Diagnosis Of Aneuploidies Research Articles

Fluorescence In situ Hybridization: Cell-Based Genetic Diagnostic and Research Applications.

Fluorescence in situ hybridization (FISH) is a macromolecule recognition technology based on the complementary nature of DNA or DNA/RNA double strands. Selected DNA strands incorporated with fluorophore-coupled nucleotides can be used as probes to hybridize onto the complementary sequences in tested cells and tissues and then visualized through a fluorescence microscope or an imaging system. This technology was initially developed as a physical mapping tool to delineate genes within chromosomes. Its high analytical resolution to a single gene level and high sensitivity and specificity enabled an immediate application for genetic diagnosis of constitutional common aneuploidies, microdeletion/microduplication syndromes, and subtelomeric rearrangements. FISH tests using panels of gene-specific probes for somatic recurrent losses, gains, and translocations have been routinely applied for hematologic and solid tumors and are one of the fastest-growing areas in cancer diagnosis. FISH has also been used to detect infectious microbias and parasites like malaria in human blood cells. Recent advances in FISH technology involve various methods for improving probe labeling efficiency and the use of super resolution imaging systems for direct visualization of intra-nuclear chromosomal organization and profiling of RNA transcription in single cells. Cas9-mediated FISH (CASFISH) allowed in situ labeling of repetitive sequences and single-copy sequences without the disruption of nuclear genomic organization in fixed or living cells. Using oligopaint-FISH and super-resolution imaging enabled in situ visualization of chromosome haplotypes from differentially specified single-nucleotide polymorphism loci. Single molecule RNA FISH (smRNA-FISH) using combinatorial labeling or sequential barcoding by multiple round of hybridization were applied to measure mRNA expression of multiple genes within single cells. Research applications of these single molecule single cells DNA and RNA FISH techniques have visualized intra-nuclear genomic structure and sub-cellular transcriptional dynamics of many genes and revealed their functions in various biological processes.

The effect of embryo selection by preimplantation genetic diagnosis for aneuploidy (PGD-A) in patients with advanced maternal age

The effect of embryo selection by preimplantation genetic diagnosis for aneuploidy (PGD-A) in patients with advanced maternal age

Commentary re: Causes and estimated incidences of sex-chromosome misdiagnosis in preimplantation genetic diagnosis of aneuploidy

Commentary re: Causes and estimated incidences of sex-chromosome misdiagnosis in preimplantation genetic diagnosis of aneuploidy

Segmental Duplication QF-PCR: A Simple and Alternative Method of Rapid Aneuploidy Testing for Developing Country Like India.

Aneuploidy screening is becoming an integral part of routine prenatal screening in developing countries like India, and the need for more cheaper and rapid aneuploidy testing methods are required to relive the anxiety and financial burden among the high-risk couples. Segmental duplication quantitative fluorescent polymerase chain reaction (SD-QF-PCR) emerged as an alternative aneuploidy diagnostic method. This study was conducted to optimize and access the utility of SD-QF-PCR in routine prenatal diagnosis to complement existing short tandem repeats (STR) based QF-PCR. About 50 control samples, 50 Down's syndrome samples, and one each trisomy 18 and Klinefelter samples were studied to optimize the assay. Later, 100 amniotic fluid samples were also studied. The assay was able to successfully identify normal and aneuploidy samples with 100% sensitivity and specificity. The results of amniotic fluid analysis by SD-QF-PCR were in agreement with results of STR-QF-PCR. Observed results qualify SD-QF-PCR as a preliminary aneuploidy diagnosis method.

Causes and estimated incidences of sex-chromosome misdiagnosis in preimplantation genetic diagnosis of aneuploidy

Preimplantation genetic diagnosis of aneuploidy (PGD-A) with comprehensive chromosome analysis has been known to improve pregnancy outcomes. Accuracy in detecting sex chromosomes becomes important when selecting against embryos at risk for sex-linked disorders. A total of 21,356 PGD-A cycles consisting of day-3 (cleavage) or day-5 (blastocyst) biopsies were received at the same laboratory for PGD-A via fluorescence in situ hybridization (FISH) or array comparative genome hybridization (aCGH) from multiple fertility centres. The misdiagnosis rates were 0.12% (Wilson 95% CI 0.05 to 0.25%) in day-3 FISH cycles, 0.48% (Wilson 95% CI 0.19 to 1.22%) in day-3 aCGH cycles and 0.0% (Wilson 95% CI 0 to 0.26) in day-5 aCGH cycles. Although rare, the likely causative biological event for true misdiagnosis is embryonic XX/XY mosaicism. Reanalysis of 1219 abnormal cleavage-stage research embryos revealed a 73% incidence of minor and major mosaicism. Only four (0.3%) embryos were found to be diploid and contained XX and XY cells that could potentially account for the misdiagnosis of sex. Our investigation identified errors leading to misdiagnosis and their attribution to specific events during PGD-A testing. The reported misdiagnosis rates suggest that PGD-A for sex determination is highly accurate, particularly when using aCGH applied to blastocyst biopsies.

Prenatal diagnosis in the modern era

Key content It may be possible to define pregnancy complication risk in the first trimester by combining biochemical and biophysical markers with obstetric history. This could allow antenatal care to be personalised, with patient and complication‐specific content. Molecular genetic testing, by both invasive and noninvasive means, can offer examination of the whole genome or exome. Noninvasive prenatal testing (NIPT) using cell‐free fetal DNA in the maternal circulation can offer screening and diagnosis of aneuploidy and single gene defects. Ultrasound can be enhanced by magnetic resonance imaging to provide imaging that is not limited by fetal and maternal characteristics, and can be used to assist preoperative planning for fetal surgery. Learning objectives To understand how pregnancy care can evolve with NIPT and a more detailed first trimester assessment. To understand how NIPT is undertaken, its capabilities and current limitations. Ethical issues With increasingly detailed cytogenetic testing there is a need to provide families with sufficient pre‐ and post‐test counselling, as well as consider the ramifications for them and the fetus.

Preimplantation genetic testing for aneuploidy: what technology should you use and what are the differences?

The purpose of the review was to define the various diagnostic platforms currently available to perform preimplantation genetic testing for aneuploidy and describe in a clear and balanced manner the various strengths and weaknesses of these technologies. A systematic literature review was conducted. We used the terms "preimplantation genetic testing," "preimplantation genetic diagnosis," "preimplantation genetic screening," "preimplantation genetic diagnosis for aneuploidy," "PGD," "PGS," and "PGD-A" to search through PubMed, ScienceDirect, and Google Scholar from the year 2000 to April 2016. Bibliographies of articles were also searched for relevant studies. When possible, larger randomized controlled trials were used. However, for some emerging data, only data from meeting abstracts were available. PGS is emerging as one of the most valuable tools to enhance pregnancy success with assisted reproductive technologies. While all of the current diagnostic platforms currently available have various advantages and disadvantages, some platforms, such as next-generation sequencing (NGS), are capable of evaluating far more data points than has been previously possible. The emerging complexity of different technologies, especially with the utilization of more sophisticated tools such as NGS, requires an understanding by clinicians in order to request the best test for their patients.. Ultimately, the choice of which diagnostic platform is utilized should be individualized to the needs of both the clinic and the patient. Such a decision must incorporate the risk tolerance of both the patient and provider, fiscal considerations, and other factors such as the ability to counsel patients on their testing results and how these may or may not impact clinical outcomes.

Challenges facing contemporary preimplantation genetic screening.

Aneuploidy is a leading cause of pregnancy failure. Although initial attempts to perform preimplantation genetic screening did not improve outcomes, validated techniques were developed to safely and effectively increase pregnancy rates. Still, many embryos designated as euploid do not implant. Current approaches are being refined to provide additional biologic insight into why this is the case. At present, the diagnosis and clinical relevance of segmental aneuploidy and mosaicism are amongst the more heavily investigated. Class I data have proven the safety of trophectoderm biopsy and validation studies have shown single nucleotide polymorphism array and quantitative PCR can accurately detect whole chromosome aneuploidy. Similar studies to validate next generation sequencing are underway. Although randomized control trials have demonstrated the clinical utility of preimplantation genetic screening, recent data on the impact of mosaicism and segmental aneuploidy require clarification. Several well powered randomized control trials have shown preimplantation genetic screening improves implantation rate. Plausible explanations for euploid failures include undetected mosaicism and segmental aneuploidy. However, the true incidence and dispersion of mosaicism within the embryo is unknown. Likewise, the resolution of detection and clinical significance of segmental aneuploidy is unclear. Further research to validate proposed detection algorithms and class I data to determine if detection impacts outcomes is needed.

Expert concensus on quantitative fluorescent polymerase chain reaction in the prenatal diagnosis of aneuploidies

Expert concensus on quantitative fluorescent polymerase chain reaction in the prenatal diagnosis of aneuploidies

Contribution of the First Trimester Ultrasound Screening in the Diagnosis of Aneuploidies

Contribution of the First Trimester Ultrasound Screening in the Diagnosis of Aneuploidies

Prenatal diagnosis of trisomy 21, 18 and 13 by quantitative pyrosequencing of segmental duplications.

Chromosomal aberration mostly occurs in chromosomes 21, 18 and 13, with an incidence approximately 1 out of 160 live births in humans, therefore making prenatal diagnosis necessary in clinics. Current methods have drawbacks such as time consuming, high cost, complicated operations and low sensitivity. In this paper, a novel method for rapid and accurate prenatal diagnosis of aneuploidy is proposed based on pyrosequencing, which quantitatively detects the peak height ratio (PHR) of different bases of segmental duplication. A direct polymerase chain reaction (PCR) approach was undertaken, where a small volume of amniotic fluid was used as the starting material without DNA extraction. Single-stranded DNA was prepared from PCR products and subsequently analyzed using pyrosequencing. The PHR between target and reference chromosome of 2.2 for euploid and 3:2 for a trisomy fetus were used as reference. The reference intervals and z scores were calculated for discrimination of aneuploidy. A total of 132 samples were collected, within trisomy 21 (n = 11), trisomy 18 (n = 3), trisomy 13 (n = 2), and unaffected controls (n = 116). A set of six segmental duplications were chosen for analysis. This method had consistent results with karyotyping analysis, a correct diagnosis with 100% sensitivity and 99.9% specificity.

The importance of determining the limit of detection of non-invasive prenatal testing methods.

Several non-invasive prenatal testing (NIPT) methods, which analyze circulating fetal cell-free DNA (cfDNA) in maternal plasma, suggest a fetal fraction (FF) ≥ 4% for a reportable result, with the assumption that fetal aneuploidies may not be detectable at lower FF. This study determined the actual limit of detection (LOD) of a massively parallel sequencing-based NIPT method and evaluated its performance in testing samples with low FF. An experimental model, involving the creation of artificial plasma mixtures with a final aneuploid FF ranging from 1% to 4%, simulated samples at different proportions of fetal cfDNA. We then analyzed 7103 blood samples, from pregnant women undergoing NIPT, to assess the impact of low FF on the performance of cfDNA testing. Detection of common aneuploidies in samples with an FF as low as 2% is well within the ability of this technology. Of 105 pregnancies confirmed chromosomally abnormal, 25 (23.8%) involving a 2% < FF < 4% were consistently detected. These high-risk pregnancies would have not been identified using the suggested 4% FF cut-off. This study underscores the importance of determining the actual LOD for each specific NIPT methodology. It may reduce the incidence of test cancelations and shorten the time required for the diagnosis of aneuploidy. © 2016 John Wiley & Sons, Ltd.

Non-invasive prenatal testing for fetal chromosome abnormalities: review of clinical and ethical issues.

Genomics-based non-invasive prenatal screening using cell-free DNA (cfDNA screening) was proposed to reduce the number of invasive procedures in current prenatal diagnosis for fetal aneuploidies. We review here the clinical and ethical issues of cfDNA screening. To date, it is not clear how cfDNA screening is going to impact the performances of clinical prenatal diagnosis and how it could be incorporated in real life. The direct marketing to users may have facilitated the early introduction of cfDNA screening into clinical practice despite limited evidence-based independent research data supporting this rapid shift. There is a need to address the most important ethical, legal, and social issues before its implementation in a mass setting. Its introduction might worsen current tendencies to neglect the reproductive autonomy of pregnant women.

Postnatal outcomes of prenatally diagnosed 45,X/46,XX.

High quality information is critical for informed decision-making in pregnancy following a prenatal diagnosis of sex chromosome aneuploidy. The goal of this study was to define the spectrum of outcomes in patients with prenatally diagnosed 45,X/46,XX mosaic Turner syndrome in order to provide a better basis for genetic counseling at the time of intrauterine diagnosis. Phenotype data for twenty-five patients with prenatally diagnosed 45,X/46,XX mosaicism were collected by retrospective chart review and, when possible, semi-structured telephone interview. Existing data from a cohort of 58 patients with postnatally diagnosed 45,X/46,XX mosaicism were used for comparison. Relative to those diagnosed postnatally, prenatal patients were more likely to have normal growth and normal secondary sexual development, less likely to manifest distinctive Turner syndrome features such as nuchal webbing and edema, and had significantly fewer renal defects. These differences underscore the need for a nuanced approach to prenatal counseling in cases of 45,X/46,XX mosaicism.

Genetic variations of 21 STR markers on chromosomes 13, 18, 21, X, and Y in the south Iranian population

Quantitative fluorescent polymerase chain reaction (QF-PCR), in recent years, has been accepted as a rapid, high throughput, and sensitive method for prenatal diagnosis of common chromosomal aneuploidies. Since short tandem repeats (STRs) are the cornerstone of QF-PCR technique, selection of the most polymorphic STR markers is an essential step for a successful QF-PCR assay. The genetic variation parameters of each STR marker differ among different populations. In this study, we investigated the size, frequency, heterozygosity, polymorphism information content, power of discrimination, and other genetic polymorphism data for 21 STR markers on chromosomes 13, 18, 21, X, and Y in 1000 amniotic fluid samples obtained from south Iranian women. Our results showed that all the 21 STR markers are highly polymorphic and informative in our population. The heterozygosity, polymorphism information content, and power of discrimination of the markers were 62-91.1%, 0.61-0.91, and 0.830-0.976, respectively. The locus D18S386 was the most polymorphic STR, while the locus DXYS218 was the least polymorphic STR among all the studied STRs. The present study has provided extensive data regarding the efficiency of the 21 STR markers for diagnosis of chromosomes 13, 18, 21, X, and Y aneuploidies in the south Iranian population.

Quantitative fluorescent polymerase chain reaction for rapid prenatal diagnosis of fetal aneuploidies in chorionic villus sampling in a single institution.

ObjectiveTo validate quantitative fluorescent polymerase chain reaction (QF-PCR) via chorionic villus sampling (CVS) for the diagnosis of fetal aneuploidies.MethodsWe retrospectively reviewed the medical records of consecutive pregnant women who had undergone CVS at Cheil General Hospital between December 2009 and June 2014. Only cases with reported QF-PCR before long-term culture (LTC) for conventional cytogenetic analysis were included, and the results of these two methods were compared.ResultsA total of 383 pregnant women underwent QF-PCR and LTC via CVS during the study period and 403 CVS specimens were collected. The indications of CVS were as follows: abnormal first-trimester ultrasonographic findings, including increased fetal nuchal translucency (85.1%), advanced maternal age (6.8%), previous history of fetal anomalies (4.2%), and positive dual test results for trisomy 21 (3.9%). The results of QF-PCR via CVS were as follows: 76 (18.9%) cases were identified as trisomy 21 (36 cases), 18 (33 cases), or 13 (seven cases), and 4 (1.0%) cases were suspected to be mosaicism. All results of common autosomal trisomies by QF-PCR were consistent with those of LTC and there were no false-positive findings. Four cases suspected as mosaicism in QF-PCR were confirmed as non-mosaic trisomies of trisomy 21 (one case) or trisomy 18 (three cases) in LTC.ConclusionQF-PCR via CVS has the advantage of rapid prenatal screening at an earlier stage of pregnancy for common chromosomal trisomies and thus can reduce the anxiety of parents. In particular, it can be helpful for pregnant women with increased fetal nuchal translucency or abnormal first-trimester ultrasonographic findings.

Noninvasive detection of fetal subchromosomal abnormalities by semiconductor sequencing of maternal plasma DNA

Noninvasive prenatal testing (NIPT) using sequencing of fetal cell-free DNA from maternal plasma has enabled accurate prenatal diagnosis of aneuploidy and become increasingly accepted in clinical practice. We investigated whether NIPT using semiconductor sequencing platform (SSP) could reliably detect subchromosomal deletions/duplications in women carrying high-risk fetuses. We first showed that increasing concentration of abnormal DNA and sequencing depth improved detection. Subsequently, we analyzed plasma from 1,456 pregnant women to develop a method for estimating fetal DNA concentration based on the size distribution of DNA fragments. Finally, we collected plasma from 1,476 pregnant women with fetal structural abnormalities detected on ultrasound who also underwent an invasive diagnostic procedure. We used SSP of maternal plasma DNA to detect subchromosomal abnormalities and validated our results with array comparative genomic hybridization (aCGH). With 3.5 million reads, SSP detected 56 of 78 (71.8%) subchromosomal abnormalities detected by aCGH. With increased sequencing depth up to 10 million reads and restriction of the size of abnormalities to more than 1 Mb, sensitivity improved to 69 of 73 (94.5%). Of 55 false-positive samples, 35 were caused by deletions/duplications present in maternal DNA, indicating the necessity of a validation test to exclude maternal karyotype abnormalities. This study shows that detection of fetal subchromosomal abnormalities is a viable extension of NIPT based on SSP. Although we focused on the application of cell-free DNA sequencing for NIPT, we believe that this method has broader applications for genetic diagnosis, such as analysis of circulating tumor DNA for detection of cancer.

Validation of next-generation sequencing for comprehensive chromosome screening of embryos

Massively parallel genome sequencing, also known as next-generation sequencing (NGS), is the latest approach for preimplantation genetic diagnosis. The purpose of this study was to determine whether NGS can accurately detect aneuploidy in human embryos. Low coverage genome sequencing was applied to trophectoderm biopsies of embryos at the blastocyst stage of development. Sensitivity and specificity of NGS was determined by comparison of results with a previously validated platform, array-comparative genomic hybridization (aCGH). In total, 156 samples (116 were blindly assessed) were tested: 40 samples were re-biopsies of blastocysts where the original biopsy specimen was previously tested for aCGH; four samples were re-biopsies of single blastomeres from embryos previously biopsied at the cleavage stage and tested using aCGH; 18 samples were single cells derived from well-characterized cell lines; 94 samples were whole-genome amplification products from embryo biopsies taken from previous preimplantation genetic screening cycles analysed using aCGH. Per embryo, NGS sensitivity was 100% (no false negatives), and 100% specificity (no false positives). Per chromosome, NGS concordance was 99.20%. With more improvement, NGS will allow the simultaneous diagnosis of single gene disorders and aneuploidy, and may have the potential to provide more detailed insight into other aspects of embryo viability.

A Cost-Effectiveness Analysis of First Trimester Non-Invasive Prenatal Screening for Fetal Trisomies in the United States.

BackgroundNon-invasive prenatal testing (NIPT) is a relatively new technology for diagnosis of fetal aneuploidies. NIPT is more accurate than conventional maternal serum screening (MSS) but is also more costly. Contingent NIPT may provide a cost-effective alternative to universal NIPT screening. Contingent screening used a two-stage process in which risk is assessed by MSS in the first stage and, based on a risk cutoff, high-risk pregnancies are referred for NIPT. The objective of this study was to (1) determine the optimum MSS risk cutoff for contingent NIPT and (2) compare the cost effectiveness of optimized contingent NIPT to universal NIPT and conventional MSS.Study DesignDecision-analytic model using micro-simulation and probabilistic sensitivity analysis. We evaluated cost effectiveness from three perspectives: societal, governmental, and payer.ResultsFrom a societal perspective, universal NIPT dominated both contingent NIPT and MSS. From a government and payer perspective, contingent NIPT dominated MSS. Compared to contingent NIPT, adopting a universal NIPT would cost $203,088 for each additional case detected from a government perspective and $263,922 for each additional case detected from a payer perspective.ConclusionsFrom a societal perspective, universal NIPT is a cost-effective alternative to MSS and contingent NIPT. When viewed from narrower perspectives, contingent NIPT is less costly than universal NIPT and provides a cost-effective alternative to MSS.

Use of microsatellite loci in prenatal and postnatal diagnosis of aneuploidy and uniparental disomy

Use of microsatellite loci in prenatal and postnatal diagnosis of aneuploidy and uniparental disomy