Cell-free DNA noninvasive prenatal screening for aneuploidy versus conventional screening: A systematic review of economic evaluations

Understanding the Normativity of Health Technology Assessment: Ontological, Moral, and Epistemological Commitments

The inherent normativity of HTA can be conceptualized as a result of normative commitments, a concept that we further specify to encompass moral, epistemological and ontological commitments at play in the practice of HTA. Based on examples from literature, and an analysis of the example of assessing Non-Invasive Prenatal Testing (NIPT), we will show that inevitable normative decisions in conducting an assessment commits the HTA practitioner to moral (regarding what makes a health technology desirable), ontological (regarding which effects of health technology are conceivable), and epistemological (regarding how to obtain reliable information about health technology) norms. This highlights and supports the need for integrating normative analysis and stakeholder participation, providing guidance to HTA practitioners when making normative choices. This will foster a shared understanding between those who conduct, use, or are impacted by assessments regarding what are conceivable and desirable outcomes of using health technology, and how to collect reliable information to assess whether these outcomes are (going to be) realized. It also provides more insight into the implications of different normative choices.

Noninvasive prenatal testing for the detection of fetal chromosome 17 microduplication: clinical implications and findings

BACKGROUND

 Noninvasive prenatal testing (NIPT) is widely used to screen for fetal aneuploidies. However, there are few reports of using NIPT for screening chromosomal microduplications and microdeletions. This study aimed to investigate the application efficiency of NIPT for detecting chromosomal microduplications.

METHODS

Four cases of copy number gains on the long arm of chromosome 17 (17q12) were detected using NIPT and further confirmed using copy number variation (CNV) analysis based on chromosome microarray analysis (CMA).

RESULTS

The prenatal diagnosis CMA results of the three cases showed that the microduplications in 17q12 (ranging from 1.5 to 1.9 Mb) were consistent with the NIPT results. The karyotypic analysis excluded other possible unbalanced rearrangements. The positive predictive value of NIPT for detecting chromosomal 17q12 microduplication was 75.0%.

CONCLUSIONS

 NIPT has a good screening effect on 17q12 syndrome through prenatal diagnosis, therefore it could be considered for screening fetal CNV during the second trimester. With the clinical application of NIPT, invasive prenatal diagnoses could be effectively reduced while also improving the detection rate of fetal CNV.

Two cases of placental trisomy 21 mosaicism causing false-negative NIPT results

BACKGROUND

Non-invasive prenatal testing (NIPT) using cell-free DNA has been widely used for prenatal screening to detect the common fetal aneuploidies (such as trisomy 21, 18, and 13). NIPT has been shown to be highly sensitive and specific in previous studies, but false positives (FPs) and false negatives (FNs) occur. Although the prevalence of FN NIPT results for Down syndrome is rare, the impact on families and society is significant.

CASE PRESENTATION

This article described two cases of foetuses that tested "negative" for trisomy 21 by NIPT technology using the semiconductor sequencing platform. However, the fetal karyotypes of amniotic fluid were 46,XY, + 21 der(21;21)(q10;q10) and 47,XY, + 21 karyotypes, respectively. Placental biopsies confirmed that, in the first case, the chromosome 21 placenta chimerism ratio ranged from 13 to 88% with the 46,XX, + 21,der(21;21)(q10;q10)[86]/46,XX[14] karyotype of placental chorionic cells (middle of fetal-side placental tissue). However, in the second case, of all the placental biopsies, percentage of total chimerism was less than 30%; and placental biopsies taken at the middle of maternal side and middle of fetal side, also had variable trisomy 2 mosaicism levels of 10% and 8%, respectively. Ultimately, the pregnancies were interrupted at 30 gestational age (GA) and 27GA, respectively.

CONCLUSIONS

In this study, we present two cases of FN NIPT results that might have been caused by biological mechanisms, as opposed to poor quality, technical errors, or negligence. Clinical geneticists and their patients must understand that NIPT is a screening procedure.

Issues associated with possible implementation of Non-Invasive Prenatal Testing (NIPT) in first-tier screening: A rapid scoping review

In recent years, as the implementation and use of Non-Invasive Prenatal Testing (NIPT) have increased, the cost of the test has been decreasing. The cost of NIPT is expected to fall further in the upcoming years. As a result of the decreasing cost of NIPT, many jurisdictions may change their prenatal screening policies toward abandoning serum-based screening and instead, implement and support NIPT as the first-tier screening for all women. There are several concerns in replacing first-trimester screening with NIPT. In this scoping review, we aimed to map the existing knowledge about possible issues in the systematic implementation of NIPT as the primary method of first-tier screening and to assess if any jurisdiction has altered its policy and discontinued serum-based prenatal screening in exchange for NIPT. The Medline database (Ovid) and Google Scholar was searched and all the studies discussing, investigating, or reporting on the systematic implementation of NIPT as the primary method of first-tier screening were included. All the studies went through a two-stage screening process and included full-text articles were reviewed. We did not find any articles indicating a country or region that replaced traditional prenatal screening by NIPT. The included articles were charted, and the data about the possible issues in the systematic implementation of NIPT as the primary method of first-tier screening are summarized narratively and presented in tables in four categories. The findings of this scoping review may be informative for stakeholders and policymakers regarding recent changes in NIPT implementation policies around the world and may aid with developing policy for NIPT implementation with a broader perspective.

Does a High-Risk (>1/50) Result for First-Trimester Combined Screening Always Entail Invasive Testing? Which Patients from This Group Might Benefit from cfDNA Testing?

Currently, cell-free DNA (cfDNA) is offered as part of a contingent screening for patients with a first-trimester combined test (FCT) risk between 1/50 and 1/250. However, most aneuploidies are within the group of patients with a risk above 1/10. An observational, retrospective, and multi-centric study was carried out, to evaluate the theorical performance of lowering the cut-off point for the high-risk group from 1/50 to 1/10. Out of the 25,920 patients included, 25,374 (97.9%) consented to the cfDNA contingent screening for aneuploidies. With the proposed strategy, knowing that the detection rate (DR) of cfDNA testing for trisomy 21 is 99.7%, the DR for trisomy 21 would have stayed in a 93.2%, just as it was with the current strategy. In this instance, 267 (1.1%) invasive tests would have been performed, while the current strategy had a total of 307 (1.2%). The false positive rate (FPR) rate would have stayed at 5.2% in both scenarios. In conclusion, the contingent screening of aneuploidies based in the result of the FCT, offering the analysis of cfDNA to patients with an intermediate risk after lowering the cut-off point from 1/50 to 1/10, is a valid alternative that might maintain the current detection rates and avoid the complications associated with invasive testing.

Cost of providing cell-free DNA screening for Down syndrome in Finland using different strategies

OBJECTIVES

A financial analysis is carried out to assess costs and benefits of providing cell-free DNA screening in Finland, using different strategies.

METHODS

Three cell-free DNA screening strategies are considered: Primary, all women; Secondary, those with positive Combined test; and Contingent, the 10-30% with the highest Combined test risks. Three costs are estimated: additional cost for 10,000 pregnancies compared with the Combined test; 'marginal' cost of avoiding a Down syndrome birth which occurs in a pregnancy that would have been false-negative using the Combined test; and marginal cost of preventing the iatrogenic loss of a non-Down syndrome birth which occurs in a pregnancy that would have been false-positive.

RESULTS

Primary cell-free DNA will require additional funds of €250,000. The marginal cost per Down syndrome birth avoided is considerably less than the lifetime medical and indirect cost; the marginal cost per unaffected iatrogenic fetal loss prevented is higher than one benefit measure but lower than another. If the ultrasound component of the Combined test is retained, as would be in Finland, the additional funds required rise to €992,000. Secondary cell-free DNA is cost-saving as is a Contingent strategy with 10% selected but whilst when 20-30% costs rise they are much less than for the Primary strategy and are cost-beneficial.

CONCLUSIONS

When considering the place of cell-free DNA screening it is important to make explicit the additional and marginal costs of different screening strategies and the associated benefits. Under most assumptions the balance is favorable for Contingent screening.

WisecondorFF: Improved Fetal Aneuploidy Detection from Shallow WGS through Fragment Length Analysis

In prenatal diagnostics, NIPT screening utilizing read coverage-based profiles obtained from shallow WGS data is routinely used to detect fetal CNVs. From this same data, fragment size distributions of fetal and maternal DNA fragments can be derived, which are known to be different, and often used to infer fetal fractions. We argue that the fragment size has the potential to aid in the detection of CNVs. By integrating, in parallel, fragment size and read coverage in a within-sample normalization approach, it is possible to construct a reference set encompassing both data types. This reference then allows the detection of CNVs within queried samples, utilizing both data sources. We present a new methodology, WisecondorFF, which improves sensitivity, while maintaining specificity, relative to existing approaches. WisecondorFF increases robustness of detected CNVs, and can reliably detect even at lower fetal fractions (<2%).

The genotype and phenotype of chromosome 18p deletion syndrome: Case series

RATIONALE

The chromosome 18p deletion syndrome is a syndrome with a deletion of all or a portion of the short arm of the chromosome 18. The phenotypes of the chromosome 18p deletion syndrome vary widely among individuals due to differences in size and breakpoints and the involved genes on the deletions. Given the varied and untypical clinical presentation of this syndrome, the prenatal diagnosis of the syndrome still presents as a challenge.

PATIENT CONCERNS

We described 4 China cases with different chromosomal breakpoints. In case 1, a woman who with mild phenotypes gave birth to a severely deformed fetus. Three other cases were for prenatal diagnosis. Their phenotypes are the increased nuchal translucency (INT) and the noninvasive prenatal testing (NIPT) indicated deletions on the chromosome 18p and severe hydronephrosis respectively.

DIAGNOSIS

The 4 cases were diagnosed with chromosome 18p deletion syndrome through karyotype analysis and array-based comparative genomic hybridization (array-CGH).

INTERVENTIONS

Karyotype analysis and array-based comparative genomic hybridization were used to analyze the abnormal chromosome.

OUTCOMES

Case 1 and case 2 revealed 11.51 and 12.39 Mb deletions in 18p11.32p11.21. Case 3 revealed 7.1 Mb deletions in 18p11.3218p11.23. Case 4 revealed 9.9 Mb deletions in 18p11.3218p11.22.

LESSONS

In our report, we are the first to report that mother and progeny who have the same chromosomal breakpoint have different phenotypes, significantly. In addition, we found a new phenotype of chromosome 18p deletion syndrome in fetus, which can enrich the phenotypes of this syndrome in the prenatal diagnosis. Finally, we demonstrate that the individuals with different chromosomal breakpoints of 18p deletion syndrome have different phenotypes. On the other hand, the individuals with the same chromosomal breakpoints of 18p deletion syndrome may also have remarkably different phenotypes.

The Emergence and Global Spread of Noninvasive Prenatal Testing

Since its introduction in 2011, noninvasive prenatal testing (NIPT) has spread rapidly around the world. It carries numerous benefits but also raises challenges, often related to sociocultural, legal, and economic contexts. This article describes the implementation of NIPT in nine countries, each with its own unique characteristics: Australia, Canada, China and Hong Kong, India, Israel, Lebanon, the Netherlands, the United Kingdom, and the United States. Themes covered for each country include the structure of the healthcare system, how NIPT is offered, counseling needs and resources, and cultural and legal context regarding disability and pregnancytermination. Some common issues emerge, including cost as a barrier to equitable access, the complexity of decision-making about public funding, and a shortage of appropriate resources that promote informed choice. Conversely, sociocultural values that underlie the use of NIPT vary greatly among countries. The issues described will become even more challenging as NIPT evolves from a second-tier to a first-tier screening test with expanded use.

Uptake of fetal aneuploidy screening after the introduction of the non-invasive prenatal test: A national population-based register study

INTRODUCTION

The introduction of the non-invasive prenatal test (NIPT) has shifted the prenatal screening landscape. Countries are exploring ways to integrate NIPT in their national prenatal screening programs, either as a first- or second-tier test. This study aimed to describe how the uptake of fetal aneuploidy screening changed after the introduction of NIPT as a second-tier and as a first-tier test within the national prenatal screening program of the Netherlands.

MATERIAL AND METHODS

A population-based register study in the Netherlands, recording uptake of fetal aneuploidy screening. Data from all pregnant women choosing to have the first-trimester combined test (FCT) or first-tier NIPT between January 2007 and March 2019 were retrospectively collected using national registration systems. Uptake percentages for fetal aneuploidy screening (FCT and NIPT) were calculated and stratified by region and maternal age. Statistical significance was determined using trend analysis and chi-squared tests.

RESULTS

Between 2007 and 2013 FCT uptake increased from 14.8% to 29.5% (P = .004). In April 2014 NIPT was introduced as a second-tier test for high-risk women after FCT (TRIDENT-1 study). FCT uptake rose from 29.5% in 2013 to 34.2% in 2015 (P < .0001). After the introduction of NIPT as a first-tier test for all women in April 2017 (TRIDENT-2 study), FCT uptake declined significantly from 35.8% in 2016 to 2.6% in 2018 (P < .0001). NIPT uptake increased to 43.4% in 2018. Regionally, NIPT uptake ranged from 31.8% to 67.9%. Total uptake (FCT and NIPT) between 2007 and 2018 increased significantly from 14.8% to 45.9% (P < .0001). However, total uptake stabilized at 46% for both years of TRIDENT-2 (April 2017-March 2019).

CONCLUSIONS

An increase in total fetal aneuploidy screening uptake up to 45.9% was observed after the introduction of NIPT. Uptake appears to have stabilized within a year after introducing first-tier NIPT.

Evaluation of Maternal Serum sHLA-G Levels for Trisomy 18 Fetuses Screening at Second Trimester

Human leukocyte antigen-G (HLA-G) has been widely acknowledged to play critical roles in fetal-maternal maintenance. However, the significance of using maternal serum sHLA-G to detect prenatal chromosomal abnormality has not been investigated. In China, prenatal screening using maternal α-fetoprotein (AFP), unconjugated estriol (uE3), and free β subunit human chorionic gonadotropin (β-hCG) in the second trimester has been widely applied. In this study, we evaluated the use of sHLA-G as a screening marker, compared with traditional second trimester prenatal screening. Serum samples from 1,019 singleton women in their second trimester were assessed. Among them, 139 infants were confirmed with trisomy 21 (T21) by karyotyping, 83 were confirmed with trisomy 18 (T18), and the remaining 797 infants had no abnormalities. The sHLA-G levels in maternal sera were significantly lower in pregnant women with T18 fetuses (median: 47.8 U/ml, range: 9.8-234.2 U/ml) and significantly higher in those with T21 fetuses (median: 125.7 U/ml, range: 28.7-831.7 U/ml), compared with the normal controls (median: 106.3 U/ml, range: 50.5-1136.4 U/ml) (p < 0.001). The risk values of the screening of T21 or T18 fetuses were assessed using mean and standard deviation log₁₀ analyte multiples of median (MoM) which showed that the predictive values of sHLA-G were the same as free β-hCG, and superior to AFP and uE3 for T18 screening. Logistic regression analysis revealed that sHLA-G MoM was the highest risk factor associated with pregnant women carrying T18 fetuses [Exp(B): 171.26, 95% CI: 36.30-807.97, p < 0.001]. Receiver operating characteristic (ROC) analysis revealed that the area under ROC curve for sHLA-G MoM was 0.915 (95% CI, 0.871-0.959, p < 0.001), for AFP MoM was 0.796 (95% CI, 0.730-0.861, p < 0.001), for free β-hCG MoM was 0.881 (95% CI, 0.829-0.934, p < 0.001), and for uE3 MoM was 0.876 (95% CI, 0.828-0.923, p < 0.001) in the T18 group. sHLA-G MoM demonstrated the best sensitivity and negative predictive value. For the first time, our findings reveal that sHLA-G is a better second trimester screening marker for the detection of T18 fetuses and the combined application of sHLA-G with AFP, free β-hCG, and uE3 could improve clinical screening for T18 fetuses.

Clinical Review of Noninvasive Prenatal Testing: Experience from 551 Pregnancies with Noninvasive Prenatal Testing-Positive Results in a Tertiary Referral Center

A total of 551 pregnancies with positive results for noninvasive prenatal testing (NIPT) using traditional karyotyping and chromosomal microarray analysis were analyzed. Confirmatory results, positive predictive values, etiology exploration of false-positive results, and pregnancy outcomes were recorded. The study demonstrated that NIPT performed better in predicting trisomy 21 and trisomy 18 for pregnancies with advanced maternal age than for pregnancies with young maternal age; as for trisomy 13 and sex chromosomal aneuploidy (SCA) prediction, there was no significant difference between the two groups. The positive predictive values for trisomy 21, trisomy 18, trisomy 13, and SCA showed no significant upward trend when compared based on specific age categories (an interval of 5 years), which suggested that NIPT-positive result deserves equal attention from both providers and patients regardless of maternal age. In addition, the termination rates of 45,X, 47,XXY, 47,XXX, and 47,XYY were 100% (2/2), 92.9% (26/28), 33.3% (5/15), and 9.5% (2/21), respectively, which demonstrated that the decision-making regarding pregnancies varied greatly according to the types of SCAs, and further reinforce the importance of confirmatory prenatal diagnosis. The current study also supported the viewpoint that confined placental mosaicism and maternal mosaicism were the important etiology of false-positive results.

A comparison of first trimester prenatal screening strategies for Down Syndrome with maternal age and preferences considerations

OBJECTIVE

Screening for Down Syndrome (DS) includes traditional ultrasound and serum-based and cell-free DNA (cfDNA) testing. While cfDNA testing usually has superior performance, it is significantly more costly. As an alternative, a hybrid strategy combining contingent cfDNA with traditional testing is recommended when universal cfDNA screening is not feasible. This study compares the efficacy of traditional, contingent cfDNA, and universal cfDNA screening strategies at various cut-offs based on maternal age and parents' preferences, which may improve testing outcomes and patients' satisfaction.

METHOD

Decision trees were used to analyze a cohort of 3 855 500 pregnancies from 12 to 50 years old. The performance of the strategies was compared using the number of adverse outcomes (undetected DS live births and euploid procedure-related losses).

RESULTS

Universal cfDNA results in the fewest number of adverse outcomes in every scenario. Contingent cfDNA performs better than traditional screening when the cut-offs used to identify high-risk cases for cfDNA testing are relatively low. These cut-offs change depending on the maternal age and parents' preference.

CONCLUSION

Maternal age and parents' preferences should be considered when choosing cut-offs for contingent cfDNA to remain as an effective strategy compared to traditional screening and to improve patient satisfaction.

Clinical and Economic Evaluation after Adopting Contingent Cell-Free DNA Screening for Fetal Trisomies in South Spain

INTRODUCTION

Contingent cell-free (cf) DNA screening on the basis of the first-trimester combined test (FCT) results has emerged as a cost-effective strategy for screening of trisomy 21 (T21).

OBJECTIVES

To assess performance, patients' uptake, and cost of contingent cfDNA screening and to compare them with those of the established FCT.

METHODS

This is a prospective cohort study including all singleton pregnancies attending to their FCT for screening of T21 at 2 university hospitals in South Spain. When the FCT risk was ≥1:50, there were major fetal malformations, or the nuchal translucency was ≥3.5 mm, women were recommended invasive testing (IT); if the risk was between 1:50 and 1:270, women were recommended cfDNA testing; and for risks bellow 1:270, no further testing was recommended. Detection rate (DR), false-positive rate (FPR), patients' uptake, and associated costs were evaluated.

RESULTS

We analyzed 10,541 women, including 46 T21 cases. DR of our contingent strategy was 89.1% (41/46) at 1.4% (146/10,541) FPR. Uptake of cfDNA testing was 91.2% (340/373), and overall IT rate was 2.0%. The total cost of our strategy was €1,462,895.7, similar to €1,446,525.7 had cfDNA testing not been available.

CONCLUSIONS

Contingent cfDNA screening shows high DR, low IT rate, and high uptake at a similar cost than traditional screening.

Making the most of the first prenatal visit: The challenge of expanding prenatal genetic testing options and limited clinical encounter time

OBJECTIVE

Advances in prenatal genetics place additional challenges as patients must receive information about a growing array of screening and testing options. This raises concerns about how to achieve a shared decision-making process that prepares patients to make an informed decision about their choices about prenatal genetic screening and testing options, calling for a reconsideration of how healthcare providers approach the first prenatal visit.

METHODS

We conducted interviews with 40 pregnant women to identify components of decision-making regarding prenatal genetic screens and tests at this visit. Analysis was approached using grounded theory.

RESULTS

Participants brought distinct notions of risk to the visit, including skewed perceptions of baseline risk for a fetal genetic condition and the implications of screening and testing. Participants were very concerned about financial considerations associated with these options, ranking out-of-pocket costs on par with medical considerations. Participants noted diverging priorities at the first visit from those of their healthcare provider, leading to barriers to shared decision-making regarding screening and testing during this visit.

CONCLUSION

Research is needed to determine how to restructure the initiation of prenatal care in a way that best positions patients to make informed decisions about prenatal genetic screens and tests.

A case of prenatal diagnosis of 18p deletion syndrome following noninvasive prenatal testing

Background

Chromosome 18p deletion syndrome is a disease caused by the complete or partial deletion of the short arm of chromosome 18, there were few cases reported about the prenatal diagnosis of 18p deletion syndrome. Noninvasive prenatal testing (NIPT) is widely used in the screening of common fetal chromosome aneuploidy. However, the segmental deletions and duplications should also be concerned. Except that some cases had increased nuchal translucency or holoprosencephaly, most of the fetal phenotype of 18p deletion syndrome may not be evident during the pregnancy, 18p deletion syndrome was always accidentally discovered during the prenatal examination.

Case presentations

In our case, we found a pure partial monosomy 18p deletion during the confirmation of the result of NIPT by copy number variation sequencing (CNV-Seq). The result of NIPT suggested that there was a partial or complete deletion of X chromosome. The amniotic fluid karyotype was normal, but result of CNV-Seq indicated a 7.56 Mb deletion on the short arm of chromosome 18 but not in the couple, which means the deletion was de novo deletion. Finally, the parents chose to terminate the pregnancy.

Conclusions

To our knowledge, this is the first case of prenatal diagnosis of 18p deletion syndrome following NIPT.NIPT combined with ultrasound may be a relatively efficient method to screen chromosome microdeletions especially for the 18p deletion syndrome.

The role of information provision in economic evaluations of non-invasive prenatal testing: a systematic review

BACKGROUND

Technological progress has led to changes in the antenatal screening programmes, most significantly the introduction of non-invasive prenatal testing (NIPT). The availability of a new type of testing changes the type of information that the parent(s) require before, during and after screening to mitigate anxiety about the testing process and results.

OBJECTIVES

To identify the extent to which economic evaluations of NIPT have accounted for the need to provide information alongside testing and the associated costs and health outcomes of information provision.

METHODS

A systematic review of economic evaluations of NIPTs (up to February 2018) was conducted. Medline, Embase, CINAHL and PsychINFO were searched using an electronic search strategy combining a published economic search filter (from NHS economic evaluations database) with terms related to NIPT and screening-related technologies. Data were extracted using the Consolidated Health Economic Evaluation Reporting Standards framework and the results were summarised as part of a narrative synthesis.

RESULTS

A total of 12 economic evaluations were identified. The majority of evaluations (n = 10; 83.3%) involved cost effectiveness analysis. Only four studies (33.3%) included the cost of providing information about NIPT in their economic evaluation. Two studies considered the impact of test results on parents' quality of life by allowing utility decrements for different outcomes. Some studies suggested that the challenges of valuing information prohibited their inclusion in an economic evaluation.

CONCLUSION

Economic evaluations of NIPTs need to account for the costs and outcomes associated with information provision, otherwise estimates of cost effectiveness may prove inaccurate.

Nicht invasive Pränataldiagnostik mittels molekulargenetischer Tests (NIPT) zur Erkennung der Trisomien 13, 18 und 21

Hintergrund

Molekulargenetische Tests (NIPT) auf Trisomie sind längst Teil der nicht invasiven Pränataldiagnostik (NIPD). In Deutschland wird derzeit geprüft, ob und für wen diese Tests von den gesetzlichen Krankenkassen künftig bezahlt werden sollen.

Fragestellung

(I) Diagnostische Eigenschaften der NIPT zur Entdeckung der Trisomien 13, 18 und 21 und (II) hypothetische Berechnung der möglichen Anwendung der NIPT in verschiedenen Gruppen.

Methoden

(I) Systematische Recherche nach Primärliteratur und systematischen Übersichten in MEDLINE und vier weiteren Datenbanken. Einschlusskriterien: Studien mit schwangeren Frauen, Indextest: NIPT mittels molekulargenetischer Analyse von cffDNA im mütterlichen Blut zur Bestimmung des Trisomie-Risikos; Referenztest: zytogenetische Diagnostik oder postnatale klinische Untersuchung. (II) Orientierende Recherche. Hypothetische Berechnungen für (1) alle schwangeren Frauen nach aktuellem Vorgehen ohne NIPT am Beispiel von Ersttrimesterscreening (ETS), (2) Anwendung bei schwangeren Frauen mit erhöhtem Risiko, z. B. nach vorgeschaltetem auffälligem ETS und (3) NIPT in einer Population mit und ohne erhöhtes Risiko für eine Trisomie.

Ergebnisse

Bei 22 eingeschlossenen Studien lagen die Sensitivität und die Spezifität zur Erkennung der Trisomie 21 bei 99,13 % (95 %-KI: [97,39 %; 99,72 %]) und 99,95 % (95 %-KI: [99,88 %; 99,98 %]). Der mögliche Einfluss von Testversagern blieb bei den Berechnungen unberücksichtigt, womit die Sensitivität oder die Spezifität der NIPT möglicherweise überschätzt wurde. Für die Erkennung der Trisomien 13 und 18 konnte jeweils die Sensitivität nicht robust geschätzt werden.

Diskussion

Bei Frauen mit erhöhtem Risiko können NIPT die Zahl der invasiven Tests und damit der testbedingten Fehlgeburten vermutlich verringern.

The contingent use of cell-free fetal DNA for prenatal screening of trisomies 21, 18, 13 in pregnant women within a national health service: A budget impact analysis

OBJECTIVE

Non-invasive prenatal testing (NIPT) based on cell-free fetal DNA (cffDNA) is highly accurate in the detection of common fetal autosomal trisomies. Aim of this project was to investigate short-term costs and clinical outcomes of the contingent use of cffDNA for prenatal screening of trisomies 21, 18, 13 within a national health service (NHS).

METHODS

An economic analysis was developed from the perspective of the Italian NHS to compare two possible scenarios for managing pregnant women: women managed according to the Standard of Care screening (SoC) vs a cffDNA scenario, where Harmony Prenatal Test was introduced as a second line screening choice for women with an "at risk" result from SoC screening.

RESULTS

The introduction of cffDNA as a second line screening test, conditional to a risk ≥ 1:1,000 from SoC screening, showed a 3% increase in the detection of trisomies, with a 71% decrease in the number of invasive tests performed. Total short-term costs (pregnancy management until childbirth) decreased by € 19 million (from € 84.5 to 65.5 million).

CONCLUSION

The adoption of the Harmony Prenatal Test in women resulting at risk from SoC screening, implied a greater number of trisomies detection, together with a reduction of the healthcare costs.

Noninvasive prenatal testing detects microdeletion abnormalities of fetal chromosome 15

OBJECTIVE

Noninvasive prenatal testing (NIPT) is widely used in clinical detection of fetal autosomal duplications or deletions. The aim of this study was to investigate the clinical application of NIPT for detection of chromosomal microdeletions.

METHODS

Microdeletions of about 5 Mb in the long arm of chromosome 15 (q11.2-q12) were detected by NIPT and were confirmed by karyotype analysis and copy number variation (CNV) analysis based on high-throughput sequencing technology.

RESULTS

The CNV results of prenatal diagnosis showed that there were approximately 4.96 Mb of microdeletions in 15q11.2-q13.1, which was consistent with the NIPT results. The karyotype analysis showed no abnormalities.

CONCLUSION

In this study, the microdeletion fragment of fetal chromosome 15 was successfully detected and diagnosed using NIPT. This suggests that NIPT is an efficient method to gain genetic information about chromosomal abnormalities.

Can cell-free DNA testing be used in pregnancies with isolated fetal omphalocele? Preliminary evidence from cytogenetic results of prenatal cases

Objective: To evaluate whether cell-free DNA (cfDNA) testing could replace an invasive procedure in pregnancies with isolated fetal omphalocele.Study design: This was a retrospective study of all pregnancies with sonographically detected fetal omphalocele at three tertiary referral centers between 2012 and 2016. Invasive diagnostic testing was performed for genetic investigations using conventional karyotyping or chromosomal microarray. cfDNA testing was assumed to be offered to patients with isolated fetal omphalocele for screening for common aneuploidies.Results: Invasive genetic testing was performed in a total of 107 pregnancies with a fetal omphalocele. Abnormal karyotype was found in 66% (31/47) of nonisolated omphalocele cases and in 1.7% (1/60) of isolated omphalocele cases. No pathogenic copy number variations (CNVs) were detected in 59 cases with isolated omphalocele and normal karyotype. If cfDNA screening was used in cases with isolated omphalocele, the affected fetus with trisomy 18 would be detected, and no rare chromosomal aberrations or submicroscopic pathogenic CNVs would be missed.Conclusions: cfDNA testing could be recommended for prenatal genetic evaluation in pregnancies with isolated fetal omphalocele after thorough pretest counseling.Key Message: A very low percentage of aneuploidies and rare chromosomal/subchromosomal abnormalities are found in prenatal cases of isolated omphalocele. It seems that for pregnancies with isolated omphalocele, cfDNA testing represents an alternative for patients who choose to continue the pregnancies and are reluctant to undertake invasive diagnostic testing.

Cell-free DNA and contingent screening: Our first year

INTRODUCTION

Analysis of cell-free DNA (cfDNA) from maternal blood has showed a great potential as a screening method for fetal aneuploidies. cfDNA can be used as a first line screening tool or in a contingent model, after the combined test.

METHODS

Prospective study of women attending for first trimester combined screening in our Hospital, in the first year of contingent cfDNA screening. According to the combined screening test result patients were divided in high-risk (offered invasive test or routine follow-up), intermediate-risk (counselled for cfDNA, invasive or routine follow-up) or low-risk (routine ultrasound follow-up). Pregnancy outcomes and performance of screening were evaluated. A cost-effectiveness analysis was also done.

RESULTS

The majority of the 1272 enrolled participants were Caucasian (82,6%), multiparous (51,7%) and the median maternal age was 30 years old. Thirty women screened high-risk and 83,3% of them opted for an invasive test. Forty-nine patients had an intermediate risk and 75,5% of them choose cfDNA testing. Our rate of invasive tests decreased from 3.5% to 2.4%.

DISCUSSION

The cut-offs used to determine high and intermediate-risk are based on a compromise between detection rate, pregnancy lost rate and cost. Above a determined cut-off in the intermediate-risk group, the cost for each additional detected trisomy case is very high. One major benefit of this contingent model was the decrease in invasive testing.

CONCLUSION

The contingent cfDNA screening model can be easily implemented in a public hospital with a low-risk population. Since cost/benefit is an important issue, further studies are needed to determine the ideal cut-off for our country.

Genomics-based non-invasive prenatal testing for detection of fetal chromosomal aneuploidy in pregnant women

BACKGROUND

Common fetal aneuploidies include Down syndrome (trisomy 21 or T21), Edward syndrome (trisomy 18 or T18), Patau syndrome (trisomy 13 or T13), Turner syndrome (45,X), Klinefelter syndrome (47,XXY), Triple X syndrome (47,XXX) and 47,XYY syndrome (47,XYY). Prenatal screening for fetal aneuploidies is standard care in many countries, but current biochemical and ultrasound tests have high false negative and false positive rates. The discovery of fetal circulating cell-free DNA (ccfDNA) in maternal blood offers the potential for genomics-based non-invasive prenatal testing (gNIPT) as a more accurate screening method. Two approaches used for gNIPT are massively parallel shotgun sequencing (MPSS) and targeted massively parallel sequencing (TMPS).

OBJECTIVES

To evaluate and compare the diagnostic accuracy of MPSS and TMPS for gNIPT as a first-tier test in unselected populations of pregnant women undergoing aneuploidy screening or as a second-tier test in pregnant women considered to be high risk after first-tier screening for common fetal aneuploidies. The gNIPT results were confirmed by a reference standard such as fetal karyotype or neonatal clinical examination.

SEARCH METHODS

We searched 13 databases (including MEDLINE, Embase and Web of Science) from 1 January 2007 to 12 July 2016 without any language, search filter or publication type restrictions. We also screened reference lists of relevant full-text articles, websites of private prenatal diagnosis companies and conference abstracts.

SELECTION CRITERIA

Studies could include pregnant women of any age, ethnicity and gestational age with singleton or multifetal pregnancy. The women must have had a screening test for fetal aneuploidy by MPSS or TMPS and a reference standard such as fetal karyotype or medical records from birth.

DATA COLLECTION AND ANALYSIS

Two review authors independently carried out study selection, data extraction and quality assessment (using the QUADAS-2 tool). Where possible, hierarchical models or simpler alternatives were used for meta-analysis.

MAIN RESULTS

Sixty-five studies of 86,139 pregnant women (3141 aneuploids and 82,998 euploids) were included. No study was judged to be at low risk of bias across the four domains of the QUADAS-2 tool but applicability concerns were generally low. Of the 65 studies, 42 enrolled pregnant women at high risk, five recruited an unselected population and 18 recruited cohorts with a mix of prior risk of fetal aneuploidy. Among the 65 studies, 44 evaluated MPSS and 21 evaluated TMPS; of these, five studies also compared gNIPT with a traditional screening test (biochemical, ultrasound or both). Forty-six out of 65 studies (71%) reported gNIPT assay failure rate, which ranged between 0% and 25% for MPSS, and between 0.8% and 7.5% for TMPS.In the population of unselected pregnant women, MPSS was evaluated by only one study; the study assessed T21, T18 and T13. TMPS was assessed for T21 in four studies involving unselected cohorts; three of the studies also assessed T18 and 13. In pooled analyses (88 T21 cases, 22 T18 cases, eight T13 cases and 20,649 unaffected pregnancies (non T21, T18 and T13)), the clinical sensitivity (95% confidence interval (CI)) of TMPS was 99.2% (78.2% to 100%), 90.9% (70.0% to 97.7%) and 65.1% (9.16% to 97.2%) for T21, T18 and T13, respectively. The corresponding clinical specificity was above 99.9% for T21, T18 and T13.In high-risk populations, MPSS was assessed for T21, T18, T13 and 45,X in 30, 28, 20 and 12 studies, respectively. In pooled analyses (1048 T21 cases, 332 T18 cases, 128 T13 cases and 15,797 unaffected pregnancies), the clinical sensitivity (95% confidence interval (CI)) of MPSS was 99.7% (98.0% to 100%), 97.8% (92.5% to 99.4%), 95.8% (86.1% to 98.9%) and 91.7% (78.3% to 97.1%) for T21, T18, T13 and 45,X, respectively. The corresponding clinical specificities (95% CI) were 99.9% (99.8% to 100%), 99.9% (99.8% to 100%), 99.8% (99.8% to 99.9%) and 99.6% (98.9% to 99.8%). In this risk group, TMPS was assessed for T21, T18, T13 and 45,X in six, five, two and four studies. In pooled analyses (246 T21 cases, 112 T18 cases, 20 T13 cases and 4282 unaffected pregnancies), the clinical sensitivity (95% CI) of TMPS was 99.2% (96.8% to 99.8%), 98.2% (93.1% to 99.6%), 100% (83.9% to 100%) and 92.4% (84.1% to 96.5%) for T21, T18, T13 and 45,X respectively. The clinical specificities were above 100% for T21, T18 and T13 and 99.8% (98.3% to 100%) for 45,X. Indirect comparisons of MPSS and TMPS for T21, T18 and 45,X showed no statistical difference in clinical sensitivity, clinical specificity or both. Due to limited data, comparative meta-analysis of MPSS and TMPS was not possible for T13.We were unable to perform meta-analyses of gNIPT for 47,XXX, 47,XXY and 47,XYY because there were very few or no studies in one or more risk groups.

AUTHORS' CONCLUSIONS

These results show that MPSS and TMPS perform similarly in terms of clinical sensitivity and specificity for the detection of fetal T31, T18, T13 and sex chromosome aneuploidy (SCA). However, no study compared the two approaches head-to-head in the same cohort of patients. The accuracy of gNIPT as a prenatal screening test has been mainly evaluated as a second-tier screening test to identify pregnancies at very low risk of fetal aneuploidies (T21, T18 and T13), thus avoiding invasive procedures. Genomics-based non-invasive prenatal testing methods appear to be sensitive and highly specific for detection of fetal trisomies 21, 18 and 13 in high-risk populations. There is paucity of data on the accuracy of gNIPT as a first-tier aneuploidy screening test in a population of unselected pregnant women. With respect to the replacement of invasive tests, the performance of gNIPT observed in this review is not sufficient to replace current invasive diagnostic tests.We conclude that given the current data on the performance of gNIPT, invasive fetal karyotyping is still the required diagnostic approach to confirm the presence of a chromosomal abnormality prior to making irreversible decisions relative to the pregnancy outcome. However, most of the gNIPT studies were prone to bias, especially in terms of the selection of participants.