Improved first-trimester Down syndrome screening performance by lowering the false-positive rate: a prospective study of 9941 low-risk women

The significance of mitochondrial haplogroups in preeclampsia risk

OBJECTIVE

To determine whether mitochondrial haplogroups function as disease-modifiers or as susceptibility factors in preeclampsia using a traditional haplogroup association model.

METHODS

This retrospective study haplotyped 235 control and 78 preeclamptic pregnancies from Denmark using either real-time PCR or Sanger sequencing depending on the rarity of the haplogroup.

RESULTS

No significant association between haplogroups and the risk of preeclampsia was found, nor was any role for haplogroups in disease severity uncovered.

CONCLUSION

Mitochondrial haplogroups are not associated with preeclampsia or the severity of preeclampsia in the Danish population. However, this study cannot exclude a role for less common mtDNA variation. Models that can examine these should be applied in preeclamptic patients.

The Effect of Vanishing Twin on First- and Second-Trimester Maternal Serum Markers and Nuchal Translucency: A Multicenter Prospective Cohort Study

BACKGROUND

The purpose of this study was to evaluate the effect of vanishing twin (VT) on maternal serum marker concentrations and nuchal translucency (NT).

METHODS

This is a secondary analysis of a multicenter prospective cohort study in 12 institutions. Serum concentrations of pregnancy-associated plasma protein-A in the first trimester and alpha-fetoprotein (AFP), total human chorionic gonadotrophin, unconjugated estriol, and inhibin A in the second trimester were measured, and NT was measured between 10 and 14 weeks of gestation.

RESULTS

Among 6,793 pregnant women, 5,381 women were measured for serum markers in the first or second trimester, including 65 cases in the VT group and 5,316 cases in the normal singleton group. The cases in the VT group had a higher median multiple of the median value of AFP and inhibin A than the normal singleton group. The values of other serum markers and NT were not different between the two groups. After the permutation test with adjustment, AFP and inhibin A remained significant differences. The frequency of abnormally increased AFP was also higher in the VT group than in the normal singleton group.

CONCLUSION

VT can be considered as an adjustment factor for risk assessment in the second-trimester serum screening test.

First-Trimester Maternal Serum Adiponectin/Leptin Ratio in Pre-Eclampsia and Fetal Growth

The serum adiponectin/leptin ratio (A/L ratio) is a surrogate marker of insulin sensitivity. Pre-eclampsia (PE) is associated with maternal metabolic syndrome and occasionally impaired fetal growth. We assessed whether the A/L ratio in first-trimester maternal serum was associated with PE and/or birth weight. Adiponectin and leptin were quantitated in first-trimester blood samples (gestational week 10+3−13+6) from 126 women who later developed PE with proteinuria (98 mild PE; 21 severe PE; 7 HELLP syndrome), and 297 controls, recruited from the Copenhagen First-Trimester Screening Study. The A/L ratio was reduced in PE pregnancies, median 0.17 (IQR: 0.12−0.27) compared with controls, median 0.32 (IQR: 0.19−0.62) (p < 0.001). A multiple logistic regression showed that PE was negatively associated with log A/L ratio independent of maternal BMI (odds ratio = 0.315, 95% CI = 0.191 to 0.519). Adiponectin (AUC = 0.632) and PAPP-A (AUC = 0.605) were negatively associated with PE, and leptin (AUC = 0.712) was positively associated with PE. However, the A/L ratio was a better predictor of PE (AUC = 0.737), albeit not clinically relevant as a single marker. No significant association was found between A/L ratio and clinical severity of pre-eclampsia or preterm birth. PE was associated with a significantly lower relative birth weight (p < 0.001). A significant negative correlation was found between relative birth weight and A/L ratio in controls (β = −0.165, p < 0.05) but not in PE pregnancies), independent of maternal BMI. After correction for maternal BMI, leptin was significantly associated with relative birth weight (β = 2.98, p < 0.05), while adiponectin was not significantly associated. Our findings suggest that an impairment of the A/L ratio (as seen in metabolic syndrome) in the first trimester is characteristic of PE, while aberrant fetal growth in PE is not dependent on insulin sensitivity, but rather on leptin-associated pathways.

Placental protein-13 (PP13) in combination with PAPP-A and free leptin index (fLI) in first trimester maternal serum screening for severe and early preeclampsia

Background:

Placental protein-13 (PP13) is involved in placental invasion and has been suggested as a maternal serum marker of preeclampsia (PE) development. However, the discriminatory ability of PP13 in first trimester has not been completely clarified.

Methods:

PP13 was measured in first trimester (week 10+3–13+6) maternal serum from 120 PE pregnancies and 267 control pregnancies and was correlated with clinical parameters. The population screening performance of PP13 in combination with the PE markers pregnancy associated plasma protein A (PAPPA) and free leptin index (fLI) was assessed by Monte Carlo simulation.

Results:

In severe PE (including HELLP) cases (n=26) the median PP13 concentration was 35.8 pg/mL (range: 17.8–85.5 pg/mL) and in PE pregnancies (n=10) with birth prior to week 34, the median PP13 concentration was 30.6 pg/mL (13.1–50.1 pg/mL), compared to controls with a median of 54.8 pg/mL (range: 15.4–142.6 pg/mL) (p<0.04). The population screening detection rate (DR) for a false-positive rate of 10% for severe PE and HELLP was 26% for PP13, 28% for PP13+PAPP-A, 33% for PP13+fLI, and 40% for PP13+PAPP-A+fLI.

Conclusions:

PP13 is a marker of severe PE and HELLP syndrome. The screening performance of PP13 can be markedly improved by combining it with fLI and PAPP-A.

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.

Screening for trisomy 18 using traditional combined screening vs. ultrasound-based protocol in tertiary center environment

OBJECTIVES

To compare the screening performances of combined screening test risk algorithm for trisomy 18 (T18) using various cutoffs with a multiparameter ultrasound-based method. To compare the general and maternal age (MA)-based screening performances for T18 by means of combined screening and an ultrasound-based method.

METHODS

This was a prospective, multicenter study based on a mixed-risk non-selected population of women referred to referral centers for a first-trimester screening. Each subject was offered a choice between either a traditional combined screening (CSG arm) or an ultrasound-based screening (USG arm). General and MA-based screening performances were measured.

RESULTS

The study population comprised 10 820 pregnancies as follows: 5132 in the CSG arm, including 28 cases of T18, and 5688 in the USG arm, including 29 cases of T18. In the CSG arm, the detection rate (DR) for T18 at a false-positive rate (FPR) of 3% was 86%, whereas the DR was 100% for the USG arm. MA influenced the T18 screening performance in the CSG arm and reduced the DR in MA ranges  <26 years and 31-35 years. This influence was not observed in the USG arm.

CONCLUSIONS

Only, a multiparameter ultrasound-based screening method may be considered an effective alternative to combined screening for T18 screening. The technique exhibits high and stable DRs irrespective of MA.

Maternal Serum Resistin Is Reduced in First Trimester Preeclampsia Pregnancies and Is a Marker of Clinical Severity

OBJECTIVE

To examine whether resistin levels in first trimester maternal serum are associated with insulin resistance or preeclampsia (PE).

METHODS

A case-control study of maternal serum resistin concentration conducted using 285 normal pregnancies and 123 PE pregnancies matched for gestational age, parity and maternal age. Samples were taken in gestational weeks 10⁺⁰-13⁺⁶.

RESULTS

There was a negative correlation between resistin and clinical severity of PE, but no correlation with IS, TNF-α, body mass index, birth weight and pregnancy length.

CONCLUSIONS

Resistin is reduced in first trimester of PE pregnancies, particularly in severe PE. Inflammation and IS cannot explain this phenomenon.

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.Noninvasive 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. However, no test can predict the severity of problems a person with Down's syndrome will have.

OBJECTIVES

The aim of this review was to estimate and compare the accuracy of first trimester serum markers for the detection of Down's syndrome in the antenatal period, both as individual markers and as combinations of markers. Accuracy is described by the proportion of fetuses with Down's syndrome detected by screening before birth (sensitivity or detection rate) and the proportion of women with a low risk (normal) screening test result who subsequently had a baby unaffected by Down's syndrome (specificity).

SEARCH METHODS

We conducted a sensitive and comprehensive literature search of 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), The Database of Abstracts of Reviews of Effectiveness (The Cochrane Library 25 August 2011), MEDION (25 August 2011), The Database of Systematic Reviews and Meta-Analyses in Laboratory Medicine (25 August 2011), The National Research Register (Archived 2007), Health Services Research Projects in Progress database (25 August 2011). We did forward citation searching ISI citation indices, Google Scholar and PubMed 'related articles'. We did not apply a diagnostic test search filter. We also searched reference lists and published review articles.  

SELECTION CRITERIA

We included studies in which all women from a given population had one or more index test(s) compared to a reference standard (either chromosomal verification or macroscopic postnatal inspection). Both consecutive series and diagnostic case-control study designs were included. Randomised trials where individuals were randomised to different screening strategies and all verified using a reference standard were also eligible for inclusion. Studies in which test strategies were compared head-to-head either in the same women, or between randomised groups were identified for inclusion in separate comparisons of test strategies. We excluded studies if they included less than five Down's syndrome cases, or more than 20% of participants were not followed up.

DATA COLLECTION AND ANALYSIS

We extracted data as test positive or 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 (Quality Assessment of Diagnostic Accuracy Studies) criteria. We used hierarchical summary ROC meta-analytical methods or random-effects logistic regression methods to analyse test performance and compare test accuracy as appropriate. Analyses of studies allowing direct and indirect comparisons between tests were undertaken.

MAIN RESULTS

We included 56 studies (reported in 68 publications) involving 204,759 pregnancies (including 2113 with Down's syndrome). Studies were generally of good quality, although differential verification was common with invasive testing of only high-risk pregnancies. We evaluated 78 test combinations formed from combinations of 18 different tests, with or without maternal age; ADAM12 (a disintegrin and metalloprotease), AFP (alpha-fetoprotein), inhibin, PAPP-A (pregnancy-associated plasma protein A, ITA (invasive trophoblast antigen), free βhCG (beta human chorionic gonadotrophin), PlGF (placental growth factor), SP1 (Schwangerschafts protein 1), total hCG, progesterone, uE3 (unconjugated oestriol), GHBP (growth hormone binding protein), PGH (placental growth hormone), hyperglycosylated hCG, ProMBP (proform of eosinophil major basic protein), hPL (human placental lactogen), (free αhCG, and free ßhCG to AFP ratio. Direct comparisons between two or more tests were made in 27 studies.Meta-analysis of the nine best performing or frequently evaluated test combinations showed that a test strategy involving maternal age and a double marker combination of PAPP-A and free ßhCG significantly outperformed the individual markers (with or without maternal age) detecting about seven out of every 10 Down's syndrome pregnancies at a 5% false positive rate (FPR). Limited evidence suggested that marker combinations involving PAPP-A may be more sensitive than those without PAPP-A.

AUTHORS' CONCLUSIONS

Tests involving two markers in combination with maternal age, specifically PAPP-A, free βhCG and maternal age are significantly better than those involving single markers with and without age. They detect seven out of 10 Down's affected pregnancies for a fixed 5% FPR. The addition of further markers (triple tests) has not been shown to be statistically superior; the studies included are small with limited power to detect a difference.The screening blood tests themselves have no adverse effects for the woman, over and above the risks of a routine blood test. However some women who have a 'high risk' screening test result, and are given amniocentesis or chorionic villus sampling (CVS) have a risk of miscarrying a baby unaffected by Down's. Parents will need to weigh up this risk when deciding whether or not to have an amniocentesis or CVS following a 'high risk' screening test result.

Reasons for declining extended information visit on prenatal screening among pregnant women and their partners

OBJECTIVE

A two-step model on information on prenatal screening consists of brief information at the first visit at the Maternal Health Care Centre and an offer of extended information at a separate visit. There is a lack of knowledge why some pregnant women and their partners refrain from the extended information visit. The aim of this study was to explore their reasons.

METHOD

Eight qualitative interviews were analyzed using Interpretive Description.

RESULTS

In the first theme 'From an individual view', the interviewees saw the invitation from their own points of view. They refrained because they did not want to receive any more information or had taken an individual position against chromosomal testing. In the theme, 'From a societal view', the interviewees perceived the offer as part of a societal view on prenatal screening that they could not support.

CONCLUSION

The findings show that these interviewees' reasons of declining an extended information visit are multidimensional and influenced by different views, from both an individual perspective and a more societal one. Health care professionals should be aware that some persons could have a different view on health care services and could be reluctant to accept offered services.

Analysis of the impact of PAPP-A, free β-hCG and nuchal translucency thickness on the advanced first trimester screening

OBJECTIVES

The intention of this study is to analyze the impact of the single parameters NT, PAPP-A and free β-hCG used in combined first trimester screening and to determine their contribution in the risk assessment.

METHODS

A retrospective risk assessment on the advanced first trimester screening (AFS) algorithm was made to determine the effect of a particular parameter while the remaining ones were fixed for calculation. Afterward data were recalculated by the AFS module. Test performance was measured by receiver operating characteristics (ROC) curves and their area under curve (AUC).

RESULTS

Among the 14,862 cases are 14,748 healthy fetuses, 86 with trisomy 21, 22 with trisomy 18 and 6 with trisomy 13. Some settings obtain at default cut-off a very high sensitivity. However, a lack of specificity, as a high false-positive rate, too. The ROC analysis was best for NT, followed by PAPP-A. Free β-hCG showed the lowest AUC. Combining PAPP-A and free β-hCG offered a better AUC than each parameter alone. Best test performance was obtained by including all three parameters.

DISCUSSION

A detection rate of 69 % for testing NT discretely is in order with present study data. PAPP-A is following and free β-hCG is not useful with a test positive rate of about a third. The detection rate of the biochemical parameters combined is higher than for NT alone, but results in a five times higher punctuation rate. All parameters together in the AFS provide the best test performance. The impact of each parameter NT, PAPP-A and free-β-hCG in a combined test strategy is nearly a third. Thus, every single parameter is needed to provide a high detection rate for all of the trisomies and minimize the number of unnecessary invasive diagnostics.

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.

Free leptin index and PAPP-A: a first trimester maternal serum screening test for pre-eclampsia

BACKGROUND

Prophylaxis with low-dose aspirin may reduce the risk of pre-eclampsia (PE) if introduced in first trimester. The performance of first trimester maternal serum screening for PE using free leptin index (fLI) and PAPP-A, where fLI = leptin/leptin soluble receptor was studied.

METHODS

First trimester serum samples from 126 PE pregnancies and 289 control pregnancies were studied. fLI and PAPP-A were converted into gestational age and maternal weight independent log MoM values of PAPP-A and fLI. The screening performance of markers was studied by receiver-operator-characteristics curves. The performance of population screening was estimated by Monte Carlo simulation.

RESULTS

fLI was significantly (p < 0.001) elevated [mean log MoM 0.2165 (SD: 0.2604)] compared to controls [mean log MoM -0.0368 (SD: 0.3132)] and PAPP-A was significantly (p < 0.001) reduced [mean log MoM -0.0133 (SD: 0.2661)] compared to controls [mean log MoM 0.0474 (SD: 0.2521)] in PE pregnancies. There was no correlation between fLI and PAPP-A in control or PE pregnancies. Combined fLI and PAPP-A screening for PE had estimated population detection rates of 22% and 35% for false positives rates of 6% and 12%, respectively.

CONCLUSION

Combining PAPP-A and fLI improves screening performance for PE compared to single marker screening.

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: Distribution of markers and comparison of assays for quantification of pregnancy‐associated plasma protein‐A

OBJECTIVE

First trimester screening for fetal chromosomal disease is now possible using the maternal serological markers pregnancy-associated plasma protein-A (PAPP-A) and the free ss-form of human chorionic gonadotrophin (sshCG) in combination with the ultrasound marker nuchal translucency (NT) thickness. The availability of well-defined analytical methods and reference ranges for the involved parameters, and knowledge of the correlation between markers and clinical parameters, e.g. maternal weight, parity and age, are important for the design of efficient screening programs.

MATERIAL AND METHODS

Women (n = 2702), with singleton pregnancies, participating in the Copenhagen First Trimester Screening Study had PAPP-A and sshCG values determined and NT measured at a gestational age of 11 to 14 weeks, as determined from crown rump length (CRL). The distribution of gestational age-independent multiples of the median (MoM) of the parameters was defined and reference intervals established. Three methods for determination of PAPP-A, one manual in-house poly-monoclonal ELISA and two commercial semi-automatic double-monoclonal methods, i.e. PAPP-A for the AutoDelfia platform and PAPP-A for the Kryptor platform, were compared in 260 women.

RESULTS

All markers had log-normally distributed MoMs. Gestational age independent reference intervals were established. Maternal weight should be included in risk algorithms. The semi-automated PAPP-A assays (AutoDelfia and Kryptor) gave similar values, mean difference 10.5 %, whereas the manual assay gave higher values, mean differences 50.4 % and 41.0 %, respectively,

CONCLUSIONS

This calls for better standardization and a uniform quality control scheme that is focused on discriminatory ability rather than adherence to mean values from a large number of laboratories.

PRENATAL SCREENING AND DIAGNOSIS OF FETAL CHROMOSOMAL ABNORMALITIES – DILEMMA BETWEEN BEST EVIDENCE-BASED MODEL AND PRACTICABILITY

There is little doubt that congenital abnormalities cause significant stresses to the affected children, their parents and the whole family. Such stresses can be physical, psychological, social and financial. To society, the cost of looking after these affected individuals properly can be substantial. In the absence of prenatal screening, birth defects affect approximately 2–4% of newborns, although there are significant variations between populations.

First-trimester screening markers are altered in pregnancies conceived after IVF/ICSI

OBJECTIVES

To determine the levels of first-trimester screening markers and to assess the false-positive rate for first-trimester combined screening for Down syndrome in a large national population of women pregnant after assisted reproductive technology (ART), in order to decide whether or not to correct risk calculation for mode of conception.

METHODS

A national prospective cohort study of 1000 pregnancies achieved after ART was compared with a control group of 2543 pregnancies conceived spontaneously. All women completed a first-trimester combined screening program. Risk calculation was performed retrospectively based on the screening parameters to avoid bias due to the use of different algorithms of risk calculation.

RESULTS

In chromosomally normal pregnancies conceived after in-vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), the pregnancy-associated plasma protein-A multiples of the median value was significantly decreased when compared with that of pregnancies conceived spontaneously (0.78 and 0.79 vs. 0.98), while there was no difference in the group treated by frozen embryo replacement. There was no difference in the level of free beta-human chorionic gonadotropin between groups. The median nuchal translucency thickness was smaller in the overall ART group compared with controls. The false-positive rate of first-trimester combined screening in the overall ART group, adjusted for maternal age, was significantly higher when compared with controls (9.0% vs. 6.0%).

CONCLUSIONS

It seems advisable to use a population of IVF/ICSI pregnancies to establish median curves for the first-trimester serum screening parameters and perhaps also for nuchal translucency thickness. However, care must be taken, as different ART treatment methods and aspects of medical history seem to alter the screening parameters in different ways.

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.

Early fetal size and growth as predictors of adverse outcome

OBJECTIVE

To evaluate the association between fetal size and growth between the first and second trimesters and subsequent adverse pregnancy outcome.

METHODS

A cohort was created of 7,642 singleton pregnancies cared for in three obstetric units associated with Copenhagen University. Data were obtained from ultrasound measurements at 11-14 weeks (crown-rump length, biparietal diameter) and 17-21 weeks (biparietal diameter). Fetal size was assessed by gestation-specific z scores, and fetal growth between the first and second trimester was calculated individually using conditional centiles. The main outcome measures were preterm delivery, smallness for gestational age, and perinatal death.

RESULTS

Slow growth of the biparietal diameter less than the 10th and less than the 2.5th conditional centiles between first and second trimesters occurred in 10.4% and 3.6% of the population, respectively. Biparietal diameter growth less than the 10th centile was associated with perinatal death before 34 weeks (risk 0.5% compared with 0.04%, odds ratio [OR] 16.0, confidence interval [CI] 2.9-88.7). Biparietal diameter growth less than the 2.5th centile was the best predictor of perinatal death at any gestation, with a positive likelihood ratio of 4.7 and an OR of 7.3 (CI 2.4-22.2). In contrast, the biparietal diameter, dated by crown-rump length, did not have an increased risk of perinatal death; however, there was a mildly increased risk of small for gestational age birth weight (less than the 10th customized centile) if the biparietal diameter was below the 10th centile in the first trimester (risk 17% compared with 12%, OR 1.5, CI 1.2-1.8) or in the second trimester (risk 15.8% compared with 12.4%, OR 1.3, CI 1.1-1.5).

CONCLUSION

Slow growth of the fetal biparietal diameter between the first and second trimesters of pregnancy is a strong predictor of perinatal death before 34 weeks.

Follow up and evaluation of the Victorian first-trimester combined screening programme for Down syndrome and trisomy 18

OBJECTIVE

The objective of this study was to follow up and evaluate the statewide first-trimester combined screening programme for Down syndrome and trisomy 18 at Genetic Health Services Victoria, Australia.

DESIGN

Retrospective population cohort.

SETTING

Maternal Serum Screening Laboratory records.

SAMPLE

All women screened between February 2000 and June 2002 (16,153 pregnancies).

METHODS

Screening results were matched to Victorian perinatal and birth defect data via record linkage, with an ascertainment of 96.8% of pregnancy outcomes. Manual follow up with health professionals increased ascertainment to more than 99%.

MAIN OUTCOME MEASURES

Fetal Down syndrome or trisomy 18, and combined screen results, to calculate test characteristics.

RESULTS

Using a risk threshold of 1 in 300 at time of ultrasound, the sensitivities for standard first-trimester combined screening and augmented 13-week combined screening for Down syndrome were 87.3 and 90.5% and the false-positive rates (FPR) were 4.1 and 3.9%, respectively. The sensitivity for trisomy 18 was 66.7% (10/15, 95% CI 42.8-90.5%) with a 0.4% FPR and 15.2% positive predictive value (1 in 250 risk threshold).

CONCLUSIONS

The combined use of record linkage and manual follow-up techniques was effective in ascertaining more than 99% of pregnancy outcomes for calculations of accurate test characteristics of the combined screen. The sensitivity for Down syndrome at Genetic Health is comparable to similar populations. However, the sensitivity for trisomy 18 is lower than that elsewhere, which may reflect the overall low birth prevalence of trisomy 18 and associated small numbers in this particular cohort.

Maternal serum free-beta-chorionic gonadotrophin, pregnancy-associated plasma protein-A and fetal nuchal translucency thickness at 10-13(+6) weeks in relation to co-variables in pregnant Saudi women

OBJECTIVE

To establish normative values and distribution parameters of first-trimester screening markers, namely, fetal nuchal translucency (NT), maternal serum free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A), at 10 to 13(+6) weeks of gestation in Saudi women and to evaluate the effect of co-variables including maternal body weight, gravidity, parity, fetal gender, twin pregnancy, smoking and ethnicity on these markers.

METHODS

A cohort of Saudi women (first cohort n = 1616) with singleton pregnancies prospectively participated in the present study, and fetal NT together with maternal serum free beta-hCG and PAPP-A were determined at 10 to 13(+6) weeks of gestation. The distribution of gestational age-independent multiples of the median (MoM) of the parameters was defined and normative values were established, and correction for maternal body weight was made accordingly. The influence of various co-variables was examined using the data collected from the first and the second (n = 1849) cohorts of women and 62 twin pregnancies, and compared with other studies.

RESULTS

All markers exhibited log-normally distributed MoMs. Gestational age-independent normative values were established. Maternal body weight was corrected, particularly for maternal free beta-hCG and PAPP-A using standard methods. Fetal NT showed a negative relationship with increasing gravidity (r = -0.296) or parity (r = -0.311), whereas both free beta-hCG and PAPP-A exhibited a significant positive relationship. There was a significant increase in the MoM of free beta-hCG in female fetuses. Smoking decreased MoM values of free beta-hCG (by 14.6%; P < 0.01) and PAPP-A (by 18.8%; P < 0.001). Twin pregnancy showed significant increases in MoM values of free beta-hCG (by 1.87-fold) and PAPP-A (by 2.24-fold), with no significant changes in fetal NT MoM values. Fetal NT MoM values were lower in Africans and Asians but higher in Orientals, as compared to Saudi women (P < 0.05; in each case). MoM values (body weight-corrected) of free beta-hCG were 25.2% higher in Africans and 19.4% higher in Orientals but 6.8% lower in other Arabian and Asian (by 5.8%) women as compared to Saudi women (P < 0.05; in each case).

CONCLUSIONS

The normative values and distribution parameters for fetal NT, maternal serum free beta-hCG and PAPP-A were established in Saudi singleton pregnancies, the maternal body weight together with smoking, twin pregnancy and ethnicity being important first-trimester screening co-variables. Gravidity, parity and fetal gender are also considered to influence one or more of the first-trimester markers examined.

Meta-analysis of first trimester Down syndrome screening studies: free beta-human chorionic gonadotropin significantly outperforms intact human chorionic gonadotropin in a multimarker protocol

OBJECTIVE

The purpose of this study was to compare free beta and intact human chorionic gonadotropin in first trimester screening with pregnancy-associated plasma protein-A and nuchal translucency.

STUDY DESIGN

A Monte Carlo simulation trial was conducted based on a literature review of the PUBMED database (1966 to November 2005).

RESULTS

In younger patients (< 35 years), detection of Down syndrome increased by 4, 5, 6, and 7 percentage points when free beta was added to pregnancy-associated plasma protein-A and nuchal translucency compared with 0, 0, 2, and 4 percentage points for intact human chorionic gonadotropin at 9-12 weeks' gestation, respectively. In advanced maternal age patients (> or = 35), inclusion of free beta-human chorionic gonadotropin reduced the false-positive rate by 2.5, 3.1, 3.8, and 4.4 percentage points compared with 0.1, 0.3, 1.0, and 2.2 percentage points for intact human chorionic gonadotropin at 9-12 weeks, respectively.

CONCLUSION

The results of our analysis suggest that in a first-trimester Down syndrome screening protocol free beta-human chorionic gonadotropin achieves higher sensitivity and lower false-positive results than intact human chorionic gonadotropin . Moreover, intact human chorionic gonadotropin does not add substantially to screening performance until the end of the first trimester.

The “Consecutive Combined Test”—using Double test from week 8 + 0 and Nuchal Translucency Scan, for first trimester screening for Down Syndrome

OBJECTIVE

To test the performance of the "Consecutive Combined Test", applied on a high-risk population. The classic "Combined Test" (Double test (DT) and Nuchal Translucency (NT) measurement on the same day at app. week 12) gives detection rates (DR) for Down syndrome (DS) of 80-90% for false positive rates (FPR) of 5%. In affected pregnancies, however, the low PAPP-A level is more pronounced, the earlier in pregnancy. Thus, we hypothesized that the Double Test could be taken as early as from week 8 + 0, without compromising the excellent performance of the Combined Test. This "Consecutive Combined Test" allows for a centralised laboratory function.

METHODS

Inclusion criteria were maternal age > 35 years (80%) or a family history (20%). Double test was taken at a median gestational age (GA) = 10 weeks. NT was measured at GA = 11 + 0 - 13 + 6. A combined risk estimate of > 1:400 at birth was used as cut-off.

RESULTS

881 had the full test. Screen positive = 34. CVS with aneuploidy = 11 (6 trisomy-21, 5 others). FPR = 3.2%. Positive Predictive Value (PPV) = 17.6% for T-21.

CONCLUSION

The "Consecutive Combined Test" applied on a high-risk population seems to be highly efficient with a remarkably high PPV.

Nuchal translucency measurements are highly correlated in both mono- and dichorionic twin pairs

OBJECTIVES

To establish the distribution of serological and ultrasound first-trimester Down syndrome markers in twins and identify correlations of significance for risk calculation.

METHODS

Nuchal translucency (NT), PAPP-A and betahCG data were extracted from 181 twin pregnancies (31 mono- and 150 dichorionic) with a normal outcome. All pregnancies were consecutively and prospectively included and examined in the Copenhagen First-Trimester Study. The variance of the sum and the difference of log MoM NT values in twin pairs was used to calculate the correlation.

RESULTS

The serological markers did not correlate and were nearly twice the value seen in singleton pregnancies with a median PAPP-A MoM of 2.14 and a median free betahCG MoM of 2.06. Chorionicity was not found to influence the level of biochemical markers. In all twin pairs (r = 0.343, p < 0.001, F-test), as well as mono- (r = 0.404, p = 0.011, F-test) and dichorionic twins (r = 0.316, p < 0.001, F-test) there was a significant correlation between log MoM NT in each pair.

CONCLUSION

As the NT values of fetuses in subsequent pregnancies from the same woman do not correlate, the correlation between NTs in twins reflects that the NT is influenced by placental and maternal factors specific for the particular pregnancy, for example, nutrient supply or vascularisation. The correlation may be useful to improve the precision of the prenatal risk assessment for Down syndrome in first-trimester twin pregnancies. The serological markers were elevated in the examined twins as previously described.

Reduction of the disintegrin and metalloprotease ADAM12 in preeclampsia

OBJECTIVES

The secreted form of ADAM12 is a metalloprotease that may be involved in placental and fetal growth. We examined whether the concentration of ADAM12 in first-trimester maternal serum could be used as a marker for preeclampsia.

METHODS

We developed a semiautomated, time-resolved, immunofluorometric assay for the quantification of ADAM12 in serum. The assay detected ADAM12 in a range of 78-1248 microg/L. Serum samples derived from women in the first trimester of a normal pregnancy (n = 324) and from women who later developed preeclampsia during pregnancy (n = 160) were obtained from the First Trimester Copenhagen Study. ADAM12 levels were assayed in these serum samples. Serum levels of ADAM12 were converted to multiples of the median (MoM) after log-linear regression of concentration versus gestational age.

RESULTS

Serum ADAM12 levels in women who developed preeclampsia during pregnancy had a mean log MoM of -0.066, which was significantly lower than the mean log MoM of -0.001 for ADAM12 levels observed in serum samples from women with normal pregnancy (P = .008). The mean log MoM was even lower in serum derived from preeclamptic women whose infant's weight at birth was less than 2,500 g (n = 27, mean log MoM of -0.120, P = .053).

CONCLUSION

The maternal serum levels of ADAM12 are significantly lower during the first trimester in women who later develop preeclampsia during pregnancy when compared with levels in women with normal pregnancies. Because the secreted form of ADAM12 cleaves insulin-like growth factor binding protein (IGFBP)-3 and IGFBP-5, the IGF axis may play a role in preeclampsia. ADAM12 may be a useful early marker for preeclampsia.

LEVEL OF EVIDENCE

II-2.

Expectation and knowledge of women undergoing first-trimester combined screening for Down syndrome in a Chinese population

OBJECTIVES

To study the preference of pregnant women regarding the time taken to report the results of first-trimester combined screening for Down syndrome and their knowledge about it.

METHODS

A questionnaire survey was conducted on a cohort of 325 pregnant participants who attended our first-trimester combined nuchal translucency and biochemical screening programme for fetal Down syndrome. This service was operated in a one-stop setting and the result of the screening test was available within 1 to 2 h after the collection of blood sample.

RESULTS

The majority of participants: (1) could recall the quoted detection rate correctly (96.6%); (2) understood that a negative test does not exclude Down syndrome (91.1%); (3) understood that a positive test does not equate to an affected fetus (91.0%), and (4) could decide on the need for further invasive tests on the basis of the screening test results (98.1%). Twenty-nine percent of participants considered that a one-stop setting was very important because any delay in releasing the results made a significant difference to them, while 48.9% considered it acceptable if the results were available on the same day. The percentage dropped dramatically to 6.3% (within 2 days), 6.7% (within 3 days), 5.7% (within 1 week), and 3.1% (more than 1 week).

CONCLUSION

The majority of the pregnant women in our test considered same day reporting of screening test results to be no different from a one-stop clinic. This would have important implications for the organisation and structuring of our service provision, since the operation of a one-stop clinic imposes significant stresses on the clinical staff involved.