIPT in the present study was 57.6%, which was divided and categorized by individual SCAs as follows: 21.4% for Turner syndrome (45,X), 75.0% for Triple X syndrome (47,XXX), 90.9% for Klinefelter syndrome (47,XXY), and 75.0% for XYY syndrome (47,XYY).

CONCLUSION

The NIPT-based SCA test cannot be used as a diagnostic method, and performing an invasive confirmation test on NIPT-based SCA-positive cases is strongly recommended.

Prenatal detection and evaluation of differences of sex development

INTRODUCTION

Differences/disorders of sex development (DSD) can be detected at different ages, including prenatally. The recent implementation of prenatal genetic testing (including cell-free DNA) may affect the frequency and impact of prenatal diagnosis of DSD. Our aims were to (1) describe prenatal detection and evaluation of differences of sex development presenting to a multidisciplinary DSD clinic and (2) explore possible parental distress accompanying this evaluation.

MATERIALS AND METHODS

A retrospective chart review of mothers presenting prenatally, and patients presenting during infancy, to a multidisciplinary DSD clinic from 2013 to 2017 was conducted. Data extracted included demographics, final diagnoses, prenatal screening, prenatal evaluation, postnatal endocrine, genetic and radiologic testing, and clinician's notes on parent/patient distress.

RESULTS

Sixty-seven patients were identified; ten (15%) had prenatal detection of a suspected DSD. Of those, 4/10 were detected prenatally in the last study year alone. Within the prenatal group, 6/10 had cell-free DNA results discordant with ultrasound, 2/10 were detected by atypical genitalia on ultrasound, and 2/10 were detected through karyotyping performed for other indications. After birth, 3/10 patients were found to not have a DSD. Final diagnoses for the full study cohort are shown in the Summary Table, comparing prenatal versus postnatal presentation to our DSD clinic. Clinicians noted distress for most parents during the prenatal evaluation of a possible DSD, including one mother who reported suicidal thoughts.

DISCUSSION AND CONCLUSIONS

Prenatal suspicion of DSD can occur through discordant prenatal testing and has been observed at our clinic in recent years, in line with other recent studies. Contributing factors to these prenatal presentations could be increased referrals to the clinic, and increased use of non-invasive prenatal testing, which can lead to inaccurate or discordant sex identification. The prenatal suspicion of a potential DSD can be associated with parental distress, underscoring the need for adequate counseling for tests that determine fetal sex, including cell-free DNA.

Non-Invasive Prenatal Testing beyond Trisomies

The last decade has seen incredible advances in the genetic era, in next-generation sequencing of cell-free DNA in the maternal plasma, detecting abnormal fetal chromosomes. Non-invasive prenatal testing (NIPT) has showed increased sensitivity and specificity for Down syndrome superior to any other screening test. Technical advances have made possible the detection of other conditions which does not necessarily mean clinical benefit for the patient. Private laboratories have added multiple conditions in the panel of NIPT, but some of these abnormalities are so rare, that their prevalence is not even clear. Data regarding clinical performance of extended NIPT is lacking. Implementation of such a test has to be carefully weighed, and not only the benefits but also the harm should be taken into account.

The personal utility of cfDNA screening: Pregnant patients' experiences with cfDNA screening and views on expanded cfDNA panels

Prenatal cell-free DNA screening (cfDNA) provides more genetic risk information about the fetus than has ever been possible. At the same time, the rapid expansion of new cfDNA panels raises important questions about how to structure patient-centered discussions that best support patients' decision-making about its use. To address this question, we conducted interviews with pregnant patients to identify decision-making needs and preferences with respect to cfDNA in patient-centered healthcare discussions, given its evolving capability to identify a range of fetal variants. Personal utility was a core concept guiding decision-making. Participants spoke of how their deeply personal values and beliefs about maternal responsibility, actionability, and tolerance of uncertainty framed their view of the personal utility of cfDNA screening. While discussing their notions of personal utility with their healthcare provider, participants also had concerns about potential ramifications for the provider-patient relationship and shared decision-making when disclosing values and preferences regarding disability, quality of life, and termination-particularly as it becomes possible to identify variants with different disease-associated severity and outcomes. The complexities associated with the introduction of genomics in prenatal care present unique challenges to structuring effective shared decision-making discussions between patients and their healthcare providers. While efforts are underway to determine how to best educate patients about the medical aspects of cfDNA, it is equally important to develop approaches in healthcare communication that enable patients to make informed, values-based decisions about the use of cfDNA and its impact on their pregnancy.

Testosterone Treatment in Infants With 47,XXY: Effects on Body Composition

Context

Boys with XXY have greater adiposity and a higher risk of cardiovascular disease. Infants with XXY have lower testosterone concentrations than typical boys, but no studies have evaluated adiposity in infants with XXY or the physiologic effects of giving testosterone replacement.

Objective

To determine the effect of testosterone on body composition in infants with XXY.

Design

Prospective, randomized trial.

Setting

Tertiary care pediatric referral center.

Participants

20 infants 6 to 15 weeks of age with 47,XXY.

Intervention

Testosterone cypionate 25 mg intramuscularly monthly for three doses vs no treatment.

Main Outcome Measures

Difference in change in adiposity (percent fat mass z scores); other body composition measures, penile length, and safety outcomes between treated and untreated infants; and comparison with typical infants.

Results

The increase in percent fat mass (%FM) z scores was greater in the untreated group than in the treated group (+0.92 ± 0.62 vs −0.12 ± 0.65, P = 0.004). Increases in secondary outcomes were greater in the testosterone-treated group for total mass, fat-free mass, length z score, stretched penile length, and growth velocity (P < 0.002 for all). At 5 months of age, adiposity in untreated infants with XXY was 26.7% compared with 23.2% in healthy male infants of the same age (P = 0.0037); there was no difference in %FM between the treated XXY boys and controls. Reported side effects were minimal and self-limited; no serious adverse events occurred.

Conclusions

Adiposity of untreated infants was 15% greater than that of male controls by 5 months of age. Testosterone treatment for infants with XXY resulted in positive changes in body composition.

Non-invasive Prenatal Testing Using Fetal DNA

Non-invasive prenatal diagnosis (NIPD) is based on fetal DNA analysis starting from a simple peripheral blood sample, thus avoiding risks associated with conventional invasive techniques. During pregnancy, the fetal DNA increases to approximately 3-13% of the total circulating free DNA in maternal plasma. The very low amount of circulating cell-free fetal DNA (ccffDNA) in maternal plasma is a crucial issue, and requires specific and optimized techniques for ccffDNA purification from maternal plasma. In addition, highly sensitive detection approaches are required. In recent years, advanced ccffDNA investigation approaches have allowed the application of non-invasive prenatal testing (NIPT) to determine fetal sex, fetal rhesus D (RhD) genotyping, aneuploidies, micro-deletions and the detection of paternally inherited monogenic disorders. Finally, complex and innovative technologies such as digital polymerase chain reaction (dPCR) and next-generation sequencing (NGS) (exhibiting higher sensitivity and/or the capability to read the entire fetal genome from maternal plasma DNA) are expected to allow the detection, in the near future, of maternally inherited mutations that cause genetic diseases. The aim of this review is to introduce the principal ccffDNA characteristics and their applications as the basis of current and novel NIPT.

Screening, prenatal diagnosis, and prenatal decision for sex chromosome aneuploidy

Objective: To assess the performance of non-invasive prenatal testing (NIPT) in screening sex chromosome aneuploidy (SCA), and explore prenatal decision-making in NIPT positive cases. Methods: The study retrospectively analyses singleton pregnancies who underwent NIPT screening. Clinical data, diagnostic results, and pregnancy outcomes were also collected. Results: There were 140 positive screens for SCA, including 62 cases of 45,X, 29 cases with 47,XXX, 28 cases of 47,XXY, 20 cases of 47,XYY, and one case of lower X chromosome. Karyotypic information was available in 103 cases. The positive predictive value was 26.09% for 45,X, 85.00% for 47,XXX, 85.00% for 47,XXY, and 68.75% for 47,XYY. The termination rates of 45,X, 47,XXX, 47,XXY, 47,XYY were 83.33%, 26.67%, 82.35%, and 54.54%, respectively (not including mosaic cases). Conclusion: Our findings demonstrated that the NIPT performed better in predicting sex chromosome trisomies than monosomy X even though false-positive cases do exist in NIPT. For prenatal decisions, pregnancies with diagnoses of fetal 45,X and 47,XXY were terminated more often than those with 47,XXX, 47,XYY. To better guide positive screening pregnancies, pre- and post-test counseling are essential in telling patients the benefits and limitations of the test, comforting their anxiety and giving them the choice for further diagnosis and pregnancy decision.

Delivering the Diagnosis of Sex Chromosome Aneuploidy: Experiences and Preferences of Parents and Individuals

Increased prenatal diagnoses of sex chromosome aneuploidies (SCAs) amid limited knowledge of their prognoses heighten the need to understand how families contend with the implications of an SCA. To explore the experiences of parents and individuals who received a genetic diagnosis of an SCA (excluding Turner syndrome), we conducted semistructured qualitative telephone interviews with 43 participants affected by these conditions. Parents (n = 35) and individuals (n = 8) expressed almost unanimous interest in more optimistic portrayals of their condition from their providers, even when the prognosis is uncertain. While some participants reported success in receiving accurate information from their provider and identifying supportive resources, numerous families received outdated or misleading information about their condition and lacked direction in accessing follow-up care and support. Parents desire greater coordination of their child's medical care and access to care that approaches an SCA holistically. Opportunities remain to improve the diagnosis and care of individuals with SCAs.

The importance of pre- and post-test counseling for prenatal cell-free DNA screening for common fetal aneuploidies

INTRODUCTION

Prenatal cell-free DNA screening for common fetal aneuploidies has rapidly changed the paradigm of prenatal care. Despite its advantages compared to conventional screening methods, its unexpectedly rapid implementation in clinical practice has generated several ethical and medical issues and misconceptions. Aggressive commercial marketing of cell-free DNA screening and media dissemination of misleading information have added confusion. Areas covered: This review provides an extensive update and will focus on the importance of pre-and post-test counseling for prenatal cell-free DNA screening not previously discussed extensively in the available literature. Additionally, we report cell-free DNA screening implementation in the largest obstetrical tertiary unit in Finland which is one of few countries that provides all prenatal screening methods free of charge for all women and has a very high uptake of first-trimester screening. This is not a systematical review, but rather a narrative overview which includes the most relevant and recent original publications and reviews covering this issue. Expert opinion: Despite being the most accurate method for screening of common fetal aneuploidies, the knowledge and counseling should be substantially improved. Cell-free DNA screening is not a replacement for diagnostic testing and its use in prenatal testing is complex and limited.

Turner syndrome: New insights from prenatal genomics and transcriptomics

In some parts of the world, prenatal screening using analysis of circulating cell-free (cf) DNA in the plasma of pregnant women has become part of routine prenatal care with limited professional guidelines and without significant input from the Turner syndrome community. In contrast to the very high positive predictive values (PPVs) achieved with cfDNA analysis for trisomy 21 (91% for high-risk and 82% for low-risk cases), the PPVs for monosomy X are much lower (~26%). This is because the maternal plasma sample contains both maternal cfDNA and placental DNA, which is a proxy for the fetal genome. Underlying biological mechanisms for false positive monosomy X screening results include confined placental mosaicism, co-twin demise, and maternal mosaicism. Somatic loss of a single X chromosome in the mother is a natural phenomenon that occurs with aging; this could explain many of the false positive cfDNA results. There is also increased awareness of women who have constitutional mosaicism for 45, X who are fertile. It is important to recognize that a positive cfDNA screen for 45, X does not mean that the fetus has Turner syndrome. A follow-up diagnostic test, either amniocentesis or neonatal karyotype/chromosome microarray, is recommended. Research studies on cell-free mRNA in second trimester amniotic fluid, which is almost exclusively fetal, demonstrate consistent dysregulation of genes involved in the hematologic, immune, and neurologic systems. This suggests that some of the pathophysiology of Turner syndrome occurs early in fetal life and presents novel opportunities for consideration of antenatal treatments.

Population-based trends in the prenatal diagnosis of sex chromosome aneuploidy before and after non-invasive prenatal testing

OBJECTIVE

To assess the impact of non-invasive prenatal testing (NIPT) on trends in the prenatal diagnosis of sex chromosome aneuploidy (SCA) in a population with >73,000 annual births.

METHOD

Retrospective population-based cohort study from 1986-2016 of all women undergoing prenatal diagnosis before 25 weeks gestation in the Australian state of Victoria. Statistical significance was tested using the chi-square test for trend or proportions.

RESULTS

There were 2,043,345 births and 842 SCA diagnoses from 1986-2016. The percentage of prenatal diagnostic tests leading to a SCA diagnosis increased significantly from 0.95% in 2010 to 2.93% in 2016 (p < 0.001) but due to a concurrent decline in testing, the annual prenatal diagnosis rate of SCA remained stable at 4.4/10,000 births. Among confirmed fetal SCAs the most common indication for testing in 1986 was advanced maternal age (63%); in 2016 it was high risk NIPT (49%).

CONCLUSION

SCAs now make up an increasing proportion of prenatal diagnostic results but due to the overall decline in diagnostic testing, the prenatal prevalence as a percentage of births remained steady. The ascertainment of fetal SCA has evolved from an incidental finding after testing for increased risk of trisomy 21, to a diagnosis obtained after suspected SCA on NIPT.

Not all chromosome aberrations can be detected by NIPT in women at advanced maternal age: A multicenter retrospective study

OBJECTIVE

To discuss the detectability of NIPT for pregnant women at advanced maternal age (AMA), and mainly focused on how many fetal abnormalities will be missed by NIPT.

METHODS

A total of 4194 women at AMA who accepted cytogenetic prenatal diagnosis were recruited in this study. All the AMA women received amniocentesis at 18-23 weeks. Combined with our detection level of NIPT and literature reports, we evaluated the detectability of NIPT.

RESULTS

After cell karyotype analysis, a total of 233 (5.56%) fetuses were confirmed to have chromosomal abnormalities, including 91.0% were abnormal chromosome number and 9.0% were abnormal chromosome structure. According to the detectability of NIPT we calculated, 87.6% abnormal results could also be detected by NIPT. However, NIPT would miss 12.4% abnormal results which could be originally found by the karyotype analysis of amniotic fluid cells. The major types of missed fetal abnormalities include structural rearrangement, mosaic and triploidy. Meanwhile, there were no relationship between the detectability of NIPT and the age of AMA pregnant women.

CONCLUSIONS

About 12.4% of fetal chromosomal abnormalities will be missed if NIPT completely replaces invasive prenatal diagnosis in AMA women. Fortunately, these types of fetal abnormalities missed by NIPT did not increase with the age elevating of pregnant women.

Rare autosomal trisomies: Important and not so rare

OBJECTIVE

Noninvasive prenatal testing (NIPT) can assess chromosomes other than 13, 18, 21, X and Y. These rare autosomal trisomies (RATs) can adversely affect pregnancy outcome.

METHODS

A prospective study of NIPT using the Illumina sequencing platform assessing all chromosomes were reported for further management.

RESULTS

There were 28 RATs identified in 23 388 samples (one in 835), the most common being trisomy 7 (n = 6), followed by trisomy 16 (n = 4) and trisomy 22 (n = 3). Abnormal outcomes occurred in 16 cases: miscarriage (n = 6), true fetal mosaicism (n = 5), and fetal structural anomaly on ultrasound (n = 5). Growth restriction was seen in eight cases and correlated with very low-pregnancy-associated plasma protein-A levels. Two of the 17 live born babies had a structural anomaly, and one had a phenotype similar to mosaic trisomy 16 despite a normal microarray result.

CONCLUSION

Rare autosomal trisomies are not rare and often associated with poor obstetric outcomes. They should be discussed with the clinician to guide management. Pregnancy outcomes varied by chromosome being generally favourable for some (eg, trisomy 7) and poor for others (eg, trisomy 22). In the presence of a RAT, pregnancy-associated plasma protein-A is predictive of placental dysfunction and fetal growth restriction.

Genetic Counselors' Perspectives About Cell-Free DNA: Experiences, Challenges, and Expectations for Obstetricians

The expansion of cell-free fetal DNA (cfDNA) screening for a larger and diverse set of genetic variants, in addition for use among the low-risk obstetric population, presents important clinical challenges for all healthcare providers involved in the delivery of prenatal care. It is unclear how to leverage the different members of the healthcare team to respond to these challenges. We conducted interviews with 25 prenatal genetic counselors to understand their experience with the continued expansion of cfDNA screening. Participants supported the use of cfDNA screening for the common autosomal aneuploidies, but noted some reservations for its use to identify fetal sex and microdeletions. Participants reported several barriers to ensuring that patients have the information and support to make informed decisions about using cfDNA to screen for these different conditions. This was seen as a dual-sided problem, and necessitated additional education interventions that addressed patients seeking cfDNA screening, and obstetricians who introduce the concepts of genetic risk and cfDNA to patients. In addition, participants noted that they have a professional responsibility to educate obstetricians about cfDNA so they can be prepared to be gatekeepers of counseling and education about this screening option for use among the general obstetric population.

Fetal sex determination in twin pregnancies using cell free fetal DNA analysis

OBJECTIVE(S)

We sought to develop an accurate sex classification method in twin pregnancies using data obtained from a standard commercial non-invasive prenatal test.

STUDY DESIGN

A total of 706 twin pregnancies were included in this retrospective analytical data study. Normalized chromosome values for chromosomes X and Y were used and adapted into a sex-score to predict fetal sex in each fetus, and results were compared with the clinical outcome at birth.

RESULTS

Outcome information at birth for sex chromosomes was available for 232 twin pregnancies. From these, a total of 173 twin pregnancies with a Y chromosome identified in non-invasive pregnancy testing were used for the development of a predictive model. Global accuracy for sex classification in the testing set with 51 samples was 0.98 (95% confidence interval [0.90,0.99]), with a specificity and sensitivity of 1 (95% confidence interval [0.82,1.00]) and 0.97 (95% confidence interval [0.84,0.99]), respectively.

CONCLUSION

While non-invasive prenatal testing is a screening method and confirmatory results must be obtained by ultrasound or genetic diagnosis, the sex-score determination presented herein offers an accurate and useful approach to characterizing fetus sex in twin pregnancies in a non-invasive manner early on in pregnancy.

Genomics-based non-invasive prenatal testing for detection of fetal chromosomal aneuploidy in pregnant women

BACKGROUND

Common fetal aneuploidies include Down syndrome (trisomy 21 or T21), Edward syndrome (trisomy 18 or T18), Patau syndrome (trisomy 13 or T13), Turner syndrome (45,X), Klinefelter syndrome (47,XXY), Triple X syndrome (47,XXX) and 47,XYY syndrome (47,XYY). Prenatal screening for fetal aneuploidies is standard care in many countries, but current biochemical and ultrasound tests have high false negative and false positive rates. The discovery of fetal circulating cell-free DNA (ccfDNA) in maternal blood offers the potential for genomics-based non-invasive prenatal testing (gNIPT) as a more accurate screening method. Two approaches used for gNIPT are massively parallel shotgun sequencing (MPSS) and targeted massively parallel sequencing (TMPS).

OBJECTIVES

To evaluate and compare the diagnostic accuracy of MPSS and TMPS for gNIPT as a first-tier test in unselected populations of pregnant women undergoing aneuploidy screening or as a second-tier test in pregnant women considered to be high risk after first-tier screening for common fetal aneuploidies. The gNIPT results were confirmed by a reference standard such as fetal karyotype or neonatal clinical examination.

SEARCH METHODS

We searched 13 databases (including MEDLINE, Embase and Web of Science) from 1 January 2007 to 12 July 2016 without any language, search filter or publication type restrictions. We also screened reference lists of relevant full-text articles, websites of private prenatal diagnosis companies and conference abstracts.

SELECTION CRITERIA

Studies could include pregnant women of any age, ethnicity and gestational age with singleton or multifetal pregnancy. The women must have had a screening test for fetal aneuploidy by MPSS or TMPS and a reference standard such as fetal karyotype or medical records from birth.

DATA COLLECTION AND ANALYSIS

Two review authors independently carried out study selection, data extraction and quality assessment (using the QUADAS-2 tool). Where possible, hierarchical models or simpler alternatives were used for meta-analysis.

MAIN RESULTS

Sixty-five studies of 86,139 pregnant women (3141 aneuploids and 82,998 euploids) were included. No study was judged to be at low risk of bias across the four domains of the QUADAS-2 tool but applicability concerns were generally low. Of the 65 studies, 42 enrolled pregnant women at high risk, five recruited an unselected population and 18 recruited cohorts with a mix of prior risk of fetal aneuploidy. Among the 65 studies, 44 evaluated MPSS and 21 evaluated TMPS; of these, five studies also compared gNIPT with a traditional screening test (biochemical, ultrasound or both). Forty-six out of 65 studies (71%) reported gNIPT assay failure rate, which ranged between 0% and 25% for MPSS, and between 0.8% and 7.5% for TMPS.In the population of unselected pregnant women, MPSS was evaluated by only one study; the study assessed T21, T18 and T13. TMPS was assessed for T21 in four studies involving unselected cohorts; three of the studies also assessed T18 and 13. In pooled analyses (88 T21 cases, 22 T18 cases, eight T13 cases and 20,649 unaffected pregnancies (non T21, T18 and T13)), the clinical sensitivity (95% confidence interval (CI)) of TMPS was 99.2% (78.2% to 100%), 90.9% (70.0% to 97.7%) and 65.1% (9.16% to 97.2%) for T21, T18 and T13, respectively. The corresponding clinical specificity was above 99.9% for T21, T18 and T13.In high-risk populations, MPSS was assessed for T21, T18, T13 and 45,X in 30, 28, 20 and 12 studies, respectively. In pooled analyses (1048 T21 cases, 332 T18 cases, 128 T13 cases and 15,797 unaffected pregnancies), the clinical sensitivity (95% confidence interval (CI)) of MPSS was 99.7% (98.0% to 100%), 97.8% (92.5% to 99.4%), 95.8% (86.1% to 98.9%) and 91.7% (78.3% to 97.1%) for T21, T18, T13 and 45,X, respectively. The corresponding clinical specificities (95% CI) were 99.9% (99.8% to 100%), 99.9% (99.8% to 100%), 99.8% (99.8% to 99.9%) and 99.6% (98.9% to 99.8%). In this risk group, TMPS was assessed for T21, T18, T13 and 45,X in six, five, two and four studies. In pooled analyses (246 T21 cases, 112 T18 cases, 20 T13 cases and 4282 unaffected pregnancies), the clinical sensitivity (95% CI) of TMPS was 99.2% (96.8% to 99.8%), 98.2% (93.1% to 99.6%), 100% (83.9% to 100%) and 92.4% (84.1% to 96.5%) for T21, T18, T13 and 45,X respectively. The clinical specificities were above 100% for T21, T18 and T13 and 99.8% (98.3% to 100%) for 45,X. Indirect comparisons of MPSS and TMPS for T21, T18 and 45,X showed no statistical difference in clinical sensitivity, clinical specificity or both. Due to limited data, comparative meta-analysis of MPSS and TMPS was not possible for T13.We were unable to perform meta-analyses of gNIPT for 47,XXX, 47,XXY and 47,XYY because there were very few or no studies in one or more risk groups.

AUTHORS' CONCLUSIONS

These results show that MPSS and TMPS perform similarly in terms of clinical sensitivity and specificity for the detection of fetal T31, T18, T13 and sex chromosome aneuploidy (SCA). However, no study compared the two approaches head-to-head in the same cohort of patients. The accuracy of gNIPT as a prenatal screening test has been mainly evaluated as a second-tier screening test to identify pregnancies at very low risk of fetal aneuploidies (T21, T18 and T13), thus avoiding invasive procedures. Genomics-based non-invasive prenatal testing methods appear to be sensitive and highly specific for detection of fetal trisomies 21, 18 and 13 in high-risk populations. There is paucity of data on the accuracy of gNIPT as a first-tier aneuploidy screening test in a population of unselected pregnant women. With respect to the replacement of invasive tests, the performance of gNIPT observed in this review is not sufficient to replace current invasive diagnostic tests.We conclude that given the current data on the performance of gNIPT, invasive fetal karyotyping is still the required diagnostic approach to confirm the presence of a chromosomal abnormality prior to making irreversible decisions relative to the pregnancy outcome. However, most of the gNIPT studies were prone to bias, especially in terms of the selection of participants.

Implications of fetoplacental mosaicism on cell-free DNA testing for sex chromosome aneuploidies

OBJECTIVE

The unique biological behavior of sex chromosomes has implications for cell-free DNA (cfDNA) testing. Our purpose is to predict the (1) false positive/negative rates of cfDNA testing consequent to fetoplacental mosaicism for any sex chromosome aneuploidies (SCA) and (2) positive predictive value (PPV) and negative predictive values of a high-risk and low-risk cfDNA result for any SCA.

METHOD

This is a retrospective analysis of 67 030 chorionic villus sampling karyotypes, including fetoplacental mosaicism cases.

RESULTS

Non-mosaic 45, X is associated with cystic hygroma/increased nuchal translucency and fetal anomalies. The false positive rate consequent to confined placental mosaicism is predicted to be 0.05%. The estimated false negative rate is in the range of 0% to 5.7% for all non-mosaic SCAs; it is 70% for mosaic 45, X with normal ultrasound. The predicted PPV on amniocytes is very high for most SCAs (94.4-99.4%). However, the stratified analysis shows that the PPV is much lower for 45, X without ultrasound anomalies compared with 45, X with abnormal scan (51% or 71%, vs 99%, respectively).

CONCLUSION

Mosaicism is a major issue for SCA cfDNA testing, and prenatal confirmation, preferentially with amniocentesis if there are no ultrasound anomalies, remains important in counseling. As PPV varies on the basis of the presence of an ultrasound anomaly, skilled evaluation is critical. © 2017 John Wiley & Sons, Ltd.

Patient-Centered Obstetric Care in the Age of Cell-Free Fetal DNA Prenatal Screening

Purpose

The clinical introduction of innovative prenatal genetic technologies challenges patients and providers to find new ways of fostering informed decision-making in a setting characterized by complexity and uncertainty. As prenatal genetic technology advances, important questions remain about how to structure patient-centered conversations that effectively prepare pregnant patients to make informed choices about the different genetic conditions for which this new form screening may be used.

Methods

Focus groups were conducted with 23 pregnant women to identify informational needs and decision-making preferences regarding emerging and anticipated applications of cell-free fetal DNA screening, the newest form of prenatal genetic screening.

Results

Participants were in favor of obtaining more genetic information about the fetus than provided by conventional screens but acknowledged the challenges inherent in navigating the unique complexities of the decision-making process. The provider-patient relationship was seen as an important resource to navigate the associated uncertainties at each stage of the screening process. Participants emphasized the need for initiatives to support a personalized, accurate, and unbiased discussion about prenatal genetic risk and assessment.

Conclusion

Continued advances in prenatal genetic screening call for new approaches to structure patient-centered communication to facilitate increasingly complex decisions about fetal genetic risk and assessment.

Cell-Free DNA Screening: Complexities and Challenges of Clinical Implementation

Screening for fetal aneuploidy in pregnant women using cell-free DNA has increased dramatically since the technology became commercially available in 2011. Since that time, numerous trials have demonstrated high sensitivity and specificity to screen for common aneuploidies in high-risk populations. Studies assessing the performance of these tests in low-risk populations have also demonstrated improved detection rates compared with traditional, serum-based screening strategies. Concurrent with the increased use of this technology has been a decrease in invasive procedures (amniocentesis and chorionic villus sampling). As the technology becomes more widely understood, available, and utilized, challenges regarding its clinical implementation have become apparent. Some of these challenges include test failures, false-positive and false-negative results, limitations in positive predictive value in low-prevalence populations, and potential maternal health implications of abnormal results. In addition, commercial laboratories are expanding screening beyond common aneuploidies to include microdeletion screening and whole genome screening. This review article is intended to provide the practicing obstetrician with a summary of the complexities of cell-free DNA screening and the challenges of implementing it in the clinical setting.

Origins, structures, and functions of circulating DNA in oncology

While various clinical applications especially in oncology are now in progress such as diagnosis, prognosis, therapy monitoring, or patient follow-up, the determination of structural characteristics of cell-free circulating DNA (cirDNA) are still being researched. Nevertheless, some specific structures have been identified and cirDNA has been shown to be composed of many “kinds.” This structural description goes hand-in-hand with the mechanisms of its origins such as apoptosis, necrosis, active release, phagocytosis, and exocytose. There are multiple structural forms of cirDNA depending upon the mechanism of release: particulate structures (exosomes, microparticles, apoptotic bodies) or macromolecular structures (nucleosomes, virtosomes/proteolipidonucleic acid complexes, DNA traps, links with serum proteins or to the cell-free membrane parts). In addition, cirDNA concerns both nuclear and/or mitochondrial DNA with both species exhibiting different structural characteristics that potentially reveal different forms of biological stability or diagnostic significance. This review focuses on the origins, structures and functional aspects that are paradoxically less well described in the literature while numerous reviews are directed to the clinical application of cirDNA. Differentiation of the various structures and better knowledge of the fate of cirDNA would considerably expand the diagnostic power of cirDNA analysis especially with regard to the patient follow-up enlarging the scope of personalized medicine. A better understanding of the subsequent fate of cirDNA would also help in deciphering its functional aspects such as their capacity for either genometastasis or their pro-inflammatory and immunological effects.