Cell-free fetal DNA: the new tool in fetal medicine

The Potential of cfDNA as Biomarker: Opportunities and Challenges for Neurodegenerative Diseases

Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), and amyotrophic lateral sclerosis (ALS), are characterized by the progressive and gradual degeneration of neurons. The prevalence and rates of these disorders rise significantly with age. As life spans continue to increase in many countries, the number of cases is expected to grow in the foreseeable future. Early and precise diagnosis, along with appropriate surveillance, continues to pose a challenge. The high heterogeneity of neurodegenerative diseases calls for more accurate and definitive biomarkers to improve clinical therapy. Cell-free DNA (cfDNA), including fragmented DNA released into bodily fluids via apoptosis, necrosis, or active secretion, has emerged as a promising non-invasive diagnostic tool for various disorders including neurodegenerative diseases. cfDNA can serve as an indicator of ongoing cellular damage and mortality, including neuronal loss, and may provide valuable insights into disease processes, progression, and therapeutic responses. This review will first cover the key aspects of cfDNA and then examine recent advances in its potential use as a biomarker for neurodegenerative disorders.

Cell-Free Fetal DNA for Prenatal Screening of Aneuploidies and Autosomal Trisomies: A Systematic Review

Aim: This study was aimed at comparing the positive predictive value of a high-risk cell-free fetal DNA test result for sex chromosome aneuploidies (45,X0, 47,XXX, 47,XXY, and 47,XYY) and autosomal trisomies (T21, T18, and T13) with confirmatory tests in singleton pregnancies. Additionally, we identify the main reason for discordant and inconclusive results. Methods: PubMed, Web of Science, and Scopus were searched from 2017 for primary research articles on cell-free fetal DNA testing of autosomal trisomies and sex chromosome aneuploidies in singleton pregnancies. The methodological characteristics and the statistical results of the studies were collected, and the risk of bias was assessed. Results: Fourteen studies were included. Among the autosomal trisomies, T21 had the highest, whereas T13 showed the lowest positive predictive values. As for the sex chromosome aneuploidies, the lowest values were found with 45,X0. Although discordant and inconclusive results were reported inconsistently, false positives were mainly caused by mosaicism, and inconclusive results were mostly secondary to a low fetal DNA fraction. Conclusion: Cell-free fetal DNA is a reliable screening tool for autosomal trisomies. It is also useful for sex chromosome aneuploidies, although the positive predictive values are lower. A positive screening result should be followed with a confirmatory test.

Plasma acellular transcriptome contains Parkinson's disease signatures that can inform clinical diagnosis

We aimed to identify plasma cell-free transcripts (cfRNA) associated with Parkinson's disease (PD) that also have a high predictive value to differentiate PD from healthy controls. Leveraging two independent populations from two different movement disorder centers we identified 2,188 differentially expressed cfRNAs after meta-analysis. The identified transcripts were enriched in PD relevant pathways, such as PD (p=9.26×10-4), ubiquitin-mediated proteolysis (p=7.41×10-5) and endocytosis (p=4.21×10-6). Utilizing in-house and publicly available brain, whole blood, and acellular plasma transcriptomic and proteomic PD datasets, we found significant overlap across dysregulated biological species in the different tissues and the different biological layers. We developed three predictive models containing increasing number of transcripts that can distinguish PD from healthy control with an area under the ROC Curve (AUC) ≥0.85. Finally, we showed that several of the predictive transcripts significantly correlate with symptom severity measured by UPDRS-III. Overall, we have demonstrated that cfRNA contains pathological signatures and has the potential to be utilized as biomarker to aid in PD diagnostics and monitoring.

Application of graft-derived cell-free DNA for solid organ transplantation

Monitoring the status of grafts and the occurrence of postoperative complications, such as rejection, is crucial for ensuring the success and long-term survival of organ transplants. Traditional histopathological examination, though effective, is an invasive procedure and poses risks of complications, making frequent use impractical. In recent years, graft-derived cell-free DNA (gd-cfDNA) has emerged as a promising non-invasive biomarker. It not only provides early warnings of rejection and other types of graft injury but also offers important information about the effectiveness of immunosuppressive therapy and prognosis. gd-cfDNA shows potential in the monitoring of organ transplants. The early, real-time information on graft injury provided by gd-cfDNA facilitates timely individualized treatment and improves patient outcomes. However, the progress of research on gd-cfDNA varies across different organs. Therefore, this article will comprehensively review the application and findings of gd-cfDNA in monitoring various solid organs, discussing the advantages, limitations, and some future research directions to aid in its clinical application.

Early fetal sex determination using a fluorescent DNA nanosensing platform capable of simultaneous detection of SRY and DYS14 sequences in cell-free fetal DNA

Early fetal sex determination is of crucial importance in the management of prenatal diagnosis of X-linked genetic abnormalities and congenital adrenal hyperplasia. The development of an efficient and simple method for high-sensitivity, affordable, and rapid screening of cell-free fetal DNA (cffDNA) is crucial for fetal sex determination in early pregnancy. In this study, single- and dual-fluorophore DNA biosensors based on multi-walled carbon nanotubes (MWCNT) were fabricated for the individual and simultaneous detection of the SRY gene and DYS14 marker in cffDNA obtained from maternal plasma samples. This nanosensing platform is based on the immobilization of single-stranded DNA (ssDNA) probes, labeled with ROX or FAM fluorophores, on MWCNT, resulting in the quenching of fluorescence emission in the absence of the targets. Upon the addition of the complementary target DNA (ctDNA) to the hybridization reaction, the fluorescence emission of fluorophore-labeled probes was significantly recovered to 79.5 % for ROX-labeled probes (i.e. SRY-specific probes), 81.5 % for FAM-labeled probes (i.e. DYS14-specific probes), and 65.9 % for dual-fluorophore biosensor compared to the quenching mode. The limit of detection (LOD) for ROX, and FAM was determined to be 4.5 nM, and 7.6 nM, respectively. For dual-color probes, LOD was found to be 5.4 (ROX) and 9.2 nM (FAM). Finally, the clinical applicability of the proposed method was confirmed through the detection of both biomarkers in maternal plasma samples, suggesting that the proposed nanosensing platform may be useful for the early detection of fetal sex using cffDNA.

Cell-free RNA signatures predict Alzheimer's disease

There is a need for affordable, scalable, and specific blood-based biomarkers for Alzheimer's disease that can be applied to a population level. We have developed and validated disease-specific cell-free transcriptomic blood-based biomarkers composed by a scalable number of transcripts that capture AD pathobiology even in the presymptomatic stages of the disease. Accuracies are in the range of the current CSF and plasma biomarkers, and specificities are high against other neurodegenerative diseases.

Next Generation Sequencing after Invasive Prenatal Testing in Fetuses with Congenital Malformations: Prenatal or Neonatal Investigation

Congenital malformations diagnosed by ultrasound screening complicate 3–5% of pregnancies and many of these have an underlying genetic cause. Approximately 40% of prenatally diagnosed fetal malformations are associated with aneuploidy or copy number variants, detected by conventional karyotyping, QF-PCR and microarray techniques, however monogenic disorders are not diagnosed by these tests. Next generation sequencing as a secondary prenatal genetic test offers additional diagnostic yield for congenital abnormalities deemed to be potentially associated with an underlying genetic aetiology, as demonstrated by two large cohorts: the ‘Prenatal assessment of genomes and exomes’ (PAGE) study and ‘Whole-exome sequencing in the evaluation of fetal structural anomalies: a prospective cohort study’ performed at Columbia University in the US. These were large and prospective studies but relatively ‘unselected’ congenital malformations, with little Clinical Genetics input to the pre-test selection process. This review focuses on the incremental yield of next generation sequencing in single system congenital malformations, using evidence from the PAGE, Columbia and subsequent cohorts, with particularly high yields in those fetuses with cardiac and neurological anomalies, large nuchal translucency and non-immune fetal hydrops (of unknown aetiology). The total additional yield gained by exome sequencing in congenital heart disease was 12.7%, for neurological malformations 13.8%, 13.1% in increased nuchal translucency and 29% in non-immune fetal hydrops. This demonstrates significant incremental yield with exome sequencing in single-system anomalies and supports next generation sequencing as a secondary genetic test in routine clinical care of fetuses with congenital abnormalities.

Noninvasive Fetal Genotyping by Droplet Digital PCR to Identify Maternally Inherited Monogenic Diabetes Variants

BACKGROUND

Babies of women with heterozygous pathogenic glucokinase (GCK) variants causing mild fasting hyperglycemia are at risk of macrosomia if they do not inherit the variant. Conversely, babies who inherit a pathogenic hepatocyte nuclear factor 4α (HNF4A) diabetes variant are at increased risk of high birth weight. Noninvasive fetal genotyping for maternal pathogenic variants would inform pregnancy management.

METHODS

Droplet digital PCR was used to quantify reference and variant alleles in cell-free DNA extracted from blood from 38 pregnant women heterozygous for a GCK or HNF4A variant and to determine fetal fraction by measurement of informative maternal and paternal variants. Droplet numbers positive for the reference/alternate allele together with the fetal fraction were used in a Bayesian analysis to derive probability for the fetal genotype. The babies' genotypes were ascertained postnatally by Sanger sequencing.

RESULTS

Droplet digital PCR assays for GCK or HNF4A variants were validated for testing in all 38 pregnancies. Fetal fraction of ≥2% was demonstrated in at least 1 cell-free DNA sample from 33 pregnancies. A threshold of ≥0.95 for calling homozygous reference genotypes and ≤0.05 for heterozygous fetal genotypes allowed correct genotype calls for all 33 pregnancies with no false-positive results. In 30 of 33 pregnancies, a result was obtained from a single blood sample.

CONCLUSIONS

This assay can be used to identify pregnancies at risk of macrosomia due to maternal monogenic diabetes variants.

Discordant fetal sex on NIPT and ultrasound

Prenatal diagnosis of sex discordance is a relatively new phenomenon. Prior to cell-free DNA testing, the diagnosis of a disorder of sexual differentiation was serendipitous, either through identification of ambiguous genitalia at the midtrimester morphology ultrasound or discovery of genotype-phenotype discordance in cases where preimplantation genetic diagnosis or invasive prenatal testing had occurred. The widespread integration of cfDNA testing into modern antenatal screening has made sex chromosome assessment possible from 10 weeks of gestation, and discordant fetal sex is now more commonly diagnosed prenatally, with a prevalence of approximately 1 in 1500-2000 pregnancies. Early detection of phenotype-genotype sex discordance is important as it may indicate an underlying genetic, chromosomal or biochemical condition and it also allows for time-critical postnatal treatment. The aim of this article is to review cfDNA and ultrasound diagnosis of fetal sex, identify possible causes of phenotype-genotype discordance and provide a systematic approach for clinicians when counseling and managing couples in this circumstance.

Evaluation of beta-thalassemia in the fetus through cffDNA with multiple polymorphisms as a haplotype in the beta-globin gene

OBJECTIVE

Invasive biopsy during the pregnancy is associated with an abortion risk of approximately 1% for the fetus. Free fetal DNA in maternal plasma is an excellent source of genetic material for prenatal molecular diagnoses. This study was conducted to investigate beta-thalassemia mutation in the fetus through maternal blood with multiple polymorphisms as haplotypes in the beta-globin gene.

METHODS

In this study, a total of 33 beta-thalassemia carrier (minor) couples were genotyped by ARMS-PCR for IVSII-IG>A mutation. During pregnancy, 10mL of blood was collected from pregnant women, and DNA was extracted by the magnetic bead-based extraction, and fetal DNA was enriched with AMPure XP kit. Five polymorphisms in 4 haplotype groups were evaluated by the Sanger Sequencing method. Finally, results were compared with those of the invasion method.

RESULTS

Participants in study were 33 couples, mean age of the men was 26±5 years, and mean age of women was 23±4 years, and mean MCV, MCH, HbA2 blood parameters were 62.4±5.3, 19.6±3.1, 4.2±2.1 respectively. A total of 33 fetuses were genotyped for IVSII-IG>A mutation. Nine fetuses were affected, 10 fetuses were normal and 14 fetuses were carrier of beta-thalassemia. Sensitivity and specificity of Sanger Sequencing were equal to 88.8% and 91.6% respectively. Positive and negative predictive values were obtained as 80% and 95.6%, respectively.

CONCLUSION

Mutational status of the fetus can be assessed by determining inheritance of paternally-derived alleles based on detection of haplotype-associated SNP in maternal plasma. Magnetic-based DNA extraction and fetal DNA enrichment are very simple and easy to perform and have satisfactory accuracy.

Non-invasive prenatal diagnosis and screening for monogenic disorders

Cell-free fetal DNA (cffDNA) can be detected in the maternal circulation from 4 weeks gestation, and is present with cell-free maternal DNA at a level of between 5 % and 20 %. Cell-free DNA (cfDNA) can be extracted from a maternal blood sample and, although it is not possible to separate the fetal from the maternal cfDNA, it has enabled non-invasive prenatal diagnosis (NIPD) without the associated miscarriage risk that accompanies invasive testing. NIPD for monogenic diseases was first reported in 2000 and since then there have been many proof of principle studies showing how analysis of cfDNA can provide a definitive diagnosis early in pregnancy for a wide range of single gene diseases. Testing for a number of these diseases has been available in the UK National Health Service (NHS) since 2012. This review highlights the main techniques that are being used for NIPD and discusses the technical limitations of the methods, as well as the advances that are being made to overcome some of the issues. NIPD is technologically challenging for a number of reasons. Firstly, because it requires the detection of low level fetal variants in a high maternal background. For de novo and paternally-inherited variants this has been achieved through the use of techniques such as next-generation sequencing (NGS) and digital PCR to detect variants in the cffDNA that are not present in the maternal cfDNA. However, for maternally-inherited variants this is much more challenging and relies on dosage-based techniques to detect small differences in the levels of mutant and wild-type alleles. Alongside the technical advances that are making NIPD more widely available in both the public healthcare and commercial settings, it is crucial that we continue to monitor the social and ethical impact to ensure that patients are being offered safe and accurate testing.

First-trimester screening-biomarkers and cell-free DNA

Background: The introduction of cell-free DNA into clinical practice has changed the screening approach. Healthcare professionals and future parents tend to overestimate NIPT (noninvasive prenatal testing) capabilities despite its relatively high cost and limited information.Objective: In this review, our aim was to survey how various countries have introduced contingent screening models and to discuss the advantages and disadvantages of the combined screening test and the use of NIPT.Data source: The Web of Science, PubMed database and institutional websites were searched for information regarding screening approaches and the implementation in different countries.Results: There are nine countries and regions that have already approved contingent screening test, while others (e.g. Australia) are discussing the implementation of contingent screening versus universal use of NIPT. There are several recent meta-analyses debating whether to use NIPT for universal screening for trisomies and other fetal conditions.Conclusions: NIPT is a reasonable option as an advanced screening test for trisomy 21, 18 and 13 only. Introducing screening by NIPT instead of a first-trimester screening will cause the loss of other valuable information including accurate dating of pregnancy, diagnosing major structural fetal abnormalities and multiple pregnancies at an early gestational age. Additionally, the opportunity to screen for early preeclampsia will be lost. Currently, the price for NIPT is still high adding extra strain on publicly funded health systems.

Novel Epigenetic Biomarkers in Pregnancy-Related Disorders and Cancers

As the majority of cancers and gestational diseases are prognostically stage- and grade-dependent, the ultimate goal of ongoing studies in precision medicine is to provide early and timely diagnosis of such disorders. These studies have enabled the development of various new diagnostic biomarkers, such as free circulating nucleic acids, and detection of their epigenetic changes. Recently, extracellular vesicles including exosomes, microvesicles, oncosomes, and apoptotic bodies have been recognized as powerful diagnostic tools. Extracellular vesicles carry specific proteins, lipids, DNAs, mRNAs, and miRNAs of the cells that produced them, thus reflecting the function of these cells. It is believed that exosomes, in particular, may be the optimal biomarkers of pathological pregnancies and cancers, especially those that are frequently diagnosed at an advanced stage, such as ovarian cancer. In the present review, we survey and critically appraise novel epigenetic biomarkers related to free circulating nucleic acids and extracellular vesicles, focusing especially on their status in trophoblasts (pregnancy) and neoplastic cells (cancers).

Donor-specific Cell-free DNA as a Biomarker in Solid Organ Transplantation. A Systematic Review

BACKGROUND

There is increasing interest in the use of noninvasive biomarkers to reduce the risks posed by invasive biopsy for monitoring of solid organ transplants (SOTs). One such promising marker is the presence of donor-derived cell-free DNA (dd-cfDNA) in the urine or blood of transplant recipients.

METHODS

We systematically reviewed the published literature investigating the use of cfDNA in monitoring of graft health after SOT. Electronic databases were searched for studies relating cfDNA fraction or levels to clinical outcomes, and data including measures of diagnostic test accuracy were extracted. Narrative analysis was performed.

RESULTS

Ninety-five articles from 47 studies met the inclusion criteria (18 kidneys, 7 livers, 11 hearts, 1 kidney-pancreas, 5 lungs, and 5 multiorgans). The majority were retrospective and prospective cohort studies, with 19 reporting diagnostic test accuracy data. Multiple techniques for measuring dd-cfDNA were reported, including many not requiring a donor sample. dd-cfDNA falls rapidly within 2 weeks, with baseline levels varying by organ type. Levels are elevated in the presence of allograft injury, including acute rejection and infection, and return to baseline after successful treatment. Elevation of cfDNA levels is seen in advance of clinically apparent organ injury. Discriminatory power was greatest for higher grades of T cell-mediated and antibody-mediated acute rejection, with high negative predictive values.

CONCLUSIONS

Cell-free DNA is a promising biomarker for monitoring the health of SOTs. Future studies will need to define how it can be used in routine clinical practice and determine clinical benefit with routine prospective monitoring.

Clinical article: screening for trisomy 13 using traditional combined screening versus an ultrasound-based protocol

AIMS

To compare the screening capability of ultrasonography in detecting trisomy 13 (T13) using a multiparameter sonographic protocol (NT+) with a classical combined screening test (CST) protocol.

METHODS

The project was a prospective, multicenter study based on a nonselected mixed-risk population of women referred for a first-trimester screening examination. Each subject was offered a choice between either the gold standard, traditional combined screening test (CSG arm) or the ultrasound-based screening protocol (USG arm). General and MA-based screening performances were checked.

RESULTS

The study population comprised 20,887 pregnancies: 12,933 in the CSG arm, including 27 cases of T13, and 7954 in the USG arm, including 30 cases of T13. The DR for T13 was higher in the CSG arm than in the USG arm for all tested cutoff points: 1/50 (88.5 versus 63.3%, respectively), 1/100 (88.5 versus 70%, respectively) and 1/300 (92.3 versus 83.3%, respectively). Using the ROC curves for fixed FPRs of 3 and 5%, the T13 detection rate in our study reached 90 and 93%, respectively, in the USG arm and 92 and 96%, respectively, in the CSG arm. MA influenced the T13 screening performance in the USG arm and reduced the DR in patients <31 years. Such influence was not detected in the CSG arm.

CONCLUSIONS

Classic CST was more effective in detecting T13 than the ultrasound-only approach. However, the recommended cutoff of 1/50 showed unsatisfactory results for both traditional CST and the multiparameter sonographic test we proposed.

Valor predictivo positivo del diagnóstico prenatal invasivo para alteraciones cromosómicas

Introducción. El diagnóstico prenatal (DP) invasivo para alteraciones cromosómicas (AC) se realiza según las indicaciones de las pruebas no invasivas y se basa en la probabilidad de encontrar un cariotipo alterado.Objetivos. Identificar las indicaciones para la realización de un procedimiento invasivo con el fin de hacer un DP de AC, calcular el valor predictivo positivo (VPP) de cada indicación y estimar la oportunidad relativa (OR) de encontrar una AC.Materiales y métodos. Estudio transversal que caracterizó las indicaciones de procedimientos invasivos para realizar cariotipos en registros de un centro de diagnóstico genético en Cali, Colombia, en el período 2013-2015.Resultados. De 738 registros de cariotipos analizados, 103 (14.0%) tuvieron AC. Las indicaciones más frecuentes fueron alteración anatómica única en ecografía del segundo trimestre (21.4%) y edad materna (18.8%). Las indicaciones con mayor VPP fueron sonolucencia nucal alterada más otro marcador ecográfico (80.0%) y antecedente de 2 o más abortos (30.8%). Las más altas OR de un cariotipo alterado también fueron la sonolucencia nucal más otro marcador ecográfico (OR=1381.6) y el antecedente de 2 o más abortos (OR=153.5).Conclusiones. La ecografía fue la principal herramienta para indicar procedimientos invasivos de DP. Los marcadores bioquímicos integrados fueron una indicación poco frecuente.

Lost in Translation? Ethical Challenges of Implementing a New Diagnostic Procedure

Since cell-free DNA (cfDNA) fragments of placental origin can be isolated and analyzed from the blood of pregnant women. Applications of this finding have been developed and implemented in clinical care pathways worldwide at an unprecedented pace and manner. Implementation patterns, however, exhibit considerable insufficiencies. Different "motors" of implementation processes, like the market or various regulatory institutions, can be identified at a national level. Each "motor" entails characteristic ethical challenges which are exemplified impressively by a rising number of case reports.Empirical data demonstrate that there are significant "losses" in the respective translational processes, especially when the results from clinical research are to be translated into the clinical reality of NIPT (the so called "second roadblock" (T2)). These "losses" are perceived in the fields of knowledge transfer, professional standardization and ethical debate. Recommendations of professional organizations often fail to reach general practitioners. Blindsided by the new diagnostic procedure in their clinical practice, professionals in prenatal care express their insecurities with regard to its handling. Ethical debate appears to adhere to pre-existing (and partly already proven to be insufficient) normative frameworks for prenatal testing. While all of these deficits are typical for the implementation processes of many new molecular diagnostic procedures, especially in NIPT, they show a high variability between different nations.A critical assessment of the preferred strategy of implementation against the background of already existing national ethical frameworks is indispensable, if potential adverse effects are to be diminished. The described translational losses seem to be significantly reducible by granting the translational process in roadblock T2 more time.

Opening Pandora's box?: ethical issues in prenatal whole genome and exome sequencing

OBJECTIVE

The development of genomic approaches to prenatal testing such as whole genome and exome sequencing offers the potential for a better understanding of prenatal structural anomalies in the fetus and ultimately for improved patient care and more informed reproductive decision making. In addition to the scientific and clinical challenges of achieving this, the introduction of new reproductive technologies also presents a number of ethical problems. The successful and appropriate development and introduction of prenatal genomics into clinical practice require these problems to be identified, understood and carefully analysed in the development of models of good ethical practice.

METHOD

We conducted a critical review of the existing literature on ethical issues in prenatal genomics.

RESULTS

We identified and discussed five areas of particular concern: valid consent, management and feed-back of information, responsibilities of health professionals, priority setting and resources and duties towards the future child.

CONCLUSION

There is a need for further discussion of the issues we have outlined here, and we hope that this brief summary of ethical arguments in the literature encourages researchers, clinicians, patients and scientists to engage in further discussion of these and other important issues raised by prenatal genomics. © 2017 The Authors. Prenatal Diagnosis published by John Wiley & Sons, Ltd.

Principles of first trimester screening in the age of non-invasive prenatal diagnosis: screening for chromosomal abnormalities

PURPOSE

First trimester risk assessment for chromosomal abnormalities plays a major role in the contemporary pregnancy care. It has evolved significantly since its introduction in the 1990s, when it essentially consisted of just the nuchal translucency measurement. Today, it involves the measurement of several biophysical and biochemical markers and it is often combined with a cell-free DNA (cfDNA) analysis as a secondary test.

METHODS

A search of the Medline and Embase databases was done looking for articles about first trimester aneuploidy screening. We performed a detailed review of the literature to evaluate the screening tests currently available and their respective test performance.

RESULTS

Combined screening for trisomy 21 based on maternal age, fetal NT, and the serum markers free beta-hCG and PAPP-A results in a detection rate of about 90% for a false positive of 3-5%. With the addition of further ultrasound markers, the false positive rate can be roughly halved. Screening based on cfDNA identifies about 99% of the affected fetuses for a false positive rate of 0.1%. However, there is a test failure rate of about 2%. The ideal combination between combined and cfDNA screening is still under discussion. Currently, a contingent screening policy seems most favorable where combined screening is offered for everyone and cfDNA analysis only for those with a borderline risk result after combined screening.

CONCLUSION

Significant advances in screening for trisomy 21 have been made over the past 2 decades. Contemporary screening policies can detect for more than 95% of affected fetuses for false positive rate of less than 3%.

Combined screening test for trisomy 21 - is it as efficient as we believe?

OBJECTIVES

To compare two first-trimester screening strategies: traditional combined screening and the one based on ultrasound markers only. We investigated the effect of maternal age (MA) on the screening performance of both of these strategies.

METHODS

This was a prospective observational study based on a non-selected mixed-risk population of 11,653 women referred for first-trimester screening. The study population was divided in two groups: combined screening (CS) and ultrasound-based screening (US). Absolute risk was calculated to determine the influence of MA on screening performance.

RESULTS

The CS arm comprised 5145 subjects including 51 cases of trisomy 21 (T21), and the US arm comprised 5733 subjects including 87 subjects with T21. Seven hundred and seventy-five subjects were excluded from the study. For a false positive rate (FPR) of 3%, the detection rate (DR) of T21 in CS arm was 78% vs. 90% in US arm. For 5% FPR, DR was 84% and 94% in CS and US arm, respectively. MA had an influence on DR positive rates in CS: both DR and FPR for T21 increased with advance in MA.

CONCLUSIONS

The US protocol showed higher DR of T21 compared to the CS one. It may be considered as a viable alternative to CS for T21 where access to biochemical testing is limited.

Three-hour analysis of non-invasive foetal sex determination: application of Plexor chemistry

Background

The knowledge of the individual genetic “status” in the prenatal era is particularly relevant in the case of positive family history for genetic diseases, in advanced maternal age and in the general screening for foetal abnormalities. In this context, here, we report an innovative molecular assay which utilizes the cell-free foetal DNA (cffDNA) as a source for the early and fast detection of the foetal sex. The study involved 132 pregnant women in their first 3 months of pregnancy, who agreed to give a blood sample. All the collected samples were immediately subjected to the separation of the plasma, which was utilized for the extraction of the cffDNA. Successively, the extracted cffDNA was analysed by a quantitative PCR (qPCR) method based on Plexor-HY chemistry, which is able to simultaneously identify, quantify and discriminate the autosomal DNA from the sex-linked DNA.

Results

Overall, the Plexor-HY assay demonstrated to be sensitive and specific for the determination of low-template DNA, such as the cffDNA. In fact, the Plexor-HY assay has been successfully performed in all the samples, identifying 70 males and 62 females. As the foetal sex can be provided in 120 min just by utilizing a maternal blood sample as cffDNA source, the assay represents a very fast, safe and non-invasive prenatal method.

Conclusions

The possibility of determining the foetal sex in the early prenatal life consents the application of our assay as a helpful screening test for subjects and families at risk of sex-linked disorders. Moreover, the early knowledge of the foetal sex may be of great help even for the specialist, who might promptly advise the patients concerning the foetal risk of inheriting sex-linked disorders and the clinical utility of performing an invasive prenatal diagnosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s40246-016-0066-2) contains supplementary material, which is available to authorized users.