Chorionic villus sampling in the cell-free DNA aneuploidy screening era: careful selection criteria can maximise the clinical utility of screening and invasive testing

Potential efficacy of digital polymerase chain reaction for non-invasive prenatal screening of autosomal aneuploidies: a systematic review and meta-analysis

BACKGROUND

Digital Polymerase Chain Reaction (dPCR) presents a promising approach for quantifying DNA and analyzing copy number variants, particularly in non-invasive prenatal testing. This method offers a streamlined and time-efficient procedure in contrast to the widely used next-generation sequencing for non-invasive prenatal testing. Studies have reported encouraging results for dPCR in detecting fetal autosomal aneuploidies. Consequently, this systematic review aimed to evaluate the effectiveness of dPCR in screening for trisomy 21, 18, and 13.

METHODS

A systematic search was conducted in PubMed, Web of Sciences, and Embase for relevant articles published up to December 30, 2023. The Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) was utilized for the quality assessment of the included articles. Furthermore, a bivariate random-effect regression model was used to conduct a meta-analysis on the utility of dPCR for trisomy 21 screening.

RESULTS

A total of 9 articles were included in this review, with all of them assessing the utility of dPCR in trisomy 21 screening, and 2 and 1 studies conducting additional analysis on the screening abilities of dPCR for trisomy 18 and 13, respectively. A bivariate random-effects model calculated pooled sensitivity and specificity with a 95% confidence interval (CI). Meta-analysis of 6 studies comparing trisomy-21 screening with karyotyping demonstrated dPCR's pooled sensitivity of 98% [95% CI: 94 -100] and specificity of 99% [95% CI: 99 -100]. While conducting a meta-analysis for trisomy 13 and 18 proved impractical, reported values for sensitivity and specificity were favorable.

CONCLUSIONS

These findings suggest that dPCR holds promise as an effective tool for non-invasive prenatal testing, presenting a less time-consuming and intricate alternative to next-generation sequencing. However, further research is necessary to evaluate dPCR's applicability in clinical settings and to delineate its specific advantages over next-generation sequencing. This study contributes valuable insights into the potential of dPCR for enhancing prenatal screening methodologies.

TRIAL REGISTRATION

The protocol of this study was registered in the International Prospective Register of Systematic Reviews (PROSPERO) on 7/3/2024, with a registration code of CRD42024517523.

Different Cutoff Values for Increased Nuchal Translucency in First-Trimester Screening to Predict Fetal Chromosomal Abnormalities

INTRODUCTION

Increased nuchal translucency (NT) is closely related to an increased risk of chromosomal abnormalities. However, the criterion of increased NT for invasive prenatal diagnosis remains controversial, as the cutoff values are inconsistent among countries. This study was conducted to compare the various cutoff values of increased NT and calculate the incidence of chromosomal abnormalities to determine the predictive ability of these cutoff values in conventional chromosome analysis.

METHODS

A total of 3223 invasive samples with increased nuchal translucency (NT) or other non-ultrasound indications were collected from singleton pregnant women. Samples with isolated increased NT were divided into five groups based on the NT thickness: 909 samples in the NT ≥2.5 mm group, 819 samples in the NT ≥95th group, 547 samples in the NT ≥99th group, 527 samples in the NT ≥3.0 mm group, and 253 samples in the NT ≥3.5 mm group; 2301 samples with normal NT were considered as the control group. All five groups were karyotyped and the results were compared. The accuracy of the NT cutoff value for the screening of chromosomal abnormalities was assessed using receiver operating characteristic curve analysis.

RESULTS

Detection of all chromosomal aberrations and trisomy 21 showed that the sensitivity and false-positive rate decreased sequentially in the NT ≥2.5 mm, NT ≥95th, NT ≥3 mm, NT ≥99th, and NT ≥3.5 mm groups, whereas the specificity, positive predictive value, and false-negative rates increased sequentially. Comprehensive analysis of various factors, including sensitivity and specificity, revealed values equal to or higher than the calculated 95th percentile of NT distribution, which showed a sensitivity of 49.2% and specificity of 75.67% for detecting all aneuploidies and a sensitivity of 64% and specificity of 75.45% for trisomy 21, exhibiting the highest ability for the screening of chromosomal defects in first-trimester screening.

CONCLUSION

For different thresholds of NT thickness, values equal to or higher than the calculated 95th percentile of the NT distribution showed the highest ability for the screening of chromosomal defects in first-trimester screening.

Utilization and uptake of clinical genetics services in high-income countries: A scoping review

Ongoing rapid growth in the need for genetic services has the potential to severely strain the capacity of the clinical genetics workforce to deliver this care. Unfortunately, assessments of the scale of this health policy challenge and potential solutions are hampered by the lack of a consolidated evidence base on the growth in genetic service utilization. To enable health policy research and strategic planning by health systems in this area, we conducted a scoping review of the literature on the utilization and uptake of clinical genetics services in high-income countries published between 2010 and 2018. One-hundred-and-ninety-five unique studies were included in the review. Most focused on cancer (85/195; 44%) and prenatal care (50/195; 26%), which are consistently the two areas with the greatest volume of genetic service utilization in both the United States and other high-income countries. Utilization and uptake rates varied considerably and were influenced by contextual factors including health system characteristics, provider knowledge, and patient preferences. Moreover, growth in genetic service utilization appears to be driven to a significant degree by technological advances and the integration of new tests into clinical care. Our review highlights both the policy challenge posed by the rapid growth in the utilization of genetic services and the variability in this trend across clinical indications and health systems.

The decline of amniocentesis and the increase of chorionic villus sampling in modern perinatal medicine

Objective The aims of this study were to determine the rate of change by type of diagnosis by transabdominal chorionic villus sampling (TA-CVS) vs. amniocentesis for aneuploidy and to describe a successful and intensive international training program for TA-CVS in ongoing pregnancies. Methods We conducted a retrospective cohort study of all deliveries from 2010 to 2018 in Sardinia. All invasive diagnostic procedures are conducted at a single regional perinatal referral center. Descriptive statistics were used to compare data across groups, and inter-correlations between variables were investigated by Pearson's correlation coefficient. We subsequently describe the international trainee experiences in TA-CVS over a 35-year period. Results A total of 101,025 deliveries occurred over 9 years. The number of deliveries (13,413-9143, P < 0.0001) and total invasive diagnostic procedures (1506-858 per year, P = 0.019) declined over this period. The percentage of deliveries undergoing invasive diagnostic procedures remained steady (mean: 12.2%). In 2010, TA-CVS made up 32.3% of all invasive diagnostic procedures, while amniocentesis made up 67.7%. By 2018, TA-CVS made up 61.3% of the invasive diagnostic procedures, and amniocentesis, only 38.7%. The rate of TA-CVS increased over 9 years, while the rate of amniocentesis declined. A total of 236 trainees from 39 different countries and 5 different continents rotated through this site. The average length of stay was 2.4 weeks. Conclusion We demonstrate an increasing prevalence of TA-CVS vs. amniocentesis in the current era of prenatal testing and underscore the importance of continuing to train specialists skilled in TA-CVS. Our global operative experience is feasible and sustainable and will have a lasting impact on physicians conducting invasive fetal procedures.

Chorionic villus sampling: 10 years of experience in a University referral center

OBJECTIVES

The purpose of this study was to estimate our center-specific CVS-related miscarriage rate.

METHODS

This is an observational retrospective study of women submitted to a CVS in our hospital, between January 1^st, 2007 and December 31^st, 2016. Maternal and pregnancy characteristics, procedure details, genetic results and pregnancy outcomes of all patients were collected. The FMF miscarriage risk algorithm was used to estimate our population expected risk of miscarriage. To establish the procedure-related risk of miscarriage, we compared the observed with the expected miscarriage rate.

RESULTS

We had a total number of 1523 women with a singleton pregnancy who did a CVS over the 10-year period. The mean maternal age was 34 years old; the majority of the women was Caucasian, multiparous and had a spontaneous pregnancy. The most common indication for CVS was a high-risk result in the 1^st trimester combined screening test. The karyotype was normal in 72,7% of cases, 11,1% were T21 and 7,2% were T13 or T18. In the study group, 33 women were diagnosed with a fetal demise, 435 had a TOP and there were 4 intrauterine deaths and 34 miscarriages. The rate of miscarriage in our population was 3,2% and the expected patient specific risk for miscarriage was 3,0%. There was no statistical significance between the two miscarriage rates p = 0,705.

CONCLUSION

In our study the risk of miscarriage in the CVS group was not significantly different from that the expected patient specific risk (3.2 % vs 3%, p = 0.7). The procedure-related risk of miscarriage was 0,2%, similar to the rates describe in the literature. An accurate risk of pregnancy loss should be used when counseling women for CVS to allow an informed decision.

Application of Differentially Methylated Loci in Clinical Diagnosis of Trisomy 21 Syndrome

AIMS

To determine the diagnostic precision of using different sets of fetal-specific methylation markers with methylation-sensitive restriction enzyme-quantitative polymerase chain reaction (MSRE-qPCR) for detection of trisomy 21 (T21).

MATERIALS AND METHODS

The diagnostic value for trisomy 21 of differential methylation of HLCS, C21orf25, and RASSF1A (a fetal-specific internal control) was examined by MSRE-qPCR.

RESULTS

The combined marker set of HLCS and RASSF1A achieved accurate quantification of fetal-specific chromosome 21 and was an excellent marker for detecting the presence of three copies of chromosome 21. MSRE-qPCR correctly identified three cases of fetal T21 from 11 clinical samples, which were 100% consistent with karyotyping results. In addition, this method was able to detect fetal-specific, T21-derived, cell-free fetal DNA at concentrations as low as 0.1%.

CONCLUSIONS

Evaluation of the HLCS and RASSF1A fetal-specific methylation marker set by MSRE-qPCR could be a highly sensitive, specific, cost-effective, and noninvasive prenatal screening method for T21. This MSRE-qPCR testable marker should be considered as an alternative to next generation sequencing technology for diagnosing fetal T21.

Hypoplastic nasal bone: A potential marker for facial dysmorphism associated with pathogenic copy number variants on microarray

OBJECTIVES

To compare the frequency of abnormal genetic diagnoses spanning a period before and after the availability of chromosomal microarray analysis (CMA). We hypothesised that microarray would provide additional clinically relevant information in cases of isolated hypoplastic nasal bone.

METHOD

Fetuses with ultrasound-detected hypoplastic nasal bone (absent or <2.5th percentile in length) between 16 and 37 weeks' gestation over a 10-year period were analysed retrospectively.

RESULTS

A total of 118 cases of hypoplastic nasal bone met the inclusion criteria. A pathogenic or potentially pathogenic karyotype was detected more frequently in the era where CMA was available (31/60, 52% vs 19/58, 33%). Of these, 25 cases (42%) had common aneuploidies, and six cases (10%) had clinically relevant copy number variants (CNVs). A clinically relevant CNV was detected in two fetuses that presented with isolated hypoplastic nasal bone on initial ultrasound.

CONCLUSION

In addition to its known association with trisomy 21, a hypoplastic nasal bone may be an objective marker of facial dysmorphism associated with clinically relevant CNVs. Our results support consideration of invasive testing with microarray for pregnancies in which a hypoplastic nasal bone has been diagnosed on ultrasound irrespective of a low-risk screening result for common chromosomal abnormalities.

Clinical results after the implementation of cell-free fetal DNA detection in maternal plasma

AIM

Detection of cell-free fetal DNA in maternal blood is a type of noninvasive prenatal diagnosis test (NIPT), which has already been known for some time but has not yet been introduced in most of public hospitals in Spain. How the implementation of cell-free fetal DNA (cffDNA) in a contingent protocol has influenced the aneuploidy screening in our hospital is described.

METHODS

Two cohorts of patients with positive combined screening were compared: the first one (years 2012-2013, 5747 patients) from a period of time in which the protocol valid until March 2016 - that included the use of invasive procedures - was applied; and the second one in which the current protocol - that included NIPT versus invasive procedures - was applied (first 7 months after protocol implementation, 898 patients).

RESULTS

Comparison of both periods resulted in a 60.5% reduction of invasive procedures (P < 0,001) preserving the same chromosomopathy detection rate. The ratio of positive invasive procedures-indicated invasive procedures was improved by 15% in the first period to 50% in the second period (P = 0.01).

CONCLUSION

NIPT introduction has caused a significant reduction of 60.5% of IP in high chromosomopathy risk patients after combined screening without modifying detection rate.