First-trimester biochemical markers for Down syndrome

Application of chromosome microarray analysis and karyotyping in diagnostic assessment of abnormal Down syndrome screening results

Background

Down syndrome (DS) is the most common congenital cause of intellectual disability and also leads to numerous metabolic and structural problems. This study aims to explore the application value of chromosomal microarray analysis (CMA) and karyotyping in prenatal diagnosis for pregnant women with abnormal DS screening results.

Methods

The study recruited 1452 pregnant women with abnormal DS screening results including 493 with an enlarged nuchal translucency thickness (NT ≥ 2.5 mm) and 959 with an abnormal second-trimester maternal serum biomarker screening results. They underwent amniocentesis to obtain amniotic fluid for CMA and karyotyping.

Results

CMA identified 74/1452 abnormal results, which was more efficient than karyotyping (51/1452, P < 0.05.) CMA is equivalent to traditional karyotyping for identifying aneuploidies. Compared to karyotyping CMA identified 1.90% more copy number variants (CNVs) ranging from 159Kb to 6496Kb. However, 34.4% of them were recurrent pathogenic CNVs associated with risk of neurodevelopmental disorders. CMA identified 13 variants of uncertain significance (VUS) results and 1 maternal uniparental disomy (UPD) of chromosome 7. Karyotyping identified 3 mosaic sex chromosome aneuploidy and 4 balanced translocation which could not be identified by CMA. In enlarged NT group, karyotyping identified 80.9% abnormal results while in serum screening group karyotyping identified 35.7%. However, the incidence of pathogenic/likely pathogenic (P/LP) CNVs was nearly the same in both groups. That was because aneuploidies and gross duplication/deletion were previously screened out by NT scan.

Conclusions

CMA and karyotyping have both advantages and disadvantages in prenatal diagnosis of pregnant women with abnormal DS screening results. However, there was not enough evidence to support routine CMA in pregnant women with abnormal DS screening results.

Differential performance of first-trimester screening in predicting small-for-gestational-age neonate or fetal growth restriction

OBJECTIVE

To assess the ability of integrated first-trimester screening, combining maternal characteristics and biophysical and biochemical markers, to predict delivery of a small-for-gestational-age (SGA) neonate, and compare this with its ability to predict fetal growth restriction (FGR).

METHODS

This was a prospective cohort study of singleton pregnancies undergoing routine first-trimester screening. SGA was defined as birth weight (BW) < 10^th percentile and FGR was defined as an ultrasound estimated fetal weight < 10^th percentile plus Doppler abnormalities, or BW < 3^rd percentile. Logistic regression-based predictive models were developed for predicting SGA and FGR. Models incorporated the a-priori risk from maternal characteristics, and mean arterial pressure, uterine artery Doppler, placental growth factor and soluble fms-like tyrosine kinase-1.

RESULTS

In total, 9150 births were included. Of these, 979 (10.7%) qualified for a postnatal diagnosis of SGA and 462 (5.0%) for a prenatal diagnosis of FGR. For predicting SGA, the model achieved a detection rate of 35% for a false-positive rate (FPR) of 5% and 42% for a 10% FPR. The model's performance was significantly higher for predicting FGR (P < 0.001), with detection rates of 59% and 67%, for a FPR of 5% and 10%, respectively.

CONCLUSION

The predictive performance of first-trimester screening for cases with growth impairment by a combination of maternal characteristics and biophysical and biochemical markers is improved significantly when a prenatal and strict definition of FGR is used rather than a postnatal definition based on BW. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Validation of a first-trimester screening model for pre-eclampsia in an unselected population

OBJECTIVE

To validate the performance of a previously constructed first-trimester predictive model for pre-eclampsia (PE) in routine care of an unselected population.

METHODS

A validation cohort of 4621 consecutive women attending their routine first-trimester ultrasound examination was used to test a prediction model for PE that had been developed previously in 5170 women. The prediction model included maternal factors, uterine artery Doppler, blood pressure and pregnancy-associated plasma protein-A. Model performance was evaluated using receiver-operating characteristics (ROC) curve analysis and ROC curves from both cohorts were compared unpaired.

RESULTS

Among the 4203 women included in the final analysis, 169 (4.0%) developed PE, including 141 (3.4%) cases of late-onset PE and 28 (0.7%) cases of early-onset PE. For early-onset PE, the model showed an area under the ROC curve of 0.94 (95% CI, 0.88-0.99), which did not differ significantly (P = 0.37) from that obtained in the construction cohort (0.88 (95% CI, 0.78-0.99)). For late-onset PE, the final model showed an area under the ROC curve of 0.72 (95% CI, 0.66-0.77), which did not differ significantly (P = 0.49) from that obtained in the construction cohort (0.75 (95% CI, 0.67-0.82)).

CONCLUSION

The prediction model for PE achieved a similar performance to that obtained in the construction cohort when tested on a subsequent cohort of women, confirming its validity as a predictive model for PE. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

First-trimester screening with specific algorithms for early- and late-onset fetal growth restriction

OBJECTIVE

To develop optimal first-trimester algorithms for the prediction of early and late fetal growth restriction (FGR).

METHODS

This was a prospective cohort study of singleton pregnancies undergoing first-trimester screening. FGR was defined as an ultrasound estimated fetal weight < 10(th) percentile plus Doppler abnormalities or a birth weight < 3(rd) percentile. Logistic regression-based predictive models were developed for predicting early and late FGR (cut-off: delivery at 34 weeks). The model included the a-priori risk (maternal characteristics), mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI), placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1).

RESULTS

Of the 9150 pregnancies included, 462 (5%) fetuses were growth restricted: 59 (0.6%) early and 403 (4.4%) late. Significant contributions to the prediction of early FGR were provided by black ethnicity, chronic hypertension, previous FGR, MAP, UtA-PI, PlGF and sFlt-1. The model achieved an overall detection rate (DR) of 86.4% for a 10% false-positive rate (area under the receiver-operating characteristics curve (AUC): 0.93 (95% CI, 0.87-0.98)). The DR was 94.7% for FGR with pre-eclampsia (PE) (64% of cases) and 71.4% for FGR without PE (36% of cases). For late FGR, significant contributions were provided by chronic hypertension, autoimmune disease, previous FGR, smoking status, nulliparity, MAP, UtA-PI, PlGF and sFlt-1. The model achieved a DR of 65.8% for a 10% false-positive rate (AUC: 0.76 (95% CI, 0.73-0.80)). The DR was 70.2% for FGR with PE (12% of cases) and 63.5% for FGR without PE (88% of cases).

CONCLUSIONS

The optimal screening algorithm was different for early vs late FGR, supporting the concept that screening for FGR is better performed separately for the two clinical forms. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Forms of Circulating Luteinizing Hormone Human Chorionic Gonadotropin Receptor for the Prediction of Early and Late Preeclampsia in the First Trimester of Pregnancy

OBJECTIVE

To explore the value of circulating luteinizing human chorionic gonadotropin receptor (LHCGR) forms for the prediction of preeclampsia (PE) in the first trimester of pregnancy.

METHODS

Case-control study, based on a cohort of 5,759 pregnancies, including 20 early PE, 20 late PE, and 300 controls. We recorded/measured maternal characteristics, mean arterial pressure (MAP), uterine artery (UtA) Doppler, placental growth factor (PlGF), soluble Fms-like tyrosine kinase-1 (sFtl-1), and LHCGR forms (hCG-LHCGR and soluble LHCGR), and their independent predictive values were analyzed by logistic regression.

RESULTS

For early PE, the model included black ethnicity, chronic hypertension, previous PE, MAP, UtA Doppler, PlGF, sFlt-1, and LHCGR forms, achieving detection rates (DR) of 83% at 10% of false-positive rates (FPR) [AUC: 0.961 (95% CI: 0.921-1)]. For late PE, the model included body mass index, previous PE, UtA Doppler, PlGF, sFlt-1, and LHCGR forms, with DR of 75% at 10% of FPR [AUC: 0.923 (95% CI: 0.871-0.976)]. In both early and late PE, LHCGR forms improved DR by 6-15%.

CONCLUSIONS

LHCGR forms improved the prediction for early and late PE. These results should be confirmed in larger prospective studies.

First trimester screening for early and late preeclampsia based on maternal characteristics, biophysical parameters, and angiogenic factors

OBJECTIVE

The aim of this article is to develop the best first-trimester screening model for preeclampsia (PE) based on maternal characteristics, biophysical parameters, and angiogenic factors in a low-risk population.

METHODS

A prospective cohort of 9462 pregnancies undergoing first-trimester screening is used. Logistic regression predictive models were developed for early and late PE (cut-off of 34 weeks' gestation at delivery). Data included the a priori risk (maternal characteristics), mean arterial pressure (MAP), and uterine artery (UtA) Doppler (11-13 weeks) in all cases. Plasma levels (8-11 weeks) of human chorionic gonadotrophin, pregnancy-associated plasma protein A, placental growth factor (PlGF), and soluble Fms-like tyrosine kinase-1 (sFlt-1) were analyzed using a nested case-control study design.

RESULTS

The best model for early PE (n = 57, 0.6%) included a priori risk, MAP, UtA Doppler, PlGF, and sFlt-1 achieving detection rates of 87.7% and 91.2% for 5% and 10% false-positive rates, respectively (AUC: 0.98 [95% CI: 0.97-0.99]). For late PE (n = 246, 2.6%), the best model included the a priori risk, MAP, UtA Doppler, PlGF, and sFlt-1 achieving detection rates of 68.3% and 76.4% at 5% and 10% of false-positive rates, respectively (AUC: 0.87 [95% CI: 0.84-0.90]).

CONCLUSION

Preeclampsia can be predicted with high accuracy in general obstetric populations with a low risk for PE, by combined algorithms. Angiogenic factors substantially improved the prediction.

Added value of angiogenic factors for the prediction of early and late preeclampsia in the first trimester of pregnancy

OBJECTIVE

To explore the predictive role of angiogenic factors for the prediction of early and late preeclampsia (PE) in the first trimester.

METHODS

A nested case-control study, within a cohort of 5,759 pregnancies, including 28 cases of early, 84 of late PE (cut-off 34 weeks) and 84 controls. Maternal characteristics, mean blood pressure (MAP), uterine artery (UtA) Doppler (11-13 weeks), vascular endothelial growth factor, placental growth factor (PlGF), soluble Fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (8-11 weeks) were measured/recorded. All parameters were normalized by logarithmic transformation; logistic regression analysis was used to predict PE.

RESULTS

For early PE, significant contributions were chronic hypertension, previous PE, MAP, UtA Doppler, PlGF and sFlt-1. A model including these predictors achieved detection rates (DR) of 77.8 and 88.9% for 5 and 10% false-positive rates (FPR), respectively (AUC 0.958; 95% CI 0.920-0.996). For late PE, significant contributions were provided by body mass index, previous PE, UtA Doppler, PlGF and sFlt-1. The model including these factors achieved DR of 51.2 and 69% at 5 and 10% FPR, respectively (AUC 0.888; 95% CI 0.840-0.936).

CONCLUSIONS

Among angiogenic factors, not only PlGF but also sFlt-1 substantially improve the prediction for early and late PE. The data need confirmation in larger studies.

First-trimester screening for early and late small-for-gestational-age neonates using maternal serum biochemistry, blood pressure and uterine artery Doppler

OBJECTIVE

To assess the effectiveness of first-trimester screening for early and late small-for-gestational-age (SGA) neonates using maternal serum biochemistry, blood pressure and uterine artery Doppler.

METHODS

This was a prospective study of 4970 women with a singleton pregnancy who underwent routine first-trimester screening between 2009 and 2011. A logistic regression-based predictive model for SGA, defined as birth weight < 10(th) percentile, divided into early- or late-onset based on gestational age at delivery before or after 34 weeks' gestation, was constructed. The model included maternal baseline characteristics: serum levels of pregnancy-associated plasma protein-A and free β-human chorionic gonadotropin at 8-12 weeks and blood pressure and uterine artery Doppler at 11 + 0 to 13 + 6 weeks.

RESULTS

The prevalence of early and late SGA was 0.6% and 7.9%, respectively. Association with pre-eclampsia was 67% and 8%, respectively. At a false-positive rate of 15%, the detection rate for early SGA was 73%; however it differed substantially for cases with and without pre-eclampsia (90% vs 40%). For late SGA, at false-positive rates of 15 and 50%, detection rates were 32% and 70%, respectively, and did not substantially differ between cases with and without pre-eclampsia.

CONCLUSIONS

First-trimester screening predicts early SGA mainly because of its strong association with pre-eclampsia. Although prediction of late SGA was poorer, at a high false-positive rate it might be considered as part of a first-trimester strategy to select women requiring ultrasound assessment in the third trimester.

Performance of a first-trimester screening of preeclampsia in a routine care low-risk setting

OBJECTIVE

We sought to evaluate the effectiveness of an integrated first-trimester screening test to predict preeclampsia (PE).

STUDY DESIGN

A prospective cohort of singleton pregnancies underwent routine first-trimester screening from 2009 through 2011 (n = 5759). A logistic regression-based predictive model for early- and late-onset PE was constructed based on: maternal characteristics; levels of pregnancy-associated plasma protein-A and free β-human chorionic gonadotropin at 8-12 weeks; and blood pressure and uterine artery Doppler at 11.0-13.6 weeks.

RESULTS

Of the 5170 enrolled participants, 136 (2.6%) developed PE (early PE: 26 [0.5%]; late PE: 110 [2.1%]). At 5% and 10% false-positive rates, detection rates were 69.2% and 80.8% for early PE (area under the curve, 0.95; 95% confidence interval, 0.94-0.98) and 29.4% and 39.6% for late PE (area under the curve, 0.71; 95% confidence interval, 0.66-0.76), respectively.

CONCLUSION

First-trimester screening combining maternal factors with uterine artery Doppler, blood pressure, and pregnancy-associated plasma protein-A is useful to predict PE in a routine care setting.

Reference interval of pregnancy-associated plasma protein-a in healthy men and non-pregnant women

OBJECTIVE

The serum pregnancy-associated plasma protein-A (PAPP-A) concentration is a predictor of ischemic cardiac events and renal impairment. However, the reference interval of PAPP-A has not been determined. This study determined the reference interval of PAPP-A in men and non-pregnant women.

METHODS

The study enrolled 126 apparently healthy individuals (52 males and 74 females). The mean age of the men and women was 34.7 (range 20-66) years and 34.6 (range 18-65) years, respectively. Serum PAPP-A concentrations were determined using an ultrasensitive enzyme-linked immunoassay kit. Reference intervals were calculated using the bootstrap method.

RESULTS

The results for three subjects were outliers, so the reference interval of PAPP-A was calculated using the data for 123 subjects. PAPP-A was undetectable in 26 subjects. The reference interval of PAPP-A for men and women (with the 90% confidence interval) was <22.9 ng/mL (19.7-23.3) and <33.6 ng/mL (25.2-36.7), respectively. In male subjects, serum PAPP-A levels of smokers [3.10 (UD, 7.30)ng/mL] were significantly lower than that of non-smokers [11.00 (UD, 24.4)ng/mL] (p<0.001) and there was a positive correlation between serum PAPP-A levels and subjects' age (r=0.439; p<0.001).

CONCLUSIONS

The reference interval of PAPP-A differed for men and non-pregnant women. In clinical practice, <22.9 ng/mL for men and <33.6 ng/mL for non-pregnant women may be used as reference intervals for PAPP-A.

First trimester Down syndrome screening with dried blood spots using a dual analyte free beta hCG and PAPP-A immunofluorometric assay

OBJECTIVE

To determine the effectiveness of first trimester Down syndrome screening with dried blood spots using a dual analyte free beta human chorionic gonadotrophin (hCG)/pregnancy-associated plasma protein A (PAPP-A) immunofluorometric assay.

METHOD

An initial retrospective study of 54 Down syndrome cases and 1064 control specimens was performed followed by a series of 146,513 specimens from routine screening. Detection rates at a fixed 5% false-positive rate were determined separately based on reference data from the retrospective study set and then adjusted based on the routine screening study set.

RESULTS

On the basis of the retrospective analysis, the estimated detection rate using free beta hCG, PAPP-A and maternal age varied from 78% at 9 weeks of pregnancy to 70% at 13 weeks of pregnancy. Using a combined protocol, including NT, the detection rate varied from 92 to 90% between 9 and 13 weeks of gestation. Adjusting distribution parameters based on the routine screening dataset reduced the detection rate by at most 1%.

CONCLUSION

Analysis of free beta hCG and PAPP-A using a dual analyte dried blood spot assay is an effective tool in Down syndrome screening, adding an important option for those considering implementation or modification of existing prenatal screening programs.

Does pregnancy-associated plasma protein A have a role in allergic rhinitis?

BACKGROUND

Pregnancy-associated plasma protein A (PAPP-A), also known as insulin-like growth factor binding protein 4 protease, is postulated to be a new inflammatory marker in various clinical situations such as cardiovascular events, dialysis, renal transplantation, and asthma. PAPP-A also is produced in high concentrations by trophoblasts during pregnancy.

METHODS

We evaluated PAPP-A levels in allergic rhinitis patients and compared these with levels in healthy subjects. Thirty-one newly diagnosed allergic rhinitis patients and 29 healthy controls were included in the study. Serum PAPP-A, IgE, urea, creatinine, aspartate aminotransferase, creatine kinase (CK), CK-MB isoenzyme, total cholesterol, and triglyceride levels were determined.

RESULTS

The serum PAPP-A level was significantly higher (p = 0.013) in the allergic rhinitis group (6.1 +/- 2.9 mU/L) than in the control group (4.5 +/- 1.7 mU/L). The PAPP-A level in patients with allergic rhinitis and asthma (6.1 +/- 2.3 mU/L) was not significantly different (p = 0.959) from that in patients with allergic rhinitis alone (6.1 +/- 3.3 mU/L). The serum PAPP-A level in allergic rhinitis patients who had turbinate hypertrophy (6.9 +/- 2.2 mU/L) had a tendency to be higher than that in patients who had no turbinate hypertrophy (5.5 +/- 3.2 mU/L); however, this difference was not statistically significant (p = 0.151).

CONCLUSION

Increased PAPP-A activity may be involved in the inflammation and tissue remodelling that occurs in allergic rhinitis.

Is there a relationship between cord blood pregnancy-associated plasma protein-A and birth weight and length?

BACKGROUND

Infants whose mothers had low serum pregnancy-associated plasma protein-A (PAPP-A) in the first trimester were observed to have intrauterine growth retardation.

AIM

Suggesting that PAPP-A plays an important role in the availability and activity of insulin-like growth factors (IGFs), which affect growth, we aimed to investigate cord blood PAPP-A levels of infants with different birth lengths and weights. STUDY DESIGN AND OUTCOME MEASURES: The study included 97 full-term, live-birth neonates. After birth, their lengths and weights were measured. Cord blood PAPP-A levels were measured with an ultra sensitive enzyme-linked immunosorbent assay (ELISA).

RESULTS

There was a significant negative correlation between cord blood PAPP-A levels and birth weight (r=-0.23; P=0.023) and length (r=-0.24; P=0.016). Using the classification made according to their length, it was found that newborns with short lengths had significantly higher mean PAPP-A levels than neonates with normal and long lengths (P=0.022; P=0.002, respectively), whereas the difference between infants with normal lengths and infants with long lengths was not found to be statistically significant (P>0.05). On the other hand, there was a difference between the mean PAPP-A levels of the neonate groups classified according to weight; however, these differences were not statistically significant (P>0.05).

CONCLUSION

We concluded that increased cord blood PAPP-A levels were associated with birth length and weight decreases; however, PAPP-A levels affected birth length more than birth weight.

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.

Pregnancy-associated plasma protein A in dialysis patients

BACKGROUND

Pregnancy-associated plasma protein A (PAPP-A) was recently described as a new marker of cardiovascular events and of inflammation in uremic patients. The aim of this study was to determine levels of PAPP-A in chronic dialysis patients and its possible relationships with renal osteodystrophy.

METHODS

A total of 99 adult chronic hemodialysis patients, 14 peritoneal dialysis patients and 41 control subjects were included in the study. Serum PAPP-A, intact parathormone (iPTH), calcium, phosphorus and alkaline phosphatase (ALP) were measured. The correlations between PAPP-A and iPTH, calcium, phosphorus and ALP were determined.

RESULTS

PAPP-A levels were significantly higher in peritoneal dialysis [4.5 (3.2-6.7) mU/L, median (interquartile range)], and hemodialysis patients [4.7 (3.8-6.5) mU/L] in comparison to control subjects [3.4 (3.0-5.0) mU/L] (p<0.05). In hemodialysis patients, post-dialysis PAPP-A levels [6.2 (4.7-9.4) mU/L] were significantly higher than pre-dialysis levels [4.7 (3.8-6.5) mU/L] (p<0.05). There was a weak but statistically significant positive correlation between serum PAPP-A and iPTH (r=0.216; p=0.041) and ALP (r=0.205; p=0.044) in the hemodialysis group. Correlation between the duration of dialysis therapy and PAPP-A levels was also significant (r=0.267; p=0.008) in the hemodialysis group.

CONCLUSIONS

PAPP-A levels are elevated in acute coronary syndromes and are closely related to inflammation and oxidative stress. We conclude that PAPP-A levels are increased in dialysis patients and may reflect a greater degree of chronic inflammation than osteodystrophy in uremic patients.

First-trimester screening for trisomy 21 in twin pregnancy: does the addition of biochemistry make an improvement?

OBJECTIVE

To evaluate the effectiveness of the addition of first-trimester biochemistry to fetal nuchal translucency (NT) measurement in the Combined Test when screening for trisomy 21 in twin pregnancies.

METHODS

Maternal serum free beta-hCG and PAPP-A were determined at 8 to 12 weeks and fetal NT was measured at 11 to 14 weeks. The individual risks were estimated for each of the fetuses using both NT screening alone and the Combined Test. An invasive diagnostic procedure was offered when the risk was 1:250 or over in either one of the fetuses. In the first period, only the results of NT screening were clinically applied. After previous analysis, the Combined Test was introduced into clinical practice.

RESULTS

In the two-and-a-half-year study period, a complete follow-up was obtained in 100 twin pregnancies. Three fetuses (two pregnancies) with trisomy 21 were detected by both methods. The false-positive rate achieved by NT screening (14.3% of pregnancies and 8.6% of fetuses) was substantially reduced when first-trimester biochemistry was added in the Combined Test (5.1% of pregnancies and 3.6% of fetuses).

CONCLUSION

The Combined Test appears to maintain the detection rate achieved by NT screening for trisomy 21 in twin pregnancies, but false-positive rates and invasive diagnostic procedures are reduced.

Pregnancy-associated plasma protein-A proteolytic activity in rat vertebral cell cultures: Stimulation by dexamethasone-a potential mechanism for glucocorticoid regulation of osteoprogenitor proliferation and differentiation

Glucocorticoids (GCs) at physiological concentrations stimulate osteoprogenitor proliferation and differentiation in rat bone cell populations, and this is mediated in part by an increased response to insulin-like growth factors (IGFs). Since IGF binding proteins (IGFBPs) modulate IGF actions, we evaluated whether the increased IGF responsiveness might be associated with decreased inhibitory IGFBP-4 peptide levels. Rat vertebral cells were cultured for up to 20 days with or without dexamethasone (Dex). Cell layer proteins were extracted at day 6, 8, 14, and 20, conditioned media (CM) collected at day 8, 14, and 20, and total RNA isolated at day 14 and 20 of culture. Western blotting showed that cell layer IGFBP-4 levels were lower, while IGFBP-4 protease activity in CM was higher, in Dex-treated cultures. Addition of pregnancy-associated plasma protein-A (PAPP-A) antibody to CM abrogated IGFBP-4 proteolysis. PAPP-A mRNA levels were the same in control and Dex-treated cultures as evaluated by RT-PCR. Our data demonstrate that activity of the IGFBP-4 protease, PAPP-A, in rat bone cell cultures is increased by Dex via post-transcriptional mechanisms. Since IGFBP-4 mRNA levels in Dex-treated cultures were the same as in controls at day 8, slightly lower than in controls at day 14, and higher than in controls at day 20 as shown previously, the decreased IGFBP-4 peptide levels in Dex-treated cultures likely result from increased IGFBP-4 proteolysis by the elevated PAPP-A enzymatic activity. Our findings underscore a novel mechanism whereby GCs increase IGF responses in rat bone cells via PAPP-A-induced IGFBP-4 proteolysis.

An outcomes analysis of five prenatal screening strategies for trisomy 21 in women younger than 35 years

OBJECTIVE

This study was undertaken to examine the cost-effectiveness and procedural-related losses associated with 5 prenatal screening strategies for fetal aneuploidy in women under 35 years old.

STUDY DESIGN

Five prenatal screening strategies were compared in a decision analysis model: triple screen: maternal age and midtrimester serum alpha-fetoprotein, human chorionic gonadotropin (hCG), and unconjugated estriol; quad screen: triple screen plus serum dimeric inhibin A; first-trimester screen: maternal age, serum pregnancy-associated plasma protein A and free beta-hCG and fetal nuchal translucency at 10 to 14 weeks' gestation; integrated screen: first-trimester screen plus quad screen, but first-trimester results are withheld until the quad screen is completed when a composite result is provided; sequential screen: first-trimester screen plus quad screen, but the first-trimester screen results are provided immediately and prenatal diagnosis offered if positive; later prenatal diagnosis is available if the quad screen is positive. Model estimates were literature derived, and cost estimates also included local sources. The 5 strategies were compared for cost, the numbers of Down syndrome fetuses detected and live births averted, and the number of procedure-related euploid losses. Sensitivity analyses were performed for parameters with imprecise point estimates.

RESULTS

In the baseline analysis, sequential screening was the least expensive strategy ($455 million). It detected the most Down syndrome fetuses (n=1213), averted the most Down syndrome live births (n=678), but led to the highest number of procedure-related euploid losses (n=859). The integrated screen had the fewest euploid losses (n=62) and averted the second most Down syndrome live births (n=520). If fewer than 70% of women diagnosed with fetal Down syndrome elect to abort, the quad screen became the least expensive strategy.

CONCLUSION

Although sequential screening was the most cost-effective prenatal screening strategy for fetal trisomy 21, it had the highest procedure-related euploid loss rate. The patient's perspective on detection versus fetal safety may help define the optimal screening strategy.

Comparison of triple-risk assessment of fetal trisomy 21 including total human choriogonadotropin (hCG) or its free beta-subunit (free beta hCG)

OBJECTIVE

Second trimester total hCG and free betahCG levels in maternal serum samples of 33 pregnancies affected by fetal trisomy 21 and of 188 matched controls were compared in a retrospective study. To find out differences of discriminating efficacy by using one of these markers a multivariate discriminant analysis was performed.

METHOD

Statistical evaluation was performed for hCG/free betahCG frequency distributions. Discriminant analysis was carried out using the status 'affected' or 'unaffected' as the group variable and the serum markers unconjugated estriol (uE3), alpha-fetoprotein (AFP), and alternatively, hCG or free betahCG, as discriminant variables.

RESULTS

The median of free betahCG MoM values in affected pregnancies was slightly higher (1.90 MoM) than the median of total hCG MoM values (1.72 MoM) but a lower standard deviation was stated for the logarithmic hCG MoM values (SD = 0.49) compared with free betahCG MoM values (SD = 0.51). A two-tailed Student's t test revealed no significant differences of hCG and free betahCG MoM values in both the affected and unaffected pregnancies. By inclusion of free betahCG the discriminant analysis classified 26 out of 33 affected cases correctly and 45 out of 188 unaffected cases incorrectly. For the inclusion of hCG these ratios were 25/33 and 41/188, respectively. Taking in account the individual maternal age risks at a defined false-positive rate of 5% including free betahCG yielded a higher detection rate than including hCG. However, using 1:380 (age-related at-term risk of a 35-year-old woman) as a cut-off risk including hCG yielded a higher detection rate than including free betahCG.

CONCLUSION

For the observed cases none of the markers, hCG or free betahCG, was superior in Down syndrome screening.

Differential regulation of pregnancy associated plasma protein (PAPP)-A during pregnancy in human and mouse

Serum IGFBP-4 proteolytic activity increases dramatically during human pregnancy and is mainly attributed to the pregnancy-associated plasma protein-A (PAPP-A). To understand the regulation and actions of PAPP-A in vivo, we evaluated the utility of a mouse model system. Serum from day-9 and day-17 pregnant mice and age-matched controls was tested for IGFBP-4 proteolytic activity using recombinant mouse IGFBP-4 as the substrate. Surprisingly, IGFBP-4 proteolytic activity in mouse pregnancy serum (mPS) was not significantly different from that of non-pregnancy serum (mNPS). Addition of IGF-II to mPS or mNPS at a dose sufficient to increase IGFBP-4 proteolysis by human PS failed to enhance IGFBP-4 proteolysis. PAPP-A neutralization antibody did not inhibit IGFBP-4 proteolysis by mPS or mNPS, but completely blocked IGFBP-4 proteolytic activity in human PS (hPS, mouse osteoblast conditioned medium, and mouse amniotic fluid). To determine whether the lack of PAPP-A activity in mPS was due to low expression of PAPP-A in the placenta, we cloned a mouse genomic DNA, which contained 1 kb of the entire exon 2 coding sequence and 2.5 kb of the flanking intron sequences. The exon 2-coded mouse and human PAPP-A shared 86% amino acid sequence identity. RT-PCR analysis revealed that the PAPP-A mRNA level in mouse placenta was lower compared to that in human placenta by at least two orders of magnitude. PAPP-A expression was also lower in mouse placenta compared to those in mouse kidney, osteoblasts, and bone marrow stromal cells.

CONCLUSIONS

(1) Serum IGFBP-4 proteolytic activity is differentially regulated by pregnancy in human and mouse. (2) The lack of an increase in serum IGFBP-4 proteolytic activity during mouse pregnancy is due to the low level of PAPP-A expression in the placenta.

Point-of-Care Time-resolved Immunofluorometric Assay for Human Pregnancy-associated Plasma Protein A: Use in First-Trimester Screening for Down Syndrome

Background: Screening for Down syndrome in the first trimester by a combination of fetal nuchal translucency thickness and maternal serum pregnancy-associated plasma protein A (PAPP-A) and free β-human chorionic gonadotropin has been shown to be effective and efficient. We aimed to develop a fast point-of-care assay that could be placed in one-stop clinics for the measurement of PAPP-A.

Methods: We developed a two-site, one-step assay that uses two monoclonal antibodies (mAbs) to PAPP-A, based on a dry-reagent, all-in-one immunoassay concept with a stable fluorescent lanthanide chelate and time-resolved fluorometry. One antibody (mAb 10E1) was biotinylated, and the other (mAb 234-5) was europium-labeled, both via the ε-amino groups of surface lysine residues. The assay was performed on an AIO immunoanalyzer at 36 °C in single, streptavidin-coated microtitration wells that contained the dry reagents. PAPP-A, either in free or complexed form, was detected by the antibodies used.

Results: The assay procedure required 20 min and used 10 μL of sample. The calibration curve was linear from 5 to 10 000 mIU/L. The detection limit was 0.5 mIU/L. Intra- and interassay imprecision (CV) was ≤4.3% and 8.3%, respectively, for whole blood, plasma, or serum samples. Recovery was 93–96% for serum, 95–108% for heparin-derived whole blood, and 98–103% for heparin-derived plasma. Parallelism was observed in all three matrices. Results correlated [slope = 0.85 (confidence interval, 0.82–0.87); intercept = −33 (confidence interval, −58 to −9); Sy|x = 85 mIU/L; r = 0.991; n = 100] with those obtained by a Delfia assay. Heparin did not affect the assay, but EDTA markedly reduced PAPP-A values. PAPP-A was stable at 4 °C for at least 18 days in serum and for 8 days in heparin-derived whole blood or plasma.

Conclusions: The present assay appears suited for use in one-stop clinics for screening for Down syndrome in the first trimester, with results available within 1 h.

Is maternal serum total hCG a marker of trisomy 21 in the first trimester of pregnancy?

In a study of 130 first trimester cases of trisomy 21 and 959 controls we have shown that the median MoM for alpha-fetoprotein (AFP) is lower (0.82) and that for total human chorionic gonadotrophin (hCG) is higher (1.31) than in the control group. For AFP 15.3% of cases were below the 5th centile and for total hCG 19. 8% were above the 95th centile. The median shift observed for AFP and total hCG is poorer than that for pregnancy associated plasma protein-A (PAPP-A) or free beta-hCG and together with maternal age, AFP and total hCG could only be expected to detect 40% of cases. In combination with PAPP-A, total hCG would identify 52% of cases, somewhat less than the 67% observed with free beta-hCG and PAPP-A. However, we have demonstrated for total hCG a significant temporal change in median MoM with gestational age. Before 70 days the median MoM was less than 0.5, between 70 and 83 days this increased to 1.13, and between 84 and 97 days this increased to 1.52. This median shift has significant implications for interpreting previous studies and even more significant implications for detection rates. When population parameters specific to the gestational age in question are used, detection rates with total hCG and PAPP-A increase from 47% at 70-83 days to 60% at 84-97 days. This observation explains much of the confusion around total hCG in the first trimester and shows the importance of selecting analyte pairs and population parameters appropriate to the time in gestation when screening is performed.

First trimester screening for aneuploidy: serum biochemical markers

The article reviews screening for Down syndrome in the first trimester (8-13 gestational weeks) with maternal serum analytes. In the first trimester, 2 serum markers stand out: pregnancy-associated plasma protein-A, a large glycoprotein tetramer, and free beta-human chorionic gonadotropin (beta-hCG), 1 of the 2 subunits of the glycoprotein hormone hCG. Some data indicate that hCG itself may be as effective as free beta-hCG in the first trimester. Maternal serum levels of pregnancy-associated plasma protein-A are low and free beta-hCG are high (consensus multiple of the medians, 0.4 and 1.8, respectively) in Down syndrome pregnancy. The consensus estimate of screening performance by using pregnancy-associated plasma protein-A and free beta-hCG in combination with maternal age is 60% detection rate at a 5% false positive rate. This is similar to the screening performance of second trimester double markers, but not as good as the screening performance of second trimester triple or quad markers. For this reason, first trimester screening with serum markers alone cannot be recommended except in cases in which second trimester screening cannot be done.