Test performance and clinical utility of expanded non-invasive prenatal test: Experience on 71,883 unselected routine cases from one single center.

OBJECTIVE: The balance between benefits and risks of discordant outcomes makes the Genome-Wide Non-Invasive Prenatal Test (GW-NIPT) controversial. This study aims to evaluate performance and clinical utility in a wide cohort of unselected clinical cases from a single center when a standardized protocol is applied and integrated with a secondary algorithm for data interpretation. METHOD: In 2 years, over 70,000 pregnant patients underwent GW-NIPT for fetal common trisomies, sex chromosome aneuploidies, rare autosomal aneuploidies, segmental abnormalities (CNVs ≥ 7 Mb) and microdeletions (CNVs < 7 Mb). All samples were uniformly processed with Veriseq NIPT Solution v2 and analyzed using all data metrics along with a home-made algorithm for sequencing data analysis. Results were retrospectively reviewed for clinical outcomes. RESULTS: Among 71,883 eligible cases including twin pregnancies, 1011 (1.4%) received a positive result and 781 were confirmed by invasive prenatal diagnosis. Clinical sensitivity ranged from 99.65% for common trisomy (T21, T18, T13) to 83.33% for microdeletions, while specificity remained high (99.98%) for each class of fetal abnormalities detected. CONCLUSIONS: Integrating a standardized protocol with an internal algorithm allowed discordant results to be reduced, yielding high accuracy. Observed reliability in detecting genome-wide chromosomal conditions reinforced the expanded NIPT utility in clinical practice.

Comprehensive Recommendations for the Clinical Management of Pregnant Women With Noninvasive Prenatal Test Results Suspicious of a Maternal Malignancy.

In this article, we defined comprehensive recommendations for the clinical follow-up of pregnant women with a malignancy-suspicious NIPT result, on the basis of the vast experience with population-based NIPT screening programs in two European countries complemented with published large data sets. These recommendations provide a tool for classifying NIPT results as malignancy-suspicious, and guide health care professionals in structured clinical decision making for the diagnostic process of pregnant women who receive such a malignancy-suspicious NIPT result.

Performance of cell-free DNA testing for common fetal trisomies in triplet pregnancies.

OBJECTIVE: In singleton pregnancies, the use of cell-free DNA (cfDNA) analysis as a screening test for common fetal trisomies has spread worldwide though we still lack sufficient data for its use in triplet pregnancies. The objective of this study is to assess the performance of cfDNA testing in detecting fetal aneuploidies in triplet pregnancies as a first-tier test. METHOD: We performed a retrospective cohort study including data from pregnant women with a triplet pregnancy who underwent cfDNA testing between May 1, 2017, and January 15, 2020. cfDNA was obtained by massive parallel sequencing (VeriSeq NIPT solution; Illumina®). The objectives of the study were to assess the diagnostic performance of cfDNA testing for trisomy 21 (T21) (primary outcome), trisomy 18 (T18) and 13 (secondary outcomes). RESULTS: During the study period, cfDNA testing was performed in 255 women with triplet pregnancy, of which 165 (64.7%) had a neonatal outcome available. Three tests were positive for T21, one of which was confirmed by an antenatal karyotype, and the other was confirmed at birth. The third case did not undergo an invasive procedure and was not confirmed at birth (false positive). In one case, cfDNA testing was positive for T18 and was confirmed by an antenatal karyotype. There were no cases of trisomy 13 in the cohort. The no-call rate was 2.4% at first sampling. Fifty-eight (22.7%) women had embryo reduction, which in 40 (69%) of whom was performed after the cfDNA test result. CONCLUSION: cfDNA testing could be offered as primary screening for main fetal aneuploidies in triplet pregnancies after provision of appropriate patient information.

Performance of noninvasive prenatal screening for fetal sex chromosome aneuploidies in a cohort of 116,862 pregnancies.

BACKGROUND: Noninvasive prenatal screening (NIPS) has shown good performance in screening common aneuploidies. However, its performance in detecting fetal sex chromosome aneuploidies (SCAs) needs to be evaluated in a large cohort. RESEARCH DESIGN AND METHODS: In this retrospective observation, a total of 116,862 women underwent NIPS based on DNA nanoball sequencing from 2015 to 2022. SCAs were diagnosed based on karyotyping or chromosomal microarray analysis (CMA). Among them, 2,084 singleton pregnancies received karyotyping and/or CMA. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of NIPS for fetal SCAs were evaluated. RESULTS: The sensitivity was 97.7% (95%CI, 87.7-99.9), 87.3% (95% CI, 76.5-94.4), 96.1% (95%CI, 86.5-99.5), and 95.7% (95% CI, 78.1-99.9), the PPV was 25.8% (95%CI, 19.2-33.2), 80.9% (95%CI, 69.5-89.4), 79.0% (95%CI, 66.8-88.3), and 53.7% (95%CI, 37.4-69.3) for 45,X, 47,XXY, 47,XXX, and 47,XYY, respectively. The specificity was 94.1% (95%CI, 93.0-95.1) for 45,X, and more than 99.0% for sex chromosome trisomy (SCT). The NPV was over 99.0% for all. CONCLUSIONS: NIPS screening for fetal SCAs has high sensitivity, specificity and NPV. The PPV of SCAs was moderate, but that of 45,X was lower than that of SCTs. Invasive prenatal diagnosis should be recommended for high-risk patients.

What's out there for parents? A systematic review of online information about prenatal microarray and exome sequencing.

OBJECTIVE: To identify what online patient information (presented in English) is available to parents about prenatal microarray (CMA) and exome sequencing (ES), and evaluate its content, quality, and readability. METHOD: Systematic searches (Google and Bing) were conducted, and websites were categorised according to their purpose. Websites categorised as patient information were included if they were: in English, directed at patients, or were a text, video, or online version of an information leaflet. Author-developed content checklists, the DISCERN Genetics tool, and readability tests (the Flesch Reading Ease Score, the Gunning Fog Index, and the Simple Measure of Gobbledygook Index) were then used to assess those sources of patient information. RESULTS: Of the 665 websites screened, 18 met the criteria. A further 8 sources were found through a targeted search of professional organisations, resulting in 26 sources available for further evaluation. In general, this was found to be low in quality, omitted details recommended by national or international guidance, and was written at a level too advanced for average readers. CONCLUSION: Improvements should be made to the content, quality, and readability of online information so that it both reinforces and complements the discussions between parents and clinicians about testing options during pregnancy.

A systematic review of maternal TORCH serology as a screen for suspected fetal infection.

BACKGROUND: The acronym 'TORCH' refers to well-recognised causes of perinatal infections: toxoplasmosis, rubella, cytomegalovirus (CMV) and herpes simplex virus (HSV). A TORCH serology panel is often used to test for maternal primary infection following detection of ultrasound abnormalities in pregnancy. AIM: This review aims to estimate the diagnostic yield of maternal TORCH serology in pregnancy following fetal ultrasound abnormalities. MATERIALS AND METHODS: Primary studies published since 2000 that assessed maternal TORCH serology for suspected fetal infection and included information on indications for testing, definition of positive TORCH serology results, and perinatal outcomes were included. RESULTS: Eight studies with a total of 2538 pregnancies were included. The main indications for testing were polyhydramnios, fetal growth restriction and hyperechogenic bowel. There were 26 confirmed cases of congenital CMV, of which 15 had multiple ultrasound abnormalities. There were no cases of congenital toxoplasmosis, rubella or HSV confirmed in any of the eight studies. CONCLUSIONS: The clinical utility of TORCH serology for non-specific ultrasound abnormalities such as isolated fetal growth restriction or isolated polyhydramnios is low. It is time to retire the TORCH acronym and the reflex ordering of 'TORCH' panels, as their continued use obscures, rather than illuminates, appropriate investigation for fetal ultrasound abnormalities.

Predicting neonatal outcomes in infants with giant omphalocele using prenatal magnetic resonance imaging calculated observed-to-expected fetal lung volumes.

OBJECTIVE: To examine the association between prenatal magnetic resonance imaging (MRI) based observed/expected total lung volume (O/E TLV) and outcome in neonates with giant omphalocele (GO). METHODS: Between 06/2004 and 12/2019, 67 cases with isolated GO underwent prenatal and postnatal care at our institution. MRI-based O/E TLVs were calculated based on normative data from Meyers and from Rypens and correlated with postnatal survival and morbidities. O/E TLV scores were grouped based on severity into <25% (severe), between 25% and 50% (moderate), and >50% (mild) for risk stratification. RESULTS: O/E TLV was calculated for all patients according to Meyers nomograms and for 49 patients according to Rypens nomograms. Survival for GO neonates with severe, moderate, and mild pulmonary hypoplasia based on Meyers O/E TLV categories was 60%, 92%, and 96%, respectively (p = 0.04). There was a significant inverse association between Meyers O/E TLV and risk of neonatal morbidities (p < 0.05). A similar trend was observed with Rypens O/E TLV, but associations were less often significant likely related to the smaller sample size. CONCLUSION: Neonatal outcomes are related to fetal lung size in isolated GO. Assessment of Meyers O/E TLV allows identification of GO fetuses at greatest risk for complications secondary to pulmonary hypoplasia.

Increased nuchal translucency after low-risk noninvasive prenatal testing: What should we tell prospective parents?

Three decades ago, the observation that first trimester fetuses with excess fluid accumulation at the back of the neck were more likely to be aneuploid, gave rise to a new era of prenatal screening. The nuchal translucency (NT) measurement in combination with serum biomarkers and maternal age, resulted in the first trimester combined screening (FTCS) program. The introduction of noninvasive prenatal testing (NIPT) over the past decade has introduced the option for parents to receive highly sensitive and specific screening information for common trisomy from as early as 10 weeks gestation, altering the traditional pathway FTCS pathway. The retention of the 11-13-week NT ultrasound remains important in the detection of structural anomalies; however, the optimal management of pregnancies with a low-risk NIPT result and an isolated increased NT measurement in an era of advanced genomic testing options is a new dilemma for clinicians. For parents, the prolonged period between the initial diagnosis in first trimester, and prognostic information at each successive stage of investigations up to 22-24 weeks, can be emotionally challenging. This article addresses the common questions from parents and clinicians as they navigate the uncertainty of having a fetus diagnosed with an increased NT after a low-risk NIPT result and presents suggested approaches to management.

Knowledge and attitudes regarding non-invasive prenatal testing among women in Saudi Arabia.

OBJECTIVES: To explore women's knowledge and attitudes regarding NIPT, its implications, the factors affecting their decision to undergo the test and actions taken following a positive result. METHODS: In this descriptive study, women who were offered NIPT through the foetal maternal clinic, were asked to complete an anonymous questionnaire about NIPT. The questionnaire consisted of 29 statements and covered four areas: demographics, knowledge, attitudes and decision-making. RESULTS: A total of 150 women who were offered NIPT participated in this study. The results showed that generally women had poor knowledge of critical aspects of NIPT. This included the conditions tested for, the implications of the test and its limitations. Over 90% of women were in favour of NIPT and it being offered to all women of advanced maternal age while 66% of the tested women agreed to having confirmatory invasive testing in the case of a positive result. CONCLUSION: This study shows that the acceptance rate for NIPT is high despite incomplete understanding of the benefits and limitations of the test. The study findings support the need for education regarding this test through dedicated genetic counselling sessions in order to ensure that an informed decision can be made.

Does non-invasive prenatal testing affect the livebirth prevalence of Down syndrome in the Netherlands? A population-based register study.

OBJECTIVE: To evaluate if non-invasive prenatal testing (NIPT) affects livebirth (LB) prevalence of Down syndrome (DS) in the Netherlands. METHOD: Data from clinical genetics laboratories and the Working Party on Prenatal Diagnosis and Therapy (2014-2018) and previous published data (1991-2013) were used to assess trends for DS LB prevalence and reduction percentage (the net decrease in DS LBs resulting from selective termination of pregnancies). Statistics Netherlands provided general population data. RESULTS: DS LB prevalence increased from 11.6/10,000 in 1991 to 15.9/10,000 in 2002 (regression coefficient 0.246 [95% CI: 0.105-0.388; p = 0.003]). After 2002, LB prevalence decreased to 11.3/10,000 in 2014 and further to 9.9/10,000 in 2018 (regression coefficient 0.234 (95% CI: -0.338 to -0.131; p < 0.001). The reduction percentage increased from 26% in 1991 to 55.2% in 2018 (regression coefficient 0.012 (95% CI: 0.010-0.013; p < 0.001)). There were no trend changes after introducing NIPT as second-tier (2014) and first-tier test (2017). CONCLUSIONS: Introducing NIPT did not change the decreasing trend in DS LB prevalence and increasing trend in reduction percentage. These trends may be caused by a broader development of more prenatal testing that had already started before introducing NIPT.

The potential of expanded noninvasive prenatal screening for detection of microdeletion and microduplication syndromes.

OBJECTIVES: To evaluate the clinical potential of a higher resolution noninvasive prenatal screening (NIPS-Plus) test for detection of microdeletion/microduplication syndromes (MMS) in addition to common aneuploidies. METHODS: In a multicenter prospective study, 37,002 pregnant women with unremarkable first-trimester ultrasound scans had a NIPS-Plus test. Ultrasound screen positive women were not included in this study. RESULTS: Of 36,970 ultrasound negative women there were 291 NIPS-Plus screen positive results indicating 237 aneuploidies and 54 MMS. Following amniocentesis, 171 (72%) were confirmed as genuine, comprising 3 T13s, 10 T18s, 61 T21s, 70 SCAs and 27 MMS. The PPV for MMS with unremarkable ultrasound findings was 50%. Routine clinical examination of children born from NIPS-Plus negative pregnancies revealed no obvious signs of chromosome disease syndromes at one year of age. CONCLUSIONS: NIPS-Plus has the potential for clinical utility not only for routine aneuploid screening but also for MMS that do not show overt signs during early pregnancy ultrasound screening. We suggest that ultrasound with NIPS-Plus in combination with appropriate counselling could be considered as a comprehensive first-tier prenatal screening approach for all pregnant women.

Prenatal prediction of fetal Rh C, c and E status by amplification of maternal cfDNA and deep sequencing.

BACKGROUND: The Rh blood group system has considerable clinical importance. The C, c, and E antigens are targets of alloantibodies. Anti-C, anti-c or anti-E alloreactive antibodies produced in pregnant women can cause anemia of a fetus carrying the corresponding antigens. AIMS: Based on NGS technology, we have developed a noninvasive diagnostic assay to predict the fetal blood group of C, c or E antigens by sequencing cell-free DNA (cfDNA) during pregnancy. MATERIALS AND METHODS: The SNVs underlying either the C, c or E antigens were PCR amplified and sequenced using NGS on a MiSeq instrument. The DNA sequences encoding the C, c or E antigen were counted, as were the number of total sequences. Based on the percentage of fetally derived target SNVs inherited from the father, the fetal blood group could be predicted. RESULTS: The results of 55 consecutive RHCE prenatal analyses with postnatal serological blood group determination of 30 newborns showed no discordant results. A threshold discerning positive from negative samples was set at 0.05% specific reads. DISCUSSION: Noninvasive, prenatal prediction of fetal blood groups by sequencing cfDNA for the detection of low-level RHCE*C, RHCE*c and RHCE*E sequences was established as an accurate and robust assay applicable for use in clinical settings.

Clinical value for the detection of fetal chromosomal deletions/duplications by noninvasive prenatal testing in clinical practice.

OBJECTIVE: This study was to report the experiences on the clinical value of noninvasive prenatal testing (NIPT) for the screening of fetal chromosomal deletions/duplications. METHODS: We performed a retrospective analysis of a cohort of 20,439 pregnancies undergoing NIPT from March 2017 to September 2020 at a single center. Patients with positive NIPT results for fetal chromosomal deletions or duplications had options of invasive diagnostic testing or no further testing. The data were complied from all cases with positive NIPT results for chromosomal deletions/duplications. The positive predictive value (PPV) was calculated from tabulated data. RESULTS: In this cohort, positive NIPT results for fetal chromosomal deletions/duplications were found in 60 pregnant women. Of the positive samples, further invasive testing was performed in 39 cases, in which 9 cases were found to be true positive. The overall PPV for chromosomal deletions/duplications was 23.1%. In addition, fetal structural anomaly was found by ultrasound examination in three cases, in which the chromosomal deletions/duplications of three cases were not verified. Moreover, an unexpected pathogenic 8p23.3 deletion was identified by invasive testing in 1 fetus with a false positive NIPT screen for 3q27.3q29 duplication. CONCLUSIONS: In summary, positive NIPT results of chromosomal deletions/duplications were not uncommon in clinical practice, whereas the PPV for the testing was low. Hence, potential risks and high percentage of false positives for these abnormal NIPT results might be informed to pregnant women before the choice made of invasive testing.

The diagnostic efficacy of exome data analysis using fixed neurodevelopmental gene lists: Implications for prenatal setting.

OBJECTIVE: Laboratories performing prenatal exome sequencing (ES) frequently limit analysis to predetermined gene lists. We used a diagnostic postnatal ES cohort to assess how many of the genes diagnosed are not included in a number of select fixed lists used for prenatal diagnosis. METHODS: Of 601 postnatal ES tests, pathogenic variants related to neurodevelopmental disorders were detected in 138 probands. We evaluated if causative genes were present in the following: (1) Developmental Disorders Genotype-Phenotype database list, (2) a commercial laboratory list for prenatal ES, (3) the PanelApp fetal anomalies panel, and (4) a published list used for prenatal diagnosis by ES (Prenatal Assessment of Genomes and Exomes study). RESULTS: The percentages of cases where the diagnosed gene was not included in the selected four lists were; 11.6%, 17.24%, 23.2%, and 10.9%, respectively. In 13/138 (9.4%) cases, the causative gene was not included in any of the lists; in 4/13 (∼30%) cases noninclusion was explained by a relatively recent discovery of gene-phenotype association. CONCLUSIONS: A significant number of genes related to neurocognitive phenotypes are not included in some of the lists used for prenatal ES data interpretation. These are not only genes related to recently discovered disorders, but also genes with well-established gene-phenotype.

Total number of reads affects the accuracy of fetal fraction estimates in NIPT.

BACKGROUND: Sufficient fetal fraction (FF) is crucial for quality control of NIPT (Non-Invasive Prenatal Test) results. Different factors influencing bioinformatic estimation of FF should be considered when implementing NIPT. To what extent the total number of sequencing reads influences FF estimate has been unexplored. In this study, to test the robustness of SeqFF FF estimation and provide additional recommendations for NIPT analysis quality control, we compared the SeqFF FF estimates with two other methods and investigated how the number of sequencing reads and FF level affects the accuracy and precision of FF estimates. METHODS: WGS data of 516 NIPT samples from a prenatal screening program was obtained. Sample data were randomly downsampled by the read count, and FF was calculated by SeqFF software. Then, the outcome was compared with FF estimates from SNP- and chrY-based methods. FF estimated with different read counts and FF levels were compared with FF at 30 M reads as a reference. RESULTS: SeqFF FF highly correlates with SNP- and chrY-based FF estimates. Raising read count from 2 M to 10 M drastically increased the accuracy of FF estimates. After adding more reads, we saw a further improvement in FF accuracy, reaching a plateau at 20 M reads. Precision of SeqFF FF estimate is independent of FF level in the sample. CONCLUSION: SeqFF is a robust method for FF estimation for both genders and for any FF level in range 2-13%. Accuracy of FF estimates highly depends on the read count. We recommend using no less than 10 M reads to achieve accurate FF estimates for NIPT analysis in clinical settings.

Non-invasive prenatal testing for the prenatal screening of sex chromosome aneuploidies: A systematic review and meta-analysis of diagnostic test accuracy studies.

BACKGROUND: There is little evidence on the performance of non-invasive prenatal testing (NIPT) for the detection of fetal sex chromosomal imbalances. In this review, we aimed to appraise and synthesize the literature on the performance of NIPT for the prenatal detection of fetal sex chromosome aneuploidies. METHODS: We performed our literature search in PubMed, Embase, Cochrane Library, Web of Science, and CADTH. Study selection and data extraction were performed by two reviewers independently. There were no restrictions on the study population. Meta-analyses were performed with "R" software. Pooled sensitivities and specificities with their 95% CI were estimated using a random-effects model. Heterogeneity between studies was assessed by a Q test. RESULTS: Based on 11 studies in high prior risk pregnancies, including 116 affected fetuses in aggregate, Massively Parallel Shotgun Sequencing (MPSS) had a sensitivity of 93.9% (95% CI 84.1%, 97.8%) and a specificity of 99.6% (95% CI 98.7%, 99.9%) for the detection of 45,X. Based on four studies in high-risk pregnancies, with 83 affected fetuses in aggregate, Targeted Massively Parallel Sequencing (TMPS) had a sensitivity of 83.2% (95% CI 49.6%, 96.2%) and specificity was 99.8% (95% CI 98.3%, 100%) for the detection of 45,X. In mixed-risk pregnancies, the sensitivity of TMPS for the detection of 45,X was 90.9% (2 studies; 95% CI 70%, 97.7%) and specificity 99.9% (2 studies; 95% CI 99.4%, 100%); MPSS data were not available in such pregnancies. Based on smaller numbers of studies, and small numbers of affected fetuses in either high-risk or mixed-risk pregnancies (using either MPSS or TMPS), the sensitivities and specificities were equal to or greater than 76.2% for 47,XXX, 47,XXY and 47, XYY. The test failures for SCAs were 0.2% (95% CI 0%, 13.6%) for MPSS and 5.6% (95% CI 3.7%, 8.4%) for TMPS. CONCLUSION: High-quality studies are still desirable in order to estimate the performance of NIPT for the detection of sex chromosome imbalances.

Not all low fetal fraction cell-free DNA screening failures are at increased risk for aneuploidy.

OBJECTIVE: To evaluate cell-free DNA (cfDNA) redraws and pregnancy outcomes following low fetal fraction (FF) cfDNA failures, as it has been suggested that a failed cfDNA screen due to insufficient FF carries increased risk for fetal aneuploidy. METHODS: Here >200,000 consecutive samples were reviewed and >1,100 patients were identified with a failed cfDNA due to low FF using genome-wide massively parallel sequencing. Redraw results following the initial low FF failure were analyzed, as well as pregnancy outcomes for patients with repeated low FF failure on redraw. RESULTS: Upon redraw 84.2% of samples yielded a reportable result with no enrichment of aneuploidy observed (p = 0.332). Higher maternal weights and multifetal pregnancy rates were observed in samples with insufficient FF. In patients with repeated low FF failure on redraw, almost all pregnancies resulted in apparently healthy liveborns. CONCLUSION: Insufficient FF was not an indicator of aneuploidy risk or adverse pregnancy outcomes in this study. Caution should be taken in generalizing aneuploidy risk to all low FF cfDNA failures. Redrawing may be an appropriate next step, as proceeding directly with diagnostic testing for aneuploidy may be unwarranted for most patients.

Patient attitudes toward prenatal diagnostic testing during antenatal care in an urban population.

OBJECTIVE: Investigate factors that influence the decision to accept or decline diagnostic testing for pregnant women referred for genetic counseling. METHODS: Cross sectional anonymous survey of pregnant women undergoing genetic counseling at a tertiary care referral center. Subjects' perceived risk of procedure related loss and fetal chromosomal problem were obtained via survey where patients rated risk from 0 (no risk) to 10 (highest risk). RESULTS: There were no differences in sociodemographic factors between women undergoing a diagnostic procedure compared to those not undergoing a procedure. As the perceived risk for having a baby with genetic problem increased by one point, the estimated odds of having the diagnostic procedure increased by 43% controlling for the perceived risk of procedure related loss (p < .0001). Similarly, as the perceived risk of miscarriage increased by one point, the odds of having the diagnostic procedure decreased by 40%, controlling for the perceived risk of having a baby with a genetic problem (p < .0001). The main reason women cited for not undergoing a procedure was fear of procedure related loss. CONCLUSIONS: Pregnant women that decline diagnostic testing have a higher perceived risk of procedure related loss and lower perceived risk of fetal chromosomal abnormality than those who accept.

Evaluation of the Z-score accuracy of noninvasive prenatal testing for fetal trisomies 13, 18 and 21 at a single center.

OBJECTIVE: To assess the correlation between Z-scores of positive noninvasive prenatal testing (NIPT) results and the positive predictive value (PPV) of NIPT. METHODS: Pregnancies with positive NIPT results at Guangzhou Women and Children's Medical Centre between July 2017 and May 2020 were included in this study. Fetal karyotyping or microarray analysis was provided to patients with abnormal NIPT results for confirmatory testing. Logistic regression analyses was applied to study the relationship between the Z scores and the PPV performance. The optimal cutoff values for indicating fetal common trisomies were obtained based on receiver operating characteristic (ROC) curve analysis, and then the PPV were calculated in pregnancies with positive NIPT results at Z-score greater than or equal to cutoff value and in patients with a Z-score between 3 and cutoff value respectively. RESULTS: A total of 214 pregnancies with positive NIPT results for fetal common trisomies were validated by invasive prenatal diagnosis and follow up in this study. Of these, NIPT indicated trisomy 13 in 25 cases, trisomy 18 in 54 cases and trisomy 21 in 135 patients. Logistic regression analyses showed a significant association (p < 0.05) between the Z-scores and true positive results for T21 and T18. For T13, the significant association was not observed (p > 0.05). The ROC curve analysis showed that the optimal cutoff Z-score for indicating fetal trisomies 13, 18, and 21 were 6.889, 7.574 and 6.612 respectively, and the corresponding area under curve were 0.706, 0.916, and 0.954. In this cohort with abnormal NIPT results, the cutoff values revealed a sensitivity of 96.8% and a specificity of 90% for indicating trisomies 21, and a sensitivity of 88.9% and a specificity of 92.6% for trisomies 18. However, probably due to the sample size, the sensitivity and specificity for indicating trisomy 13 were lower (85.7% and 61.1%) than that for trisomies 21 and 18. The PPVs in pregnancies with positive NIPT results at Z-score greater than or equal to cutoff value were 99.18% (121/122) for trisomy 21, 92.31% (24/26) for trisomy 18 and 46.15% (6/13) for trisomy 13. In patients with a Z-score between 3 and cutoff Z-score, the PPV of NIPT for trisomies 21, 18, and 13 were 30.77% (4/13), 10.71% (3/28), and 8.33% (1/12) respectively. Moreover, by classifying Z scores as 3 ≤ Z < 5, 5 ≤ Z < 10, and Z ≥ 10, the majority of Z scores were above 10 with a PPV of 99% for T21 and just 5.2% were between 3 and 5 with a PPV of 14.3%. In contrast for T18, over a third of tests had Z scores between 3 and 5. The PPV in this group is just over 5%. CONCLUSIONS: The present results show that the PPV performance of NIPT for fetal trisomies 13, 18, and 21 are closely associated with Z-score. The higher the Z-score, the greater the likelihood that the aneuploidy result is correct. Our experience in evaluating the Z-score accuracy of NIPT in this study could be of use in similar work.

Exploring the predicted yield of prenatal testing by evaluating a postnatal population with structural abnormalities using a novel mathematical model.

OBJECTIVE: To determine the yield of prenatal testing and screening options after identification of fetal structural abnormalities using a novel mathematical model. METHOD: A retrospective chart review was conducted to collect structural abnormality and genetic testing data on infants who were evaluated postnatally by a medical geneticist. A novel mathematical model was used to determine and compare the predicted diagnostic yields of prenatal testing and screening options. RESULTS: Over a quarter of patients with at least one structural abnormality (28.1%, n = 222) had a genetic aberration identified that explained their phenotype. Chromosomal microarray (CMA) had the highest predicted diagnostic yield (26.8%, P < .001). Karyotype (20.8%) had similar yields as genome wide NIPT (21.2%, P = .859) and NIPT with select copy number variants (CNVs) (17.9%, P = .184). Among individuals with an isolated structural abnormality, whole exome sequencing (25.9%) and CMA (14.9%) had the highest predicted yields. CONCLUSION: This study introduces a novel mathematical model for predicting the potential yield of prenatal testing and screening options. This study provides further evidence that CMA has the highest predicted diagnostic yield in cases with structural abnormalities. Screening with expanded NIPT options shows potential for patients who decline invasive testing, but only in the setting of adequate pre-test counseling.