Low-level mosaic trisomy 13 at amniocentesis in a pregnancy associated with a positive NIPT result suspicious of trisomy 13, a CVS result of mosaic trisomy 13, cytogenetic discrepancy in various tissues and a favorable fetal outcome.

OBJECTIVE: We present low-level mosaic trisomy 13 at amniocentesis in a pregnancy associated with a positive non-invasive prenatal testing (NIPT) result suspicious of trisomy 13, a chorionic villus sampling (CVS) result of mosaic trisomy 13, cytogenetic discrepancy in various tissues and a favorable fetal outcome. CASE REPORT: A 29-year-old, gravida 2, para 1, woman underwent amniocentesis at 20 weeks of gestation because of a positive NIPT result (Z-score = 20.9, positive ≥3) suspicious of trisomy 13 at 11 weeks of gestation and a CVS result of mosaic trisomy 13 at 14 weeks of gestation. At 14 weeks of gestation, CVS revealed the multiplex ligation-dependent probe amplification (MLPA) result of rea X,Y (P095) × 1, 13 (P095) × 3, 18,21 (P095) × 2/X,Y (P095) × 1, 13,18,21 (P095) × 2 and a karyotype of 48,XY,+13,+mar [9]/47,XY,+mar[16]. She was referred to the hospital for genetic counseling at 15 weeks of gestation, and cytogenetic analysis of parental blood revealed 47,XY,+mar in the father and 46, XX in the mother. Fluorescence in situ hybridization (FISH) analysis on the paternal blood showed that the extra dicentric marker was derived from chromosome 15 without the locus SNRPN (15q11.2), and the result was 47,XY,+mar.ish dic(15) (D15Z1++, SNRPN-, PML-)[20]. Amniocentesis at 20 weeks of gestation revealed a karyotype of 47,XY,+mar pat (20/20). Simultaneous interphase FISH analysis on uncultured amniocytes revealed 32% (32/100 cells) mosaicism for trisomy 13. Quantitative fluorescence polymerase chain reaction (QF-PCR) analysis using the DNA extracted from the parental bloods and uncultured amniocytes excluded uniparental disomy (UPD) 13. Prenatal ultrasound findings were normal. The woman was advised to continue the pregnancy, and a phenotypically normal 2708-g male baby was delivered at 38 weeks of gestation, The cord blood, umbilical cord and placenta had the karyotypes of 47,XY,+mar pat and did not have UPD 13. When follow-up at age two months, the neonate was phenotypically normal. FISH analysis on buccal mucosal cells detected 5.3% (5/95 cells) mosaicism for trisomy 13, compared with 0% in the normal control. CONCLUSION: Low-level mosaic trisomy 13 at amniocentesis can be associated with a positive NIPT result suspicious of trisomy 13, a CVS result of mosaic trisomy 13, cytogenetic discrepancy in various tissues and a favorable fetal outcome.

Phenotypic and cytogenetic variability of patau syndrome in Morocco.

The objective of this work was to identify phenotypic features and cytogenetic aspects of trisomy 13 in Moroccan population. The retrospective study was conducted on a group of 9 cases diagnosed cytogenetically with trisomy 13. The study of sex ratio showed a slight female dominance in our group of cases. The major clinical findings included: Holoprosencephaly, microphthalmia and anophthalmia, coloboma of iris, cleft lip and palate, nasal and ear abnormalities, retrognathism and sloping forehead, polydactyly, capillary hemangiomas, omphalocele, congenital heart defect, renal abnormalities, cryptorchidism, language delay. The cytogenetic study showed the dominance of the free and homogeneous trisomy 13 (56%). Patients who have this formula are dead at an early age (does not exceed one month). However, each of the chromosomal formula, trisomy 13 by translocation and partial trisomy 13 t (13;18), was found in 20% of our patients. The partial trisomy 13 t (13;18) is the only variant that is still alive and the patients with this anomaly suffer mainly from renal and cardiac anomalies with slight dysmorphia and psychomotor retardation. Our study shows the interest of the cytogenetic analysis in the diagnosis accuracy and in the genetic counseling of patients with Patau syndrome and their parents.

Improving survival in patients with trisomy 18.

The effects of medical and surgical interventions on the survival of patients with trisomy 18 have been reported, leading to changes in perinatal management and decision-making. However, few studies have fully reported the recent changes in survival and treatment of trisomy 18. We examined how treatment and survival of patients with trisomy 18 have changed over a decade in a Japanese pediatric tertiary referral center. This retrospective cohort study included patients with trisomy 18 who were admitted within the first 7 days of life at the Hyogo Prefectural Kobe Children's Hospital between 2008 and 2017. The patients were divided into early period (EP) and late period (LP) groups based on the birth year of 2008-2012 and 2013-2017, respectively. Changes in treatment and survival rates were compared between the two groups. A total of 56 patients were studied (29 in the EP group and 27 in the LP group). One-year survival rates were 34.5% and 59.3% in the EP and LP groups, respectively. The survival to discharge rate significantly increased from 27.6% in the EP group to 81.5% in the LP group (p < 0.001). The proportion of patients receiving surgery, especially for congenital heart defects, significantly increased from 59% in the EP group to 96% in the LP group (p = 0.001). In our single-center study, survival and survival to discharge were significantly improved in patients with trisomy 18, probably because of increased rate of surgical interventions. These findings may facilitate better decision-making by patients' families and healthcare providers.

[Genetic study of a trisomy 13 fetus with a false-negative karyotype by chorionic villi analysis].

OBJECTIVE: To explore the mechanism of a false-negative result from karyotyping of chorionic villi cells for a trisomy 13 fetus featuring multiple malformations. METHODS: For a fetus with multiple malformations by ultrasonography and a 46,XY karyotype by chorionic villi analysis, amniocytes were further analyzed with quantitative fluorescence PCR (QF-PCR), G-banded karyotyping and chromosomal microarray analysis (CMA). Meanwhile, non-invasive prenatal testing (NIPT) was conducted on peripheral blood sample from the pregnant woman to determine the chromosomal composition of cytotrophoblast. After induction of labor, common aneuploidies in placenta and fetal tissue were also analyzed by QF-PCR. RESULTS: QF-PCR, chromosomal karyotyping and CMA analysis of the amniocytes all suggested complete trisomy 13 (47,XY,+13) in the fetus. NIPT also suggested existence of fetal trisomy 13. QF-PCR analysis of the placenta and fetal tissues revealed that cells derived from the maternal surface and right side of fetal surface harbored mosaic trisomy 13, while those derived from other sites of fetal surface of the placenta, umbilical cord, amniotic membrane and fetal muscle tissue harbored trisomy 13. CONCLUSION: Karyotyping of long-term cultured chorionic villus sample may give rise to false negative results due to placental mosaicism. To ensure accurate prenatal diagnosis, discordance between karyotyping of chorionic villi cells, fetal ultrasound and NIPT result should be verified by amniocentesis or cordocentesis and application of multiple cytogenetic and molecular techniques.

Trisomía 9, trisomía 13 y trisomía 18: resultados del análisis citogenético prenatal, Hospital Clínico Universidad de Chile, años 2000-2017 / Trisomy 9, trisomy 13 and trisomy 18: results of the prenatal cytogenical analysis, Hospital Clínico Universidad de Chile, years 2000-2017

INTRODUCCIÓN: En Chile, la norma técnica de la Ley N° 21.030 de 2017 considera tres aneuploidías como letales; las trisomías 9, 13 y 18, cuyo diagnóstico se confirma con un cariograma. No existe a la fecha registro nacional de frecuencia prenatal de estas patologías. OBJETIVO: Determinar la frecuencia de trisomías 9, 13 y 18 en los estudios citogenéticos prenatales en muestras de células obtenidas con amniocentesis y cordocentesis, procesados en el Laboratorio de Citogenética del Hospital Clínico Universidad de Chile. MATERIALES Y MÉTODOS: Estudio descriptivo y retrospectivo de los resultados de cariograma de líquido amniótico (LA) y sangre fetal (SF), procesados desde enero de 2000 a diciembre de 2017. RESULTADOS: Se incluyeron 2.305 muestras (402 de SF y 1.903 de LA), de ellas 442 (19%) fueron trisomías letales (TL), dentro de ellas fueron TL libres 416 (95%), TL estructurales 15 (2,7%) y mosaicos 11 (2,3%). La trisomía 18 fue en ambos tipos de muestra la más frecuente (73,5%), seguida de trisomía 13 (24,2%) y trisomía 9 (2,3%). Se desglosan resultados conforme al tipo de TL, muestra, motivo de derivación, edad materna y edad gestacional. CONCLUSIONES: El cariograma confirma el diagnóstico de aneuploidías y aporta datos relevantes para el consejo genético. La cromosomopatía letal más frecuente fue la trisomía 18. Se observó que uno de cada cinco cariogramas referidos por anomalías congénitas y/o marcadores de aneuploidía revelaban una TL.

INTRODUCTION: In Chile, the technical standard of Law No. 21,030 of 2017 considers three aneuploidies as lethal; trisomies 9, 13 and 18, whose diagnosis is confirmed with a Karyotype. To date there is not a national registry of prenatal frequency of these pathologies. OBJECTIVE: To determine the frequency of trisomies 9, 13 and 18 in prenatal cytogenetic studies in samples of cells obtained with amniocentesis and cordocentesis, processed in the Cytogenetics Laboratory of the Universidad de Chile Clinical Hospital. MATERIALS AND METHODS: Descriptive and retrospective study of the results of karyotypes of amniotic fluid (LA) and fetal blood (SF) processed from January 2000 to December 2017. Results: 2,305 samples (402 of SF and 1,903 of LA) were included, of which 438 (19%) were lethal trisomies (TL), corresponding to free TL 416 (95%), structural TL 12 (2,7%) and mosaics 10 (2.3%). Trisomy 18 was the most frequent in both types of sample (73,5 %), followed by trisomy 13 (24,2%) and trisomy 9 (2.3%). RESULTS are shown according to the type of TL, sample, reason for referral, maternal age and gestational age. CONCLUSIONS: The karyotype confirms the diagnosis of aneuploidies and provides relevant data for genetic counseling. The most frequent lethal chromosomopathy was trisomy 18. It was observed that one in five karyotypes referred for congenital anomalies and / or aneuploidy markers revealed a TL.

Cell-free DNA screening for aneuploidies in 7113 pregnancies: single Italian centre study.

INTRODUCTION: Non-invasive prenatal testing (NIPT) using cell-free foetal DNA has been widely accepted in recent years for detecting common foetal chromosome aneuploidies, such as trisomies 13, 18 and 21, and sex chromosome aneuploidies. In this study, the practical clinical performance of our foetal DNA testing was evaluated for analysing all chromosome aberrations among 7113 pregnancies in Italy. METHODS: This study was a retrospective analysis of collected NIPT data from the Ion S5 next-generation sequencing platform obtained from Altamedica Medical Centre in Rome, Italy. RESULTS: In this study, NIPT showed 100% sensitivity and 99.9% specificity for trisomies 13, 18 and 21. Out of the 7113 samples analysed, 74 cases (1%) were positive by NIPT testing; foetal karyotyping and follow-up results validated 2 trisomy 13 cases, 5 trisomy 18 cases, 58 trisomy 21 cases and 10 sex chromosome aneuploidy cases. There were no false-negative results. CONCLUSION: In our hands, NIPT had high sensitivity and specificity for common chromosomal aneuploidies such as trisomies 13, 18 and 21.

Is there still a role for nuchal translucency measurement in the changing paradigm of first trimester screening?

OBJECTIVES: To give an overview of the genetic and structural abnormalities occurring in fetuses with nuchal translucency (NT) measurement exceeding the 95th percentile at first-trimester screening and to investigate which of these abnormalities would be missed if cell-free fetal DNA (cfDNA) were used as a first-tier screening test for chromosomal abnormalities. METHODS: This is a national study including 1901 pregnancies with NT≥95th percentile referred to seven university hospitals in the Netherlands between 1 January 2010 and 1 January 2016. All cases with unknown pregnancy outcome were excluded. Results of detailed ultrasound examinations, karyotyping, genotyping, pregnancy and neonatal outcomes, investigation by a clinical geneticist and post-mortem investigations were collected. RESULTS: In total, 821 (43%) pregnancies had at least one abnormality. The rate of abnormalities was 21% for fetuses with NT between 95th and 99th percentile and 62% for fetuses with NT≥99th percentile. Prevalence of single-gene disorders, submicroscopic, chromosomal and structural abnormalities was 2%, 2%, 30% and 9%, respectively. CONCLUSION: Although cfDNA is superior to the combined test, especially for the detection of trisomy 21, 34% of the congenital abnormalities occurring in fetuses with increased NT may remain undetected in the first trimester of pregnancy, unless cfDNA is used in combination with fetal sonographic assessment, including NT measurement.

Sinus of Valsalva Aneurysm in a Patient With Mosaic Trisomy 13: Case Report and Brief Review of the Literature.

This report describes a unique case involving an obese 16-year-old boy with a mosaic form of trisomy 13 and no previous cardiac history who presented with a new murmur, hypertension, pleural effusions, and congestive heart failure in the context of sore throat and fever. Evaluation revealed a diagnosis of ruptured noncoronary sinus of Valsalva (SOV) aneurysm. The diagnosis and surgical management of a ruptured noncoronary SOV aneurysm in a pediatric patient are briefly outlined. An SOV aneurysm is an anatomic dilation of one of the sinuses of the aortic root. Aneurysmal dilation occurs more commonly in the right aortic sinus (70%-80%), compared to the noncoronary sinus (23%-25%), and more rarely the left coronary sinus (5%). Rupture of these aneurysms has been reported to be both spontaneous and secondary to physical exertion, hypertension, or trauma. Signs of rupture include a continuous murmur, patients may present with chest pain or with symptoms of acute congestive heart failure. Diagnosis, in this case, was made by transthoracic echocardiography with careful interpretation of color Doppler images.

Implementation of cell-free DNA-based non-invasive prenatal testing in a National Health Service Regional Genetics Laboratory.

BACKGROUND: Non-invasive prenatal testing (NIPT) for the detection of foetal aneuploidy through analysis of cell-free DNA (cfDNA) in maternal blood is offered routinely by many healthcare providers across the developed world. This testing has recently been recommended for evaluative implementation in the UK National Health Service (NHS) foetal anomaly screening pathway as a contingent screen following an increased risk of trisomy 21, 18 or 13. In preparation for delivering a national service, we have implemented cfDNA-based NIPT in our Regional Genetics Laboratory. Here, we describe our validation and verification processes and initial experiences of the technology prior to rollout of a national screening service. METHODS: Data are presented from more than 1000 patients (215 retrospective and 840 prospective) from 'high- and low-risk pregnancies' with outcome data following birth or confirmatory invasive prenatal sampling. NIPT was by the Illumina Verifi® test. RESULTS: Our data confirm a high-fidelity service with a failure rate of ~0.24% and a high sensitivity and specificity for the detection of foetal trisomy 13, 18 and 21. Secondly, the data show that a significant proportion of patients continue their pregnancies without prenatal invasive testing or intervention after receiving a high-risk cfDNA-based result. A total of 46.5% of patients referred to date were referred for reasons other than high screen risk. Ten percent (76/840 clinical service referrals) of patients were referred with ultrasonographic finding of a foetal structural anomaly, and data analysis indicates high- and low-risk scan indications for NIPT. CONCLUSIONS: NIPT can be successfully implemented into NHS regional genetics laboratories to provide high-quality services. NHS provision of NIPT in patients with high-risk screen results will allow for a reduction of invasive testing and partially improve equality of access to cfDNA-based NIPT in the pregnant population. Patients at low risk for a classic trisomy or with other clinical indications are likely to continue to access cfDNA-based NIPT as a private test.

TRIDENT-2: National Implementation of Genome-wide Non-invasive Prenatal Testing as a First-Tier Screening Test in the Netherlands.

The Netherlands launched a nationwide implementation study on non-invasive prenatal testing (NIPT) as a first-tier test offered to all pregnant women. This started on April 1, 2017 as the TRIDENT-2 study, licensed by the Dutch Ministry of Health. In the first year, NIPT was performed in 73,239 pregnancies (42% of all pregnancies), 7,239 (4%) chose first-trimester combined testing, and 54% did not participate. The number of trisomies 21 (239, 0.33%), 18 (49, 0.07%), and 13 (55, 0.08%) found in this study is comparable to earlier studies, but the Positive Predictive Values (PPV)-96% for trisomy 21, 98% for trisomy 18, and 53% for trisomy 13-were higher than expected. Findings other than trisomy 21, 18, or 13 were reported on request of the pregnant women; 78% of women chose to have these reported. The number of additional findings was 207 (0.36%); these included other trisomies (101, 0.18%, PPV 6%, many of the remaining 94% of cases are likely confined placental mosaics and possibly clinically significant), structural chromosomal aberrations (95, 0.16%, PPV 32%,) and complex abnormal profiles indicative of maternal malignancies (11, 0.02%, PPV 64%). The implementation of genome-wide NIPT is under debate because the benefits of detecting other fetal chromosomal aberrations must be balanced against the risks of discordant positives, parental anxiety, and a potential increase in (invasive) diagnostic procedures. Our first-year data, including clinical data and laboratory follow-up data, will fuel this debate. Furthermore, we describe how NIPT can successfully be embedded into a national screening program with a single chain for prenatal care including counseling, testing, and follow-up.

Routine first-trimester screening for fetal trisomies in twin pregnancy: cell-free DNA test contingent on results from combined test.

OBJECTIVE: To report on the routine clinical implementation of cell-free DNA (cfDNA) analysis of maternal blood for trisomies 21, 18 and 13, contingent on the results of the first-trimester combined test in twin pregnancy. METHODS: Screening for trisomies 21, 18 and 13 was carried out in 959 twin pregnancies by assessment of a combination of maternal age, fetal nuchal translucency thickness, and serum free ß-human chorionic gonadotropin and pregnancy-associated plasma protein-A at 11-13 weeks' gestation in two UK NHS hospitals. Women in the high-risk group (risk ≥ 1 in 100) were offered the option of invasive testing, cfDNA testing or no further testing, and those in the intermediate-risk group (risk 1 in 101 to 1 in 2500 in the first phase of the study and 1 in 101 to 1 in 500 in the second phase) were offered cfDNA or no further testing. The trisomic status of the pregnancies was determined by prenatal or postnatal karyotyping or examination of the neonates. RESULTS: In 42 (4.4%) of the 959 pregnancies, there was termination, miscarriage or stillbirth with no known karyotype or there was loss to follow-up. The 917 pregnancies with known trisomic status of both twins included six that were discordant for trisomy 21, four that were discordant for trisomy 18 and 907 with no trisomy 21, 18 or 13. Following combined screening, 47 (5.1%), 203 (22.1%) and 667 (72.7%) of the pregnancies were classified as high risk, intermediate risk and low risk, respectively. The high-risk group included five (83.3%) cases of trisomy 21 and three (75.0%) of trisomy 18. The cfDNA test was carried out in 224 pregnancies and results were provided in 214 (95.5%); this group included six pregnancies with trisomy 21, three with trisomy 18 and 206 with no trisomy 21, 18 or 13. The cfDNA test classified correctly as screen positive all six cases of trisomy 21 and two of the three with trisomy 18, and as screen negative for each of the trisomies all 206 unaffected pregnancies. Contingent screening led to prenatal detection of all cases of trisomy 21 and three of four with trisomy 18. CONCLUSION: This study has demonstrated the feasibility of introducing cfDNA testing, contingent on the results of the first-trimester combined test for major trisomies, in a routine population of twin pregnancies. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Role of Overexpressed Transcription Factor FOXO1 in Fatal Cardiovascular Septal Defects in Patau Syndrome: Molecular and Therapeutic Strategies.

Patau Syndrome (PS), characterized as a lethal disease, allows less than 15% survival over the first year of life. Most deaths owe to brain and heart disorders, more so due to septal defects because of altered gene regulations. We ascertained the cytogenetic basis of PS first, followed by molecular analysis and docking studies. Thirty-seven PS cases were referred from the Department of Pediatrics, King Abdulaziz University Hospital to the Center of Excellence in Genomic Medicine Research, Jeddah during 2008 to 2018. Cytogenetic analyses were performed by standard G-band method and trisomy13 were found in all the PS cases. Studies have suggested that genes of chromosome 13 and other chromosomes are associated with PS. We, therefore, did molecular pathway analysis, gene interaction, and ontology studies to identify their associations. Genomic analysis revealed important chr13 genes such as FOXO1, Col4A1, HMGBB1, FLT1, EFNB2, EDNRB, GAS6, TNFSF1, STARD13, TRPC4, TUBA3C, and TUBA3D, and their regulatory partners on other chromosomes associated with cardiovascular disorders, atrial and ventricular septal defects. There is strong indication of involving FOXO1 (Forkhead Box O1) gene-a strong transcription factor present on chr13, interacting with many septal defects link genes. The study was extended using molecular docking to find a potential drug lead for overexpressed FOXO1 inhibition. The phenothiazine and trifluoperazine showed efficiency to inhibit overexpressed FOXO1 protein, and could be potential drugs for PS/trisomy13 after validation.

Clinical courses of children with trisomy 13 receiving intensive neonatal and pediatric treatment.

Management of children with trisomy 13 (T13) is controversial because of a paucity of evidence of the natural history, especially focusing on efficacy of treatment. There has been no report regarding natural history of children with T13 receiving intensive neonatal and pediatric treatment without cardiac surgery, although several reports have suggested efficacy of cardiac surgery. To describe the detailed and comprehensive natural history of children with T13 receiving intensive neonatal and pediatric treatment without cardiac surgery, we reviewed clinical information of 24 children with full T13 (15 boys, 9 girls) who were admitted to Nagano Children's Hospital from 1994 to 2016. Intensive neonatal and pediatric treatment without cardiac surgery was provided through careful discussion with the parents. We detailed accurate frequencies of complications, survival, underlying factors and the final modes of death, and psychomotor development of survivors. Unpublished complications including aortopulmonary window, pulmonary-ductus-descending aorta-trunk, biliary system abnormalities, eosinophilic enteritis, and neuroblastoma were described. Accurate frequencies of congenital heart defects (92%) and laryngomalacia and/or tracheomalacia (42%) were determined. The median survival time was 451 days and the 1-year survival rate was 54%. The major underlying factor associated with death was congenital heart defects and heart failure (63%) and the major final mode of death was heart failure (50%). Long-term survivors appeared to show slow but constant psychomotor development. Intensive neonatal and pediatric treatment without cardiac surgery for children with T13 is efficient for survival and psychomotor development, and could be a reasonable choice for parents having fetuses or children with T13.

The Combining Effects of Cell-Free Circulating Tumor DNA of Breast Tumor to the Noninvasive Prenatal Testing Results: A Simulating Investigation.

Massively parallel sequencing of circulating fetal DNA in the plasma of pregnant women is a common method for noninvasive prenatal testing (NIPT) of fetal trisomy 13, 18, and 21. However, circulating DNA is not restricted to pregnant women, with increased levels of plasma DNA also frequently detected in the plasma of cancer patients. Among pregnant women whose NIPT results were inconsistent with the fetal karyotype, a small number of patients have subsequently been diagnosed with a previously undetected malignancy. However, the extent to which circulating tumor DNA (ctDNA) affects the results of NIPT is still unclear. We examined serum from 50 nonpregnant women with breast tumors by NIPT. These samples were then added to serum containing trisomy 13, 18, and 21 fetal DNA to figure out the extent to which maternal tumors can interrupt NIPT results in pregnant women with breast tumors. Concentrations of cell-free DNA (cfDNA) were higher in both pregnant women and breast tumor patients, relative to nonpregnant healthy controls. Among the 50 samples evaluated, 3 produced false positive NIPT results for trisomy 13, 18, or 21, indicating that genomic copy number variations (CNVs) had occurred. Simulation testing also showed that ctDNA can increase the standard deviation of the associated z-scores, which lower absolute z-scores by decreasing the proportion of circulating fetal DNA relative to total DNA. Of the 50 samples tested, 9 fell within the equivocal range and 8 produced false negative results for trisomy 13, 18, or 21. Data presented here show for the first time that ctDNA is able to affect NIPT results in two ways. First, ctDNA can lead to false positive results due to the detection of genomic CNVs in tumor DNA. Alternatively, ctDNA can increase the likelihood of a false negative by decreasing the proportion of circulating fetal DNA in serum.

Prenatal reflex DNA screening for trisomies 21, 18, and 13.

PURPOSE: The purpose of the study was to determine the screening performance of prenatal reflex DNA screening for trisomies 21 (T21), 18 (T18), and 13 (T13) as part of a routine service at five hospitals. METHODS: Women who accepted screening had a first-trimester combined test (pregnancy-associated plasma protein A, free ß-human chorionic gonadotropin, nuchal translucency interpreted with maternal age). Those with a risk of having an affected pregnancy ≥1 in 800 were reflexed to a DNA sequencing test using stored plasma from the original blood sample, thereby avoiding the need to recall them. RESULTS: Of 22,812 women screened (including 106 with affected pregnancies), 2,480 (10.9%) were reflexed to DNA testing; 101/106 were detected (69/73 T21, 24/25 T18, and 8/8 T13), a 95% detection rate (95% confidence interval 89-98%) with four false positives (0.02%, 95% confidence interval 0.00-0.05%). The odds of being affected given a positive result were 25:1. Of the 105 screen-positive pregnancies, 91 (87%) had an invasive diagnostic test. Reflex DNA screening avoided up to 530 invasive diagnostic tests compared with using the combined test. CONCLUSION: Reflex DNA screening was successfully implemented in routine care, achieving a high detection rate, low false-positive rate, and, consequently, greater safety with fewer invasive diagnostic tests than other methods of screening.

Positive predictive value estimates for cell-free noninvasive prenatal screening from data of a large referral genetic diagnostic laboratory.

BACKGROUND: Since its debut in 2011, cell-free fetal DNA screening has undergone rapid expansion with respect to both utilization and coverage. However, conclusive data regarding the clinical validity and utility of this screening tool, both for the originally included common autosomal and sex-chromosomal aneuploidies as well as the more recently added chromosomal microdeletion syndromes, have lagged behind. Thus, there is a continued need to educate clinicians and patients about the current benefits and limitations of this screening tool to inform pre- and posttest counseling, pre/perinatal decision making, and medical risk assessment/management. OBJECTIVE: The objective of this study was to determine the positive predictive value and false-positive rates for different chromosomal abnormalities identified by cell-free fetal DNA screening using a large data set of diagnostic testing results on invasive samples submitted to the laboratory for confirmatory studies. STUDY DESIGN: We tested 712 patient samples sent to our laboratory to confirm a cell-free fetal DNA screening result, indicating high risk for a chromosome abnormality. We compiled data from all cases in which the indication for confirmatory testing was a positive cell-free fetal DNA screen, including the common trisomies, sex chromosomal aneuploidies, microdeletion syndromes, and other large genome-wide copy number abnormalities. Testing modalities included fluorescence in situ hybridization, G-banded karyotype, and/or chromosomal microarray analysis performed on chorionic villus samples, amniotic fluid, or postnatally obtained blood samples. Positive predictive values and false-positive rates were calculated from tabulated data. RESULTS: The positive predictive values for trisomy 13, 18, and 21 were consistent with previous reports at 45%, 76%, and 84%, respectively. For the microdeletion syndrome regions, positive predictive values ranged from 0% for detection of Cri-du-Chat syndrome and Prader-Willi/Angelman syndrome to 14% for 1p36 deletion syndrome and 21% for 22q11.2 deletion syndrome. Detection of sex chromosomal aneuploidies had positive predictive values of 26% for monosomy X, 50% for 47,XXX, and 86% for 47,XXY. CONCLUSION: The positive predictive values for detection of common autosomal and sex chromosomal aneuploidies by cell-free fetal DNA screening were comparable with other studies. Identification of microdeletions was associated with lower positive predictive values and higher false-positive rates, likely because of the low prevalence of the individual targeted microdeletion syndromes in the general population. Although the obtained positive predictive values compare favorably with those seen in traditional screening approaches for common aneuploidies, they highlight the importance of educating clinicians and patients on the limitations of cell-free fetal DNA screening tests. Improvement of the cell-free fetal DNA screening technology and continued monitoring of its performance after introduction into clinical practice will be important to fully establish its clinical utility. Nonetheless, our data provide valuable information that may aid result interpretation, patient counseling, and clinical decision making/management.

Monozygotic Twins Discordant for Trisomy 13: A Case of Trisomic Rescue Supporting the Continued Need for First-Trimester Ultrasound.

Monozygotic twins with discordant karyotypes for trisomy 13 are rare. We report a case of a spontaneously conceived pregnancy who presented with first-trimester ultrasound finding of umbilical cord cyst and increased nuchal translucency in Twin A and no abnormalities in Twin B. Amniocentesis revealed 47,XY,+13 karyotype in Twin A and 46,XY karyotype in Twin B. Selective fetal reduction was performed for Twin A. Twin B was delivered at 32 weeks gestation with normal phenotype. Peripheral blood karyotype revealed 15% mosaicism for trisomy 13 and skin fibroblast revealed 46,XY karyotype. The surviving twin will be monitored for potential complication of uniparental disomy 13 and mosaic trisomy 13. This case reinforces the need for early ultrasound and nuchal translucency measurements, especially in twin gestations.