Clinical utility of array comparative genomic hybridisation in prenatal setting

Prenatal Chromosomal Microarray Analysis: Does Increased Resolution Equal Increased Yield?

Chromosomal microarray analysis (CMA) is considered a first-tier test for patients with developmental disabilities and congenital anomalies and is also routinely applied in prenatal diagnosis. The current consensus size cut-off for reporting copy number variants (CNVs) in the prenatal setting ranges from 200 Kb to 400 Kb, with the intention of minimizing the impact of variants of uncertain significance (VUS). Very limited data are currently available on the application of higher resolution platforms prenatally. The aim of this study is to investigate the feasibility and impact of applying high-resolution CMA in the prenatal setting. To that end, we report on the outcomes of applying CMA with a size cut-off of 20 Kb in 250 prenatal samples and discuss the findings and diagnostic yield and also provide follow-up for cases with variants of uncertain significance. Overall, 19.6% (49) showed one or more chromosomal abnormalities, with the findings classified as Pathogenic (P) or Likely Pathogenic (LP) in 15.6% and as VUS in 4%. When excluding the cases with known familial aberrations, the diagnostic yield was 12%. The smallest aberration detected was a 32 Kb duplication of the 16p11.2 region. In conclusion, this study demonstrates that prenatal diagnosis with a high-resolution aCGH platform can reliably detect smaller CNVs that are often associated with neurodevelopmental phenotypes while providing an increased diagnostic yield, regardless of the indication for testing, with only a marginal increase in the VUS incidence. Thus, it can be an important tool in the prenatal setting.

Comparative Genomic Hybridization to Microarrays in Fetuses with High-Risk Prenatal Indications: Polish Experience with 7400 Pregnancies

The aim of this study was to determine the suitability of the comparative genomic hybridization to microarray (aCGH) technique for prenatal diagnosis, but also to assess the frequency of chromosomal aberrations that may lead to fetal malformations but are not included in the diagnostic report. We present the results of the aCGH in a cohort of 7400 prenatal cases, indicated for invasive testing due to ultrasound abnormalities, high-risk for serum screening, thickened nuchal translucency, family history of genetic abnormalities or congenital abnormalities, and advanced maternal age (AMA). The overall chromosomal aberration detection rate was 27.2% (2010/7400), including 71.2% (1431/2010) of numerical aberrations and 28.8% (579/2010) of structural aberrations. Additionally, the detection rate of clinically significant copy number variants (CNVs) was 6.8% (505/7400) and 0.7% (57/7400) for variants of unknown clinical significance. The detection rate of clinically significant submicroscopic CNVs was 7.9% (334/4204) for fetuses with structural anomalies, 5.4% (18/336) in AMA, 3.1% (22/713) in the group of abnormal serum screening and 6.1% (131/2147) in other indications. Using the aCGH method, it was possible to assess the frequency of pathogenic chromosomal aberrations, of likely pathogenic and of uncertain clinical significance, in the groups of cases with different indications for an invasive test.

Molecular Approaches in Fetal Malformations, Dynamic Anomalies and Soft Markers: Diagnostic Rates and Challenges-Systematic Review of the Literature and Meta-Analysis

Fetal malformations occur in 2-3% of pregnancies. They require invasive procedures for cytogenetics and molecular testing. "Structural anomalies" include non-transient anatomic alterations. "Soft markers" are often transient minor ultrasound findings. Anomalies not fitting these definitions are categorized as "dynamic". This meta-analysis aims to evaluate the diagnostic yield and the rates of variants of uncertain significance (VUSs) in fetuses undergoing molecular testing (chromosomal microarray (CMA), exome sequencing (ES), genome sequencing (WGS)) due to ultrasound findings. The CMA diagnostic yield was 2.15% in single soft markers (vs. 0.79% baseline risk), 3.44% in multiple soft markers, 3.66% in single structural anomalies and 8.57% in multiple structural anomalies. Rates for specific subcategories vary significantly. ES showed a diagnostic rate of 19.47%, reaching 27.47% in multiple structural anomalies. WGS data did not allow meta-analysis. In fetal structural anomalies, CMA is a first-tier test, but should be integrated with karyotype and parental segregations. In this class of fetuses, ES presents a very high incremental yield, with a significant VUSs burden, so we encourage its use in selected cases. Soft markers present heterogeneous CMA results from each other, some of them with risks comparable to structural anomalies, and would benefit from molecular analysis. The diagnostic rate of multiple soft markers poses a solid indication to CMA.

Should prenatal chromosomal microarray analysis be offered for isolated fetal growth restriction? A French multicenter study

BACKGROUND

Compared with standard karyotype, chromosomal microarray analysis improves the detection of genetic anomalies and is thus recommended in many prenatal indications. However, evidence is still lacking on the clinical utility of chromosomal microarray analysis in cases of isolated fetal growth restriction.

OBJECTIVE

This study aimed to estimate the proportion of copy number variants detected by chromosomal microarray analysis and the incremental yield of chromosomal microarray analysis compared with karyotype in the detection of genetic abnormalities in fetuses with isolated fetal growth restriction.

STUDY DESIGN

This retrospective study included all singleton fetuses diagnosed with fetal growth restriction and no structural ultrasound anomalies and referred to 13 French fetal medicine centers over 1 year in 2016. Fetal growth restriction was defined as an estimated fetal weight of <tenth percentile for gestational age identified in ultrasound reports. For this analysis, we selected fetuses who underwent invasive genetic testing with karyotype and chromosomal microarray analysis results. Data were obtained from medical records and ultrasound databases and postmortem and placental examination reports in case of spontaneous stillbirths and terminations of pregnancy. Following the American College of Medical Genetics and Genomics guidelines, copy number variants were classified into 5 groups as following: pathogenic, likely pathogenic, variant of unknown significance, likely benign, and benign.

RESULTS

Of 682 referred fetuses diagnosed with isolated fetal growth restriction, both karyotype and chromosomal microarray analysis were performed in 146 fetuses. Overall, the detection rate of genetic anomalies found by chromosomal microarray analysis was estimated to be 7.5% (11 of 146 [95% confidence interval, 3.3-11.8]), including 10 copy number variants classified as pathogenic and 1 copy number variant classified as likely pathogenic. Among the 139 fetuses with normal karyotype, 5 were detected with pathogenic and likely pathogenic copy number variants, resulting in an incremental yield of 3.6% (95% confidence interval, 0.5-6.6) in chromosomal microarray analysis compared with karyotype. All fetuses detected with pathogenic or likely pathogenic copy number variants resulted in terminations of pregnancy. In addition, 3 fetuses with normal karyotype were detected with a variant of unknown significance (2.1%). Among the 7 fetuses with abnormal karyotype, chromosomal microarray analysis did not detect trisomy 18 mosaicism in all fetuses.

CONCLUSION

Our study found that compared with karyotype, chromosomal microarray analysis improves the detection of genetic anomalies in fetuses diagnosed with isolated fetal growth restriction. These results support the use of chromosomal microarray analysis in addition to karyotype for isolated fetal growth restriction.

Prenatal characterization of a novel inverted SMAD2 duplication by mate pair sequencing in a fetus with dextrocardia

This case report underlines the importance of molecular characterization of genomic duplications and other structural variants in the prenatal setting to guide clinical interpretation, genetic counseling, and perinatal medical care.

[Application of Array-based Comparative Genomic Hybridization in the Prenatal Diagnosis of Fetal Chromosomal Aberration in Gravidas with Advanced Age]

OBJECTIVE

To evaluate the clinical application of array-based comparative genomic hybridization (a-CGH) in the prenatal diagnosis of fetal chromosomal aberrations in gravidas with advanced maternal age (AMA).

METHODS

A total of 3 677 amniotic fluid samples from pregnant women who underwent amniocentesis for prenatal diagnosis solely due to AMA were selected. Array-CGH was performed on the Agilent CGX TM (8X60K) platform and the data were analyzed by the Genoglyphix software.

RESULTS

The overall detection rate of chromosomal aberration was 2.04% (75/3677), with 53.33% (40/75) being aneuploidies, including 22 cases of trisomy-21, 5 cases of trisomy-18, 8 cases with XXY, 3 cases of XYY and 2 cases of mosaic monosomy X, 32.00% (24/75) being pathogenic copy number variations (pCNVs), including 19 cases of microdeletion and 5 cases of microduplication, with the fragment size ranging from 323 kb to 26 780 kb, and 14.67% (11/75) being likely pathogenic CNVs (lpCNVs), including 7 cases of microdeletion and 7 cases of microduplication, with the fragment size ranging from 358 kb to 16 873 kb. Besides, the detection rate of CNVs of unknown clinical significance (VUS) was 0.84% (31/3 677). The detection rate of aneuploidies increased significantly with increased maternal age ( P<0.05). However, there were no significant differences in the detection rate of p/lpCNVs among different maternal age groups ( P>0.05).

CONCLUSION

Our findings suggest that, compared with traditional karyotype analysis, a-CGH not only detects aneuploidies, but also detect pathogenic CNVs, including microdeletion/microduplication syndromes. The detection rate of fetal aneuploidies was closely correlated to maternal age. However, no correlation was found between the detection rate of p/lpCNVs and maternal age.

Prenatal array comparative genomic hybridization in a well-defined cohort of high-risk pregnancies. A 3-year implementation results in a public tertiary academic referral hospital

OBJECTIVE

To find out whether the diagnostic yield of prenatal array comparative genomic hybridization (aCGH) can be improved by targeting preselected high-risk pregnancies.

METHOD

All the in-house arrays ordered by the Fetomaternal Medical Center from February 2016 until December 2018 were retrospectively analyzed. The indications for array analysis included fetal structural abnormalities, increased nuchal translucency ≥3.5 mm and a chromosomal abnormality in a parent or a sibling. Common aneuploidies were excluded.

RESULTS

Diagnostic yield was 15.1% in the entire patient cohort and as high as 20% in fetuses with multiple structural anomalies. The diagnostic yield was lowest in the group with isolated growth retardation. A total of 76 copy number variants (CNVs) were reported from a total of 65 samples, including 16 CNVs associated with a well-described microdeletion/microduplication syndrome, six autosomal trisomies in mosaic form, and three pathogenic single-gene deletions with dominant inheritance and 12 CNVs known to be risk factors for eg developmental delay.

CONCLUSION

The diagnostic yield of aCGH was higher than what has previously been reported in less defined patient cohorts. However, the number of CNVs with unclear correlation to the fetal ultrasound findings was still relatively high. The importance of adequate pre- and posttest counseling must therefore be emphasized.

Chromosomal microarray analysis in fetuses with central nervous system anomalies: An 8-year long observational study from a tertiary care university hospital

OBJECTIVES

To evaluate the prevalence of DNA copy number variants (CNVs) detected with array comparative genomic hybridization (CGH) in fetuses with central nervous system (CNS) anomalies. Secondary objectives were to describe the prevalence of CNV in specific CNS abnormalities, in isolated defects or associated with other malformations or fetal growth restriction (FGR).

METHODS

Observational cohort study in 238 fetuses with CNS anomalies in which an array-CGH had been performed between January 2009 and December 2017. Pathogenic CNV and variants of unknown significance (VUS) were reported.

RESULTS

Pathogenic CNVs were found in 16/238 cases (6.7%), VUS in 18/238 (7.6%), and normal result in 204/238 (85.7%) cases. Pathogenic CNVs were more frequent in posterior fossa anomalies (cerebellar hypoplasia 33%, megacisterna magna 20%), moderate ventriculomegaly (11%) and spina bifida (3.7%). Pathogenic CNVs and VUS were found in 7/182 (3.8%) and 14/182 (7.7%) cases of isolated anomalies, in 9/49 (18.4%) and 4/49 (8.2%) presenting another malformation, and in 0/7 and 0/7 cases with associated FGR (P = .001, P = .741, respectively).

CONCLUSION

These results provide strong evidence toward performing array in fetuses with CNS anomalies, particular in cases of posterior fossa anomalies. The prevalence of pathogenic CNVs is higher in association with other malformations.

Copy number variations in ultrasonically abnormal late pregnancy fetuses with normal karyotypes

Many fetuses are found to have ultrasonic abnormalities in the late pregnancy. The association of fetal ultrasound abnormalities in late pregnancy with copy number variations (CNVs) is unclear. We attempted to explore the relationship between types of ultrasonically abnormal late pregnancy fetuses and CNVs. Fetuses (n = 713) with ultrasound-detected abnormalities in late pregnancy and normal karyotypes were analyzed. Of these, 237 showed fetal sonographic structural malformations and 476 showed fetal non-structural abnormalities. Single nucleotide polymorphism (SNP)-based chromosomal microarray (CMA) was performed on the Affymetrix CytoScan HD platform. Using the SNP array, abnormal CNVs were detected in 8.0% (57/713) of the cases, with pathogenic CNVs in 32 cases and variants of uncertain clinical significance (VUS) in 25 cases. The detection rate of abnormal CNVs in fetuses with sonographic structural malformations (12.7%, 30/237) was significantly higher (P = 0.001) than that in the fetuses with non-structural abnormalities (5.7%, 27/476). Overall, we observed that when fetal sonographic structural malformations or non-structural abnormalities occurred in the third trimester of pregnancy, the use of SNP analysis could improve the accuracy of prenatal diagnosis and reduce the rate of pregnancy termination.

The frequency of CNVs in a cohort population of consecutive fetuses with congenital anomalies after the termination of pregnancy

BACKGROUND

The implementation of molecular karyotyping has resulted in an improved diagnostic yield in the genetic diagnostics of congenital anomalies, detected prenatally or after the termination of pregnancy. However, the systematic epidemiologic ascertainment of copy number variations in the etiology of congenital anomalies has not yet been sufficiently explored.

METHODS

Consecutive fetuses, altogether 204, with major single or multiple congenital anomalies were ascertained by using the SLOCAT registry for the period from 2011 to 2015. After excluding aneuploidies by using conventional karyotyping or Quantitative Fluorescence-Polymerase Chain Reaction, array comparative genomic hybridization was performed for the detection of copy number variations.

RESULTS

We identified pathogenic or likely pathogenic copy number variations in 14 fetuses (6.8%); 2.9% in fetuses with isolated, and 3.9% in fetuses with multiple congenital anomalies. Additionally, aneuploidies and major structural chromosomal abnormalities were detected in 40.2%.

CONCLUSION

Our systematic approach of ascertaining congenital anomalies resulted in explaining the etiology of congenital anomalies in 47% of fetuses after the termination of pregnancy. By using array comparative genomic hybridization, we found that copy number variations represent an important part in the etiology of multiple, as well as isolated congenital anomalies, which indicates the importance of analyzing copy number variations in the diagnostic approach of fetuses with congenital anomalies after the termination of pregnancy.

Chromosome copy number variants in fetuses with syndromic malformations

Chromosome copy number variants (CNVs; gains and losses of DNA sequences >1 kb) are wide-spread throughout the genome of healthy individuals. Laboratory studies show that a subset of CNVs are pathogenic, and not only can be responsible for the pathogenesis of major birth defects and cancer, but are also associated with neurodevelopmental disorders at birth. The characteristics of the pathogenic microdeletions and microduplications are important for both clinical implications and genetic counselling regarding test selection for prenatal screening and diagnosis. Unfortunately, our knowledge of the phenotypic effects of most CNV is still minimal, leading to the classification of many CNVs as "genomic imbalances of unknown clinical significance". Microdeletions and microduplications can occur in all pregnancies and the spectrum of pathogenic CNVs in fetuses with syndromic malformations is not well studied. This review summarizes our current understanding of CNVs, the common detection methods, and the characteristics of pathogenic CNVs identified in fetuses with syndromic malformations. Birth Defects Research 109:725-733, 2017. © 2017 Wiley Periodicals, Inc.

Genomic study of severe fetal anomalies and discovery of GREB1L mutations in renal agenesis

PURPOSE

Fetal anomalies represent a poorly studied group of developmental disorders. Our objective was to assess the impact of whole-exome sequencing (WES) on the investigation of these anomalies.

METHODS

We performed WES in 101 fetuses or stillborns who presented prenatally with severe anomalies, including renal a/dysgenesis, VACTERL association (vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities), brain anomalies, suspected ciliopathies, multiple major malformations, and akinesia.

RESULTS

A molecular diagnosis was obtained in 19 cases (19%). In 13 of these cases, the diagnosis was not initially suspected by the clinicians because the phenotype was nonspecific or atypical, corresponding in some cases to the severe end of the spectrum of a known disease (e.g., MNX1-, RYR1-, or TUBB-related disorders). In addition, we identified likely pathogenic variants in genes (DSTYK, ACTB, and HIVEP2) previously associated with phenotypes that were substantially different from those found in our cases. Finally, we identified variants in novel candidate genes that were associated with perinatal lethality, including de novo mutations in GREB1L in two cases with bilateral renal agenesis, which represents a significant enrichment of such mutations in our cohort.

CONCLUSION

Our study opens a window on the distinctive genetic landscape associated with fetal anomalies and highlights the power-but also the challenges-of WES in prenatal diagnosis.