The Impact of cfDNA Screening on the Frequency of Invasive Procedures in a Geographically Diverse Private Network

Systematic evidence-based review: The application of noninvasive prenatal screening using cell-free DNA in general-risk pregnancies

PURPOSE

Noninvasive prenatal screening (NIPS) using cell-free DNA has been assimilated into prenatal care. Prior studies examined clinical validity and technical performance in high-risk populations. This systematic evidence review evaluates NIPS performance in a general-risk population.

METHODS

Medline (PubMed) and Embase were used to identify studies examining detection of Down syndrome (T21), trisomy 18 (T18), trisomy 13 (T13), sex chromosome aneuploidies, rare autosomal trisomies, copy number variants, and maternal conditions, as well as studies assessing the psychological impact of NIPS and the rate of subsequent diagnostic testing. Random-effects meta-analyses were used to calculate pooled estimates of NIPS performance (P < .05). Heterogeneity was investigated through subgroup analyses. Risk of bias was assessed.

RESULTS

A total of 87 studies met inclusion criteria. Diagnostic odds ratios were significant (P < .0001) for T21, T18, and T13 for singleton and twin pregnancies. NIPS was accurate (≥99.78%) in detecting sex chromosome aneuploidies. Performance for rare autosomal trisomies and copy number variants was variable. Use of NIPS reduced diagnostic tests by 31% to 79%. Conclusions regarding psychosocial outcomes could not be drawn owing to lack of data. Identification of maternal conditions was rare.

CONCLUSION

NIPS is a highly accurate screening method for T21, T18, and T13 in both singleton and twin pregnancies.

Comparison of indications and results of prenatal invasive diagnostic tests before and after the implementation of the use of cell-free fetal DNA: a tertiary referral center experience

PURPOSE

In this study, we aimed to compare the changes in the number, yield, and the percentage of karyotyping indications of the invasive prenatal diagnostic tests between the periods before and after cell-free fetal DNA was introduced to clinical use.

METHOD

The number of invasive prenatal diagnostic procedures such as amniocentesis and chorionic villus sampling, indication percentages and karyotype results in the periods before (January 1, 2009-December 31, 2010), (n = 1412) and after (January 1, 2016-December 31, 2017), and (n = 593) the introduction of cell-free fetal DNA was retrospectively evaluated.

RESULTS

When compared with the period before cell-free fetal DNA came into clinical use, the number of invasive prenatal diagnostic tests decreased by 58% while their yield was found to have increased (4.4% vs. 10.3%) in the period after cell-free DNA began to be used (p < 0.001). While there was a decrease in the indications due to advanced maternal age, an increase was found in ultrasonography indications for structural anomaly and the risk of a single-gene disorder (p < 0.001). Amniocentesis rate was found to have decreased in invasive prenatal diagnostic procedure types, while an increase was reported in CVS rates (p < 0.001).

CONCLUSIONS

Invasive prenatal diagnosis gradually decreases over the years, but the yield of invasive prenatal diagnostic tests increases. In parallel with the rapid development of modern molecular technologies and cheaper and easier access to the tests, we think that the number of invasive prenatal diagnostic tests will experience a more dramatic decrease in the following years.

Evaluation of a novel screening method for fetal aneuploidy using cell-free DNA in maternal plasma

Objective

To evaluate the test performance of a novel sequencing technology using molecular inversion probes applied to cell-free DNA screening for fetal aneuploidy.

Methods

Two cohorts were included in the evaluation; a risk-based cohort of women receiving diagnostic testing in the first and second trimesters was combined with stored samples from pregnancies with fetuses known to be aneuploid or euploid. All samples were blinded to testing personnel before being analyzed, and validation occurred after the study closed and results were merged.

Results

Using the new sequencing technology, 1414 samples were analyzed. The findings showed sensitivities and specificities for the common trisomies and the sex chromosome aneuploidies at >99% (Trisomy 21 sensitivity 99.2 CI 95.6–99.2; specificity 99.9 CI 99.6–99.9). Positive predictive values among the trisomies varied from 85.2% (Trisomy 18) to 99.0% (Trisomy 21), reflecting their prevalence rates in the study. Comparisons with a meta-analysis of recent cell-free DNA screening publications demonstrated equivalent test performance.

Conclusion

This new technology demonstrates equivalent test performance compared with alternative sequencing approaches, and demonstrates that each chromosome can be successfully interrogated using a single probe.

Magnetic resonance imaging for prenatal estimation of birthweight in pregnancy: review of available data, techniques, and future perspectives

Fetuses at the extremes of growth abnormalities carry a risk of perinatal morbidity and death. Their identification traditionally is done by 2-dimensional ultrasound imaging, the performance of which is not always optimal. Magnetic resonance imaging superbly depicts fetal anatomy and anomalies and has contributed largely to the evaluation of high-risk pregnancies. In 1994, magnetic resonance imaging was introduced for the estimation of fetal weight, which is done by measuring the fetal body volume and converting it through a formula to fetal weight. Approximately 10 studies have shown that magnetic resonance imaging is more accurate than 2-dimensional ultrasound imaging in the estimation of fetal weight. Yet, despite its promise, the magnetic resonance imaging technique currently is not implemented clinically. Over the last 5 years, this technique has evolved quite rapidly. Here, we review the literature data, provide details of the various measurement techniques and formulas, consider the application of the magnetic resonance imaging technique in specific populations such as patients with diabetes mellitus and twin pregnancies, and conclude with what we believe could be the future perspectives and clinical application of this challenging technique. The estimation of fetal weight by ultrasound imaging is based mainly on an algorithm that takes into account the measurement of biparietal diameter, head circumference, abdominal circumference, and femur length. The estimation of fetal weight by magnetic resonance imaging is based on one of the 2 formulas: (1) magnetic resonance imaging-the estimation of fetal weight (in kilograms)=1.031×fetal body volume (in liters)+0.12 or (2) magnetic resonance imaging-the estimation of fetal weight (in grams)=1.2083×fetal body volume (in milliliters)ˆ0.9815. Comparison of these 2 formulas for the detection of large-for-gestational age neonates showed similar performance for preterm (P=.479) and for term fetuses (P=1.000). Literature data show that the estimation of fetal weight with magnetic resonance imaging carries a mean or median relative error of 2.6 up to 3.7% when measurements were performed at <1 week from delivery; whereas for the same fetuses, the relative error at 2-dimensional ultrasound imaging varied between 6.3% and 11.4%. Further, in a series of 270 fetuses who were evaluated within 48 hours from birth and for a fixed false-positive rate of 10%, magnetic resonance imaging detected 98% of large-for-gestational age neonates (≥95th percentile for gestation) compared with 67% with ultrasound imaging estimates. For the same series, magnetic resonance imaging applied to the detection of small-for-gestational age neonates ≤10th percentile for gestation, for a fixed 10% false-positive rate, reached a detection rate of 100%, compared with only 78% for ultrasound imaging. Planimetric measurement has been 1 of the main limitations of magnetic resonance imaging for the estimation of fetal weight. Software programs that allow semiautomatic segmentation of the fetus are available from imaging manufacturers or are self-developed. We have shown that all of them perform equally well for the prediction of large-for-gestational age neonates, with the advantage of the semiautomatic methods being less time-consuming. Although many challenges remain for this technique to be generalized, a 2-step strategy after the selection of a group who are at high risk of the extremes of growth abnormalities is the most likely scenario. Results of ongoing studies are awaited (ClinicalTrials.gov Identifier # NCT02713568).

Profile of women choosing the Harmony® Prenatal Test

INTRODUCTION

The Harmony® Prenatal Test, a noninvasive cell-free DNA (cfDNA) method for major trisomies has been available since January 2013 at our unit, and tests were sent to the Ariosa Clinical Laboratory Improvement Amendments (CLIA) laboratory in California. From July 2017 onward, prenatal cfDNA has been reimbursed in Belgium for all pregnancies; however, since then samples are sent to a local laboratory. Little data are available on patient's profile and choices toward cfDNA and on the performance of local technology transfer centers. Areas covered: The profiles and choices of women regarding this test were evaluated. Further, the performance of cfDNA at the local laboratory was compared to the one in California. Our results showed that women from the Netherlands, as compared to Belgium, were more likely to undergo cfDNA testing for maternal request and would be less likely to undergo karyotyping if cfDNA were unavailable, therefore are better candidates for cfDNA testing, when this is used as first-line screening. Expert commentary: Our findings highlight the importance of conducting these types of studies, before decisions about clinical implementation are made by national governments and ministries of health.

Postmortem microfocus computed tomography for early gestation fetuses: a validation study against conventional autopsy

BACKGROUND

Perinatal autopsy provides useful clinical information in up to 40% of cases. However, there is a substantial unmet clinical need with regards to postmortem investigation of early gestation fetal loss for parents for whom standard autopsy is either not available or not acceptable. Parents dislike the invasive nature of autopsy, but current clinical imaging techniques do not provide high-enough imaging resolution in small fetuses. We hypothesized that microfocus computed tomography, which is a rapid high-resolution imaging technique, could give accurate diagnostic imaging after early gestation fetal loss.

OBJECTIVE

The objective of the study was to evaluate the diagnostic accuracy of microfocus computed tomography for noninvasive human fetal autopsy for early gestation fetuses, with the use of conventional autopsy as the reference standard.

STUDY DESIGN

We compared iodinated whole body microfocus computed tomography in 20 prospectively recruited fetuses (11-21 weeks gestation from 2 centers) with conventional autopsy in a double-blinded manner for a main diagnosis and findings in specific body organs. Fetuses were prepared with 10% formalin/potassium tri-iodide. Images were acquired with a microfocus computed tomography scanner with size-appropriate parameters. Images were evaluated independently by 2 pediatric radiologists, who were blinded to formal perinatal autopsy results, across 40 individual indices to reach consensus. The primary outcome was agreement between microfocus computed tomography and conventional autopsy for overall diagnosis.

RESULTS

Postmortem whole body fetal microfocus computed tomography gave noninvasive autopsy in minutes, at a mean resolution of 27μm, with high diagnostic accuracy in fetuses at <22 weeks gestation. Autopsy demonstrated that 13 of 20 fetuses had structural abnormalities, 12 of which were also identified by microfocus computed tomography (92.3%). Overall, microfocus computed tomography agreed with overall autopsy findings in 35 of 38 diagnoses (15 true positive, 18 true negative; sensitivity 93.8% [95% confidence interval, 71.7-98.9%], specificity 100% [95% confidence interval, 82.4-100%]), with 100% agreement for body imaging diagnoses. Furthermore, after removal of nondiagnostic indices, there was agreement for 700 of 718 individual body organ indices that were assessed on microfocus computed tomography and autopsy (agreement, 97.5%; 95% confidence interval, 96.1-98.4%), with no overall differences between fetuses at ≤14 or >14 weeks gestation (agreement, 97.2% and 97.9%, respectively). Within first-trimester fetal loss cases (<14 weeks gestation), microfocus computed tomography analysis yielded significantly fewer nondiagnostic indices than autopsy examination (22/440 vs 48/348, respectively; P<.001).

CONCLUSION

Postmortem whole-body fetal microfocus computed tomography gives noninvasive, detailed anatomic examinations that are achieved in minutes at high resolution. Microfocus computed tomography may be preferable to magnetic resonance imaging in early gestation fetuses and may offer an acceptable method of examination after fetal loss for parents who decline invasive autopsy. This will facilitate autopsy and subsequent discussions between medical professionals who are involved in patient care and counselling for future pregnancies.