Rapid methods for targeted prenatal diagnosis of common chromosome aneuploidies

Privacy and ethical challenges of the Amelogenin sex test in forensic paternity/kinship analysis: Insights from a 13-year case history

The Amelogenin sex test included in forensic DNA typing kits has the potential to identify congenital conditions such as differences/disorders of sex development (DSD). It can also reveal mismatches between genotypic sex and gender marker in identity documents of transgender persons who obtained legal gender recognition. In a 13-year case history of paternity/kinship tests, involving n = 962 females and n = 1001 males, two mismatches between Amelogenin sex test (male) and gender marker (female), and three cases of chromosomal DSD (Klinefelter syndrome) were observed. The concrete risk of observing Amelogenin anomalies, their potential causes, and the context in which they occur (forensic, i.e. non-medical) mean that laboratory operators are called to strike a complex balance between privacy interests and individual health rights when providing preliminary information and reporting Amelogenin incidental findings. This case history argues for the need of a more responsible approach towards the Amelogenin sex test in the forensic community.

Development and validation of a novel 26-plex system for prenatal diagnosis with forensic markers

Short tandem repeat (STR) loci are commonly used in forensic casework, such as personal identification and paternity testing. In recent years, STR has also been widely used for rapid, accurate and automated prenatal diagnosis, known as quantitative fluorescent PCR (QF-PCR). Despite their usefulness, the current systems often lack the power to detect mosaicism for Turner syndrome. In this study, we developed a novel 26-plex system that combined the 22 STRs in chromosome 21/18/13/X, 3 sex loci and 1 quality control marker (TAF9L). The system was generated to achieve greater diagnostic power of trisomy 21/18/13 and sex chromosome abnormalities. Studies of the sensitivity, specificity, stability and accuracy were performed according to the Scientific Working Group on DNA Analysis Methods (SWGDAM) guidelines. Compared with the results of the chromosomal microarray analysis (CMA)/copy number variation sequencing (CNV-seq), the detection ratio of non-mosaic chromosome abnormalities of this system in the identification of chromosome 21/18/13/X/Y aneuploidies reached 100%, and the rate of negative results was consistently 100% based on 203 prenatal diagnosis sample analyses. In addition, our results suggested that this panel was a useful tool for mosaicism for Turner syndrome cases. Interestingly, we found one case with large segment loss of chromosome X, which indicated that we should be alert to this situation when the STR genotype of the parent-child is inconsistent in forensic genetics. In summary, this study demonstrated that our system is an accurate, cost-effective and rapid approach for the detection of chromosome numerical abnormalities in prenatal diagnosis.

Simple and rapid detection of common fetal aneuploidies using peptide nucleic acid probe-based real-time polymerase chain reaction

To examine the detection performance of a peptide nucleic acid (PNA) probe-based real-time time polymerase chain reaction (PCR) assay to detect common aneuploidies. Using amniotic fluid samples, PNA probe based real-time PCR (Patio DEP Detection Kit; SeaSun Biomaterials, Korea) assay was performed. PNA probe was designed to hybridize to similar sequences located on different segments of target chromosomes (21, 18, and 13) and a reference chromosome. Amplification of target sequences and melting curve analysis was performed. When analyzing the melting curve, the ratio of the peak height of the target and reference chromosome was calculated and determined as aneuploidy if the ratio of peak height was abnormal. All the results from the PNA probe-based real-time PCR and melting curve analyses were compared to those from conventional karyotyping. Forty-two cases with common aneuploidies (24 of trisomy 21, 12 of trisomy 18, and 6 of trisomy 13) and 131 cases with normal karyotype were analyzed. When comparing the karyotyping results, the sensitivity and specificity of the PNA probe-based real-time PCR assay were both 100%. The level of agreement was almost perfect (k = 1.00). PNA real-time PCR assay is a rapid and easy method for detecting common aneuploidies.

BDdb: a comprehensive platform for exploration and utilization of birth defect multi-omics data

Background

Birth defects pose a major challenge to infant health. Thus far, however, the causes of most birth defects remain cryptic. Over the past few decades, considerable effort has been expended on disclosing the underlying mechanisms related to birth defects, yielding myriad treatises and data. To meet the increasing requirements for data resources, we developed a freely accessible birth defect multi-omics database (BDdb, http://t21omics.cngb.org) consisting of multi-omics data and potential disease biomarkers.

Results

In total, omics datasets from 136 Gene Expression Omnibus (GEO) Series records, including 5245 samples, as well as 869 biomarkers of 22 birth defects in six different species, were integrated into the BDdb. The database provides a user-friendly interface for searching, browsing, and downloading data of interest. The BDdb also enables users to explore the correlations among different sequencing methods, such as chromatin immunoprecipitation sequencing (ChIP-Seq) and RNA sequencing (RNA-Seq) from different studies, to obtain the information on gene expression patterns from diverse aspects.

Conclusion

To the best of our knowledge, the BDdb is the first comprehensive database associated with birth defects, which should benefit the diagnosis and prevention of birth defects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-021-01110-x.

The Influence of Maternal Cell Contamination on Fetal Aneuploidy Detection Using Chip-Based Digital PCR Testing

Prenatal samples obtained by amniocentesis or chorionic villus sampling are at risk of maternal cell contamination (MCC). In traditional prenatal analysis, MCC is recommended to be assayed by special tests, such as the short tandem repeat analysis and, if detected at a high level, may result in failed analysis report. The objective of this study was to test the ability of chip-based digital PCR to detect fetal aneuploidies in the presence of MCC. To determine the level of accuracy of MCC detection, an aneuploid male sample was subjected to serial dilution with an euploid female sample. DNA was extracted from prenatal samples and analyzed with QuantStudio 3D Digital PCR. Digital PCR analysis allowed the detection of trisomy 21, trisomy 18, and X monosomy accurately in samples with 90%, 85%, and 92% of MCC, respectively. Moreover, our results indicated that digital PCR was able to accurately confirm the presence of Y chromosome at up to 95% contamination. The amniotic fluid and chorionic villus sampling (CVS) received in our clinical laboratory was subjected to further analysis of MCC based on the aneuploidy assessment algorithm, resulting in the identification of 10 contaminated samples and four cases of true fetal mosaicism. We conclude that chip-based digital PCR analysis enables the detection of fetal aneuploidy with high levels of accuracy, even in cases of significant MCC. Importantly, the algorithm eliminates the need for maternal DNA and additional MCC tests, which reduces costs and simplifies the diagnostic procedure. The method is easy to set up and suitable for routine clinical practice.

Chip-Based Digital PCR Approach Provides A Sensitive and Cost-Effective Single-Day Screening Tool for Common Fetal Aneuploidies-A Proof of Concept Study

In the prenatal period, the copy number aberrations of chromosomes 13, 18, 21, X and Y account for over 80% of the clinically significant chromosome abnormalities. Classical cytogenetic analysis is the gold standard in invasive prenatal diagnostics but the long test waiting time affects its clinical utility. Several molecular rapid tests have been developed and employed in clinical practice, however all have substantial drawbacks. The aim of the study was to design and evaluate an optimized tool for rapid molecular detection of fetal aneuploidies. We established a novel single-day method using a chip-based platform, the QuantStudio 3D Digital PCR system. In order to assess the clinical usefulness of our screening test, we analyzed 133 prenatal samples. The difference in distributions of euploid and aneuploid samples identified the ploidy of each of the target chromosomes with high precision. The distribution of the chromosome ratio for euploid and aneuploid samples showed a statistically significant result (p = 0.003 for trisomy 13, p = 0.001 for trisomies 18 and 21, Mann–Whitney U test). Our results suggest that this novel chip-based approach provides a tool for rapid, technically simple, cost-effective screening for common fetal aneuploidies.

BACs-on-Beads™ assay, a rapid aneuploidy test, improves the diagnostic yield of conventional karyotyping

BACs-on-Beads (BoBs™) assay is a rapid aneuploidy test (RAT) that detects numerical chromosomal aneuploidies and multiple microdeletion/microduplication syndromes. This study was conducted to appraise the usefulness of the BoB™ assay as a complementary diagnostic tool to conventional karyotyping for the rapid detection of chromosomal aneuploidies. A total of 485 prenatal (amniotic fluid and chorionic villi) and blood/products of conception samples were collected between July 2013 and August 2018, and analyzed by the BoBs™ assay and cytogenetic karyotyping and further validated by fluorescence in situ hybridization (FISH). Forty-three of 484 qualifying samples (8.9%) were identified as abnormal by the BoBs™ assay. The assay was comparable to karyotyping in the detection of common structural abnormalities (trisomy 21, trisomy 18, X, and Y), with a sensitivity of 96.0% and a specificity of 100%. BoBs™ assay detected 20 microdeletion and microduplication syndromes that were missed by karyotyping. BoBs™, however, missed 10 cases of polyploidies and chromosomal rearrangements which were identified by conventional karyotyping. Our findings suggest that BoBs™ is a reliable RAT which is suitable in combination with conventional karyotyping for the detection of common aneuploidies. The assay also improves the diagnostic yield by recognizing clinically relevant submicroscopic copy number gains and losses.

Comparison of quantitative fluorescent polymerase chain reaction and karyotype analysis for prenatal screening of chromosomal aneuploidies in 270 amniotic fluid samples

Background Quantitative fluorescent polymerase chain reaction (QF-PCR) technique is a rapid prenatal aneuploidy detection method. This method can diagnose abnormality in chromosome 13, 18, 21, X and Y. Karyotyping is a technique in which, by the process of pairing and painting, all the chromosomes of an organism are displayed under a microscope. In the present study, a statistical comparison was made between karyotyping and QF-PCR for prenatal diagnosis. Methods A total of 270 samples were tested for QF-PCR and the results were compared with karyotyping. We also investigated heterozygosity of short tandem repeat (STR) markers by QF-PCR. Deoxyribonucleic acid (DNA) samples (n = 270) were extracted from amniotic fluid (AF) cells. After PCR amplifications, analysis was performed using GeneMarker. A Devyser QF-PCR kit containing 26 primers was used to estimate the observed heterozygosity of STR markers located on chromosome 13, 18, 21, X and Y. Results The results of karyotyping and QF-PCR were as follows: trisomy 13 (one case), trisomy 18 (five cases), trisomy 21 (five cases) and triploidy (one case). Chromosomal rearrangements and mosaicisms were not detected by QF-PCR but were detected by karyotyping. Maternal cell contamination (MCC) made the karyotyping fail but not the QF-PCR. Conclusion The QF-PCR method is especially important because it is fast, accurate, low cost and has a short turnaround time. This method will avoid ambiguity of karyotype results and parental anxiety. It will also shorten clinical management for high-risk families.

Satellite DNA at the Centromere is Dispensable for Segregation Fidelity

The typical vertebrate centromeres contain long stretches of highly repeated DNA sequences (satellite DNA). We previously demonstrated that the karyotypes of the species belonging to the genus Equus are characterized by the presence of satellite-free and satellite-based centromeres and represent a unique biological model for the study of centromere organization and behavior. Using horse primary fibroblasts cultured in vitro, we compared the segregation fidelity of chromosome 11, whose centromere is satellite-free, with that of chromosome 13, which has similar size and a centromere containing long stretches of satellite DNA. The mitotic stability of the two chromosomes was compared under normal conditions and under mitotic stress induced by the spindle inhibitor, nocodazole. Two independent molecular-cytogenetic approaches were used—the interphase aneuploidy analysis and the cytokinesis-block micronucleus assay. Both assays were coupled to fluorescence in situ hybridization with chromosome specific probes in order to identify chromosome 11 and chromosome 13, respectively. In addition, we tested if the lack of centromeric satellite DNA affected chromatid cohesion under normal and stress conditions. We demonstrated that, in our system, the segregation fidelity of a chromosome is not influenced by the presence of long stretches of tandem repeats at its centromere. To our knowledge, the present study is the first analysis of the mitotic behavior of a natural satellite-free centromere.

Validation of QF-PCR for prenatal diagnoses in a Brazilian population

OBJECTIVES:

Quantitative fluorescence polymerase chain reaction (QF-PCR) is a rapid and reliable method for screening aneuploidies, but in Brazil, it is not used in public services. We investigated the accuracy of QF-PCR for the prenatal recognition of common aneuploidies and compared these results with cytogenetic results in our laboratory.

METHOD:

A ChromoQuant QF-PCR kit containing 24 primer pairs targeting loci on chromosomes 21, 13, 18, X and Y was employed to identify aneuploidies of the referred chromosomes.

RESULTS:

A total of 162 amniotic fluid samples analyzed using multiplex QF-PCR were compared with karyotyping analysis. The QF-PCR results were consistent with the results of cytogenetic analysis in 95.4% of all samples.

CONCLUSION:

QF-PCR was demonstrated to be efficient and reliable for prenatal aneuploidy screening. This study suggests that QF-PCR can be used as a rapid diagnostic method. However, rearrangements and some mosaic samples cannot be detected with this test; thus, those exceptions must undergo cytogenetic analysis.

Rapid and simultaneous detection of common aneuploidies by quadruplex real-time polymerase chain reaction combined with melting curve analysis

BACKGROUND

During the prenatal period, the number variation of chromosomes 13, 18, 21, X and Y accounts for more than 80% of the clinically significant chromosomal abnormalities diagnosed. Rapid tests for prenatal diagnosis of these abnormalities can improve pregnancy management and alleviate parental anxiety. Here, we present a molecular alternative method for detecting common aneuploidies.

METHODS

This method is based on co-amplification of segmental duplications located on two different chromosomes using a single pair of primers. Segmental duplications have a high degree of sequence identity, but have single-nucleotide differences in some regions. These sequence differences can be quantified using melting curve analysis of dual-labeled probes to estimate the relative dosages of different chromosomes. We designed two quadruplex real-time PCR assays to detect aneuploidies of chromosomes 13, 18, 21, X and Y.

RESULTS

We examined 75 aneuploid DNA samples and 56 unaffected DNA control samples using these two assays and correctly identified all samples. Four cases of unbalanced translocation were also accurately detected. The observed averaged ratio for each chromosomal disorder was similar to the theoretically expected value.

CONCLUSIONS

Our real-time assay is a robust, rapid, and easy to conduct technique for prenatal diagnosis of common aneuploidies, representing a competitive alternative for use in diagnostic laboratories.

Maternal Plasma DNA and RNA Sequencing for Prenatal Testing

Cell-free DNA (cfDNA) testing has recently become indispensable in diagnostic testing and screening. In the prenatal setting, this type of testing is often called noninvasive prenatal testing (NIPT). With a number of techniques, using either next-generation sequencing or single nucleotide polymorphism-based approaches, fetal cfDNA in maternal plasma can be analyzed to screen for rhesus D genotype, common chromosomal aneuploidies, and increasingly for testing other conditions, including monogenic disorders. With regard to screening for common aneuploidies, challenges arise when implementing NIPT in current prenatal settings. Depending on the method used (targeted or nontargeted), chromosomal anomalies other than trisomy 21, 18, or 13 can be detected, either of fetal or maternal origin, also referred to as unsolicited or incidental findings. For various biological reasons, there is a small chance of having either a false-positive or false-negative NIPT result, or no result, also referred to as a "no-call." Both pre- and posttest counseling for NIPT should include discussing potential discrepancies. Since NIPT remains a screening test, a positive NIPT result should be confirmed by invasive diagnostic testing (either by chorionic villus biopsy or by amniocentesis). As the scope of NIPT is widening, professional guidelines need to discuss the ethics of what to offer and how to offer. In this review, we discuss the current biochemical, clinical, and ethical challenges of cfDNA testing in the prenatal setting and its future perspectives including novel applications that target RNA instead of DNA.

Prenatal diagnosis of fetuses with increased nuchal translucency using an approach based on quantitative fluorescent polymerase chain reaction and genomic microarray

OBJECTIVE

To assess the clinical value of prenatal diagnosis of fetuses with increased nuchal translucency (NT) using an approach based on quantitative fluorescent polymerase chain reaction (QF-PCR) and chromosomal microarray (CMA).

STUDY DESIGN

From January 2013 to October 2014, we included 175 pregnancies with fetal NT ≥ 3.5mm at 11-13 weeks' gestation who received chorionic villus sampling. QF-PCR was first used to rapidly detect common aneuploidies. The cases with a normal QF-PCR result were analyzed by CMA.

RESULTS

Of the 175 cases, common aneuploidies were detected by QF-PCR in 53 (30.2%) cases (30 cases of trisomy 21, 12 cases of monosomy X, 7 cases of trisomy 18, 3 cases of trisomy 13 and 1 case of 47, XXY). Among the 122 cases with a normal QF-PCR result, microarray detected additional pathogenic copy number variants (CNVs) in 5.7% (7/122) of cases. Four cases would have expected to be detectable by conventional karyotyping because of large deletions/duplications (>10 Mb), leaving three cases (2.5%; 3/118) with pathogenic CNVs only detectable by CMA.

CONCLUSION

It is rational to use a diagnostic strategy in which CMA is preceded by the less expensive, rapid, QF-PCR to detect common aneuploidies. CMA allows detection of a number of pathogenic chromosomal aberrations in fetuses with a high NT.

Genetic polymorphisms of short tandem repeat loci D13S305, D13S631 and D13S634 in the Han population of Tianjin, China

Short tandem repeat (STR) markers, also known as microsatellites, are extensively used in mapping studies, forensics and disease diagnosis due to their small dimension and low mutation and high polymorphism rates. In recent years quantitative fluorescence polymerase chain reaction (QF-PCR) has been successfully used to amplify STR markers in the prenatal diagnosis of common chromosomal abnormalities. This method provides a diagnosis of common aneuploidies 24-48 h after sampling with low error rates and cost; however, the size of different alleles, frequency, heterozygosity and distribution of STR markers vary among different populations. In the present study three STR markers, D13S305, D13S631 and D13S634, on chromosome 13 were analyzed in 350 unrelated individuals (200 males and 150 females) from the Han population of Tianjin, China using QF-PCR. Eleven, seven and 11 alleles of each marker were observed, respectively. The frequencies of the genotypes were in good agreement with Hardy-Weinberg equilibrium (P>0.05). The results showed that these three STR markers were highly polymorphic in the Han population of Tianjin, China. The study has provided basic data for use in the prenatal diagnosis of Patau syndrome.

Effects of subtelomeric copy number variations in miscarriages

PURPOSE

This study was performed on miscarriage samples for chromosome analysis to detect copy number variations (CNVs) related to subtelomeric regions, and with these results we aimed to adapt multiplex ligation-dependent probe amplification (MLPA) method for prenatal diagnosis.

MATERIALS AND METHODS

The cell cultures and DNA isolations were performed on 60 miscarriage samples. For maternal contamination analysis, DNA isolations and quantitative fluorescent polymerase chain reactions were done using peripheric blood of mothers who had miscarriages. We compared short tandem repeat peak profiles of miscarriage samples and mothers. The subtelomeric regions of the chromosomes were assessed using the MLPA method.

RESULTS

Of 43 miscarriage samples, 19 had normal karyotype (44.2%), 10 had numerical abnormalities (23.3%), and 2 had structural abnormalities (4.7%). Subtelomeric 16q duplication was determined in 2 of the 30 miscarriage samples investigated with MLPA method (6.6%).

CONCLUSION

There is no statistically significant difference between two groups (p > 0.05). However, the fact that the 6.6% subtelomeric CNV found in miscarriage samples was not found in controls, showed that further studies are required. We recommend that the miscarriage samples of the couples with recurrent miscarriage should be analyzed in terms of subtelomeric CNV after the exclusion of other clinical reasons.

The combined QF-PCR and cytogenetic approach in prenatal diagnosis

In this study, the importance of quantitative fluorescence polymerase chain reaction (QF-PCR) aneuploidy diagnosis test which provides earlier and easier results were discussed. The cell cultures and DNA isolations were performed on 100 amniotic fluids. DNA isolations were made from peripheral blood samples of mothers who had blood-stained amniotic fluid samples. The reasons of references of these pregnant women to our division were increased maternal age, positive double/triple screening test and fetal anomaly history. QF-PCR applied to 19 short tandem repeat markers in the chromosomes 13, 18, 21 and genes X and Y chromosomes. All electropherogram peaks were evaluated on ABI3130. Thirty two (32%) samples have high maternal age, seven (7%) have fetal anomaly and the others have double/triple screening test positivity. Ninety-nine (99%) of the 100 amniotic fluid samples were resulted, but one (1%) of them could not examined because of the culture failure. The maternal contamination rates were determined as 3%. Of 100 samples, 2 had trisomy 21 (2%), 1 had trisomy 13 (1%), 1 had structural abnormalities (1%) and the others (97%) have not any aneuploidy. The results of QF-PCR were in compatible with the results of cell culture and chromosome analysis. Although QF-PCR is an easier and an earlier test, it has a limitation of not to able to scan full genome. It is also sensitive for maternal contamination, so it should be tested together with maternal blood samples. QF-PCR aneuploidy test is the fastest diagnostic test for prenatal diagnosis and so it provides less stressful period for pregnant women.

Chorionic villus sampling for early prenatal diagnosis: Experience at a mainland Chinese hospital

The aim of this study was to describe the experience of transabdominal chorionic villus sampling (CVS) at a mainland Chinese hospital. During a 7-year period, 1,172 pregnant women chose to have CVS for prenatal diagnosis. Details and outcome of all of these cases were reviewed. The median maternal age was 29 years (range 19-45). The median gestational age was 12 weeks (range 10-14). Fetal karyotyping and thalassaemia couples were the main indications (97.2%). Overall, 112 (9.7%) chromosomal abnormalities were identified. There were 91 (7.8%) major chromosomal abnormalities, including autosomal trisomy in 70 patients, sex chromosomal abnormalities in 17, triploidy in two and unbalanced chromosomal rearrangement abnormality in two. Additionally, 137 fetuses with severe thalassaemia syndrome were found, including 86 homozygous β-thalassaemia, and 51 homozygous α-thalassaemia or non-deletional haemoglobin H disease. The procedure failed to obtain an adequate sample in four (0.3%) patients. There were 229 pregnancies terminated for medical indications after CVS. There were three (0.3%) potentially procedure-related fetal losses. CVS is a safe and reliable prenatal diagnostic technique. It should be one of the options available to pregnant women who require prenatal diagnosis.

BACs-on-Beads technology: a reliable test for rapid detection of aneuploidies and microdeletions in prenatal diagnosis

The risk of fetal aneuploidies is usually estimated based on high resolution ultrasound combined with biochemical determination of criterion in maternal blood, with invasive procedures offered to the population at risk. The purpose of this study was to investigate the effectiveness of a new rapid aneuploidy screening test on amniotic fluid (AF) or chorionic villus (CV) samples based on BACs-on-Beads (BoBs) technology and to compare the results with classical karyotyping by Giemsa banding (G-banding) of cultured cells in metaphase as the gold standard technique. The prenatal-BoBs kit was used to study aneuploidies involving chromosomes 13, 18, 21, X, and Y as well as nine microdeletion syndromes in 321 AF and 43 CV samples. G-banding of metaphase cultured cells was performed concomitantly for all prenatal samples. A microarray-based comparative genomic hybridization (aCGH) was also carried out in a subset of samples. Prenatal-BoBs results were widely confirmed by classical karyotyping. Only six karyotype findings were not identified by Prenatal-BoBs, all of them due to the known limitations of the technique. In summary, the BACs-on-Beads technology was an accurate, robust, and efficient method for the rapid diagnosis of common aneuploidies and microdeletion syndromes in prenatal samples.

Microarrays as a diagnostic tool in prenatal screening strategies: ethical reflection

Genomic microarray analysis is increasingly being applied as a prenatal diagnostic tool. Microarrays enable searching the genome at a higher resolution and with higher sensitivity than conventional karyotyping for identifying clinically significant chromosomal abnormalities. As yet, no clear guidelines exist on whether microarrays should be applied prenatally for all indications or only in selected cases such as ultrasound abnormalities, whether a targeted or genome-wide array should be used, and what these should include exactly. In this paper, we present some ethical considerations on the prenatal use of microarrays. There is a strong consensus, at least in Western countries, that the aim of prenatal screening for foetal abnormalities should be understood as facilitating autonomous reproductive choice for prospective parents. The tests offered should be valid and useful to reach that purpose. Against this background, we address several ethical issues raised by the prenatal application of microarrays. First, we argue that the general distinction between a targeted and a genome-wide microarray needs to be scrutinised. Then we examine whether microarrays are 'suitable tests' to serve either a screening or a diagnostic purpose. Given the wide range of findings possibly generated by microarrays, the question arises whether microarrays actually promote or interfere with autonomous reproductive decision-making. Moreover, if variants of unknown clinical significance are identified, this adds to the burden and complexity of reproductive decision-making. We suggest a qualified use of microarrays in the prenatal context.

Women's Attitudes towards the Option to Choose between Karyotyping and Rapid Targeted Testing during Pregnancy

Objectives. Pregnant women, referred because of an increased risk of fetal Down syndrome, who underwent an invasive prenatal procedure were offered a choice between karyotyping and rapid targeted testing. This study aims to assess women's attitudes and experiences towards what option to choose. Methods. A retrospective multicentre survey (2008–2010) was conducted among 1370 women. General questions were asked about decision making issues, followed by personal questions about their experiences in choice making, test preference, influence of others, and possible regrets. Results. In total, 90.1% of the respondents (N = 825) indicated that pregnant women are able to choose, although 33.1% stated that the choice can best be made by a professional. 18.4% indicated that making a choice places a burden on women. In 96.4%, respondents preferred to have the option to choose again in case of a next pregnancy, whereas 2.7% preferred the choice to be made by a professional. Regret was indicated by 1.2%. Decision making was influenced by others in 64.9%. A slightly higher preference for karyotyping was indicated by 52.7% of the respondents. Conclusions. Positive attitudes and experiences were expressed towards the option to choose. Respondents took decisions freely, although sometimes influenced by a partner or a professional, to follow their individual perspectives.

Antenatal diagnosis and management of life-limiting conditions

Whereas structural fetal abnormalities are relatively frequent occurrences, many of these do not impact measurably on future life and/or are amenable to postnatal therapy. A small minority are considered to be potentially lethal or life-limiting. Examples include specific skeletal dysplasias, urinary tract abnormalities - typically those which lead to anhydramnios and pulmonary hypoplasia, some disorders of the central nervous system and trisomies 13 and 18. Without seeking to compile an exhaustive list of such conditions, we discuss the principles and new considerations in relation to antenatal diagnosis and perinatal management of such disorders.

Noninvasive detection of fetal trisomy 21: systematic review and report of quality and outcomes of diagnostic accuracy studies performed between 1997 and 2012

BACKGROUND

Research on noninvasive prenatal testing (NIPT) of fetal trisomy 21 is developing fast. Commercial tests have become available. To provide an up-to-date overview of NIPT of trisomy 21, an evaluation of the methodological quality and outcomes of diagnostic accuracy studies was made.

METHODS

We undertook a systematic review of the literature published between 1997 and 2012 after searching PubMed, using MeSH terms 'RNA', 'DNA' and 'Down Syndrome' in combination with 'cell-free fetal (cff) RNA', 'cffDNA', 'trisomy 21' and 'noninvasive prenatal diagnosis' and searching reference lists of reported literature. From 79 abstracts, 16 studies were included as they evaluated the diagnostic accuracy of a molecular technique for NIPT of trisomy 21, and the test sensitivity and specificity were reported. Meta-analysis could not be performed due to the use of six different molecular techniques and different cutoff points. Diagnostic parameters were derived or calculated, and possible bias and applicability were evaluated utilizing the revised tool for Quality Assessment of Diagnostic Accuracy (QUADAS-2).

RESULTS

Seven of the included studies were recently published in large cohort studies that examined massively parallel sequencing (MPS), with or without pre-selection of chromosomes, and reported sensitivities between 98.58% [95% confidence interval (CI) 95.9-99.5%] and 100% (95% CI 96-100%) and specificities between 97.95% (95% CI 94.1-99.3%) and 100% (95% CI 99.1-100%). None of these seven large studies had an overall low risk of bias and low concerns regarding applicability. MPS with or without pre-selection of chromosomes exhibits an excellent negative predictive value (100%) in conditions with disease odds from 1:1500 to 1:200. However, positive predictive values were lower, even in high-risk pregnancies (19.7-100%). The other nine cohort studies were too small to give precise estimates (number of trisomy 21 cases: ≤25) and were not included in the discussion.

CONCLUSIONS

NIPT of trisomy 21 by MPS with or without pre-selection of chromosomes is promising and likely to replace the prenatal serum screening test that is currently combined with nuchal translucency measurement in the first trimester of pregnancy. Before NIPT can be introduced as a screening test in a social insurance health-care system, more evidence is needed from large prospective diagnostic accuracy studies in first trimester pregnancies. Moreover, we believe further assessment, of whether NIPT can be provided in a cost-effective, timely and equitable manner for every pregnant woman, is required.

The scope of prenatal diagnosis for women at increased risk for aneuploidies: views and preferences of professionals and potential users

The increasing number of prenatal diagnostic tests in prenatal screening strategies, raises the question what tests to offer and why. This qualitative study investigated the views and preferences of professionals and potential users regarding four diagnostic test options for women at increased risk for common aneuploidies. Seven focus group sessions were conducted in The Netherlands between October 2009 and June 2010, with various categories of participants (n = 55): professionals engaged in prenatal testing and potential users of this testing (meaning pregnant women and parents of young children). Participants were invited to mention all pros and cons and their preferences regarding four hypothetical diagnostic test options, presented on vignettes: a standard offer of rapid aneuploidy detection, karyotyping or array comparative genomic hybridization, representing a narrow, traditional and broad test, respectively, and the option of individualised choice. Then, a semi-structured group interview was conducted. The data were analysed by the constant comparative method. Participants identified similar test-specific pros and cons but showed different preferences. Users' opinion on what test to offer as a general policy differed from what they would choose themselves. All participants agreed that in theory, users should be enabled to make an informed choice about what test to apply, but they disagreed about the feasibility of this ideal. Standard narrow testing was favoured for its limiting effects on emotional and organisational burdens; individualised choice was preferred for assuring women's decisive influence. The varying opinions reflect different views on what autonomy in the prenatal screening context means, suggest that a single standard test offer is inadequate and that differentiation will be needed.

Advances in prenatal screening: the ethical dimension

Prenatal screening strategies are undergoing rapid changes owing to the introduction of new testing techniques. The overall tendency is towards broadening the scope of prenatal testing through increasingly sensitive ultrasound scans and genome-wide molecular tests. In addition, non-invasive prenatal diagnosis is likely to be introduced in the near future. These developments raise important ethical questions concerning meaningful reproductive choice, the autonomy rights of future children, equity of access and the proportionality of testing.

Biomarker development for non-invasive prenatal diagnosis of fetal aneuploidies: predictive reliability and potential clinical application

Current non-invasive prenatal diagnosis for fetal aneuploidies is based on biochemical and ultrasound markers and needs to be improved in order to reduce the number of pregnant women subjected to invasive diagnostic procedures. Proteomic technologies allow for new strategies for discovering biomarkers in complex biological fluids in a high-throughput and sensitive manner. Application of advance proteomic tools to profile pathology-specific proteins in maternal plasma obtained from pregnancies with aneuploid fetuses revealed biomarker-candidates that can potentially revolutionize the diagnostic and treatment procedure in favor of better prediction and improved individual outcomes. The current review focuses on studies of maternal peripheral blood using proteomic technologies, describes alterations noted in the presence of fetal aneuploidies and discuss their potential use as biomarkers for non-invasive prenatal diagnosis.