Evaluation of the clinical utility of extended non-invasive prenatal testing in the detection of chromosomal aneuploidy and microdeletion/microduplication.

BACKGROUND: With the development of whole-genome sequencing technology, non-invasive prenatal testing (NIPT) has been applied gradually to screen chromosomal microdeletions and microduplications that cannot be detected by traditional karyotyping. However, in NIPT, some false positives and false negatives occur. This study aimed to investigate the applicability of extended NIPT (NIPT-PLUS) in the detection of chromosomal aneuploidy and microdeletion/microduplication syndrome (MMS). METHODS: A total of 452 pregnancies that underwent prenatal diagnostic testing (amniocentesis or chorionic villus sampling) by chromosomal microarray analysis (CMA), were screened by NIPT-PLUS from the peripheral blood sample of the pregnant women. The results of the two tested items were compared and analysed. RESULTS: Of the 452 cases, 335 (74.12%) had positive CMA results, and 117 (25.88%) had no abnormal results. A total of 86 cases of trisomy 21, 18 and 13 and sex chromosome aneuploidy (SCA) were detected by CMA and NIPT-PLUS, with a detection rate of 96.51% (83/86). Among them, the detection rates of T18, T13; 47, XXY; 47, XXX and 47 XYY were 100%, and the detection rates of T21 and 45 XO were 96.55% and 90%, respectively. The detection sensitivity of rare chromosomal trisomy (RAT) was 80% (4/5). The positive predictive values of NIPT-PLUS for chromosome aneuploidy T21, T18 and T13 and for SCA and RAT were 90.32%, 87.50%, 25.00%, 88.89% and 50%, respectively. A total of 249 cases (74.32%) of chromosomal MMS were detected by CMA. The detection rate of NIPT-PLUS was 63.86% (159/249), and 90 cases (36.14%) were missed. The larger the MMS fragment, the higher the NIPT-PLUS detection sensitivity. In addition, most small fragments were of maternal origin. CONCLUSION: The comparison between the CMA and NIPT-PLUS techniques shows that NIPT-PLUS has high sensitivity for detecting chromosomal aneuploidy and chromosomal copy number variations (CNVs) with fragments > 5 M. However, the sensitivity of CNV for fragments < 5 M is low, and the missed detection rate is high. Additionally, confined placental mosaicism and foetal mosaicism are the key factors causing false negatives in NIPT-PLUS, while maternal chromosomal abnormalities and confined placental mosaicism are key contributors to false positives, so appropriate genetic counselling is especially important for pregnant women before and after NIPT-PLUS testing.

Performance of noninvasive prenatal testing for twin pregnancies in South China.

OBJECTIVE: The purpose of this study was to evaluate the performance of noninvasive prenatal testing (NIPT) for the detection of chromosomal aneuploidies and copy number variations (CNVs) in twin pregnancies. METHOD: A cohort of 2010 women with twin pregnancies was recruited. 1331 patients opted for NIPT, and 679 patients opted for expanded NIPT (NIPT-plus). All high-risk patients were advised to undergo invasive prenatal diagnosis. All participants were followed up until 6 months after birth. RESULTS: Twenty-two cases were predicted to have a high risk of chromosome abnormalities by NIPT, of which 14 pregnant women underwent invasive prenatal diagnosis. The 14 cases included 3 cases of trisomy 21, 1 case of trisomy 18, 1 case of trisomy 7, 2 cases of sex chromosome aneuploidies (SCAs), and 7 cases of CNVs, of which the confirmed cases numbered 2, 1, 0, 1, and 0, respectively. Twenty cases were predicted to have a high risk of chromosome abnormalities by NIPT-plus, of which 16 pregnant women underwent invasive prenatal diagnosis. The 16 cases included 1 case of trisomy 21, 1 case of trisomy 7, 7 cases of SCAs, and 7 cases of CNVs, of which were confirmed in 1, 0, 3, and 2, respectively. No false-negative result was reported during the follow-up period. CONCLUSION: The NIPT/NIPT-plus has excellent performance in the detection of chromosome aneuploidies in twin pregnancies. But for CNVs, the effectiveness of NIPT is poor, and the NIPT-plus have a certain detection efficiency. It is worth noting that pre- and post-genetic counseling is especially important, and the chorionicity, mode of conception, clinical indications, and fetal fraction should be considered as influencing factors.

Clinical application of expanded noninvasive prenatal testing for fetal chromosome abnormalities in a cohort of 39,580 pregnancies.

The aim of this study was to determine the predictive value of expanded noninvasive prenatal testing (NIPT-plus) for fetal chromosome abnormalities in the second trimester (12-26 weeks). We conducted a retrospective cohort study of 39,580 pregnancies with NIPT-plus. Screening positive cases were diagnosed with karyotyping and single-nucleotide polymorphism array analysis (SNP array)/copy number variation sequencing (CNV-seq) with follow-up. The positive predictive values (PPVs) of trisomy 21, 18, and 13 (T21, T18, and T13), sex chromosome aneuploidies (SCAs), and microdeletion and microduplication syndromes (MMS) by NIPT-plus were recorded. We assessed the predictive value of NIPT-plus based on maternal age and conventional indications. Of 39,580 pregnancies with NIPT-plus, 511 (1.3%) had prenatal screening positive results of fetal chromosome abnormality, of which 87.7% (448/511) had invasive prenatal diagnosis. NIPT-plus performed better in predicting fetal SCAs and chromosome aneuploidies for pregnancies with advanced maternal age (AMA) than young maternal age (YMA). Besides, the PPVs of T21, T13, and chromosome aneuploidies showed an upward trend when comparison was based on maternal age in 5-year subintervals. The termination rates of 45,X, 47,XXX, 47,XXY, and 47,XYY were 100% (11/11), 20.0% (3/15), 91.7% (22/24), and 7.1% (1/14) with postnatal follow-up. Last but not least, the PPV for MMS is 41.7% (30/72), which may have a positive correlation between the size of CNVs. Pregnant women with screen-positive results for common trisomies (T13, T18, and T21) were more willing to conduct invasive prenatal diagnosis compared to those with positive results for SCAs or MMS. However, the current study demonstrated SCAs and MMS had the lowest PPV. This highlights the importance of confirmatory prenatal diagnosis in those patients and the potential impact on genetic counseling and informative decision-making.

Performance of expanded non-invasive prenatal testing for fetal aneuploidies and copy number variations: A prospective study from a single center in Jiangxi province, China.

To evaluate the performance of expanded non-invasive prenatal testing (expanded noninvasive prenatal testing, NIPT-Plus) in screening for fetal chromosomal abnormalities includes aneuploidies and copy number variations, a total of 23,116 pregnant women with a singleton pregnancy were recruited for NIPT-Plus. Screening positive results were verified by karyotype analysis and chromosomal microarray analysis after amniocentesis. A total of 264 pregnancies (1.14%) were positive results as predicted by NIPT-Plus, including 233 aneuploidies and 31 copy number variations. Following genetic counseling, 233 (88.26%) pregnant women underwent invasive prenatal diagnosis and 136 were verified as true positives, comprising 72 common trisomies (T21, T18, T13), 47 sex chromosomal abnormalities two rare autosomal aneuploidies (RATs) and 15 copy number variations The positive predictive value for common trisomies, SCAs, RATs and CNVs were 68.57%, 68.12%, 6.67% and 51.72%, respectively. Pregnant women with screen-positive results for common trisomies have higher rates of invasive prenatal diagnosis and pregnancy termination than those with positive results for SCAs, RATs, and CNVs. NIPT-Plus showed a good performance in detecting common trisomies, SCAs and also contributed to detecting pathogenic CNVs, but higher accuracy was required in the detection of RATs. In summary, this study provides a reference for the clinical application of NIPT-Plus for screening fetal chromosomal abnormalities in this region. Therefore, we suggest that NIPT-Plus could be widely used in clinical screening for fetal chromosomal abnormalities in combination with prenatal diagnosis and genetic counseling.

Application of expanded noninvasive prenatal test in prenatal diagnosis of fetuses with increased nuchal translucency.

OBJECTIVES: To investigate the efficiency of the upgraded noninvasive prenatal test (NIPT-Plus) in fetuses with increased nuchal translucency (NT). METHODS: Fetuses with an increased NT at or above 2.5 mm were selected for prenatal diagnosis. Amniotic fluid was collected from all cases for karyotype analysis and copy number variation sequencing (CNV-seq), and cell-free fetal DNA (cfDNA) in maternal blood was tested using Noninvasive Prenatal Test (NIPT-Plus) before amniocentesis in some cases. The results of amniocentesis with different NT thicknesses were analyzed and compared with those of NIPT-Plus. RESULTS: A total of 125 eligible patients were divided into group A (2.5 mm ≤ NT < 3.0 mm) and group B (NT ≥ 3.0 mm). In group A, the detection rate of chromosomal aneuploidy and pathogenic copy number variation (CNV) was 10.6% and 6.4%, respectively. The total chromosome abnormality rate in group B (34.7%) was significantly higher than that in group A (17%). In 72 patients who underwent NIPT-Plus and amniocentesis, chromosomal aneuploidy accounted for 80.8% of the total chromosomal abnormalities. Among 21 cases of chromosomal aneuploidy, NIPT-Plus detected 20 cases. The sensitivity and specificity of NIPT-Plus toward aneuploidy detection were 95.2% and 100%, respectively. Among the five cases of pathogenic CNV, only two were detected using NIPT-Plus. CONCLUSION: NIPT-plus is recommended as the first choice for fetal diagnosis in pregnant women with 2.5 mm ≤ NT < 3.0 mm who do not accept invasive prenatal diagnosis. When NT ≥ 3.0 mm and NIPT-Plus detects chromosomal aneuploidy, a rapid prenatal diagnosis can be performed through amniocentesis. In cases where NIPT-Plus yields negative results, amniocentesis still needs to be performed to detect chromosome microdeletions/duplications in order to avoid a missed diagnosis.