Noninvasive prenatal diagnosis of fetal chromosomal aneuploidy by massively parallel genomic sequencing of DNA in maternal plasma. Proc Natl Acad Sci U S A. 2008;105:20458-20463. [PMID: 19073917 DOI: 10.1073/pnas.0810641105]

A clinically feasible algorithm for the parallel detection of glioma-associated copy number variation markers based on shallow whole genome sequencing

Molecular features are incorporated into the integrated diagnostic system for adult diffuse gliomas. Of these, copy number variation (CNV) markers, including both arm-level (1p/19q codeletion, +7/-10 signature) and gene-level (EGFR gene amplification, CDKN2A/B homozygous deletion) changes, have revolutionized the diagnostic paradigm by updating the subtyping and grading schemes. Shallow whole genome sequencing (sWGS) has been widely used for CNV detection due to its cost-effectiveness and versatility. However, the parallel detection of glioma-associated CNV markers using sWGS has not been optimized in a clinical setting. Herein, we established a model-based approach to classify the CNV status of glioma-associated diagnostic markers with a single test. To enhance its clinical utility, we carried out hypothesis testing model-based analysis through the estimation of copy ratio fluctuation level, which was implemented individually and independently and, thus, avoided the necessity for normal controls. Besides, the customization of required minimal tumor fraction (TF) was evaluated and recommended for each glioma-associated marker to ensure robust classification. As a result, with 1× sequencing depth and 0.05 TF, arm-level CNVs could be reliably detected with at least 99.5% sensitivity and specificity. For EGFR gene amplification and CDKN2A/B homozygous deletion, the corresponding TF limits were 0.15 and 0.45 to ensure the evaluation metrics were both higher than 97%. Furthermore, we applied the algorithm to an independent glioma cohort and observed the expected sample distribution and prognostic stratification patterns. In conclusion, we provide a clinically applicable algorithm to classify the CNV status of glioma-associated markers in parallel.

Massive parallel sequencing-based non-invasive prenatal test (NIPT) identifies aberrations on chromosome 13

OBJECTIVE

We report data of non-invasive prenatal testing (NIPT) at Uppsala University Hospital between 2017-2022. Furthermore, we illustrate the potential capacity of massive parallel sequencing-based NIPT beyond identification of common trisomies.

METHODS

Maternal blood samples were analyzed using the Verifi NIPT or VeriSeq NIPT assays. Diagnostic testing, performed on amniotic fluid samples, included QF-PCR, microarray (SNP-array) and metaphase FISH.

RESULTS

Among 4532 NIPT tests performed between 2017-2022, 125 samples (2.76%) showed increased risk for trisomies 13, 18, 21 and sex chromosome aneuploidy. For three patients with normal NIPT result further microarray indicated other types of chromosomal rearrangement which were not analyzed by NIPT. For another patient (case 1) the Verifi NIPT indicated trisomy 13. Fetal fraction (FF) was estimated to be 10%. Confirmatory microarray detected a segmental duplication on chromosome 13, as well as a terminal duplication and a terminal deletion on chromosome 10. A complex karyotype was observed in the fetus with metaphase FISH. In the second case the VeriSeq NIPT indicated trisomy 13. FF was estimated to be 11%. Confirmatory microarray detected a mosaicism of trisomy 13 in 30 % of cells.

CONCLUSION

This study illustrates detection of peculiar abnormalities of chromosome 13 and supports potential to screen copy number variations with genome-wide NIPT.

Comparison of the performance of NIPT and NIPT-plus for fetal chromosomal aneuploidy and high Z-score increases the positive predictive value

OBJECTIVE

To evaluate non-invasive prenatal testing (NIPT) and expanded non-invasive prenatal testing (NIPT-plus) for detecting aneuploidies at different sequencing depths and assess Z-score accuracy in predicting trisomies 21, 18, 13, 45X, and 47XXX.

METHODS

Pregnancies with positive NIPT or NIPT-plus results detected at the prenatal diagnosis center of Nanfang Hospital were included in this retrospective study, between January 2017 and December 2022. Invasive prenatal diagnostic results were collected. Logistic regression analyses were used to study the relationship between Z-score and positive predictive value (PPV). Optimal cut-off values were obtained based on receiver operating characteristic analysis, and PPVs were calculated in different groups.

RESULTS

We evaluated 1348 pregnant women with positive results, including 930 reported by NIPT and 418 reported by NIPT-plus. NIPT reported significantly more rare chromosomal aneuploidies (RCAs), and NIPT-plus had a significantly higher PPV for trisomy 21 (T21). Logistic regression analyses showed a significant association (P < 0.001) between Z-score and PPVs for T21 and trisomy 18 (T18). A linear relationship was observed between fetal fraction (FF) and Z-values in the true positive cases of T21 and T18.The high Z-score group had significantly higher PPVs than the low Z-score group for T21, T18, trisomy 13, and 47XXX, but not for 45X.

CONCLUSION

The Z-score is helpful in assessing NIPT or NIPT-plus results. Therefore, we suggest including the Z-score and FF in the results. By combining the Z-score, FF, and maternal age, clinicians can interpret NIPT results more accurately and improve personal counsel to reduce patients' anxiety.

Clinical applications of circulating tumor DNA in hematological malignancies: From past to the future

Liquid biopsy, particularly circulating tumor DNA (ctDNA), has drawn a lot of attention as a non- or minimal-invasive detection approach for clinical applications in patients with cancer. Many hematological malignancies are well suited for serial and repeated ctDNA surveillance due to relatively high ctDNA concentrations and high loads of tumor-specific genetic and epigenetic abnormalities. Progress of detecting technology in recent years has improved sensitivity and specificity significantly, thus broadening and strengthening the potential utilities of ctDNA including early diagnosis, prognosis estimation, treatment response evaluation, minimal residual disease monitoring, targeted therapy selection, and immunotherapy surveillance. This manuscript reviews the detection methodologies, clinical application and future challenges of ctDNA in hematological malignancies, especially for lymphomas, myeloma and leukemias.

Impact of the new government-involved noninvasive prenatal testing certification system on the awareness of pregnant women about noninvasive prenatal testing in Japan

AIM

In Japan, noninvasive prenatal testing (NIPT) has been performed by facilities accredited by the Japanese Society of Obstetrics and Gynecology since 2013. However, since 2016, with the implementation of NIPT, which can only be performed by blood sampling, non-obstetricians have been involved in prenatal testing. Therefore, in July 2022, a new government-involved NIPT certification system based on Health Sciences Council guidelines was introduced to ensure access to prenatal testing information for pregnant women.

METHODS

This survey was conducted in February 2023 and was the first survey after the certification system implementation. We conducted a web-based survey of 1227 pregnant women and nursing mothers who underwent NIPT after July 2022 to evaluate their experiences.

RESULTS

Respondents were categorized by certification status as certified (C: 56%), non-certified (non-C: 23%), or uncertain (Q: 20%). The C group with a higher mean age at examination (35.0 ± 4.5 years) paid lower examination fees, received longer pre- and post-examination explanations, and underwent more weekday examinations (80%) than the other groups. Most respondents, 67%, 48%, and 53% in the C, non-C, and Q groups, respectively (p < 0.0001), stated that "NIPT needs to be regulated by the government or academic societies." The non-C group was more likely to say, "Insufficient post-test explanations at the laboratory made me more anxious," than the other groups when the testing results were non-negative (p = 0.015).

CONCLUSIONS

Despite government regulation, some pregnant women choose convenience over certified facilities, risking inadequate care. The government should ensure that NIPT is a safe option for all pregnant women.

A capture-based method of prenatal cell-free DNA screening for autosomal recessive non-syndromic hearing loss

OBJECTIVE

This study aimed to develop and validate a prenatal cell-free DNA (cfDNA) screening method that uses capture-based enrichment to genotype fetal autosomal recessive disorders. This method was applied in pregnancies at high risk of autosomal recessive non-syndromic hearing loss (ARNSHL) to assess its accuracy and effectiveness.

METHODS

This assay measured the allele counts in both white blood cell DNA and cfDNA from the blood samples of pregnant women using a capture-based next-generation sequencing method. It then applied a binomial model to infer the fetal genotypes with the maximum likelihood. Ninety-four pregnant couples that were carriers of variants of ARNSHL in GJB2 or SLC26A4 were enrolled. The fetal genotypes deduced using this screening method were compared with the results of genetic diagnosis using amniocentesis.

RESULTS

Of the 94 couples, 65 carried more than one variant, resulting in 170 single-nucleotide polymorphism (SNP) loci to be inferred in the fetuses. Of the 170 fetal SNP genotypes, 150 (88.2%) had high confidence calls and 139 (92.7%) of these matched the genotypes obtained by amniocentesis result. Out of the remaining 20 (11.8%) cases with low-confidence calls, only 14 (70.0%) were concordant with genetic diagnosis using amniocentesis. The concordance rate was 100% for sites where the maternal genotype was wild-type homozygous. The discordance was site-biased, with each locus showing a consistent direction of discordance. Genetic diagnosis identified a total of 19 wild-type homozygotes, 46 heterozygotes, 19 compound heterozygotes, and 10 pathogenic homozygotes. This screening method correctly genotyped 81.9% (77/94) of fetuses and demonstrated a sensitivity of 89.7% and a specificity of 89.2% for correctly identifying ARNSHL.

CONCLUSION

This capture-based method of prenatal screening by cfDNA demonstrated strong potential for fetal genotyping of autosomal recessive disorders.

Targeted Linked-Read Sequencing for Direct Haplotype Phasing of Parental GJB2/SLC26A4 Alleles: A Universal and Dependable Noninvasive Prenatal Diagnosis Method Applied to Autosomal Recessive Nonsyndromic Hearing Loss in At-Risk Families

Noninvasive prenatal diagnosis (NIPD) for autosomal recessive nonsyndromic hearing loss (ARNSHL) has been rarely reported until recent years. Additionally, the existing method can not be used for challenging genome loci (eg, copy number variations, deletions, inversions, or gene recombinants) or on families without proband genotype. This study assessed the performance of relative haplotype dosage analysis (RHDO)-based NIPD for identifying fetal genotyping in pregnancies at risk of ARNSHL. Fifty couples carrying pathogenic variants associated with ARNSHL in either GJB2 or SLC26A4 were recruited. The RHDO-based targeted linked-read sequencing combined with whole gene coverage probes was used to genotype the fetal cell-free DNA of 49 families who met the quality control standard. Fetal amniocyte samples were genotyped using invasive prenatal diagnosis (IPD) to assess the performance of NIPD. The NIPD results showed 100% (49/49) concordance with those obtained through IPD. Two families with copy number variation and recombination were also successfully identified. Sufficient specific informative single-nucleotide polymorphisms for haplotyping, as well as the fetal cell-free DNA concentration and sequencing depth, are prerequisites for RHDO-based NIPD. This method has the merits of covering the entire genes of GJB2 and SLC26A4, qualifying for copy number variation and recombination analysis with remarkable sensitivity and specificity. Therefore, it has clinical potential as an alternative to traditional IPD for ARNSHL.

Liquid Biopsy Based on Cell-Free DNA and RNA

This review delves into the rapidly evolving landscape of liquid biopsy technologies based on cell-free DNA (cfDNA) and cell-free RNA (cfRNA) and their increasingly prominent role in precision medicine. With the advent of high-throughput DNA sequencing, the use of cfDNA and cfRNA has revolutionized noninvasive clinical testing. Here, we explore the physical characteristics of cfDNA and cfRNA, present an overview of the essential engineering tools used by the field, and highlight clinical applications, including noninvasive prenatal testing, cancer testing, organ transplantation surveillance, and infectious disease testing. Finally, we discuss emerging technologies and the broadening scope of liquid biopsies to new areas of diagnostic medicine.

MaterniCode: New Bioinformatic Pipeline to Detect Fetal Aneuploidies and Rearrangements Using Next-Generation Sequencing

Objective: The present study is aimed at introducing and evaluating MaterniCode, a state-of-the-art bioinformatic pipeline for noninvasive prenatal testing (NIPT) that leverages the Ion Torrent semiconductor sequencing platform. The initiative strives to revolutionize prenatal diagnostics by offering a rapid and cost-effective method without sacrificing accuracy. Methods: Two distinct bioinformatic strategies were employed for fetal sex determination, one of which achieved 100% accuracy. We analyzed 1225 maternal blood samples for fetal aneuploidies, benchmarking against the industry standard Illumina VeriSeq™ NIPT Solution v2. The capability of MaterniCode to detect and characterize complex chromosomal anomalies was also assessed. Results: MaterniCode achieved near-perfect accuracy in fetal sex determination through chromosome Y (chrY )-specific gene analysis, whereas the alternative method, employing the ratio of high-quality mapped reads on chrY relative to all reads, delivered 100% accuracy. For fetal aneuploidy detection, both the integrated WisecondorX and NIPTeR algorithms demonstrated a 100% sensitivity and specificity rate, consistent with Illumina VeriSeq™ NIPT Solution v2. The pipeline also successfully identified and precisely mapped significant chromosomal abnormalities, exemplified by a 2.4 Mb deletion on chromosome 13 and a 3 Mb duplication on chromosome 2. Conclusion: MaterniCode has proven to be an innovative and highly efficient tool in the domain of NIPT, demonstrating excellent sensitivity and specificity. Its robust capability to effectively detect a wide range of complex chromosomal aberrations, including rare and subtle variations, positions it as a promising and valuable addition to prenatal diagnostic technologies. This enhancement to diagnostic precision significantly aids clinicians in making informed decisions during pregnancy management.

NIPT-PG: empowering non-invasive prenatal testing to learn from population genomics through an incremental pan-genomic approach

Non-invasive prenatal testing (NIPT) is a quite popular approach for detecting fetal genomic aneuploidies. However, due to the limitations on sequencing read length and coverage, NIPT suffers a bottleneck on further improving performance and conducting earlier detection. The errors mainly come from reference biases and population polymorphism. To break this bottleneck, we proposed NIPT-PG, which enables the NIPT algorithm to learn from population data. A pan-genome model is introduced to incorporate variant and polymorphic loci information from tested population. Subsequently, we proposed a sequence-to-graph alignment method, which considers the read mis-match rates during the mapping process, and an indexing method using hash indexing and adjacency lists to accelerate the read alignment process. Finally, by integrating multi-source aligned read and polymorphic sites across the pan-genome, NIPT-PG obtains a more accurate z-score, thereby improving the accuracy of chromosomal aneuploidy detection. We tested NIPT-PG on two simulated datasets and 745 real-world cell-free DNA sequencing data sets from pregnant women. Results demonstrate that NIPT-PG outperforms the standard z-score test. Furthermore, combining experimental and theoretical analyses, we demonstrate the probably approximately correct learnability of NIPT-PG. In summary, NIPT-PG provides a new perspective for fetal chromosomal aneuploidies detection. NIPT-PG may have broad applications in clinical testing, and its detection results can serve as a reference for false positive samples approaching the critical threshold.

DNA methylation in necrotizing enterocolitis

Epigenetic modifications, such as DNA methylation, are enzymatically regulated processes that directly impact gene expression patterns. In early life, they are central to developmental programming and have also been implicated in regulating inflammatory responses. Research into the role of epigenetics in neonatal health is limited, but there is a growing body of literature related to the role of DNA methylation patterns and diseases of prematurity, such as the intestinal disease necrotizing enterocolitis (NEC). NEC is a severe intestinal inflammatory disease, but the key factors that precede disease development remain to be determined. This knowledge gap has led to a failure to design effective targeted therapies and identify specific biomarkers of disease. Recent literature has identified altered DNA methylation patterns in the stool and intestinal tissue of neonates with NEC. These findings provide the foundation for a new avenue in NEC research. In this review, we will provide a general overview of DNA methylation and then specifically discuss the recent literature related to methylation patterns in neonates with NEC. We will also discuss how DNA methylation is used as a biomarker for other disease states and how, with further research, methylation patterns may serve as potential biomarkers for NEC.

Prospective prenatal cell-free DNA screening for genetic conditions of heterogenous etiologies

Prenatal cell-free DNA (cfDNA) screening uses extracellular fetal DNA circulating in the peripheral blood of pregnant women to detect prevalent fetal chromosomal anomalies. However, numerous severe conditions with underlying single-gene defects are not included in current prenatal cfDNA screening. In this prospective, multicenter and observational study, pregnant women at elevated risk for fetal genetic conditions were enrolled for a cfDNA screening test based on coordinative allele-aware target enrichment sequencing. This test encompasses the following three of the most frequent pathogenic genetic variations: aneuploidies, microdeletions and monogenic variants. The cfDNA screening results were compared to invasive prenatal or postnatal diagnostic test results for 1,090 qualified participants. The comprehensive cfDNA screening detected a genetic alteration in 135 pregnancies with 98.5% sensitivity and 99.3% specificity relative to standard diagnostics. Of 876 fetuses with suspected structural anomalies on ultrasound examination, comprehensive cfDNA screening identified 55 (56.1%) aneuploidies, 6 (6.1%) microdeletions and 37 (37.8%) single-gene pathogenic variants. The inclusion of targeted monogenic conditions alongside chromosomal aberrations led to a 60.7% increase (from 61 to 98) in the detection rate. Overall, these data provide preliminary evidence that a comprehensive cfDNA screening test can accurately identify fetal pathogenic variants at both the chromosome and single-gene levels in high-risk pregnancies through a noninvasive approach, which has the potential to improve prenatal evaluation of fetal risks for severe genetic conditions arising from heterogenous molecular etiologies. ClinicalTrials.gov registration: ChiCTR2100045739 .

Rapid non-invasive prenatal screening test for trisomy 21 based on digital droplet PCR

Non-invasive prenatal tests for the detection of fetal aneuploidies are predominantly based on the analysis of cell-free DNA (cfDNA) from the plasma of pregnant women by next-generation sequencing. The development of alternative tests for routine genetic laboratories is therefore desirable. Multiplex digital droplet PCR was used to detect 16 amplicons from chromosome 21 and 16 amplicons from chromosome 18 as the reference. Two fluorescently labeled lock nucleic acid probes were used for the detection of reaction products. The required accuracy was achieved by examining 12 chips from each patient using Stilla technology. The plasma cfDNA of 26 pregnant women with euploid pregnancies and 16 plasma samples from pregnancies with trisomy 21 were analyzed to determine the cutoff value for sample classification. The test was validated in a blind study on 30 plasma samples from pregnant patients with a risk for trisomy 21 ranging from 1:4 to 1:801. The results were in complete agreement with the results of the invasive diagnostic procedure (sensitivity, specificity, PPV, and NPV of 100%). Low cost, and speed of analysis make it a potential screening method for implementation into the clinical workflow to support the combined biochemical and ultrasound results indicating a high risk for trisomy 21.

Cell-free DNA-based prenatal screening via rolling circle amplification: Identifying and resolving analytic issues

OBJECTIVE

A rolling circle amplification (RCA) based commercial methodology using cell-free (cf)DNA to screen for common trisomies became available in 2018. Relevant publications documented high detection but with a higher than expected 1% false positive rate. Preliminary evidence suggested assay variability was an issue. A multi-center collaboration was created to explore this further and examine whether subsequent manufacturer changes were effective.

METHODS

Three academic (four devices) and two commercial (two devices) laboratories provided run date, chromosome 21, 18, and 13 run-specific standard deviations, number of samples run, and reagent lot identifications. Temporal trends and between-site/device consistency were explored. Proportions of run standard deviations exceeding pre-specified caps of 0.4%, 0.4% and 0.6% were computed.

RESULTS

Overall, 661 RCA runs between April 2019 and July 30, 2022 tested 39,756 samples. In the first 24, subsequent 9, and final 7 months, proportions of capped chromosome 21 runs dropped from 39% to 22% to 6.0%; for chromosome 18, rates were 76%, 36%, and 4.0%. Few chromosome 13 runs were capped using the original 0.60%, but capping at 0.50%, rates were 28%, 16%, and 7.6%. Final rates occurred after reformulated reagents and imaging software modifications were fully implemented across all devices. Revised detection and false positive rates are estimated at 98.4% and 0.3%, respectively. After repeat testing, failure rates may be as low as 0.3%.

CONCLUSION

Current RCA-based screening performance estimates are equivalent to those reported for other methods, but with a lower test failure rate after repeat testing.

Noninvasive prenatal screening with conventional sequencing depth to screen fetal copy number variants: A retrospective study of 19 144 pregnant women

AIM

To investigate the detectability of noninvasive prenatal screening (NIPS) with conventional sequencing depth to detect fetal copy number variants.

METHODS

We performed a retrospective study in a total of 19 144 pregnant women. Their cell-free plasma DNA were assessed for trisomy 21, trisomy 18, trisomy 13, sex chromosome aneuploidies, and genome-wide copy number variants by NIPS at conventional sequencing depth.

RESULTS

Three hundred seventy-four cases (2.0%, 374/19 144) with abnormal results were detected, which including 84 cases (0.4%, 84/19 144) with high risk of trisomy 21, 18, and 13, 90 cases (0.5%, 90/19 144) with high risk of sex chromosome abnormalities (SCA), and 44 cases (0.2%, 44/19 144) with high risk of other chromosome aneuploidies. One hundred fifty-six cases (0.8%, 156/19 144) with high risk of copy number variations (CNVs) were also detected. In following prenatal diagnosis, composite positive predictive value (PPV) of trisomy 21, 18, and 13 was 69.6% (48/69). The PPV of SCAs was 37.3% (19/51). And the PPVs for CNVs was detected as 51.0% (<5 Mb), 71.4% (5 Mb ≤ CNV ≤10 Mb), 56.5% (>10 Mb). Finally, a follow-up about the pregnancy outcomes were conducted for all available cases.

CONCLUSIONS

NIPS yielded high PPVs for trisomy 21, 18, and 13 aneuploidies and moderate PPVs for SCAs and CNVs. The screening effectiveness was closely related to the size of CNV fragments. Larger CNVs, especially larger than 5 Mb, could be detected more accurately by NIPS in our analytic technique. Meanwhile, diagnostic confirmation by microarray analysis was highly recommended.

Exploration of a Novel Noninvasive Prenatal Testing Approach for Monogenic Disorders Based on Fetal Nucleated Red Blood Cells

BACKGROUND

Due to technical issues related to cell-specific capture methods, amplification, and sequencing, noninvasive prenatal testing (NIPT) based on fetal nucleated red blood cells (fNRBCs) has rarely been used for the detection of monogenic disorders.

METHODS

Maternal peripheral blood was collected from 11 families with hereditary hearing loss. After density gradient centrifugation and cellular immunostaining for multiple biomarkers, candidate individual fetal cells were harvested by micromanipulation and amplified by whole-genome amplification (WGA). Whole-exome sequencing/whole-genome sequencing (WGS) and Sanger sequencing were performed on the identified fNRBCs to determine the fetal genotype. The impact of single-cell and pooled WGA products on the sequencing quality and results was compared. A combined analysis strategy, encompassing whole-exome sequencing/WGS, haplotype analysis, and Sanger sequencing, was used to enhance the NIPT results.

RESULTS

fNRBCs were harvested and identified in 81.8% (9/11) of families. The results of cell-based-NIPT (cb-NIPT) were consistent with those of invasive prenatal diagnosis in 8 families; the coincidence rate was 88.9% (8/9). The combined analysis strategy improved the success of cb-NIPT. The overall performance of pooled WGA products was better than that of individual cells. Due to a lack of alternative fetal cells or sufficient sequencing data, cb-NIPT failed in 3 families.

CONCLUSIONS

We developed a novel fNRBC-based NIPT method for monogenic disorders. By combining multiple analysis strategies and multiple fetal cell WGA products, the problem of insufficient genome information in a single cell was remedied. Our method has promising prospects in the field of NIPT for the detection of monogenic disorders.

Discordant performances of non-invasive prenatal testing for foetal trisomy 21 screening in subgroups of pregnancies

BACKGROUND

Non-invasive prenatal testing (NIPT) has been widely adopted as an approach for foetal aneuploidy screening. This study was to evaluate the performance of NIPT for foetal T21 detection in subgroups of pregnancies and the correlation between Z-score and discordant positive predictive values (PPVs).

METHODS

We retrospectively reviewed the NIPT results among 22361 pregnancies undergoing combined second-trimester screening (cSTS) previously. Sixty-four cases with positive NIPT results for foetal T21 were validated by invasive prenatal diagnosis.

RESULTS

In pregnancies with cSTS-T21 low-, intermediate-, and high-risk, the PPVs at NIPT were 14.3%, 64.3%, and 86.4%, respectively. Mean Z-scores of positive NIPT cases with cSTS-T21 high- and intermediate-risk were comparable, while were higher than that of cases with pre-test low-risk. Furthermore, PPVs for positive NIPT cases at 3 < Z < 5, 5 ≤ Z < 9, and Z ≥ 9 were 16.7%, 63.2%, and 100.0%, respectively.

CONCLUSIONS

This study suggested that Z-score value of positive cases might be associated with discordant PPVs for T21 screening in subgroups of pregnancies.

Clinical Potential of Expanded Noninvasive Prenatal Testing for Detection of Aneuploidies and Microdeletion/Microduplication Syndromes

OBJECTIVE

We aimed to evaluate the clinical performance of expanded noninvasive prenatal testing (NIPT-Plus) for the detection of aneuploidies and microdeletion/microduplication syndromes.

METHODS

A total of 7177 pregnant women were enrolled in the study from June 2020 to March 2022 at Xijing Hospital, China. Cases with NIPT-Plus-positive results were further confirmed by chromosomal karyotyping and a chromosomal microarray analysis.

RESULTS

A total of 112 positive cases (1.56%) were identified by NIPT-Plus, including 60 chromosome aneuploidies and 52 microdeletion/microduplication syndromes. Ninety-five cases were validated by amniocentesis, and 57 were confirmed with true-positive results, comprising 18 trisomy 21, 4 trisomy 18, 1 trisomy 13, 17 sex chromosome aneuploidies, 1 other aneuploidy, and 16 microdeletion/microduplication syndromes. The positive predictive value of total chromosomal abnormalities was 60% (57/95). For trisomy 21, trisomy 18, trisomy 13, sex chromosome aneuploidies, other aneuploidies and microdeletion/microduplication syndromes, the sensitivity was all 100%, the specificity was 100, 99.986, 100, 99.888, 99.958, and 99.636%, and the positive predictive value was 100, 80, 100, 68, 25, and 38.10%, respectively. For all clinical characteristics, the abnormal maternal serum screening group was found to have the highest prevalence of chromosomal abnormalities (1.54%), and the ultrasound abnormality group presented the highest positive predictive value (73.33%).

CONCLUSIONS

NIPT-Plus has great potential for the detection of aneuploidies and microdeletion/microduplication syndromes owing to its high sensitivity, safety, and specificity, which greatly reduces unnecessary invasive procedures and the risk of miscarriage and allows informed maternal choice.

Combinational antibody detection approach increases the clinical validity of colorectal cancer screening

BACKGROUND

At different stages of the disease, biomarkers can help to determine disease progression and recurrence and provide a personalized indicator of therapeutic effectiveness. The serological identification of antigens by recombinant cDNA expression cloning (SEREX) has identified five SEREX antigens.

RESULTS

Compared with healthy donors, anti-FIRΔexon2 and anti-SOHLH antibodies (Abs) in the sera of patients with colorectal cancer (CRC) were markedly higher. Furthermore, no correlation was noted between five SEREX antigens and the three tumor markers (CEA, CA19-9, and anti-p53 Abs), indicating that anti-FIRΔexon2 Abs are an independent candidate marker for patients with CRC. Generally, the levels of anti-FIRΔexon2 Abs combined with clinically available tumor markers were determined to be significantly higher compared with CEA, CA19-9. Moreover, in early-stage CRC, the levels of anti-FIRΔexon2 Abs combined with existing tumor markers were higher than those of CEA, CA19-9.

CONCLUSION

Due to the highly heterogeneous nature of CRC, a single tumor marker is unlikely to become a standalone diagnostic test due to its commonly insufficient sensitivity and/or specificity. Using a combination antibody detection approach of tumor markers for CRC diagnosis has the potential to be an effective approach. Therefore, the use of serum protein biomarker candidates holds promise for the development of inexpensive, noninvasive, and inexpensive tests for the detection of CRC.

Application of non-invasive prenatal testing to 91,280 spontaneous pregnancies and 3477 pregnancies conceived by in vitro fertilization

BACKGROUND

Many clinical studies based on spontaneous pregnancies (SPs) have demonstrated the superiority of non-invasive prenatal testing (NIPT), and the question of whether this technology is suitable for offspring conceived by assisted reproductive technology has attracted attention. This study aimed to evaluate the application value of NIPT in screening for trisomy (T)21, T18, T13 and sex chromosome aneuploidy (SCA) in pregnant women who conceived by in vitro fertilization (IVF).

RESULTS

In total, there were 804 high-risk cases [0.88% (804/91280), singleton = 795, twin = 9] in the SP group. Among the 558 invasive prenatal diagnosis (IPD) cases (singleton = 556, twin = 2), 343 (singleton = 342, twin = 1) were true positive, including 213 cases of T21, 28 of T18, 5 of T13 and 97 (singleton = 96, twin = 1) of SCA. The positive predictive values (PPVs) of T21, T18, T13, SCA and T21/T18/T13 combined in singleton pregnancy were 89.12% (213/239), 51.85% (28/54), 21.74% (5/23), 40.00% (96/240), and 77.85% (246/316), respectively, and the PPV of SCA in twin pregnancy was 100.00%. In the IVF group, IPD was performed in 19 (singleton = 16, twin = 3) of the 27 high-risk cases [0.78% (27/3477), singleton = 16, twin = 3], of which 9 (singleton = 8, twin = 1) were true positive, including 5 cases (singleton = 4, twin = 1) of T21 and 4 of SCA. The PPVs of singleton T21, SCA and T21/T18/T13 combined were 66.67% (4/6), 50.00% (4/8) and 57.14% (4/7), respectively, and the PPV of twin T21 was 100.00% (1/1). There were no significant differences in PPV among T21, SCA and T21/T18/T13 combined in singletons between the groups (89.12% vs. 66.67%, p = 0.09; 40.00% vs. 50.00%, p = 0.57; 77.85% vs. 57.14%, p = 0.20). The sensitivity and specificity were higher for singleton and twin pregnancies in the two groups. Based on follow-up results, 1 case of false negative T21 was found in the singleton SP group. Additionally, the mean foetal fraction (FF) of the IVF group was lower than that of the SP group (11.23% vs. 10.51%, p < 0.05).

CONCLUSION

NIPT has high sensitivity and specificity in screening chromosomal aneuploidies in both IVF pregnancy and spontaneous pregnancy, so it is an ideal screening method for IVF pregnancy.

Overview of Noninvasive Prenatal Testing (NIPT) for the Detection of Fetal Chromosome Abnormalities; Differences in Laboratory Methods and Scope of Testing

Although nearly all noninvasive prenatal testing is currently based on analyzing circulating maternal cell-free DNA, the technical methods usedvary considerably. We review the different methods. Based on validation trials and clinical experience, there are mostly relatively small differences in screening performance for trisomies 21, 18, and 13 in singleton pregnancies. Recent reports show low no-call rates for all methods, diminishing its importance when choosing a laboratory. However, method can be an important consideration for twin pregnancies, screening for sex chromosome abnormalities, microdeletion syndromes, triploidy, molar pregnancies, rare autosomal trisomies, and segmental imbalances, and detecting maternal chromosome abnormalities.

Analysis of retest reliability for pregnant women undergoing cfDNA testing with a no-call result

BACKGROUND

Determining the reasons for unreportable or no-call cell-free DNA (cfDNA) test results has been an ongoing issue, and a consensus on subsequent management is still lacking. This study aimed to explore potential factors related to no-call cfDNA test results and to discuss whether retest results are reliable.

METHODS AND RESULTS

This was a retrospective study of women with singleton pregnancies undergoing cfDNA testing in 2021. Of the 9871 pregnant patients undergoing cfDNA testing, 111 had a no-call result, and their results were compared to those of 170 control patients. The no-call rate was 1.12% (111/9871), and the primary cause for no-call results was data fluctuation (88.29%, 98/111). Medical conditions were significantly more frequent in the no-call group than in the reportable results group (P < 0.001). After retesting, 107 (107/111, 96.40%) patients had a result, and the false-positive rate (FPR) of retesting was 10.09% (10.09%, 11/109). In addition, placental lesions were more frequent in the no-call group than in the reportable results group (P = 0.037), and 4 patients, all in the no-call group, experienced pregnancy loss.

CONCLUSIONS

Pregnant women with medical conditions are more likely to have a no-call result. A retest is suggested for patients with a no-call result, but retests have a high FPR. In addition, pregnant women with a no-call result are at increased risk of adverse pregnancy outcomes. In conclusion, more attention should be given to pregnant women for whom a no-call cfDNA result is obtained.

Non-invasive prenatal test findings in 41,819 pregnant women: results from a clinical laboratory in southern China

BACKGROUND

This paper evaluated the clinical utility of massively parallel sequencing-based non-invasive prenatal testing (NIPT) for detecting trisomy 21 (T21), T18, T13, sex chromosome aneuploidies (SCA), and rare chromosome aneuploidies (RCA) among the data collected by a clinical laboratory in southern China.

METHODS

In a 3-year period between January 2017 and December 2019, over 40,000 pregnant women underwent NIPT clinical screening test for fetal T21, T18, T13, SCA, and RCA in our laboratory. NIPT samples were processed using the NextSeq CN500 platform. The positive results were confirmed by karyotyping, and chromosomal microarray analysis (CMA) or copy number variants (CNV) sequencing. Details of the pregnancy outcomes were collected via telephone interview.

RESULTS

NIPT results were available for 41,819 cases; 691 positive cases were reported. The overall sensitivity for detection of T21, T18, T13, SCA, and RCA was 99.21, 100.00, 100.00, 98.55, and 100.00%, and the specificity was 99.95, 99.94, 99.98, 99.69, and 99.92%, respectively. The positive predictive values (PPVs) for detection of T21, T18, T13, SCA, and RCA were 85.62, 45.24, 40.00, 34.17, and 13.51%, respectively, and those for detection of 45,X, 47,XXY, 47,XXX, 47,XYY, and 46,XY(delX) 20.00, 59.18, 28.95, 61.54, and 25.00%, respectively. Regarding pregnancy outcomes, 92.38% of the pregnancies with confirmed aneuploidies were terminated, and 91.20% of those identified as having a false-positive result were carried to term. Among 252 unconfirmed cases, 24.60% of the pregnancies were terminated and 38.10% carried to term, while 37.30% declined interview.

CONCLUSIONS

NIPT is widely used to screen fetal aneuploidies based on its high sensitivity and specificity. However, in this study, the PPVs of NIPT in terms of detecting T18, T13, XO, XXX and RCA were < 50%. In addition, more than one-third of NIPT-positive women did not accept invasive prenatal diagnosis. Confirmatory diagnosis is strongly recommended for women with positive NIPT outcomes before any further decision is made.

Cell-free DNA Screening for Aneuploidy

Cell-free DNA (cfDNA) screening has high detection for the common fetal autosomal aneuploidies, but is not diagnostic. The positive predictive value should be utilized in counseling after a positive cell-free DNA screen, and diagnostic testing should be offered for confirmation. cfDNA screening does not report a result in ~3% of cases; nonreportable results indicate an increased risk for aneuploidy and some adverse perinatal outcomes. False-positive cfDNA screening occurs due to confined placental mosaicism, maternal copy number variants, mosaicism, and cancer. Pretest education and counseling should be provided with emphasis on the potential benefits, risks, and limitations before cfDNA screening.

Noninvasive Prenatal Testing Using Circulating DNA and RNA: Advances, Challenges, and Possibilities

Prenatal screening using sequencing of circulating cell-free DNA has transformed obstetric care over the past decade and significantly reduced the number of invasive diagnostic procedures like amniocentesis for genetic disorders. Nonetheless, emergency care remains the only option for complications like preeclampsia and preterm birth, two of the most prevalent obstetrical syndromes. Advances in noninvasive prenatal testing expand the scope of precision medicine in obstetric care. In this review, we discuss advances, challenges, and possibilities toward the goal of providing proactive, personalized prenatal care. The highlighted advances focus mainly on cell-free nucleic acids; however, we also review research that uses signals from metabolomics, proteomics, intact cells, and the microbiome. We discuss ethical challenges in providing care. Finally, we look to future possibilities, including redefining disease taxonomy and moving from biomarker correlation to biological causation.

A Novel Paradigm for Non-Invasive Prenatal Genetic Screening: Trophoblast Retrieval and Isolation from the Cervix (TRIC)

As the prevalence of pregnancies with advanced maternal age increases, the risk of fetal chromosomal abnormalities is on the rise. Therefore, prenatal genetic screening and diagnosis have become essential elements in contemporary obstetrical care. Trophoblast retrieval and isolation from the cervix (TRIC) is a non-invasive procedure that can be utilized for prenatal genetic diagnosis. The method involves the isolation of fetal cells (extravillous trophoblasts) by transcervical sampling; along with its non-invasiveness, TRIC exhibits many other advantages such as its usefulness in early pregnancy at 5 weeks of gestation, and no interference by various fetal and maternal factors. Moreover, the trophoblast yields from TRIC can provide valuable information about obstetrical complications related to abnormal placentation even before clinical symptoms arise. The standardization of this clinical tool is still under investigation, and the upcoming advancements in TRIC are expected to meet the increasing need for a safe and accurate option for prenatal diagnosis.

Non-invasive prenatal testing for the diagnosis of congenital abnormalities: Insights from a large multicenter study in southern China

Although non-invasive prenatal testing (NIPT) is widely used to detect fetal abnormalities, the results of NIPT vary by population, and data for the screening efficiency of NIPT positive predictive value (PPV) from different populations is limited. Herein, we retrospectively analyzed the NIPT results in a large multicenter study involving 52,855 pregnant women. Depending on gestational age, amniotic fluid or umbilical cord blood was extracted for karyotype and/or chromosome microarray analysis (CMA) in NIPT-positive patients, and the PPV and follow-up data were evaluated to determine its clinical value. Among the 52,855 cases, 754 were NIPT-positive, with a positivity rate of 1.4%. Karyotype analysis and/or CMA confirmed 323 chromosomal abnormalities, with a PPV of 45.1%. PPV for trisomy 21 (T21), trisomy 18 (T18), trisomy 13 (T13), sex chromosomal aneuploidies (SCAs), and copy number variations (CNVs) were 78.9, 35.3, 22.2, 36.9, and 32.9%, respectively. The PPVs for T21, T18, and T13 increased with age, whereas the PPVs for SCAs and CNVs had little correlation with age. The PPV was significantly higher in patients with advanced age and abnormal ultrasound. The NIPT results are affected by population characteristics. NIPT had a high PPV for T21 and a low PPV for T13 and T18, and screening for SCAs and CNVs showed clinical significance in southern China.

Position statement from the International Society for Prenatal Diagnosis on the use of non-invasive prenatal testing for the detection of fetal chromosomal conditions in singleton pregnancies

What is already known about this topic?

What does this study add?

Clinical application of noninvasive prenatal testing in twin pregnancies: a single-center experience

OBJECTIVES

To evaluate the clinical efficiency of noninvasive prenatal testing (NIPT) for fetal chromosomal aneuploidy screening in twin pregnancies.

METHODS

A total of 1650 women with twin pregnancies were enrolled in the study, which underwent NIPT at the Southwest Hospital, Army Medical University, Chongqing, China from January 2013 to June 2022. Fetal karyotyping analysis was conducted in high-risk patients, with subsequent follow-up on pregnancy outcomes.

RESULTS

In 1650 pregnancies, NIPT results showed ten cases of the fetal chromosome aneuploidy, of which six cases were true positive and four cases were false positive. The sensitivity, specificity, positive predictive value (PPV), and false-positive rate (FPR) of trisomy 21 were 100%, 99.79%, 57.14%, and 0.18%, respectively. Sensitivity, specificity, PPV, and FPR of trisomy 18 were 100%, 99.94%, 50%, and 0.06%, respectively. The sensitivity, specificity, PPV, and FPR of trisomy 13 were 100%, 100%, 100%, and 0%, respectively. No false negatives were detected and the negative predictive value (NPV) was 100% of the total. Eleven pregnancies failed the NIPT test with no-call due to the low fetal fraction (< 4%).

CONCLUSIONS

NIPT is a high-performing routine primary prenatal screening test in twin pregnancies, with high sensitivity and specificity in screening for fetal aneuploidy.

Combined fetal fraction to analyze the Z-score accuracy of noninvasive prenatal testing for fetal trisomies 13, 18, and 21

OBJECTIVE

This study aims to evaluate the correlation combined fetal fraction and Z-score for fetal trisomies 13, 18, and 21 of NIPT by the semiconductor sequencing platform and further analyze the differences of different sequencing depths.

METHODS

A cohort of 61,581 pregnancies were recruited for NIPT. Invasive prenatal diagnostic confirmation is recommended in all high-risk NIPT cases. Logistic regression and rank correlation analysis were applied to analyze the relationship between different parameters. ROC curve analysis was adopted to analyze the cutoff values of Z-score and fetal fraction.

RESULTS

A total of 278 common trisomy pregnancies were verified in 377 NIPT-positive results. The fitted logistic regression models revealed that Z-scores of NIPT-positive results were significantly associated with PPVs (p < 0.05). The ROC curve analysis showed that the optimal cutoff value of Z-scores for T21, T18, and T13 was 7.597, 4.944, and 9.135 for NIPT and 9.489, 8.004, and 12.4 for NIPT-plus. If combing fetal fraction as another evaluation factor, the PPV of trisomy 21 gradually improved. We analyzed the correlation between the fetal fraction and the PPV, which revealed that the fetal fraction was significantly correlated with PPV. By analyzing the PPV of different groups divided by the associated criteria obtained from ROC curve, the PPV of high Z-score and high fetal fraction is higher in groups of Z-score > the optimal cutoff value.

CONCLUSION

The results of this study show that the fetal fraction is significantly correlated with the PPV. Combining fetal fraction with Z-score is significantly better than in groups of Z-score-associated criteria; clinicians can give more accurate and efficient prenatal genetic counseling.

Non-invasive fetal genotyping for maternal alleles with droplet digital PCR: A comparative study of analytical approaches

OBJECTIVES

To develop a flexible droplet digital PCR (ddPCR) workflow to perform non-invasive prenatal diagnosis via relative mutation dosage (RMD) for maternal pathogenic variants with a range of inheritance patterns, and to compare the accuracy of multiple analytical approaches.

METHODS

Cell free DNA (cfDNA) was tested from 124 archived maternal plasma samples: 88 cases for sickle cell disease and 36 for rare Mendelian conditions. Three analytical methods were compared: sequential probability ratio testing (SPRT), Bayesian and z-score analyses.

RESULTS

The SPRT, Bayesian and z-score analyses performed similarly well with correct prediction rates of 96%, 97% and 98%, respectively. However, there were high rates of inconclusive results for each cohort, particularly for z-score analysis which was 31% overall. Two samples were incorrectly classified by all three analytical methods; a false negative result predicted for a fetus affected with sickle cell disease and a false positive result predicting the presence of an X-linked IDS variant in an unaffected fetus.

CONCLUSIONS

ddPCR can be applied to RMD for diverse conditions and inheritance patterns, but all methods carry a small risk of erroneous results. Further evaluation is required both to reduce the rate of inconclusive results and explore discordant results in more detail.

Comparison of Single Molecule, Real-Time Sequencing and Nanopore Sequencing for Analysis of the Size, End-Motif, and Tissue-of-Origin of Long Cell-Free DNA in Plasma

BACKGROUND

Recent studies using single molecule, real-time (SMRT) sequencing revealed a substantial population of analyzable long cell-free DNA (cfDNA) in plasma. Potential clinical utilities of such long cfDNA in pregnancy and cancer have been demonstrated. However, the performance of different long-read sequencing platforms for the analysis of long cfDNA remains unknown.

METHODS

Size biases of SMRT sequencing by Pacific Biosciences (PacBio) and nanopore sequencing by Oxford Nanopore Technologies (ONT) were evaluated using artificial mixtures of sonicated human and mouse DNA of different sizes. cfDNA from plasma samples of pregnant women at different trimesters, hepatitis B carriers, and patients with hepatocellular carcinoma were sequenced with the 2 platforms.

RESULTS

Both platforms showed biases to sequence longer (1500 bp vs 200 bp) DNA fragments, with PacBio showing a stronger bias (5-fold overrepresentation of long fragments vs 2-fold in ONT). Percentages of cfDNA fragments 500 bp were around 6-fold higher in PacBio compared with ONT. End motif profiles of cfDNA from PacBio and ONT were similar, yet exhibited platform-dependent patterns. Tissue-of-origin analysis based on single-molecule methylation patterns showed comparable performance on both platforms.

CONCLUSIONS

SMRT sequencing generated data with higher percentages of long cfDNA compared with nanopore sequencing. Yet, a higher number of long cfDNA fragments eligible for the tissue-of-origin analysis could be obtained from nanopore sequencing due to its much higher throughput. When analyzing the size and end motif of cfDNA, one should be aware of the analytical characteristics and possible biases of the sequencing platforms being used.

Genetics in prenatal diagnosis

The options for prenatal genetic testing have evolved rapidly in the past decade, and advances in sequencing technology now allow genetic diagnoses to be made down to the single-base-pair level, even before the birth of the child. This offers women the opportunity to obtain information regarding the foetus, thereby empowering them to make informed decisions about their pregnancy. As genetic testing becomes increasingly available to women, clinician knowledge and awareness of the options available to women is of great importance. Additionally, comprehensive pretest and posttest genetic counselling about the advantages, pitfalls and limitations of genetic testing should be provided to all women. This review article aims to cover the range of genetic tests currently available in prenatal screening and diagnosis, their current applications and limitations in clinical practice as well as what the future holds for prenatal genetics.

Synthesis of positive plasmas with known chromosomal abnormalities for validation of non-invasive prenatal screening

Non-invasive prenatal screening (NIPS) is a DNA sequencing-based screening test for fetal aneuploidies and possibly other pathogenic genomic abnormalities, such as large deletions and duplications. Validation and quality assurance (QA) of this clinical test using plasmas with and without targeted chromosomal abnormalities from pregnant women as negative and positive controls are required. However, the positive plasma controls may not be available for many laboratories that are planning to establish NIPS. Limited synthetic positive plasmas are commercially available, but the types of abnormalities and the number/quantity of synthetic plasmas for each abnormality are insufficient to meet the minimal requirements for the initial validation. We report here a method of making synthetic positive plasmas by adding cell-free DNA (cfDNA) isolated from culture media of prenatal cells with chromosomal abnormalities to the plasmas from non-pregnant women. Thirty-eight positive plasmas with various chromosomal abnormalities, including autosomal and sex chromosomal aneuploidies, large deletions and duplications, were synthesized. The synthetic plasmas were characterized side-by-side with real positive plasmas from pregnant women and commercially available synthetic positive plasmas using the Illumina VeriSeq NIPT v2 system. All chromosomal abnormalities in the synthetic plasmas were correctly identified with the same testing sensitivity and specificity as in the real and commercial synthetic plasmas. The findings demonstrate that the synthetic positive plasmas are excellent alternatives of real positive plasmas for validation and QA of NIPS. The method described here is simple and straightforward, and can be readily used in clinical genetics laboratories with accessibility to prenatal cultures.

Focus on the frontier issue: progress in noninvasive prenatal screening for fetal trisomy from clinical perspectives

The discovery of cell-free fetal DNA (cffDNA) in maternal blood and the rapid development of massively parallel sequencing have revolutionized prenatal testing from invasive to noninvasive. Noninvasive prenatal screening (NIPS) based on cffDNA enables the detection of fetal trisomy through sequencing, comparison, and bioassays. Its accuracy is better than that of traditional screening methods, and it is the most advanced clinical application of high-throughput sequencing technologies. However, the existing sequencing methods are limited by high costs and complex sequencing procedures. These limitations restrict the availability of NIPS for pregnant women. Many amplification methods have been developed to overcome the limitations of sequencing methods. The rapid development of non-sequencing methods has not been accompanied by reviews to summarize them. In this review, we initially describe the detection principles for sequencing-based NIPS. We summarize the rapidly evolving amplification technologies, focusing on the need to reduce costs and simplify the procedures. To ensure that the testing systems are feasible and that the testing processes are reliable, we expand our vision to the clinic. We evaluate the clinical validity of NIPS in terms of sensitivity, specificity, and positive predictive value. Finally, we summarize the application guidelines and discuss the corresponding quality control methods for NIPS. In addition to cffDNA, extracellular vesicle DNA, RNA, protein/peptide, and fetal cells can also be detected as biomarkers of NIPS. With the development of prenatal testing, NIPS has become increasingly important. Notably, NIPS is a screening test instead of a diagnostic test. The testing methods and procedures used in the NIPS process require standardization.

Noninvasive Prenatal Screening for Common Fetal Aneuploidies Using Single-Molecule Sequencing

Amplification biases caused by next-generation sequencing (NGS) for noninvasive prenatal screening (NIPS) may be reduced using single-molecule sequencing (SMS), during which PCR is omitted. Therefore, the performance of SMS-based NIPS was evaluated. We used SMS-based NIPS to screen for common fetal aneuploidies in 477 pregnant women. The sensitivity, specificity, positive predictive value, and negative predictive value were estimated. The GC-induced bias was compared between the SMS- and NGS-based NIPS methods. Notably, a sensitivity of 100% was achieved for fetal trisomy 13 (T13), trisomy 18 (T18), and trisomy 21 (T21). The positive predictive value was 46.15% for T13, 96.77% for T18, and 99.07% for T21. The overall specificity was 100% (334/334). Compared with NGS, SMS (without PCR) had less GC bias, a better distinction between T21 or T18 and euploidies, and better diagnostic performance. Overall, our results suggest that SMS improves the performance of NIPS for common fetal aneuploidies by reducing the GC bias introduced during library preparation and sequencing.

Maternal and fetal factors influencing fetal fraction: A retrospective analysis of 153,306 pregnant women undergoing noninvasive prenatal screening

Background

Genetic factors are important causes of birth defects. Noninvasive prenatal screening (NIPS) is widely used for prenatal screening of trisomy 21, trisomy 18, and trisomy 13, which are the three most common fetal aneuploidies. Fetal fraction refers to the proportion of cell-free fetal DNA in maternal plasma, which can influence the accuracy of NIPS. Elucidating the factors that influence fetal fraction can provide guidance for the interpretation of NIPS results and genetic counseling. However, there is currently no broad consensus on the known factors that influence fetal fraction.

Objective

The study aimed to explore the maternal and fetal factors influencing fetal fraction.

Methods

A total of 153,306 singleton pregnant women who underwent NIPS were included. Data on gestational age; maternal age; body mass index (BMI); z-scores for chromosomes 21, 18, and 13; and fetal fraction in NIPS were collected from the study population, and the relationships between fetal fraction and these factors were examined. The relationship between fetal fraction and different fetal trisomy types was also analyzed.

Results

The results showed that the median gestational age, maternal age, and BMI of the pregnant women were 18 (16, 20) weeks, 29 (25, 32) years, and 22.19 (20.40, 24.24) kg/m², respectively. The median fetal fraction was 11.62 (8.96, 14.7)%. Fetal fraction increased with gestational age and decreased with maternal age and BMI (P < 0.001). Fetal fraction of fetuses with trisomies 21, 18, and 13 was similar to that of the NIPS-negative group. The z-scores of pregnant women with trisomy 21 and 18 fetuses were positively correlated with fetal fraction, but not with that of the trisomy 13 cases.

Conclusions

The factors that influence fetal fraction need to be taken into consideration before NIPS for quality control and after NIPS for result interpretation.

Clinical impacts of genome-wide noninvasive prenatal testing for rare autosomal trisomy

BACKGROUND

Genome-wide noninvasive prenatal testing identifies several rare autosomal trisomies in the general obstetrical population, but its use is questioned by its low positive predictive value. Furthermore, the origin of rare autosomal trisomies and the clinical effect of reporting them has not been sufficiently investigated. In addition, professional societies express their need for data assessing the clinical use of genome-wide noninvasive prenatal testing for rare autosomal trisomies for years.

OBJECTIVE

This study aimed to investigate the origin of rare autosomal trisomies and the clinical effect of disclosing rare autosomal trisomies in clinical settings.

STUDY DESIGN

Women who received noninvasive prenatal testing between March 2021 and March 2022 were prospectively enrolled. Clinical follow-up and cytogenetic and molecular investigations were performed. Posthoc analysis was performed to investigate the association between placental mosaicism and clinical outcomes.

RESULTS

Overall, 154 rare autosomal trisomies were identified in 89,242 pregnancies (0.17%) through noninvasive prenatal testing. In the 120 cases in which cytogenetic and molecular investigations were carried out, the rare autosomal trisomies were found to originate from true fetal mosaicism (n=5), uniparental disomy (n=5), maternal mosaic trisomy (n=3), maternal malignancy (n=1), and confined placental mosaicism (n=106). Clinical follow-up showed that 40% of all rare autosomal trisomy cases had adverse perinatal outcomes. In women with false-positive noninvasive prenatal testing results originating from confined placental mosaicism, the frequency of adverse perinatal outcomes was 26%. More importantly, the placental mosaicism ratio revealed by noninvasive prenatal testing was significantly higher in women who experienced adverse perinatal outcomes than those who did not (0.688 vs 0.332; P<.001).

CONCLUSION

Women with noninvasive prenatal testing results indicative of rare autosomal trisomies are at risk of adverse perinatal outcomes, and that risk can be stratified using chromosomes and the mosaicism ratio revealed by noninvasive prenatal testing. Our data are valuable for obstetrical caregivers advising a patient with a noninvasive prenatal testing result indicative of a rare autosomal trisomy and a false-positive diagnosis and for managing risks during pregnancy.

Rare autosomal trisomies detected by non-invasive prenatal testing: an overview of current knowledge

Non-invasive prenatal testing has been introduced for the detection of Trisomy 13, 18, and 21. Using genome-wide screening also other "rare" autosomal trisomies (RATs) can be detected with a frequency about half the frequency of the common trisomies in the large population-based studies. Large prospective studies and clear clinical guidelines are lacking to provide adequate counseling and management to those who are confronted with a RAT as a healthcare professional or patient. In this review we reviewed the current knowledge of the most common RATs. We compiled clinical relevant parameters such as incidence, meiotic or mitotic origin, the risk of fetal (mosaic) aneuploidy, clinical manifestations of fetal mosaicism for a RAT, the effect of confined placental mosaicism on placental function and the risk of uniparental disomy (UPD). Finally, we identified gaps in the knowledge on RATs and highlight areas of future research. This overview may serve as a first guide for prenatal management for each of these RATs.

Positive predictive values and outcomes for uninformative cell-free DNA tests: An Italian multicentric Cytogenetic and cytogenomic Audit of diagnOstic testing (ICARO study)

OBJECTIVES

To establish the positive predictive values (PPV) of cfDNA testing based on data from a nationwide survey of independent clinical cytogenetics laboratories.

METHODS

Prenatal diagnostic test results obtained by Italian laboratories between 2013 and March 2020 were compiled for women with positive non-invasive prenatal tests (NIPT), without an NIPT result, and cases where there was sex discordancy between the NIPT and ultrasound. PPV and other summary data were reviewed.

RESULTS

Diagnostic test results were collected for 1327 women with a positive NIPT. The highest PPVs were for Trisomy (T) 21 (624/671, 93%) and XYY (26/27, 96.3%), while rare autosomal trisomies (9/47, 19.1%) and recurrent microdeletions (8/55, 14.5%) had the lowest PPVs. PPVs for T21, T18, and T13 were significantly higher when diagnostic confirmation was carried out on chorionic villi (97.5%) compared to amniotic fluid (89.5%) (p < 0.001). In 19/139 (13.9%), of no result cases, a cytogenetic abnormality was detected. Follow-up genetic testing provided explanations for 3/6 cases with a fetal sex discordancy between NIPT and ultrasound.

CONCLUSIONS

NIPT PPVs differ across the conditions screened and the tissues studied in diagnostic testing. This variability, issues associated with fetal sex discordancy, and no results, illustrate the importance of pre- and post-test counselling.

Whole-Chromosome Karyotyping of Fetal Nucleated Red Blood Cells Using the Ion Proton Sequencing Platform

The current gold standard for the definitive diagnosis of fetal aneuploidy uses either chorionic villus sampling (CVS) or amniocentesis, both of which are which are invasive procedures carrying a procedure-related risk of miscarriage of up to 0.1-0.2%. Non-invasive prenatal diagnosis using fetal nucleated red blood cells (FNRBCs) isolated from maternal peripheral venous blood would remove this risk of miscarriage since these cells can be isolated from the mother's blood. We aimed to detect whole-chromosome aneuploidies from single nucleated fetal red blood cells using whole-genome amplification followed by massively parallel sequencing performed on a semiconductor sequencing platform. Twenty-six single cells were picked from the placental villi of twelve patients thought to have a normal fetal genotype and who were undergoing elective first-trimester surgical termination of pregnancy. Following karyotyping, it was subsequently found that two of these cases were also abnormal (one trisomy 15 and one mosaic genotype). One single cell from chorionic villus samples for two patients carrying a fetus with trisomy 21 and two single cells from women carrying fetuses with T18 were also picked. Pooled libraries were sequenced on the Ion Proton and data were analysed using Ion Reporter software. We correctly classified fetal genotype in all 24 normal cells, as well as the 2 T21 cells, the 2 T18 cells, and the two T15 cells. The two cells picked from the fetus with a mosaic result by CVS were classified as unaffected, suggesting that this was a case of confined placental mosaicism. Fetal sex was correctly assigned in all cases. We demonstrated that semiconductor sequencing using commercially available software for data analysis can be achieved for the non-invasive prenatal diagnosis of whole-chromosome aneuploidy with 100% accuracy.

Combined Model-Based Prediction for Non-Invasive Prenatal Screening

The risk of chromosomal abnormalities in the child increases with increasing maternal age. Although non-invasive prenatal testing (NIPT) is a safe and effective prenatal screening method, the accuracy of the test results needs to be improved owing to various testing conditions. We attempted to achieve a more accurate and robust prediction of chromosomal abnormalities by combining multiple methods. Here, three different methods, namely standard Z-score, normalized chromosome value, and within-sample reference bin, were used for 1698 reference and 109 test samples of whole-genome sequencing. The logistic regression model combining the three methods achieved a higher accuracy than any single method. In conclusion, the proposed method offers a promising approach for increasing the reliability of NIPT.

Development and performance evaluation of an artificial intelligence algorithm using cell-free DNA fragment distance for non-invasive prenatal testing (aiD-NIPT)

With advances in next-generation sequencing technology, non-invasive prenatal testing (NIPT) has been widely implemented to detect fetal aneuploidies, including trisomy 21, 18, and 13 (T21, T18, and T13). Most NIPT methods use cell-free DNA (cfDNA) fragment count (FC) in maternal blood. In this study, we developed a novel NIPT method using cfDNA fragment distance (FD) and convolutional neural network-based artificial intelligence algorithm (aiD-NIPT). Four types of aiD-NIPT algorithm (mean, median, interquartile range, and its ensemble) were developed using 2,215 samples. In an analysis of 17,678 clinical samples, all algorithms showed &gt;99.40% accuracy for T21/T18/T13, and the ensemble algorithm showed the best performance (sensitivity: 99.07%, positive predictive value (PPV): 88.43%); the FC-based conventional Z-score and normalized chromosomal value showed 98.15% sensitivity, with 40.77% and 36.81% PPV, respectively. In conclusion, FD-based aiD-NIPT was successfully developed, and it showed better performance than FC-based NIPT methods.

Non-invasive Prenatal Testing in Pregnancies Following Assisted Reproduction

In the decade since non-invasive prenatal testing (NIPT) was first implemented as a prenatal screening tool, it has gained recognition for its sensitivity and specificity in the detection of common aneuploidies. This review mainly focuses on the emerging role of NIPT in pregnancies following assisted reproductive technology (ART) in the light of current evidence and recommendations. It also deals with the challenges, shortcomings and interpretational difficulties related to NIPT in ART pregnancies, with particular emphasis on twin and vanishing twin pregnancies, which are widely regarded as the Achilles' heel of most pre-natal screening platforms. Future directions for exploration towards improving the performance and extending the scope of NIPT are also addressed.

Endogenous cell-free DNA in fetal bovine serum introduces artifacts to in vitro cell-free DNA models

Cell-free DNA (cfDNA) is of growing clinical and research significance. In vitro cfDNA models are a useful tool in cfDNA research; however, artifacts in these models may have implications for the interpretation of new and published data. This report aimed to establish how endogenous cfDNA in fetal bovine serum (FBS) may influence in vitro cfDNA measurements. Three commercial cell culture media, supplemented with 10% FBS, were analyzed for the presence of cfDNA, with and without culture with ovarian cancer cell lines. cfDNA from FBS was identified with all three commercial media and contributed a major portion of 167-bp cfDNA. Future studies should account for bovine cfDNA in FBS-supplemented media when conducting in vitro cfDNA research.

A study on the placenta in stillbirth: an evaluation of molecular alterations through next generation sequencing

INTRODUCTION

Placental dysfunction is one of the most common causes of Intrauterine Fetal Demise (IUFD). Due to its characteristics, the placenta may be the target of molecular research aimed to investigate potential causes of IUFD. In the literature, there are no studies on human placentas that have investigated possible associations between somatic mutations and the occurrence of IUFD. The aim of this study was to identify the presence of gene mutations in placental tissues in a series of cases of IUFD and to evaluate potential correlations with placental microscopic findings.

MATERIALS AND METHODS

Thirty-seven samples of formalin-fixed and paraffin-embedded placental tissues were retrospectively selected from pregnancies ending in IUFD between 23rd to 40th week. Six control placentas of physiological pregnancies were included as controls. After sampling, made according to standardized protocol and conventional histopathological examination, placental tissues were subjected to DNA extraction and sequencing by means of Next Generation Sequencing with a 56-gene panel.

RESULTS

The most frequent mutation observed in 32/37 IUFD cases (86.5%) and absent in any of the 6 control placentas was in c-KIT gene, which is implicated in placental tissue differentiation. However, no significant correlation was found between the presence of individual gene mutations and placental histopatological findings.

DISCUSSION

As the present study found an elevated frequency of c-KIT mutation in IUFD, it further supports the hypothesis that c-KIT is involved in abnormal tissue differentiation leading to altered placental vascularization and function.

Genetic deconvolution of fetal and maternal cell-free DNA in maternal plasma enables next-generation non-invasive prenatal screening

Current non-invasive prenatal screening (NIPS) analyzes circulating fetal cell-free DNA (cfDNA) in maternal peripheral blood for selected aneuploidies or microdeletion/duplication syndromes. Many genetic disorders are refractory to NIPS largely because the maternal genetic material constitutes most of the total cfDNA present in the maternal plasma, which hinders the detection of fetus-specific genetic variants. Here, we developed an innovative sequencing method, termed coordinative allele-aware target enrichment sequencing (COATE-seq), followed by multidimensional genomic analyses of sequencing read depth, allelic fraction, and linked single nucleotide polymorphisms, to accurately separate the fetal genome from the maternal background. Analytical confounders including multiple gestations, maternal copy number variations, and absence of heterozygosity were successfully recognized and precluded for fetal variant analyses. In addition, fetus-specific genomic characteristics, including the cfDNA fragment length, meiotic error origins, meiotic recombination, and recombination breakpoints were identified which reinforced the fetal variant assessment. In 1129 qualified pregnancies tested, 54 fetal aneuploidies, 8 microdeletions/microduplications, and 8 monogenic variants were detected with 100% sensitivity and 99.3% specificity. Using the comprehensive cfDNA genomic analysis tools developed, we found that 60.3% of aneuploidy samples had aberrant meiotic recombination providing important insights into the mechanism underlying meiotic nondisjunctions. Altogether, we show that the genetic deconvolution of the fetal and maternal cfDNA enables thorough and accurate delineation of fetal genome which paves the way for the next-generation prenatal screening of essentially all types of human genetic disorders.