Merryn V. E. Macville

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

BACKGROUNDnResearch 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.nnnMETHODSnWe 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).nnnRESULTSnSeven 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.nnnCONCLUSIONSnNIPT 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.

Trial by Dutch Laboratories for Evaluation of Non-Invasive Prenatal Testing. Part I - Clinical Impact

To evaluate the clinical impact of nationwide implementation of genome‐wide non‐invasive prenatal testing (NIPT) in pregnancies at increased risk for fetal trisomies 21, 18 and 13 (TRIDENT study).

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

AbstractnGenomic 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.

Absence of Heterozygosity Due to Template Switching during Replicative Rearrangements

We investigated complex genomic rearrangements (CGRs) consisting of triplication copy-number variants (CNVs) that were accompanied by extended regions of copy-number-neutral absence of heterozygosity (AOH) in subjects with multiple congenital abnormalities. Molecular analyses provided observational evidence that in humans, post-zygotically generated CGRs can lead to regional uniparental disomy (UPD) due to template switches between homologs versus sister chromatids by using microhomology to prime DNA replication-a prediction of the replicative repair model, MMBIR. Our findings suggest that replication-based mechanisms might underlie the formation of diverse types of genomic alterations (CGRs and AOH) implicated in constitutional disorders.

Trial by Dutch laboratories for evaluation of non-invasive prenatal testing. Part II—women's perspectives†

To evaluate preferences and decision‐making among high‐risk pregnant women offered a choice between Non‐Invasive Prenatal Testing (NIPT), invasive testing or no further testing.

Congenital hydrocephalus in clinical practice: A genetic diagnostic approach

Congenital hydrocephalus is a common and often disabling disorder. The etiology is very heterogeneous. Little is known about the genetic causes of congenital hydrocephalus. A retrospective survey was performed including patients with primary congenital hydrocephalus referred to the Department of Clinical Genetics between 1985 and 2010 by perinatologists, (child) neurologists or pediatricians. Patients with hydrocephalus secondary to other pathology were excluded from this survey. We classified patients with primary congenital hydrocephalus into two main groups: non-syndromic hydrocephalus (NSH) and syndromic hydrocephalus (SH). Seventy-five individuals met the inclusion criteria, comprising 36% (27/75) NSH and 64% (48/75) SH. In 11% (8/75) hydrocephalus was familial. The cause of hydrocephalus was unknown in 81% (61/75), including all patients with NSH. The male-female ratio in this subgroup was 2.6:1, indicating an X-linked factor other than the L1CAM gene. In the group of SH patients, 29% (14/48) had a known cause of hydrocephalus including chromosomal abnormalities, L1 syndrome, Marden-Walker syndrome, Walker-Warburg syndrome and hemifacial microsomia. We performed this survey in order to evaluate current knowledge on the genetic etiology of primary congenital hydrocephalus and to identify new candidate genes or regulatory pathways for congenital hydrocephalus. Recommendations were made concerning the evaluation and genetic workup of patients with primary congenital hydrocephalus. We conclude that further molecular and functional analysis is needed to identify new genetic forms of congenital hydrocephalus.

Multiplex ligation-dependent probe amplification versus karyotyping in prenatal diagnosis: the M.A.K.E. study

BackgroundIn the past 30 years karyotyping was the gold standard for prenatal diagnosis of chromosomal aberrations in the fetus. Traditional karyotyping (TKT) has a high accuracy and reliability. However, it is labor intensive, the results take 14–21 days, the costs are high and unwanted findings such as abnormalities with unknown clinical relevance are not uncommon. These disadvantages challenged the practice of karyotyping. Multiplex ligation-dependent probe amplification (MLPA) is a new molecular genetic technique in prenatal diagnosis. Previous preclinical evidence suggests equivalence of MLPA and traditional karyotyping (TKT) regarding test performance.Methods/DesignThe proposed study is a multicentre diagnostic substitute study among pregnant women, who choose to have amniocentesis for the indication advanced maternal age and/or increased risk following prenatal screening test. In all subjects, both MLPA and karyotyping will be performed on the amniotic fluid sample. The primary outcome is diagnostic accuracy. Secondary outcomes will be maternal quality of life, womens preferences and costs. Analysis will be intention to treat and per protocol analysis. Quality of life analysis will be carried out within the study population. The study aims to include 4500 women.DiscussionThe study results are expected to help decide whether MLPA can replace traditional karyotyping for low-risk pregnancies in terms of diagnostic accuracy, quality of life and womens preferences. This will be the first clinical study to report on all relevant aspects of the potential replacement.Trial RegistrationThe protocol is registered in the clinical trial register number ISRCTN47252164

Spectral Karyotypic and Comparative Genomic Analysis of the Endocrine Pancreatic Tumor Cell Line BON-1

BON-1 is a human serotonin-producing endocrine pancreatic tumor (EPT) cell line, which has been used for various studies of tumorigenesis and treatment. Because its genotype, phenotype and degree of differentiation may underlie events that are instrumental to the development of endocrine tumors and, moreover, may vary between labs and over time, we decided to comprehensively characterize the chromosomal constitution of BON-1 by applying conventional GTG-banding, spectral karyotyping (SKY), comparative genomic hybridization (CGH) and fluorescence in situ hybridization (FISH). BON-1 cells proved to be hyperdiploid containing a modal chromosome number of 57 (range 56–64). SKY identified a stemline containing 6 clonal aberrations including del(1p), t(9;12)del(9p)x2, der(10)t(5;10), der(19)t(8;19), der(14)t(9;14)t(9;10), and a sideline harboring an additional del(12q). CGH and FISH confirmed the SKY results and, in addition, highlighted the chromosomal regions involved in the rearrangements. Moreover, they identified a homozygous deletion of the key tumor suppressor genes CDKN2A and CDKN2B at 9p21.3, in accordance with absence of p16INK4A and p14ARF expression as revealed by immunocytochemistry. Apart from deregulation of the cell cycle and p53 pathway this finding indicates escape from replicative senescence (induced by mutated NRAS) and detachment-induced apoptosis as molecular mechanisms underlying the tumorigenesis of BON-1 cells. Immunostaining results for p53, MDM2 and pRb expression were consistent with previously published data using Western analysis. In conclusion, we provide here a comprehensive cytogenetic profile of BON-1. This cell line harbors both numerical and structural genomic alterations indicative for malignant EPTs.

Cell-Free RNA Is a Reliable Fetoplacental Marker in Noninvasive Fetal Sex Determination

BACKGROUNDnNoninvasive genetic tests that use cell-free fetal DNA (cffDNA) are used increasingly in prenatal care. A low amount of cffDNA can have detrimental effects on the reliability of these tests. A marker to confirm the presence of fetal nucleic acids is therefore required that is universally applicable and easy to incorporate.nnnMETHODSnWe developed a novel multiplex, single-tube, noninvasive fetal sex determination assay by combining amplification of AMELY cffDNA with one-step reverse transcription (RT)-PCR of trophoblast-derived cell-free RNA (cfRNA), which functions as a sex-independent fetoplacental marker. We tested plasma samples from 75 pregnant women in duplicate in a blinded fashion. The fetus was considered to be male in the case of a positive result for AMELY and cfRNA amplification in both RT-PCRs. The fetus was considered to be female in the case of negative AMELY and positive cfRNA result in both RT-PCRs. In other cases, the test was repeated. We compared the results with invasive prenatal testing and pregnancy outcomes.nnnRESULTSnThe AMELY cffDNA amplification and cfRNA result was unambiguous and identical in duplicate in 71 of 75 plasma samples (95%). Four samples (5%) required an extra replicate because of an absent fetoplacental marker. Thereafter, fetal sex was correctly determined in all 75 plasma samples.nnnCONCLUSIONSnAmplification of trophoblast-derived cfRNA is a reliable marker for the confirmation of the presence of fetoplacentally derived nucleic acids in noninvasive fetal sex determination.

Economic evaluation of multiplex ligation-dependent probe amplification and karyotyping in prenatal diagnosis: a cost-minimization analysis

PurposeTo assess the cost-effectiveness of Multiplex Ligation-dependent Probe Amplification (MLPA, P095 kit) compared to karyotyping.MethodsA cost-minimization analysis alongside a nationwide prospective clinical study of 4,585 women undergoing amniocentesis on behalf of their age (≥36xa0years), an increased risk following first trimester prenatal screening or parental anxiety.ResultsDiagnostic accuracy of MLPA (P095 kit) was comparable to karyotyping (1.0 95% CI 0.999–1.0). Health-related quality of life did not differ between the strategies (summary physical health: mean difference 0.31, pxa0=xa00.82; summary mental health: mean difference 1.91, pxa0=xa00.22). Short-term costs were lower for MLPA: mean difference €315.68 (bootstrap 95% CI €315.63–315.74; −44.4%). The long-term costs were slightly higher for MLPA: mean difference €76.42 (bootstrap 95% CI €71.32–81.52; +8.6%). Total costs were on average €240.13 (bootstrap 95% CI €235.02–245.23; −14.9%) lower in favor of MLPA. Cost differences were sensitive to proportion of terminated pregnancies, sample throughput, individual choice and performance of tests in one laboratory, but not to failure rate or the exclusion of polluted samples.ConclusionFrom an economic perspective, MLPA is the preferred prenatal diagnostic strategy in women who undergo amniocentesis on behalf of their age, following prenatal screening or parental anxiety.