Multi-centre first-trimester screening for Down syndrome in the Netherlands in routine clinical practice

Prenatal Diagnostic Testing Following High-Risk Result from Serological Screening: Which Shall We Select?

Purpose

We retrospectively analyzed the results of prenatal diagnosis in women with high-risk (HR) serological screening results, and discussed the reasonable application of diagnostic testing.

Patients and Methods

Diagnostic testing was done in 2239 pregnant women who had HR results from serological screening in two prenatal diagnosis centers. According to the HR results, they were divided into simple HR, HR combined with ultrasound abnormalities, and HR combined with other indication groups. After receiving counselling from clinicians, they were allowed to choose either the traditional karyotype analysis and/or chromosomal microarray analysis (CMA).

Results

Those who underwent CMA comprised 49.3%, 97.6%, and 100% of the HR group, HR combined with ultrasound abnormalities, and HR combined with other indication groups, respectively. Among the 100 (4.47%) clinically significant results, 55 (2.46%), 15 (0.67%), and 30 (1.34%) were chromosomal aneuploidies, chromosomal structural abnormalities, and pathogenic copy number variations (CNVs), respectively. The rate of abnormalities was 3.77%, 13.71%, and 19.05% in the simple HR, HR combined with ultrasound abnormalities, and HR combined with other indication groups, respectively. The increasing rate of clinical pathogenic CNVs was 1.34% using CMA in HR pregnant women, 9.52% in the HR combined with other indication group, and 1.24% in the simple HR group. Among the 573 women who chose both diagnostic tests, 45 had abnormal results. Only one case detected using karyotype analysis was missed on CMA. The incidence of chromosomal aneuploidy tended to increase with increase in HR values. However, chromosomal structural abnormalities and pathogenic CNVs did not increase.

Conclusion

CMA should be recommended as the first-line diagnostic testing for women with HR screening results, especially combined with other abnormal indications.

Analysis of Down syndrome failed to be diagnosed after prenatal screening: A multicenter study

To analyze the characters of Down syndrome (DS) who failed to be diagnosed after prenatal screening and hope to be able to improve the programs of prenatal screening and reduce the missed diagnosis of DS. In this multicenter study, we collected the missed cases from 3 prenatal diagnosis centers and analyzed their characters. A total of 126 DS babies failed to be diagnosed after prenatal screening. Their mothers accepted the prenatal screening in second trimester. We collected the mothers' blood and detected the levels of alpha-fetoprotein (AFP) and the free beta subunit of human chorionic gonadotropin (fβhCG) by time-resolved fluoroimmunoassay. The values were also presented as multiples of the median (MoM) and determined the risk of carrying a fetus with DS by Wallace LifeCycle Elipse analysis software. Compared with normal control group, the level of fβhCG and hCG MoM were dramatically increased, while AFP and AFP MoM were decreased. The area under the receiver-operating-characteristic curve of trisomy 21 was 0.8387 for hCG-MoM and AFP-MoM testing. The sensitivity, specificity, positive predictive value, and negative predictive value were 84.6%, 74.8%, 75.4%, and 83.6%, respectively. Meanwhile, the prediction mode was "0.39957 + 1.90897HCG-MOM -3.32713AFP-MOM". It was worthwhile noting that the risk of 65.9% DS missed diagnosis group were higher than 1/1000, 92.9% higher than 1/3000. However, 72.5% cases in normal control group were lower than 1/3000. Only 9.2% mothers would be higher than the value of risk in 1/1000. The prediction mode of hCG MoM and AFP MoM might be able to help us reduce the missed diagnosis. It is also necessary to adjust more reasonable range of noninvasive prenatal testing with further clinical researches.

First trimester ultrasound tests alone or in combination with first trimester serum tests for Down's syndrome screening

BACKGROUND

Down's syndrome occurs when a person has three, rather than two copies of chromosome 21; or the specific area of chromosome 21 implicated in causing Down's syndrome. It is the commonest congenital cause of mental disability and also leads to numerous metabolic and structural problems. It can be life-threatening, or lead to considerable ill health, although some individuals have only mild problems and can lead relatively normal lives. Having a baby with Down's syndrome is likely to have a significant impact on family life.Non-invasive screening based on biochemical analysis of maternal serum or urine, or fetal ultrasound measurements, allows estimates of the risk of a pregnancy being affected and provides information to guide decisions about definitive testing.Before agreeing to screening tests, parents need to be fully informed about the risks, benefits and possible consequences of such a test. This includes subsequent choices for further tests they may face, and the implications of both false positive and false negative screening tests (i.e. invasive diagnostic testing, and the possibility that a miscarried fetus may be chromosomally normal). The decisions that may be faced by expectant parents inevitably engender a high level of anxiety at all stages of the screening process, and the outcomes of screening can be associated with considerable physical and psychological morbidity. No screening test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

To estimate and compare the accuracy of first trimester ultrasound markers alone, and in combination with first trimester serum tests for the detection of Down's syndrome.

SEARCH METHODS

We carried out extensive literature searches including MEDLINE (1980 to 25 August 2011), Embase (1980 to 25 August 2011), BIOSIS via EDINA (1985 to 25 August 2011), CINAHL via OVID (1982 to 25 August 2011), and The Database of Abstracts of Reviews of Effects (the Cochrane Library 2011, Issue 7). We checked reference lists and published review articles for additional potentially relevant studies.

SELECTION CRITERIA

Studies evaluating tests of first trimester ultrasound screening, alone or in combination with first trimester serum tests (up to 14 weeks' gestation) for Down's syndrome, compared with a reference standard, either chromosomal verification or macroscopic postnatal inspection.

DATA COLLECTION AND ANALYSIS

Data were extracted as test positive/test negative results for Down's and non-Down's pregnancies allowing estimation of detection rates (sensitivity) and false positive rates (1-specificity). We performed quality assessment according to QUADAS criteria. We used hierarchical summary ROC meta-analytical methods to analyse test performance and compare test accuracy. Analysis of studies allowing direct comparison between tests was undertaken. We investigated the impact of maternal age on test performance in subgroup analyses.

MAIN RESULTS

We included 126 studies (152 publications) involving 1,604,040 fetuses (including 8454 Down's syndrome cases). Studies were generally good quality, although differential verification was common with invasive testing of only high-risk pregnancies. Sixty test combinations were evaluated formed from combinations of 11 different ultrasound markers (nuchal translucency (NT), nasal bone, ductus venosus Doppler, maxillary bone length, fetal heart rate, aberrant right subclavian artery, frontomaxillary facial angle, presence of mitral gap, tricuspid regurgitation, tricuspid blood flow and iliac angle 90 degrees); 12 serum tests (inhibin A, alpha-fetoprotein (AFP), free beta human chorionic gonadotrophin (ßhCG), total hCG, pregnancy-associated plasma protein A (PAPP-A), unconjugated oestriol (uE3), disintegrin and metalloprotease 12 (ADAM 12), placental growth factor (PlGF), placental growth hormone (PGH), invasive trophoblast antigen (ITA) (synonymous with hyperglycosylated hCG), growth hormone binding protein (GHBP) and placental protein 13 (PP13)); and maternal age. The most frequently evaluated serum markers in combination with ultrasound markers were PAPP-A and free ßhCG.Comparisons of the 10 most frequently evaluated test strategies showed that a combined NT, PAPP-A, free ßhCG and maternal age test strategy significantly outperformed ultrasound markers alone (with or without maternal age) except nasal bone, detecting about nine out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). In both direct and indirect comparisons, the combined NT, PAPP-A, free ßhCG and maternal age test strategy showed superior diagnostic accuracy to an NT and maternal age test strategy (P < 0.0001). Based on the indirect comparison of all available studies for the two tests, the sensitivity (95% confidence interval) estimated at a 5% FPR for the combined NT, PAPP-A, free ßhCG and maternal age test strategy (69 studies; 1,173,853 fetuses including 6010 with Down's syndrome) was 87% (86 to 89) and for the NT and maternal age test strategy (50 studies; 530,874 fetuses including 2701 Down's syndrome pregnancies) was 71% (66 to 75). Combinations of NT with other ultrasound markers, PAPP-A and free ßhCG were evaluated in one or two studies and showed sensitivities of more than 90% and specificities of more than 95%.High-risk populations (defined before screening was done, mainly due to advanced maternal age of 35 years or more, or previous pregnancies affected with Down's syndrome) showed lower detection rates compared to routine screening populations at a 5% FPR. Women who miscarried in the over 35 group were more likely to have been offered an invasive test to verify a negative screening results, whereas those under 35 were usually not offered invasive testing for a negative screening result. Pregnancy loss in women under 35 therefore leads to under-ascertainment of screening results, potentially missing a proportion of affected pregnancies and affecting test sensitivity. Conversely, for the NT, PAPP-A, free ßhCG and maternal age test strategy, detection rates and false positive rates increased with maternal age in the five studies that provided data separately for the subset of women aged 35 years or more.

AUTHORS' CONCLUSIONS

Test strategies that combine ultrasound markers with serum markers, especially PAPP-A and free ßhCG, and maternal age were significantly better than those involving only ultrasound markers (with or without maternal age) except nasal bone. They detect about nine out of 10 Down's affected pregnancies for a fixed 5% FPR. Although the absence of nasal bone appeared to have a high diagnostic accuracy, only five out of 10 affected Down's pregnancies were detected at a 1% FPR.

Diagnostic accuracy of the BACs-on-Beads™ assay versus karyotyping for prenatal detection of chromosomal abnormalities: a retrospective consecutive case series

OBJECTIVE

To evaluate the diagnostic performance of the BACs-on-Beads(™) (BoBs(™)) assay for prenatal detection of chromosomal abnormalities.

DESIGN

Retrospective study.

SETTING

Tertiary prenatal diagnosis centre.

POPULATION

Women referred for prenatal diagnosis.

METHODS

We retrieved 2153 archived DNA samples collected between January 2010 and August 2011 for the BoBs(™) assay. These samples had previously been tested by quantitative fluorescence polymerase chain reaction (QF-PCR) and karyotyping. In the BoBs(™) assay a sample was defined as normal disomic when the ratio of the fluorescence intensities in a chromosome locus lay within the threshold (mean ratio ± 2SD), and as deleted or duplicated when the ratio was below the lower threshold (0.6-0.8) or above the upper threshold (1.3-1.4), respectively. The BoBs(™) results were further validated by microarray and compared in a blinded manner with the original QF-PCR and karyotyping results.

MAIN OUTCOME MEASURES

Concordance of any numerical, structural, and submicroscopic chromosomal abnormalities between the methods.

RESULTS

BACs-on-Beads(™) was similar to karyotyping and QF-PCR in detecting trisomy 13, trisomy 18, trisomy 21, and sex chromosomal aneuploidies, and superior to QF-PCR in detecting major structural abnormalities (53.3 versus 13.3%) and mosaicism (28.6 versus 0%) involving chromosomal abnormalities other than the common aneuploidies. BoBs(™) detected six microdeletion syndromes missed by karyotyping and QF-PCR; however, BoBs(™) missed two cases of triploidy identified by QF-PCR. Therefore, the sensitivity of BoBs(™) is 96.7% (95% CI 92.6-98.7%), and its specificity is 100% (95% CI 99.8-100%).

CONCLUSIONS

BACs-on-Beads(™) can replace QF-PCR for triaging in prenatal diagnosis, and gives a better diagnostic yield than current rapid aneuploidy tests.

Unchanged prevalence of Down syndrome in the Netherlands: results from an 11-year nationwide birth cohort

OBJECTIVE

This study aims to evaluate trends in prevalence of Down syndrome (DS) births in the Netherlands over an 11-year period and how they have been affected by maternal age and introduction of prenatal screening.

METHOD

Nationwide data of an 11-year birth cohort (1997-2007) from the Netherlands Perinatal Registry were analyzed. First-trimester combined screening was introduced in 2002, free of charge only for women 36 years of age or older and only on patients' request. Changes in maternal age, prevalence of DS births, and rates of births at <24 weeks (legal limit for termination of pregnancy in the Netherlands) during the study period were evaluated using logistic and linear regression analyses.

RESULTS

In total, 1,972,058 births were registered (91% of the births in 1997-2007). Mean prevalence of DS was 14.57 per 10,000 births (95% confidence interval 14.43; 14.73); 85% of DS were live births. No significant trend in overall prevalence of DS births was observed (p = 0.385), in spite of a significant increase of mean maternal age during the same period (p < 0.001). The increased prevalence of DS births at ≥ 24 weeks among women ≥ 36 years of age (p = 0.011) was offset by a significant increase in the proportion of DS births at <24 weeks among women aged <36 years (p = 0.013).

CONCLUSION

The proportion of DS births in the Netherlands has not changed during the period 1997-2007.

Preliminary proteomic-based identification of a novel protein for Down's syndrome in maternal serum

Prenatal screening for Down's syndrome (DS) is in need of improvement. As a powerful platform, proteomics techniques could also be used for identification of new biomarkers for DS screening. In this case-control proteome study, pregnant women were diagnosed prenatally by karyotype analysis from amniotic fluid (AF). Maternal serum samples were collected from six pregnancies with fetuses affected by DS and six pregnancies with normal fetuses. First, we used two-dimensional electrophoresis and mass spectrometry to identify the different levels of expression of proteins in maternal serum between the DS and control groups in the second trimester. Second, we used bioinformatics to analyze the proteins by DAVID. Then, the interesting candidates were further tested by enzyme-linked immunosorbent assay (ELISA). Twenty-nine proteins were successfully identified in maternal serum obtained from pregnancies with fetuses affected by DS. The top five proteins up-regulated were serotransferrin (TF), alpha-1b-glycoprotein (A1BG), desmin (DES), alpha-1-antitrypsin (SERPINA1) and ceruloplasmin (CP), while serum amyloid P-component (APCS) was the most down-regulated protein. These 29 proteins were categorized based on binding, catalytic activity and enzyme regulator activity. The biological roles were involved in biological regulation, metabolic processes, cellular processes and response to a stimulus. Based on ELISA, the median concentrations of CP and complement factor B (CFB) were 332.3 and 412.3 ng/mL, respectively. The concentrations of CP and CFB were significantly higher in the DS group than in the control group ( P < 0.05). In conclusion, proteomic approaches offer the possibility of further improving the performance of DS screening and our identification of up- and down-regulated proteins may lead to new candidates for DS screening.

Performance of first-trimester combined test for Down syndrome in different maternal age groups: reason for adjustments in screening policy?

OBJECTIVE

To evaluate the performance of the first-trimester combined test (FCT) in different maternal age groups and to discuss whether adjustments in screening policies should be made.

METHODS

In this retrospective study data (n = 26 274) from a fetal medicine center on FCT (maternal age, fetal NT, free β-human chorionic gonadotrophin, pregnancy-associated plasma protein-A) were studied.

RESULTS

70.6% of cases was <36 years and 43% of the Down syndrome (DS) cases were detected in this age group. For women <36 years and advanced maternal age (AMA) women (≥36 years) detection rate (DR) and false positive rate (FPR) were 94.5% and 4.1%, and 95.8% and 13.0%, respectively (cut-off 1:200). Lowering the cut-off showed an improved balance in DR and FPR. With increasing maternal age FPR and DR increased and odds of being affected given a positive result (OAPR) decreased.

CONCLUSION

FCT is effective in women <36 and ≥36 years. The balance between FPR and DR is more favourable in women <36 years with comparable OAPR. Although FPR increases with increasing maternal age, performance of FCT in AMA women is more effective than screening based on maternal age alone. Lowering the cut-off to 1:100 in AMA women is suggested to improve screening performance. Routinely offering diagnostic testing to AMA women as a screening policy for the detection of DS seems not reasonable.

Modeling Down syndrome screening performance using first-trimester serum markers

OBJECTIVE

To evaluate the modeled predictive value of three current screening markers (pregnancy-associated plasma protein-A (PAPP-A), free β-human chorionic gonadotropin (free β-hCG), and nuchal translucency (NT)) and four potential screening markers (a disintegrin and metalloprotease 12 (ADAM12), total hCG, placental protein 13 (PP13), and placental growth factor (PlGF)) for Down syndrome using different screening strategies.

METHODS

All markers were measured in stored first-trimester serum of 151 Down syndrome cases and 847 controls. All marker levels were expressed as gestational age-specific multiples of the median (MoMs) and comparisons were made using the Mann-Whitney U-test. Detection rates (DRs) for fixed false-positive rates (FPRs) were modeled using different screening strategies.

RESULTS

Significantly different median MoMs for Down syndrome cases compared to controls were found for PAPP-A (0.49 vs. 1.00; P < 0.0001), free β-hCG (1.70 vs. 1.01; P < 0.0001), ADAM12 (0.89 vs. 1.00; P < 0.0001), total hCG (1.28 vs. 1.00; P < 0.0001), PlGF (0.80 vs. 1.00; P < 0.0001) and NT (1.74 vs. 1.01; P < 0.0001). The lower PP13 MoM in Down syndrome cases (0.91 vs. 1.00) was not statistically significant (P = 0.061). Adding the four new markers to the current screening strategy (i.e. first-trimester combined test) led to an increase in DR from 77% to 80% at a 5% FPR. The modeled application of a two-sample screening strategy (with some markers assessed early and others later in the first trimester) increased the DR to 89%. In a two-step contingent screening model, using an intermediate risk range of 1 in 100 to 1 in 2000 at biochemical screening (using all markers), the overall DR was 77%, but it was predicted that only 33% of women would require referral for NT measurement.

CONCLUSIONS

First-trimester Down syndrome screening may be improved by adding new markers to the current screening test and by applying different screening strategies. The application of a two-sample screening model resulted in the highest predicted DR, but this should be confirmed in population-based prospective studies.

Erroneous production of PAPP-A kits: the impact of a downward shift in PAPP-A concentration on the test performance of first-trimester combined screening for Down syndrome

OBJECTIVE

To evaluate a 20% downward shift in the pregnancy-associated plasma protein A (PAPP-A) concentration on the test performance of first-trimester combined screening (FTS) for Down syndrome (DS) following a flaw in the production of PAPP-A kits on FTS for DS.

METHODS

A retrospective re-evaluation of PAPP-A in stored sera. Inclusion criteria were a maternal weight-corrected PAPP-A multiple of the median value ≥ 0.9 and a biochemical risk of DS ≤ 1:200 at the time of testing.

RESULTS

Of the 3100 women, 473 (15%) fulfilled the inclusion criteria. After combining the biochemical risk based on the incorrect PAPP-A values with nuchal translucency findings, an increased risk for DS was initially found in 107 women [false positive rate (FPR): 3.1]. Eighty-two (77%) of the 107 women opted for invasive testing. Following re-analysis of PAPP-A, the biochemical risk and the combined risk were statistically significantly different from the initial risk estimates (p < 0.001.). We noticed that 25 women (30%) had invasive testing, while this was unjustified given the re-analysed PAPP-A.

CONCLUSION

Erroneous PAPP-A kits resulted in an increase in the FPR by 1.2%. There were no reports of iatrogenic miscarriage. The occurrence of this problem reaffirms the importance of continuous monitoring of quality in FTS.

Gene expression profiling in a mouse model identifies fetal liver- and placenta-derived potential biomarkers for Down Syndrome screening

Background

As a first step to identify novel potential biomarkers for prenatal Down Syndrome screening, we analyzed gene expression in embryos of wild type mice and the Down Syndrome model Ts1Cje. Since current Down Syndrome screening markers are derived from placenta and fetal liver, these tissues were chosen as target.

Methodology/Principal Findings

Placenta and fetal liver at 15.5 days gestation were analyzed by microarray profiling. We confirmed increased expression of genes located at the trisomic chromosomal region. Overall, between the two genotypes more differentially expressed genes were found in fetal liver than in placenta. Furthermore, the fetal liver data are in line with the hematological aberrations found in humans with Down Syndrome as well as Ts1Cje mice. Together, we found 25 targets that are predicted (by Gene Ontology, UniProt, or the Human Plasma Proteome project) to be detectable in human serum.

Conclusions/Significance

Fetal liver might harbor more promising targets for Down Syndrome screening studies. We expect these new targets will help focus further experimental studies on identifying and validating human maternal serum biomarkers for Down Syndrome screening.

Proteomics and Down syndrome screening: a validation study

OBJECTIVE

In a previous discovery study, we identified seven potential screening markers for Down syndrome (DS). Here, we report on an extended study to validate the discriminative potential of these markers.

METHODS

Concentrations of the seven analytes were measured using bead-based multiplexed immunoassays in maternal serum from 27 DS pregnancies and 27 matched controls. Control samples were matched to the cases by gestational age (exact day), maternal weight ( ± 5 kg), and maternal age ( ± 1 year) and by closest sample date. Prediction values were obtained for current screening markers [pregnancy-associated plasma protein A (PAPP-A), free beta human chorionic gonadotrophin (fβ-hCG) and nuchal translucency (NT)] and seven markers identified before based on concentration fold ratios between DS and controls. Models were fitted based on data of the discovery study or this study and also tested on both datasets.

RESULTS

A significantly higher fold ratio was only found for epidermal growth factor (EGF) (-1.96; p = 0.006). In the prediction model for the current dataset, EGF improved the detection rate (DR) of DS by 5.7% [at a fixed 5% false-positive rate (FPR)] when added to the currently used screening markers.

CONCLUSIONS

Validation of previously identified biomarkers only confirmed EGF for further consideration as a DS screening marker. This underlines the importance of validating biomarkers; in this study, limiting the range of plausible biomarkers to only one suitable biomarker.

Down syndrome screening: imagining the screening test of the future

Prenatal screening for Down syndrome (DS) is performed by risk calculation based on biochemical and biometric parameters. This way, approximately 75-85% of all DS cases can be detected. A way to improve detection rates is to search for new screening markers. Since the majority of biomarkers used in current DS screening are predominantly produced by the placenta, and the presence of an extra chromosome (as in DS) complicates placental development and function, it is plausible to assume that new potential screening markers may also originate from the placenta. Any alterations in these markers can be attributed to abnormal placental development and function. This article focuses on normal early placental development and function compared with that in DS pregnancies. Using this knowledge, we reason towards candidate biomarkers that may be useful in screening for DS.

Bead-based multiplexed immunoassays to identify new biomarkers in maternal serum to improve first trimester Down syndrome screening

OBJECTIVES

To identify new discriminative biomarkers for Down syndrome (DS) pregnancies using a bead-based multiplexed immunoassay, and to use the newly identified biomarkers to construct a prediction model for non-invasive DS screening.

METHODS

Maternal serum samples of 14 DS pregnancies and 15 matched controls were analyzed with a bead-based multiplexed immunoassay containing immunoassays for 90 different analytes. Potential biomarkers were selected on the basis of concentration fold ratios between DS and control samples. For these markers and the current screening markers (pregnancy-associated plasma protein-A, PAPP-A; free beta subunit of human chorion gonadotrophin (fbeta-hCG) and nuchal translucency) prediction values were obtained and used to calculate detection rates (DR) at a 5% false positive rate.

RESULTS

Seven potential biomarkers of which the fold ratio exceeded 1.3 or -1.3 were selected for further analysis. All 14 DS cases in this study were detected using the combination of all currently used and newly identified markers. The modelled DR for all markers extrapolated to the general pregnant population was 82.5%, compared to a modelled DR of 56.2% for the current screening markers.

CONCLUSION

This study demonstrates the possibility of improving the performance of the current first-trimester DS screening by addition of new biomarkers, which were identified using bead-based multiplexed immunoassays.

ADAM12s as a first-trimester screening marker of trisomy

OBJECTIVE

To evaluate the potential of maternal serum A Disintegrin And Metalloprotease 12-S (ADAM12s) as an additional marker for the combined test in the Dutch first-trimester national Down syndrome (DS) screening program.

METHODS

Serum samples were collected between 2004 and 2007 as part of the national program. A total of 218 singleton cases of trisomy 21 (DS), 62 trisomy 18 (Edwards syndrome) and 29 trisomy 13 (Patau syndrome) were identified. All cases were matched with controls for gestation, maternal weight and maternal age. The serum concentration of ADAM12s was determined 'blind' to outcome and expressed in multiples of the gestation-specific median for controls (MoM).

RESULTS

The median ADAM12s was 1.00 MoM in controls and in the DS cases at 8, 9, 10, 11, 12, 13 weeks it was 0.45 (n = 3), 0.73 (22), 0.74 (53), 0.85 (37), 0.92 (71), 1.06 (32) MoM, respectively. The median for trisomy 18 was 0.85 MoM and for trisomy 13 0.63 MoM.

CONCLUSION

The ADAM12s MoM values were clearly reduced in early first-trimester for all trisomies. However, the screening performance for DS did not greatly improve adding ADAM12s. ADAM12s could be an additional biochemical marker for first-trimester screening for trisomies other than DS.

First-trimester Down syndrome screening in women younger than 35 years old and cost-effectiveness analysis in Taiwan population

OBJECTIVES

Outcome of the first-trimester Down syndrome screening in younger population was less reported before. We present the outcome of this screening in Taiwanese women younger than 35 years old. We also test whether or not the first-trimester Down syndrome screening of women <35 years of age and women >35 years old routinely receiving amniocentesis is cost-effective compared with all pregnant women screened with this test in the setting of increased maternal age.

METHODS

From 1999 to 2007, the first-trimester Down syndrome screening including nuchal thickness, pregnancy-associated plasma protein A and free beta-hCG are provided to 10 811 singleton women <35 years of age with the cut-off of 1/270. A cost-effectiveness analysis of young women receiving this screening and older women undergo amniocentesis versus all women undergo this screening was performed in Taiwan population from 1987 to 2006, in which advanced age pregnancies increased from 2.8% to 11.6% of total pregnancies.

RESULTS

Detection rates of trisomy 21, trisomy 18, Turner syndrome and other chromosome anormalies in women <35 years of age are 87.5% (14/16), 50% (2/4), 80% (8/10) and 63% (12/19), respectively, with a false-positive rate of 5.5% (590/10 811). As advanced age pregnancies reached 11.6%, the average cost per one case averted for all women screened ranged from $77 204 to $98 421, while the cost ranged from $99 647 to $116 433 for only women <35 years of age receiving this screening.

CONCLUSIONS

In an aging population, the first-trimester Down syndrome screening should be implemented for all pregnant women when it is available.

First-trimester Down syndrome screening performance in the Dutch population; how to achieve further improvement?

OBJECTIVE

To study the performance of the first-trimester combined test between 2004 and 2006 compared to a previous period to investigate changes in time and identify reasons for sub-optimal performance.

METHODS

Serum samples were analysed for pregnancy-associated plasma protein A (PAPP-A) and the free beta subunit of human chorionic gonadotrophin (f beta-hCG). Nuchal translucency (NT) was measured between 10 and 14 weeks. Tests were considered screen positive, if their calculated Down syndrome (DS) risk was at least 1 in 250 at term.

RESULTS

A total of 20,293 singleton pregnancies were included in the analysis. The median maternal age fell from 35.7 to 34.3 years. The overall median weight-corrected multiple of the median (MoM) values of PAPP-A and f beta-hCG were 1.12 and 1.03, respectively. The median MoM value of NT was 0.89 and increased from 0.82 to 0.96. Sixty-six DS cases were detected by the screening test. The detection rate (DR) for DS was 75.9%, with a FPR of 3.3%.

CONCLUSION

The performance of the first-trimester test has improved over the years. A better performance of the NT measurement was the main reason, although NT assessment should further be improved. In addition, a better setting of the medians for the biochemical parameters may contribute to a higher DR.

Quality of nuchal translucency measurements in The Netherlands: a quantitative analysis

OBJECTIVE

The Dutch Centre for Population Research has specified quality demands for nuchal translucency (NT) measurement in The Netherlands. We performed an analysis of the quality of NT measurement in 2005-2006 and its influence on screening performance.

METHODS

This was a retrospective study of records of NT measurements (n = 27,738) obtained between January 2005 and December 2006 retrieved from the Dutch National Institute for Public Health and the Environment (RIVM). The performance of each individual operator was analyzed with regard to the quality standards, which involved calculation of operator-specific median NT-multiples of the median (MoM) values. For the entire population of operators, a curve was determined describing the relationship between crown-rump length and NT. Detection rates (DR) and false-positive rates (FPR) for Down syndrome were modeled with this new curve and compared to those originally obtained using previously published reference data.

RESULTS

Only 22% of all operators met the quality requirement of performing more than 150 NT measurements per year. However, no relationship was found between the number of measurements per operator and their median NT-MoM. The mean of all operator-specific median NT-MoM values was 0.94 (target value 1.0). Overall, operators with The Fetal Medicine Foundation certificate measured a significantly higher median NT-MoM (mean of operator-specific medians, 0.98) as compared to the non-certified operators (0.92). During the study period, the monthly median NT-MoM of all operators rose steadily, from 0.86 in January 2005 to 0.96 in December 2006. Recalculation of the risk for Down syndrome after adjusting the reference NT medians using our own data led to a modeled 4% increase in DR at a 5% FPR.

CONCLUSION

Improved monitoring of NT measurement put into effect during the study period seems to have led to an improvement in the accuracy of measurements. Strict quality demands, continued monitoring and scrupulous evaluation of individual operators is likely to lead to an even better performance.

Performance of free β-human chorionic gonadotrophin (free β-hCG) and pregnancy associated plasma protein-A (PAPP-A) analysis between Delfia Xpress and AutoDelfia systems in The Netherlands

: The VU University Medical Center (VUmc) was the first hospital in the Netherlands to introduce the Delfia Xpress for the analysis of free β-human chorionic gonadotrophin (β-hCG) and pregnancy associated plasma protein-A (PAPP-A) in the first trimester screening program for Down syndrome. Since then, others have implemented this system. In this study, we tested the equality of measurements for free β-hCG and PAPP-A between Delfia Xpress systems and one AutoDelfia system.

: A total of 40 serum samples were aliquoted and stored at –20°C. Samples were analyzed by six Delfia Xpress systems and one AutoDelfia system over a time period of 2 years.

: The relationships between free β-hCG and PAPP-A were excellent for the different Delfia Xpress systems (r>0.99, p<0.0001). For PAPP-A, the agreement between the main system at VUmc and five other systems was linear with slopes between 0.99 and 1.06. Similarly, agreement for free β-hCG was linear with slopes between 0.99 and 1.09. Likewise, agreement for PAPP-A and free β-hCG was excellent for the AutoDelfia vs. the main Delfia Xpress at the VUmc (r>0.99, p<0.0001). For both PAPP-A and free β-hCG, the relationships were linear with slopes of 1.08 and 1.07.

: We demonstrate an excellent agreement for the analysis of PAPP-A and free β-hCG between Delfia Xpress systems and one AutoDelfia system.

Clin Chem Lab Med 2009;47:222–6.

Impact of a new national screening policy for Down's syndrome in Denmark: population based cohort study

OBJECTIVES

To evaluate the impact of a screening strategy in the first trimester, introduced in Denmark during 2004-6, on the number of infants born with Down's syndrome and the number of chorionic villus samplings and amniocenteses, and to determine detection and false positive rates in the screened population in 2005 and 2006.

DESIGN

Population based cohort study.

SETTING

19 Danish departments of gynaecology and obstetrics and a central cytogenetic registry 2000-7.

PARTICIPANTS

65 000 pregnancies per year.

MAIN OUTCOME MEASURES

The primary outcomes measured were number of fetuses and newborn infants with Down's syndrome diagnosed prenatally and postnatally and number of chorionic villus samplings and amniocenteses carried out. Secondary outcomes measured were number of women screened in 2005 and 2006, screen positive rate, and information on screening in 2005 and 2006 for infants with a postnatal diagnosis of Down's syndrome.

RESULTS

The number of infants born with Down's syndrome decreased from 55-65 per year during 2000-4 to 31 in 2005 and 32 in 2006. The total number of chorionic villus samplings and amniocenteses carried out decreased from 7524 in 2000 to 3510 in 2006. The detection rate in the screened population in 2005 was 86% (95% confidence interval 79% to 92%) and in 2006 was 93% (87% to 97%). The corresponding false positive rates were 3.9% (3.7% to 4.1%) and 3.3% (3.1% to 3.4%).

CONCLUSION

The introduction of a combined risk assessment during the first trimester at a national level in Denmark halved the number of infants born with Down's syndrome. The strategy also resulted in a sharp decline in the number of chorionic villus samplings and amniocenteses carried out, even before full implementation of the policy.