Prediction using serum glycosylated fibronectin of imminent pre-eclampsia in women with new-onset hypertension

OBJECTIVE

To compare the predictive performance for delivery with pre-eclampsia (PE) within 2 weeks after assessment in women with new-onset hypertension at 24-41 weeks' gestation between serum glycosylated fibronectin (GlyFn) concentration, serum placental growth factor (PlGF) concentration and soluble fms-like tyrosine kinase-1 (sFlt-1) to PlGF concentration ratio.

METHODS

This was a prospective observational study of 409 women with a singleton pregnancy presenting at 24-41 weeks' gestation with new-onset hypertension. The recommended cut-off for sFlt-1/PlGF ratio for the prediction of PE in the platform used in this study is 85; the appropriate cut-offs for GlyFn and PlGF were determined to achieve the same screen-positive rate as that of sFlt-1/PlGF ratio > 85. We then compared the predictive performance for delivery with PE within 2 weeks after presentation between GlyFn, PlGF and sFlt-1/PlGF, both overall and in subgroups according to gestational age at presentation.

RESULTS

Delivery with PE within 2 weeks occurred in 93 (22.7%) cases. The screen-positive rate for sFlt-1/PlGF ratio > 85 was 46.2%. The cut-off corresponding to a screen-positive rate of 46.2% was 75 pg/mL for PlGF and 510 µg/mL for GlyFn. The overall detection rate for delivery with PE within 2 weeks after presentation was 62.4% (95% CI, 51.7-72.2%) for GlyFn and sFlt-1/PlGF and 60.2% (95% CI, 49.5-70.2%) for PlGF. In all women who delivered with PE within 2 weeks after presentation at < 34 weeks' gestation and in about 60-70% of those presenting at < 38 weeks, GlyFn and sFlt-1/PlGF were increased and PlGF was reduced. However, the screen-positive rate for these tests was very high at about 45%. The predictive performance for delivery with PE within 2 weeks after presentation at ≥ 38 weeks' gestation was poorer for all three methods of screening, with detection rates of 47-63% at screen-positive rates of 40-50%.

CONCLUSIONS

In women with new-onset hypertension, the predictive performance for delivery with PE within 2 weeks after presentation for serum GlyFn is similar to that of PlGF and the sFlt-1/PlGF ratio, but GlyFn may be the preferred option because it is a rapid point-of-care test. However, the predictive performance for all tests is relatively poor. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

The sFlt-1/PlGF Ratio Trend Is Useful in Predicting Preeclampsia Severity in Hyperreactio Luteinalis Complicated with Preeclampsia

Hyperreactio luteinalis (HL) is a rare condition that presents as bilateral ovarian enlargement during pregnancy. Typically, it is thought to be caused by increased production of human chorionic gonadotropin (hCG) associated with gestational trophoblastic diseases or multiple pregnancies. The prognosis is relatively good, with many cases resulting in term birth. However, some obstetric complications, such as preeclampsia (PE) and preterm births, have been reported. We present a serious case of HL with subsequent PE that resulted in preterm delivery at 31 weeks of gestation. The soluble fms-like tyrosine kinase-1 (sFlt-1)/placental growth factor (PlGF) ratio was very high at the onset of PE at 24 weeks of gestation, followed by a modest decline, which then increased in proportion to the exacerbation of symptoms. Since HL cases have also been reported to be associated with PE, repeated measurement of the sFlt-1/PlGF ratio proved useful for better pregnancy management.

Accuracy of placental growth factor alone or in combination with soluble fms-like tyrosine kinase-1 or maternal factors in detecting preeclampsia in asymptomatic women in the second and third trimesters: a systematic review and meta-analysis

OBJECTIVE

This study aimed to: (1) identify all relevant studies reporting on the diagnostic accuracy of maternal circulating placental growth factor) alone or as a ratio with soluble fms-like tyrosine kinase-1), and of placental growth factor-based models (placental growth factor combined with maternal factors±other biomarkers) in the second or third trimester to predict subsequent development of preeclampsia in asymptomatic women; (2) estimate a hierarchical summary receiver-operating characteristic curve for studies reporting on the same test but different thresholds, gestational ages, and populations; and (3) select the best method to screen for preeclampsia in asymptomatic women during the second and third trimester of pregnancy by comparing the diagnostic accuracy of each method.

DATA SOURCES

A systematic search was performed through MEDLINE, Embase, CENTRAL, ClinicalTrials.gov, and the World Health Organization International Clinical Trials Registry Platform databases from January 1, 1985 to April 15, 2021.

STUDY ELIGIBILITY CRITERIA

Studies including asymptomatic singleton pregnant women at >18 weeks' gestation with risk of developing preeclampsia were evaluated. We included only cohort or cross-sectional test accuracy studies reporting on preeclampsia outcome, allowing tabulation of 2×2 tables, with follow-up available for >85%, and evaluating performance of placental growth factor alone, soluble fms-like tyrosine kinase-1- placental growth factor ratio, or placental growth factor-based models. The study protocol was registered on the International Prospective Register Of Systematic Reviews (CRD 42020162460).

METHODS

Because of considerable intra- and interstudy heterogeneity, we computed the hierarchical summary receiver-operating characteristic plots and derived diagnostic odds ratios, β, θi, and Λ for each method to compare performances. The quality of the included studies was evaluated by the QUADAS-2 tool.

RESULTS

The search identified 2028 citations, from which we selected 474 studies for detailed assessment of the full texts. Finally, 100 published studies met the eligibility criteria for qualitative and 32 for quantitative syntheses. Twenty-three studies reported on performance of placental growth factor testing for the prediction of preeclampsia in the second trimester, including 16 (with 27 entries) that reported on placental growth factor test alone, 9 (with 19 entries) that reported on the soluble fms-like tyrosine kinase-1-placental growth factor ratio, and 6 (16 entries) that reported on placental growth factor-based models. Fourteen studies reported on performance of placental growth factor testing for the prediction of preeclampsia in the third trimester, including 10 (with 18 entries) that reported on placental growth factor test alone, 8 (with 12 entries) that reported on soluble fms-like tyrosine kinase-1-placental growth factor ratio, and 7 (with 12 entries) that reported on placental growth factor-based models. For the second trimester, Placental growth factor-based models achieved the highest diagnostic odds ratio for the prediction of early preeclampsia in the total population compared with placental growth factor alone and soluble fms-like tyrosine kinase-1-placental growth factor ratio (placental growth factor-based models, 63.20; 95% confidence interval, 37.62-106.16 vs soluble fms-like tyrosine kinase-1-placental growth factor ratio, 6.96; 95% confidence interval, 1.76-27.61 vs placental growth factor alone, 5.62; 95% confidence interval, 3.04-10.38); placental growth factor-based models had higher diagnostic odds ratio than placental growth factor alone for the identification of any-onset preeclampsia in the unselected population (28.45; 95% confidence interval, 13.52-59.85 vs 7.09; 95% confidence interval, 3.74-13.41). For the third trimester, Placental growth factor-based models achieved prediction for any-onset preeclampsia that was significantly better than that of placental growth factor alone but similar to that of soluble fms-like tyrosine kinase-1-placental growth factor ratio (placental growth factor-based models, 27.12; 95% confidence interval, 21.67-33.94 vs placental growth factor alone, 10.31; 95% confidence interval, 7.41-14.35 vs soluble fms-like tyrosine kinase-1-placental growth factor ratio, 14.94; 95% confidence interval, 9.42-23.70).

CONCLUSION

Placental growth factor with maternal factors ± other biomarkers determined in the second trimester achieved the best predictive performance for early preeclampsia in the total population. However, in the third trimester, placental growth factor-based models had predictive performance for any-onset preeclampsia that was better than that of placental growth factor alone but similar to that of soluble fms-like tyrosine kinase-1-placental growth factor ratio. Through this meta-analysis, we have identified a large number of very heterogeneous studies. Therefore, there is an urgent need to develop standardized research using the same models that combine serum placental growth factor with maternal factors ± other biomarkers to accurately predict preeclampsia. Identification of patients at risk might be beneficial for intensive monitoring and timing delivery.

Perspectives on the Use of Placental Growth Factor (PlGF) in the Prediction and Diagnosis of Pre-Eclampsia: Recent Insights and Future Steps

Pre-eclampsia (PE) is a complex multisystem disease of pregnancy that is becoming increasingly recognized as a state of angiogenic imbalance characterized by low concentrations of placental growth factor (PlGF) and elevated soluble fms-like tyrosine kinase (sFlt-1). PlGF is a protein highly expressed by the placenta with vasculogenic and angiogenic properties, which has a central role in spiral artery remodeling and the development of a low-resistance placental capillary network. PlGF concentrations are significantly lower in women with preterm PE, and these reduced levels have been shown to precede the clinical onset of disease. Subsequently, the clinical utility of maternal serum PlGF has been extensively studied in singleton gestations from as early as 11 to 13 weeks' gestation, utilizing a validated multimarker prediction model, which performs superiorly to the National Institute for Health and Care Excellence (NICE) and American College of Obstetricians and Gynecologists (ACOG) guidelines in the detection of preterm PE. There is extensive research highlighting the role of PlGF-based testing utilizing commercially available assays in accelerating the diagnosis of PE in symptomatic women over 20 weeks' gestation and predicting time-to-delivery, allowing individualized risk stratification and appropriate antenatal surveillance to be determined. "Real-world" data has shown that interpretation of PlGF-based test results can aid clinicians in improving maternal outcomes and a growing body of evidence has implied a role for sFlt-1/PlGF in the prognostication of adverse pregnancy and perinatal events. Subsequently, PlGF-based testing is increasingly being implemented into obstetric practice and is advocated by NICE. This literature review aims to provide healthcare professionals with an understanding of the role of angiogenic biomarkers in PE and discuss the evidence for PlGF-based screening and triage. Prospective studies are warranted to explore if its implementation significantly improves perinatal outcomes, explore the value of repeat PlGF testing, and its use in multiple pregnancies.

Comparison of ophthalmic artery Doppler with PlGF and sFlt-1/PlGF ratio at 35-37 weeks' gestation in prediction of imminent pre-eclampsia

OBJECTIVE

To compare the predictive performance for delivery with pre-eclampsia (PE) at < 3 weeks and at any stage after assessment at 35 + 0 to 36 + 6 weeks' gestation of serum placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1)/PlGF ratio with that of a competing-risks model utilizing maternal risk factors, mean arterial pressure (MAP) and ophthalmic artery peak systolic velocity (PSV) ratio.

METHODS

This was a prospective observational study of women attending for a routine hospital visit at 35 + 0 to 36 + 6 weeks' gestation. This visit included recording of maternal demographic characteristics and medical history, ultrasound examination of fetal anatomy and growth, assessment of flow velocity waveforms from the maternal ophthalmic arteries and measurement of MAP, serum PlGF and serum sFlt-1. The performance of screening for delivery with PE at < 3 weeks and at any time after the examination was assessed using areas under the receiver-operating-characteristics curves and detection rates (DRs), at a 10% false-positive rate (FPR). McNemar's test was used to compare DRs, at a 10% FPR, between screening by PlGF concentration, the sFlt-1/PlGF concentration ratio and the competing-risks model utilizing maternal risk factors, MAP and ophthalmic artery PSV ratio. Model-based estimates of screening performance for different methods of screening were also produced.

RESULTS

The study population of 2338 pregnancies contained 75 (3.2%) cases that developed PE, including 30 (1.3%) that delivered with PE at < 3 weeks from assessment, and 2263 cases unaffected by PE. The DR of PE at < 3 weeks from assessment, at a 10% FPR, of sFlt-1/PlGF ratio (70.0% (95% CI, 50.6-85.3%)) was superior to that of PlGF (50.0% (95% CI, 31.3-68.7%)) or PSV ratio (56.7% (95% CI, 37.4-74.5%)) but inferior to that of the combination of maternal risk factors, MAP multiples of the median (MoM) and PSV ratio delta (96.7% (95% CI, 82.8-99.9%)). Similarly, the DR of PE at any stage after assessment of sFlt-1/PlGF ratio (62.7% (95% CI, 50.7-73.6%)) was superior to that of PlGF (52.0% (95% CI, 40.2-63.7%)) or PSV ratio (41.3% (95% CI, 30.1-53.3%)) but inferior to that of the combination of maternal risk factors, MAP MoM and PSV ratio delta (78.7% (95% CI, 67.7-87.3%)). The empirical results for DR at a 10% FPR were consistent with the modeled results, both for delivery with PE at < 3 weeks and at any time after assessment.

CONCLUSION

Ophthalmic artery Doppler in combination with maternal risk factors and blood pressure could potentially replace measurement of PlGF and sFlt-1/PlGF ratio in the prediction of imminent PE. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Placental and maternal sFlt1/PlGF expression in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) and preeclampsia (PE) are both characterized by endothelial dysfunction and GDM women have higher incidence of PE. The placenta plays a key role in PE pathogenesis but its contribution to PE during GDM remains unclear. Herein, we compared placental and maternal blood anti-angiogenic soluble fms-like tyrosine kinase-1 (sFlt1) and pro-angiogenic Placental Growth Factor (PlGF) expressions in GDM and GDM-PE pregnancies compared to controls (CTRL) and PE cases. Electrochemiluminescence immunoassays showed a significantly higher maternal blood sFlt1/PlGF values in GDM-PE relative to CTRL and GDM pregnancies. We reported that placental PlGF gene expression was significantly decreased in GDM, PE and GDM-PE relative to CTRL. However, PlGF protein levels were significantly increased in GDM and GDM-PE relative to CTRL and PE placentae. Finally, sFlt1 gene expression was significantly increased in PE relative to CTRL, GDM and GDM-PE placentae. In contrast, sFlt1 protein expression was significantly decreased in GDM-PE relative to CTRL, GDM and PE placentae. Finally, higher sFlt1/PlGF ratio in GDM-PE maternal blood suggest that sFlt1 overproduction is related to PE onset also in GDM pregnancies even though characterized by a less severe endothelial dysfunction in terms of angiogenic biomarkers.

External validation of prognostic models predicting pre-eclampsia: individual participant data meta-analysis

BACKGROUND

Pre-eclampsia is a leading cause of maternal and perinatal mortality and morbidity. Early identification of women at risk during pregnancy is required to plan management. Although there are many published prediction models for pre-eclampsia, few have been validated in external data. Our objective was to externally validate published prediction models for pre-eclampsia using individual participant data (IPD) from UK studies, to evaluate whether any of the models can accurately predict the condition when used within the UK healthcare setting.

METHODS

IPD from 11 UK cohort studies (217,415 pregnant women) within the International Prediction of Pregnancy Complications (IPPIC) pre-eclampsia network contributed to external validation of published prediction models, identified by systematic review. Cohorts that measured all predictor variables in at least one of the identified models and reported pre-eclampsia as an outcome were included for validation. We reported the model predictive performance as discrimination (C-statistic), calibration (calibration plots, calibration slope, calibration-in-the-large), and net benefit. Performance measures were estimated separately in each available study and then, where possible, combined across studies in a random-effects meta-analysis.

RESULTS

Of 131 published models, 67 provided the full model equation and 24 could be validated in 11 UK cohorts. Most of the models showed modest discrimination with summary C-statistics between 0.6 and 0.7. The calibration of the predicted compared to observed risk was generally poor for most models with observed calibration slopes less than 1, indicating that predictions were generally too extreme, although confidence intervals were wide. There was large between-study heterogeneity in each model's calibration-in-the-large, suggesting poor calibration of the predicted overall risk across populations. In a subset of models, the net benefit of using the models to inform clinical decisions appeared small and limited to probability thresholds between 5 and 7%.

CONCLUSIONS

The evaluated models had modest predictive performance, with key limitations such as poor calibration (likely due to overfitting in the original development datasets), substantial heterogeneity, and small net benefit across settings. The evidence to support the use of these prediction models for pre-eclampsia in clinical decision-making is limited. Any models that we could not validate should be examined in terms of their predictive performance, net benefit, and heterogeneity across multiple UK settings before consideration for use in practice.

TRIAL REGISTRATION

PROSPERO ID: CRD42015029349 .

The competing risk approach for prediction of preeclampsia

The established method of the assessment of the risk for development of preeclampsia is to identify risk factors from maternal demographic characteristics and medical history; in the presence of such factors, the patient is classified as high risk and in their absence as low risk. Although this approach is simple to perform, it has poor performance of the prediction of preeclampsia and does not provide patient-specific risks. This review describes a new approach that allows the estimation of patient-specific risks of delivery with preeclampsia before any specified gestational age by maternal demographic characteristics and medical history with biomarkers obtained either individually or in combination at any stage in pregnancy. In the competing risks approach, every woman has a personalized distribution of gestational age at delivery with preeclampsia; whether she experiences preeclampsia or not before a specified gestational age depends on competition between delivery before or after the development of preeclampsia. The personalized distribution comes from the application of Bayes theorem to combine a previous distribution, which is determined from maternal factors, with likelihoods from biomarkers. As new data become available, what were posterior probabilities take the role as the previous probability, and data collected at different stages are combined by repeating the application of Bayes theorem to form a new posterior at each stage, which allows for dynamic prediction of preeclampsia. The competing risk model can be used for precision medicine and risk stratification at different stages of pregnancy. In the first trimester, the model has been applied to identify a high-risk group that would benefit from preventative therapeutic interventions. In the second trimester, the model has been used to stratify the population into high-, intermediate-, and low-risk groups in need of different intensities of subsequent monitoring, thereby minimizing unexpected adverse perinatal events. The competing risks model can also be used in surveillance of women presenting to specialist clinics with signs or symptoms of hypertensive disorders; combination of maternal factors and biomarkers provide patient-specific risks for preeclampsia that lead to personalized stratification of the intensity of monitoring, with risks updated on each visit on the basis of biomarker measurements.

Use of Placental Growth Factor for Trisomy 21 Screening in Pregnancy: A Systematic Review

Background  Prenatal serum screening is an important modality to screen for aneuploidy in pregnancy. The addition of placental growth factor (PLGF) to screen for trisomy 21 remains controversial. Objective  To determine whether the addition of PLGF to combined serum aneuploidy screening improves detection rates (DRs) for trisomy 21. Study Design  We performed a systematic review of the literature until October 2019 to determine the benefits of adding PLGF to prenatal screening. We performed a goodness-of-fit test and retrieved the coefficient of determinations ( R ² ) as a function of false positive rates (FPRs), providing mean-weighted improvements in the DRs after accounting for PLGF levels. Results  We identified 51 studies, of which 8 met inclusion criteria (834 aneuploidy cases and 105,904 euploid controls). DRs were proportional to FPR across all studies, ranging from 59.0 to 95.3% without PLGF and 61.0 to 96.3% with PLGF (FPR 1-5%). Goodness-of-fit regression analysis revealed a logarithmic distribution of DRs as a function of the FPR, with R ²  = 0.109 (no PLGF) and R ²  = 0.06 (PLGF). Two-sample Kolmogorov-Smirnov's test reveals a p -value of 0.44. Overall, addition of PLGF improves DRs of 3.3% for 1% FPR, 1.7% for 3% FPR, and 1.4% for 5% FPR, respectively. Conclusion  Addition of PLGF to prenatal screening using serum analytes mildly improves trisomy 21 DRs as a function of FPRs.

Maternal Cardiac Assessment at 35 to 37 Weeks Improves Prediction of Development of Preeclampsia

Preeclampsia at term accounts for half of maternal deaths from hypertensive disorders. We aimed to assess differences in maternal cardiac indices at 35⁺⁰ to 36⁺⁶ weeks' gestation between women who subsequently developed preeclampsia at term compared with those with uncomplicated pregnancy and to evaluate whether cardiac indices offer incremental prognostic value to the available screening algorithm for preeclampsia. We recruited 1602 women with singleton pregnancies who attended for a routine hospital visit at 35⁺⁰ to 36⁺⁶ weeks' gestation between April and November 2018. We recorded maternal characteristics and preeclampsia-risk-score derived from a competing risks model and measured cardiac indices. Preeclampsia developed in 3.12% (50/1602) of participants. Women with preeclampsia, compared with those without, had increased mean arterial pressure (97.6, SD, 5.53 versus 87.9, SD, 6.82 mm Hg), systemic vascular resistance (1500, interquartile range, 1393-1831 versus 1400, interquartile range, 1202-1630 PRU) and preeclampsia-risk-score (23.4, interquartile range, 9.13-40 versus 0.9, interquartile range, 0.32-3.25). Multivariable analysis demonstrated independent association between the incidence of preeclampsia and E/e' (hazard ratio, 1.19/unit [95% CI, 1.03-1.37]; P=0.018) as well as left ventricular mass indexed for body surface area (hazard ratio, 1.03/[g·m²] [95% CI, 1.003-1.051]; P=0.029). Women with E/e' ≥7.3 and left ventricular mass indexed for body surface area ≥63.2 g/m² had an increased risk for developing preeclampsia, despite low preeclampsia-risk-score <5% (hazard ratio, 20.1 [95% CI, 10.5-38.7], P<0.001). Increased left ventricular mass and E/e' offer incremental information to available scoring systems and better stratify women at risk of developing preeclampsia at term.

The role of biomarkers in predicting pre-eclampsia in high-risk women

Background

There are limited data on performance of biomarkers to predict pre-eclampsia (PE) in high-risk women. This study investigated the ability of FABP4, PAPP-A, PlGF, sFlt-1 and sEng to predict PE in a high-risk group.

Methods

Non-fasting samples were analysed at 11 + 0–13 + 6 (V1) and 19 + 0–21 + 6 weeks (V2) ( n = 195). Logistic regression models were determined. Area under (AUC) the receiver operating characteristic (ROC) curve analysis was performed. The added value of biomarkers to clinical characteristics for PE prediction was quantified using integrated discrimination improvement (IDI) and net reclassification improvement (NRI) indices.

Results

Prevalence of PE was 12%. Lower concentrations of sFlt-1:PlGF (V1) and PlGF and PlGF:sEng (V2) were seen in women who developed PE. Controlling for baseline characteristics (V1), a doubling of sFlt-1 (pg/mL) (median 896.0, IQR 725.5–1097.0) and sFlt-1:PlGF (median 21.2, IQR 14.7–32.3) was associated with reduction in odds of PE (OR 0.20, 95% CI 0.06–0.65, P = 0.007 and OR 0.48, 95% CI 0.25–0.92, P = 0.04). Addition of sFlt-1 and sFlt-1:PlGF to baseline characteristics non-significantly improved AUC (0.74) (AUC 0.77, P = 0.40 and 0.76, P = 0.39). NRI and IDI analyses confirmed added clinical utility of sFlt-1 (NRI = 0.539, P = 0.01 and IDI = 0.052, P = 0.03). In V2, doubling of PlGF:sEng (median 71.9, IQR 47.0–102.8) was associated with reduction in the risk of PE (OR 0.56, 95% CI 0.35–0.98, P = 0.04). The addition of PlGF:sEng to baseline characteristics non-significantly improved AUC from 0.78 to 0.82 ( P = 0.25) and improved reclassification of cases (NRI = 0.682, P = 0.002).

Conclusions

Screening tests incorporating first trimester sFlt-1 and second trimester PlGF:sEng have potential to aid PE prediction in high-risk pregnancies.

Predictive Performance of PlGF (Placental Growth Factor) for Screening Preeclampsia in Asymptomatic Women: A Systematic Review and Meta-Analysis

Preeclampsia is a systemic syndrome that seems to originate from the placenta and is associated with an imbalance between angiogenic factors in the maternal circulation. One of the well-studied and widely used factors is PlGF (placental growth factor), the levels of which drop in women destined to develop preeclampsia. This drop is known to precede the development of actual signs and symptoms of preeclampsia, thus proving to be a useful screening tool in predicting the disease. The literature varies widely in terms of the clinical usefulness of the test. We conducted a meta-analysis to study the predictive accuracy of PlGF in asymptomatic women. Our analysis included 40 studies with 3189 cases of preeclampsia and 89 498 controls. The overall predictive odds ratio of the test was 9 (6-13). Subgroup analysis evaluating various PlGF thresholds demonstrated that the predictive values were highest for PlGF levels between 80 and 120 pg/mL with a high predictive odds ratio of 25 (7-88), a sensitivity of 0.78 (95% CI, 0.67-0.86), a specificity of 0.88 (95% CI, 0.75-0.95), a positive likelihood ratio of 6.3 (95% CI, 2.7-14.7), and a negative likelihood ratio of 0.26 (95% CI, 0.16-0.42). Additionally, the accuracy was higher when the test was performed after 14 weeks of gestation (OR, 10 [7-15]) and for prediction of early onset preeclampsia (OR, 18 [9-37]). We conclude that PlGF is a useful screening tool to predict preeclampsia. Nonetheless, its utility should be judged with caution and randomized controlled trials are warranted to explore if its implementation improves perinatal outcomes in asymptomatic women.

Prediction of imminent preeclampsia at 35-37 weeks gestation

BACKGROUND

In the weeks preceding the clinical onset of preeclampsia, the maternal serum level of the angiogenic placental growth factor is decreased and that of the antiangiogenic factor soluble fms-like tyrosine kinase-1 is increased. Women presenting at specialist clinics with signs or symptoms of hypertensive disorders have been stratified according to concentrations of placental growth factor or the ratio of concentrations of soluble fms-like tyrosine kinase-1 and placental growth factor to determine clinical management for the subsequent 1-4 weeks. An alternative approach for the prediction of preeclampsia is use of the competing risks model, a Bayes' theorem based method, to derive patient-specific risk for preeclampsia by various combinations of maternal characteristics and medical history with multiples of the median values of biomarkers.

OBJECTIVE

The purpose of this study was to compare the performance of screening for delivery with preeclampsia at ≤2 and ≤4 weeks after assessment at 35⁺⁰-36⁺⁶ weeks gestation between the use of percentile cut-offs in placental growth factor alone or the soluble fms-like tyrosine kinase-1/placental growth factor ratio and the competing risks model.

STUDY DESIGN

This was a prospective observational study in women who attended a routine hospital visit at 35⁺⁰-36⁺⁶ weeks gestation in 2 maternity hospitals in England. The visits included the recording of maternal demographic characteristics and medical history and the measurement of serum placental growth factor and soluble fms-like tyrosine kinase-1 and mean arterial pressure. The areas under the receiver operating characteristics curves were used to compare the predictive performance for preeclampsia with delivery at ≤2 and ≤4 weeks from assessment of screening by placental growth factor alone and the soluble fms-like tyrosine kinase-1/placental growth factor ratio with that of a previously developed competing risks model with a combination of maternal factors, placental growth factor, soluble fms-like tyrosine kinase-1, and mean arterial pressure (triple test).

RESULTS

First, the study population of 15,247 pregnancies included 326 pregnancies (2.1%) that subsequently experienced preeclampsia. Second, in the screening for delivery with preeclampsia at ≤2 and ≤4 weeks from assessment, the performance of the triple test was superior to that of placental growth factor alone or the soluble fms-like tyrosine kinase-1/placental growth factor ratio. The area under the receiver operating characteristics curves for preeclampsia at ≤2 weeks in screening by the triple test (0.975; 95% confidence interval, 0.964-0.985) was higher than that of placental growth factor alone (0.900; 95% confidence interval, 0.866-0.935; P<.0001) and the soluble fms-like tyrosine kinase-1/placental growth factor ratio (0.932; 95% confidence interval, 0.904-0.960; P=.0001). Similarly, the areas under the receiver operating characteristics curves for preeclampsia at ≤4 weeks in screening by the triple test (0.907; 95% confidence interval, 0.886-0.928) was higher than that of placental growth factor alone (0.827; 95% confidence interval, 0.800-0.854; P<.0001) or the soluble fms-like tyrosine kinase-1/placental growth factor ratio (0.857; 95% confidence interval, 0.830-0.883; P<.0001). Third, at most, screen-positive rates of 2-30% the detection rate of delivery with preeclampsia at ≤2 and ≤4 weeks that was achieved by the triple test was approximately 10% higher than that of the soluble fms-like tyrosine kinase-1/placental growth factor ratio and 20% higher than that of placental growth factor alone; the negative predictive value was similar for the 3 tests.

CONCLUSION

At 35⁺⁰-36⁺⁶ weeks gestation, the performance of screening for imminent delivery with preeclampsia by the competing risks model is superior to that of placental growth factor alone or the soluble fms-like tyrosine kinase-1/placental growth factor ratio.

Biochemical tests of placental function versus ultrasound assessment of fetal size for stillbirth and small-for-gestational-age infants

BACKGROUND

Stillbirth affects 2.6 million pregnancies worldwide each year. Whilst the majority of cases occur in low- and middle-income countries, stillbirth remains an important clinical issue for high-income countries (HICs) - with both the UK and the USA reporting rates above the mean for HICs. In HICs, the most frequently reported association with stillbirth is placental dysfunction. Placental dysfunction may be evident clinically as fetal growth restriction (FGR) and small-for-dates infants. It can be caused by placental abruption or hypertensive disorders of pregnancy and many other disorders and factorsPlacental abnormalities are noted in 11% to 65% of stillbirths. Identification of FGA is difficult in utero. Small-for-gestational age (SGA), as assessed after birth, is the most commonly used surrogate measure for this outcome. The degree of SGA is associated with the likelihood of FGR; 30% of infants with a birthweight < 10th centile are thought to be FGR, while 70% of infants with a birthweight < 3rd centile are thought to be FGR. Critically, SGA is the most significant antenatal risk factor for a stillborn infant. Correct identification of SGA infants is associated with a reduction in the perinatal mortality rate. However, currently used tests, such as measurement of symphysis-fundal height, have a low reported sensitivity and specificity for the identification of SGA infants.

OBJECTIVES

The primary objective was to assess and compare the diagnostic accuracy of ultrasound assessment of fetal growth by estimated fetal weight (EFW) and placental biomarkers alone and in any combination used after 24 weeks of pregnancy in the identification of placental dysfunction as evidenced by either stillbirth, or birth of a SGA infant. Secondary objectives were to investigate the effect of clinical and methodological factors on test performance.

SEARCH METHODS

We developed full search strategies with no language or date restrictions. The following sources were searched: MEDLINE, MEDLINE In Process and Embase via Ovid, Cochrane (Wiley) CENTRAL, Science Citation Index (Web of Science), CINAHL (EBSCO) with search strategies adapted for each database as required; ISRCTN Registry, UK Clinical Trials Gateway, WHO International Clinical Trials Portal and ClinicalTrials.gov for ongoing studies; specialist abstract and conference proceeding resources (British Library's ZETOC and Web of Science Conference Proceedings Citation Index). Search last conducted in Ocober 2016.

SELECTION CRITERIA

We included studies of pregnant women of any age with a gestation of at least 24 weeks if relevant outcomes of pregnancy (live birth/stillbirth; SGA infant) were assessed. Studies were included irrespective of whether pregnant women were deemed to be low or high risk for complications or were of mixed populations (low and high risk). Pregnancies complicated by fetal abnormalities and multi-fetal pregnancies were excluded as they have a higher risk of stillbirth from non-placental causes. With regard to biochemical tests, we included assays performed using any technique and at any threshold used to determine test positivity.

DATA COLLECTION AND ANALYSIS

We extracted the numbers of true positive, false positive, false negative, and true negative test results from each study. We assessed risk of bias and applicability using the QUADAS-2 tool. Meta-analyses were performed using the hierarchical summary ROC model to estimate and compare test accuracy.

MAIN RESULTS

We included 91 studies that evaluated seven tests - blood tests for human placental lactogen (hPL), oestriol, placental growth factor (PlGF) and uric acid, ultrasound EFW and placental grading and urinary oestriol - in a total of 175,426 pregnant women, in which 15,471 pregnancies ended in the birth of a small baby and 740 pregnancies which ended in stillbirth. The quality of included studies was variable with most domains at low risk of bias although 59% of studies were deemed to be of unclear risk of bias for the reference standard domain. Fifty-three per cent of studies were of high concern for applicability due to inclusion of only high- or low-risk women.Using all available data for SGA (86 studies; 159,490 pregnancies involving 15,471 SGA infants), there was evidence of a difference in accuracy (P < 0.0001) between the seven tests for detecting pregnancies that are SGA at birth. Ultrasound EFW was the most accurate test for detecting SGA at birth with a diagnostic odds ratio (DOR) of 21.3 (95% CI 13.1 to 34.6); hPL was the most accurate biochemical test with a DOR of 4.78 (95% CI 3.21 to 7.13). In a hypothetical cohort of 1000 pregnant women, at the median specificity of 0.88 and median prevalence of 19%, EFW, hPL, oestriol, urinary oestriol, uric acid, PlGF and placental grading will miss 50 (95% CI 32 to 68), 116 (97 to 133), 124 (108 to 137), 127 (95 to 152), 139 (118 to 154), 144 (118 to 161), and 144 (122 to 161) SGA infants, respectively. For the detection of pregnancies ending in stillbirth (21 studies; 100,687 pregnancies involving 740 stillbirths), in an indirect comparison of the four biochemical tests, PlGF was the most accurate test with a DOR of 49.2 (95% CI 12.7 to 191). In a hypothetical cohort of 1000 pregnant women, at the median specificity of 0.78 and median prevalence of 1.7%, PlGF, hPL, urinary oestriol and uric acid will miss 2 (95% CI 0 to 4), 4 (2 to 8), 6 (6 to 7) and 8 (3 to 13) stillbirths, respectively. No studies assessed the accuracy of ultrasound EFW for detection of pregnancy ending in stillbirth.

AUTHORS' CONCLUSIONS

Biochemical markers of placental dysfunction used alone have insufficient accuracy to identify pregnancies ending in SGA or stillbirth. Studies combining U and placental biomarkers are needed to determine whether this approach improves diagnostic accuracy over the use of ultrasound estimation of fetal size or biochemical markers of placental dysfunction used alone. Many of the studies included in this review were carried out between 1974 and 2016. Studies of placental substances were mostly carried out before 1991 and after 2013; earlier studies may not reflect developments in test technology.

[Potential value of placental angiogenic factors as biomarkers in preeclampsia for clinical physicians]

The role of angiogenic factors in the onset of clinical manifestations of preeclampsia was demonstrated in 2003 by the implication of sFlt-1, PlGF and VEGF, and in 2006 by the implication of soluble endoglin. Placental ischemia and inflammation observed in preeclampsia alter both the production and progression of angiogenic factors during pregnancy. During the first trimester, the combination of PlGF with clinical, biophysical and biological factors results in a better test than the conventional one. However, the clinical value of this method remains to be confirmed. During the second and third trimesters, the sFlt-1/PlGF ratio may be used, with or without pre-existing renal disease, for short-term prediction, diagnosis, and prognosis, and to evaluate the effectiveness of preeclampsia treatment. While a sFlt-1/PlGF ratio<38 and≤33, respectively, rules out the short-term onset and diagnosis of preeclampsia, a sFlt-1/PlGF ratio≥85 between 20 and 34 weeks of pregnancy and≥110 beyond 34 weeks of pregnancy confirms a diagnosis of preeclampsia. Angiogenic and non-angiogenic preeclampsia are identified by a sFlt-1PlGF≥85 and<85, respectively, with the risk of maternal and fetal complications at two weeks differing between the two. Similarly, a sFlt-1/PlGF ratio>665 and>205, respectively, is a good short-term predictor of adverse outcomes of early and late-onset preeclampsia. These values could be incorporated into future guidelines for better clinical management of preeclampsia.

Relationships of serum placental growth factor and soluble fms-like tyrosine kinase-1 with fetal and uterine artery Doppler indices in pre-eclampsia

OBJECTIVE

To compare serum placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) concentrations among women with pre-eclampsia and healthy control women and to evaluate the associations of serum PlGF and sFlt-1 with fetal and uterine artery Doppler indices in pre-eclampsia.

METHODS

A prospective cross-sectional study of 33 women with pre-eclampsia and 33 normotensive pregnant women attending a university hospital in China between January and November 2014. Serum PlGF and sFlt-1 were assayed by enzyme linked immunosorbent assays. Doppler indices of the uterine artery, umbilical artery, fetal middle cerebral artery, and ductus venosus were measured.

RESULTS

The pulsatility index of the uterine artery was negatively correlated with PlGF (r, -0.487; P=0.004) and positively correlated with sFlt-1 (r, 0.420; P=0.015). Gestational age at birth was positively correlated with PlGF (r, 0.601, P<0.001) and negatively correlated with sFlt-1 (r, -0.568; P=0.001). Birth weight was positively correlated with PlGF (r, 0.555; P=0.001) and negatively correlated with sFlt-1 (r, -0.552; P=0.001). Apgar score was negatively correlated with sFlt-1 (r, -0.427; P=0.017).

CONCLUSION

Lower PlGF and higher sFlt-1 levels in maternal serum were significantly associated with increased uterine arterial impedance in pre-eclampsia.

Sequential concentrations of placental growth factor and haptoglobin, and their relation to oestrone sulphate and progesterone in pregnant Spanish Purebred mare

The objectives of this study were to establish reference values for serum concentrations of placental growth factor (PlGF) and haptoglobin (Hp), and to analyze whether the levels of oestrone sulphate (E₁S) and progesterone (P₄) are physiologically involved in the dynamic modifications of the above parameters in pregnant mares. A total of 30 healthy Spanish Purebred mares ranging in age 9.33 ± 3.31 years were studied during the 11 months of gestation. Serum concentrations of PlGF were detected by EIA, Hp using commercial Phase Haptoglobin assay and E₁S and P₄ levels through RIA. The serum concentrations of PlGF ranged between 31.70 and 223.60 ng/mL, with a mean value of 57.64 ± 18.05 ng/mL. Serum PlGF levels increased significantly during the 1st and 2nd months, reaching the maximum value in the 3rd month and the minimum value in the 10th month. Hp concentrations increased progressively and significantly from the 5th until the 10th month of gestation (P < 0.05), decreasing in the 11th month of pregnancy. E₁S increased significantly from the 3rd until the 7th month, decreasing progressively towards the end of gestation. P₄ increased significantly in the 3rd and 4th month and decreased significantly in the 6th and 7th (P < 0.05), with variable oscillations during last months of pregnancy. PlGF and Hp were significantly and negatively correlated (r = -0.27; P < 0.05). In the healthy mare, PlGF and Hp act asynchronously and independent of steroid E₁S and P_4.

Placental growth factor (alone or in combination with soluble fms-like tyrosine kinase 1) as an aid to the assessment of women with suspected pre-eclampsia: systematic review and economic analysis

BACKGROUND

Pre-eclampsia (PE) prediction based on blood pressure, presence of protein in the urine, symptoms and laboratory test abnormalities can result in false-positive diagnoses. This may lead to unnecessary antenatal admissions and preterm delivery. Blood tests that measure placental growth factor (PlGF) or the ratio of soluble fms-like tyrosine kinase 1 (sFlt-1) to PlGF could aid prediction of PE if either were added to routine clinical assessment or used as a replacement for proteinuria testing.

OBJECTIVES

To evaluate the diagnostic accuracy and cost-effectiveness of PlGF-based tests for patients referred to secondary care with suspected PE in weeks 20-37 of pregnancy.

DESIGN

Systematic reviews and an economic analysis.

DATA SOURCES

Bibliographic databases including MEDLINE, EMBASE, Web of Science and The Cochrane Library and Database of Abstracts of Reviews of Effects were searched up to July 2015 for English-language references. Conferences, websites, systematic reviews and confidential company submissions were also accessed.

REVIEW METHODS

Systematic reviews of test accuracy and economic studies were conducted to inform an economic analysis. Test accuracy studies were required to include women with suspected PE and report quantitatively the accuracy of PlGF-based tests; their risk of bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) criteria. The economic studies review had broad eligibility criteria to capture any types of economic analysis; critical appraisal employed standard checklists consistent with National Institute for Health and Care Excellence criteria. Study selection, critical appraisal and data extraction in both reviews were performed by two reviewers.

ECONOMIC ANALYSIS

An independent economic analysis was conducted based on a decision tree model, using the best evidence available. The model evaluates costs (2014, GBP) from a NHS and Personal Social Services perspective. Given the short analysis time horizon, no discounting was undertaken.

RESULTS

Four studies were included in the systematic review of test accuracy: two on Alere's Triage^® PlGF test (Alere, Inc., San Diego, CA, USA) for predicting PE requiring delivery within a specified time and two on Roche Diagnostics' Elecsys^® sFlt-1 to PlGF ratio test (Roche Diagnostics GmbH, Mannheim, Germany) for predicting PE within a specified time. Three studies were included in the systematic review of economic studies, and two confidential company economic analyses were assessed separately. Study heterogeneity precluded meta-analyses of test accuracy or cost-analysis outcomes, so narrative syntheses were conducted to inform the independent economic model. The model predicts that, when supplementing routine clinical assessment for rule-out and rule-in of PE, the two tests would be cost-saving in weeks 20-35 of gestation, and marginally cost-saving in weeks 35-37, but with minuscule impact on quality of life. Length of neonatal intensive care unit stay was the most influential parameter in sensitivity analyses. All other sensitivity analyses had negligible effects on results.

LIMITATIONS

No head-to-head comparisons of the tests were identified. No studies investigated accuracy of PlGF-based tests when used as a replacement for proteinuria testing. Test accuracy studies were found to be at high risk of clinical review bias.

CONCLUSIONS

The Triage and Elecsys tests would save money if added to routine clinical assessment for PE. The magnitude of savings is uncertain, but the tests remain cost-saving under worst-case assumptions. Further research is required to clarify how the test results would be interpreted and applied in clinical practice.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42015017670.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Metformin, the aspirin of the 21st century: its role in gestational diabetes mellitus, prevention of preeclampsia and cancer, and the promotion of longevity

Metformin is everywhere. Originally introduced in clinical practice as an antidiabetic agent, its role as a therapeutic agent is expanding to include treatment of prediabetes mellitus, gestational diabetes mellitus, and polycystic ovarian disease; more recently, experimental studies and observations in randomized clinical trials suggest that metformin could have a place in the treatment or prevention of preeclampsia. This article provides a brief overview of the history of metformin in the treatment of diabetes mellitus and reviews the results of metaanalyses of metformin in gestational diabetes mellitus as well as the treatment of obese, non-diabetic, pregnant women to prevent macrosomia. We highlight the results of a randomized clinical trial in which metformin administration in early pregnancy did not reduce the frequency of large-for-gestational-age infants (the primary endpoint) but did decrease the frequency of preeclampsia (a secondary endpoint). The mechanisms by which metformin may prevent preeclampsia include a reduction in the production of antiangiogenic factors (soluble vascular endothelial growth factor receptor-1 and soluble endoglin) and the improvement of endothelial dysfunction, probably through an effect on the mitochondria. Another potential mechanism whereby metformin may play a role in the prevention of preeclampsia is its ability to modify cellular homeostasis and energy disposition, mediated by rapamycin, a mechanistic target. Metformin has a molecular weight of 129 Daltons and therefore readily crosses the placenta. There is considerable evidence to suggest that this agent is safe during pregnancy. New literature on the role of metformin as a chemotherapeutic adjuvant in the prevention of cancer and in prolonging life and protecting against aging is reviewed briefly. Herein, we discuss the mechanisms of action and potential benefits of metformin.

Development of pre-eclampsia within 4 weeks of sFlt-1/PlGF ratio > 38: comparison of performance at 31-34 vs 35-37 weeks' gestation

OBJECTIVE

To compare the performance of screening by soluble fms-like tyrosine kinase 1 (sFlt-1) to placental growth factor (PlGF) ratio > 38 for the prediction of delivery with pre-eclampsia (PE) at < 1 week and < 4 weeks from assessment when the test is carried out at 31-34 vs 35-37 weeks' gestation.

METHODS

This was a prospective observational study in women attending a third-trimester ultrasound scan as part of routine pregnancy care; the visit was at 30-34 weeks' gestation in the first phase of the study and at 35-37 weeks in the second phase. Serum sFlt-1 and PlGF were measured and their ratio calculated. We estimated the detection rate (DR) and false-positive rate (FPR) of sFlt-1/PlGF ratio > 38 for predicting delivery with PE at < 1 week and < 4 weeks after assessment and compared the performance of screening when the test was carried out at 31 + 0 to 33 + 6 vs 35 + 0 to 36 + 6 weeks' gestation.

RESULTS

The study population included 8063 singleton pregnancies that were examined at 31-34 weeks and 3703 at 35-37 weeks. Delivery with PE occurred at < 1, < 4 and ≥ 4 weeks from assessment in five (0.1%), 29 (0.4%) and 202 (2.5%) women assessed at 31-34 weeks, respectively, and in seven (0.2%), 39 (1.1%) and 21 (0.6%) of those assessed at 35-37 weeks. In women without PE, the median sFlt-1/PlGF ratio increased with gestational age at screening and a ratio of 38 was just below the 99^th percentile at 32 weeks' gestation and just below the 90^th percentile at 36 weeks. In the two gestational windows, the DR of PE delivering < 4 weeks from assessment was similar (75.9% (95% CI, 56.5-89.7%) vs 79.5% (95% CI, 63.5-90.7%)), but the FPR was substantially lower at 31-34 weeks than at 35-37 weeks (1.7% (95% CI, 1.4-2.0%) vs 9.6% (95% CI, 8.7-10.6%)). The number of cases with PE delivering < 1 week from assessment was small, but similarly, in the two gestational windows, the DR was comparable (80.0% (95% CI, 28.4-99.5%) vs 85.7% (95% CI, 42.1-99.6%)), and the FPR was substantially lower at 31-34 weeks than at 35-37 weeks (1.9% (95% CI, 1.6-2.2%) vs 10.2% (95% CI, 9.3-11.3%)).

CONCLUSION

The performance of sFlt-1/PlGF ratio > 38 in the prediction of delivery with PE at < 1 and < 4 weeks from assessment is substantially different when the assessment is at 31-34 weeks' gestation compared to at 35-37 weeks. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Comparison of screening for pre-eclampsia at 31-34 weeks' gestation by sFlt-1/PlGF ratio and a method combining maternal factors with sFlt-1 and PlGF

OBJECTIVE

To estimate the patient-specific risk of pre-eclampsia (PE) at 31-34 weeks' gestation by a combination of maternal characteristics and medical history with multiples of the median (MoM) values of serum placental growth factor (PlGF) and serum soluble fms-like tyrosine kinase-1 (sFlt-1) and to compare the performance of screening to that achieved by the sFlt-1/PlGF ratio.

METHODS

This was a prospective observational study in women attending a third-trimester ultrasound scan at 31-34 weeks as part of routine pregnancy care. We estimated the performance of screening for PE with delivery within 4 weeks of assessment and PE with delivery from 4 weeks after assessment up to 40 weeks' gestation by the sFlt-1/PlGF ratio and by a method utilizing Bayes' theorem that combines maternal factors and MoM values of sFlt-1 and PlGF. The significance of the difference in screening performance between the two methods was assessed by comparison of the areas under the receiver-operating characteristics curves (AUC).

RESULTS

The study population of 8063 singleton pregnancies included 231 (2.9%) that subsequently developed PE. In the prediction of delivery with PE at < 4 weeks from assessment, the performance of the method utilizing Bayes' theorem was similar to that using the sFlt-1/PlGF ratio (AUC, 0.987 (95% CI, 0.979-0.995) vs 0.988 (95% CI, 0.981-0.994); P = 0.961). In contrast, the performance of screening for delivery with PE at ≥ 4 weeks after assessment up to 40 weeks' gestation was better with the method utilizing Bayes' theorem than that with the sFlt-1/PlGF ratio (AUC, 0.884 (95% CI, 0.854-0.914) vs 0.818 (95% CI, 0.775-0.860); P < 0.0001).

CONCLUSION

At 31-34 weeks' gestation the performance of screening for PE delivering at < 4 weeks from assessment by the method utilizing Bayes' theorem is similar to that using the sFlt-1/PlGF ratio, but the former is superior to the latter in prediction of PE delivering ≥ 4 weeks from assessment. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Screening for pre-eclampsia using sFlt-1/PlGF ratio cut-off of 38 at 30-37 weeks' gestation

OBJECTIVE

To evaluate a soluble fms-like tyrosine kinase-1 (sFlt-1) to placental growth factor (PlGF) ratio cut-off of 38 for the prediction of pre-eclampsia (PE) in routine assessment in singleton pregnancies at 30-37 weeks' gestation.

METHODS

This was a prospective observational study in women attending a third-trimester ultrasound scan at 30-37 weeks as part of routine pregnancy care. Serum sFlt-1 and PlGF were measured and their ratio was calculated. We estimated the detection rate (DR), false-positive rate (FPR), positive predictive value (PPV) and negative predictive value (NPV) of sFlt-1/PlGF ratio >38 for the prediction of delivery with PE at < 1, < 4 and ≥ 4 weeks after assessment.

RESULTS

The study population of 12 305 singleton pregnancies was examined at a median of 32.4 (range, 30.0-36.9) weeks and included 14 (0.11%), 77 (0.63%) and 227 (1.84%) cases that subsequently delivered with PE at < 1, < 4 or ≥ 4 weeks' after assessment, respectively. The DR, FPR, PPV and NPV of sFlt-1/PlGF ratio > 38 in the prediction of delivery with PE at < 1 week were 78.6%, 4.5%, 1.9% and 99.97%, respectively; the values for delivery with PE at < 4 weeks were 76.6%, 4.1%, 10.4% and 99.85% and for delivery with PE ≥ 4 weeks were 20.7%, 4.3%, 8.3% and 98.47%.

CONCLUSION

In routine screening of singleton pregnancies, the performance of a sFlt-1/PlGF ratio > 38 is modest for the prediction of delivery with PE at < 1 and at < 4 weeks after assessment and poor for the prediction of delivery with PE at ≥ 4 weeks after assessment. A sFlt-1/PlGF ratio > 38 predicted 79% of cases delivering with PE at < 1 week after assessment, at a FPR of 4.5%; consequently, a policy of hospitalizing patients with a ratio > 38 would potentially lead to unnecessary hospitalization in 4.5% of pregnancies and a ratio of ≤ 38 would falsely reassure one fifth of women who will deliver with PE within 1 week of assessment. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Serum biomarkers combined with uterine artery Doppler in prediction of preeclampsia

First-trimester screening may be a major advantage over a second-trimester approach since it opens prospects for early and more efficient interventions. The aim of the current study was to evaluate whether the measurement of maternal serum inhibin A, activin A and placental growth factor (PlGF) at three to four months gestation with the second-trimester uterine artery pulsatility index (PI) are useful in predicting preeclampsia in a group of nulliparous women. All the patients also underwent uterine artery Doppler examination to measure the PI at 22–24 weeks gestation. Inhibin A, activin A and PlGF were measured using an ELISA by an examiner who was blinded to the pregnancy outcome. Thirty-eight cases with preeclampsia and 100 controls were analyzed. Second-trimester uterine artery PI and marker levels were expressed as multiples of the median (MoM). The uterine artery PI was increased in pregnancies with preeclampsia compared with controls. In pregnancies that developed preeclampsia, the uterine artery PI was increased (1.61±0.047 vs. 1.02±0.049, P<0.001), as was the level of inhibin A (1.72±0.023 vs. 1.03±0.063, P<0.001) and the level of activin A (1.68±0.38 vs. 1.06±0.42, P<0.001) compared with the controls. In contrast, the level of PlGF was decreased in pregnancies that developed preeclampsia compared with the controls (0.69±0.23 vs. 1.00±0.26, P<0.001). A combination of activin A, PlGF and uterine artery PI gave an AUC of 0.915 (95% CI, 0.812–0.928; P<0.001) with a sensitivity of 91% at a specificity of 82%. In our study, we demonstrated that both serum inhibin A and activin A levels were increased, while the PlGF level was decreased in the early second-trimester in women who developed preeclampsia.

The association between angiogenic markers and fetal sex: Implications for preeclampsia research

OBJECTIVE

Current research suggests sexual dimorphism between the male and female fetoplacental units, but with unknown relevance for preeclampsia. We investigated the association between fetal sex and concentrations of the angiogenic markers soluble Fms-like kinase 1 (sFlt-1), placental growth factor (PlGF), and sFlt-1/PlGF ratio in first and second-third trimester in women with/without preeclampsia, and the impact of fetal sex on the prognostic value of angiogenic markers for preeclampsia.

STUDY DESIGN

Observational study in a prospective, population-based cohort of 2110 singleton pregnancies with 150 preeclampsia cases.

RESULTS

Higher sFlt-1 concentrations were observed for women carrying female fetuses in first trimester (all, 1107.65 vs. 992.27pg/ml; preeclampsia cases, 1118.79 vs. 934.49pg/ml, p<0.05) and in second-third trimester (all, 1130.03 vs. 1043.15pg/ml; preeclampsia, 1480.30 vs. 1152.86pg/ml, p<0.05), with similar findings for the sFlt-1/PlGF ratio concentrations in first (29.67 vs. 27.39 p<0.05) and second-third trimester (3.56 vs. 3.22, p<0.05). In first trimester, log transformed concentrations of PlGF, sFlt-1 and sFlt-1/PlGF (all participants) and sFlt-1 (preeclampsia cases) associated with fetal sex in adjusted analyses (p<0.05). In second-third trimester, only log(sFlt-1) associated with fetal sex (all, p=0.028; preeclampsia, p=0.067) In receiver operating curve analysis, prediction of early-onset preeclampsia by sFlt-1/PlGF tended to be superior in pregnancies with female vs. male fetuses (p=0.06).

CONCLUSION

Sexual dimorphism was observed for concentrations of angiogenic markers. Female fetal sex was associated to higher sFlt-1 and sFlt-1/PlGF ratio concentrations in both healthy pregnancies and women developing preeclampsia. Fetal sex should be considered in research and clinical use of angiogenic markers.

Maternal serum soluble fms-like tyrosine kinase-1 at 22 and 32 weeks in the prediction of pre-eclampsia

OBJECTIVE

To investigate the potential value of repeat measurements of maternal serum concentration of soluble fms-like tyrosine kinase-1 (sFlt-1) at 22 and 32 weeks' gestation in the prediction of pre-eclampsia (PE) in women delivering after 32 weeks.

METHODS

The data were derived from prospective screening for adverse obstetric outcomes in women attending their routine hospital visit at 19-24 and/or 30-34 weeks' gestation in one of two maternity hospitals in England. Serum sFlt-1 was measured in 7565 and 8264 singleton pregnancies at 19-24 and 30-34 weeks, respectively. Bayes' theorem was used to combine the a-priori risk from maternal factors with sFlt-1 multiples of the median (MoM) values. The performance of screening for PE developing after the 30-34-week visit by sFlt-1, measured at 19-24, 30-34 and at both 19-24 and 30-34 weeks was examined.

RESULTS

In pregnancies with PE, sFlt-1 in both the second and third trimesters was increased and the deviation from normal was inversely related to the gestational age at which delivery became necessary for maternal or fetal indications. Serum sFlt-1 at 19-24 weeks was not useful in predicting PE beyond the 30-34-week visit, but the addition of sFlt-1 at 19-24 weeks improved the prediction of PE provided by sFlt-1 at 30-34 weeks. Screening by maternal factors and sFlt-1 at 30-34 weeks predicted 94% of preterm PE and 54% of term PE, at a false-positive rate of 10%; this was improved to 99% and 64%, respectively, by the additional measurement of sFlt-1 at 19-24 weeks.

CONCLUSIONS

Measurement of sFlt-1 in the second trimester improves the prediction of PE provided by screening in the early third-trimester. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Maternal serum placental growth factor at 12, 22, 32 and 36 weeks' gestation in screening for pre-eclampsia

OBJECTIVE

To examine the distribution of maternal serum placental growth factor (PlGF) at 12, 22, 32 and 36 weeks' gestation in singleton pregnancies which develop pre-eclampsia (PE) and examine the performance of this biomarker in screening for PE.

METHODS

Serum PlGF was measured in 40 212 cases at 11-13 weeks, in 10 282 cases at 19-24 weeks, in 10 400 at 30-34 weeks and 4043 at 35-37 weeks. Bayes' theorem was used to combine the a-priori risk from maternal characteristics and medical history with serum PlGF. The performance of screening for PE requiring delivery < 32, at 32 + 0 to 36 + 6 and ≥ 37 weeks' gestation was estimated.

RESULTS

In pregnancies that developed PE, serum PlGF was decreased and the separation in multiples of the median (MoM) values from normal was greater with earlier, compared to later, gestational age at which delivery for PE became necessary. Additionally, the slope of the regression lines of PlGF MoM with gestational age at delivery in pregnancies that developed PE increased with advancing gestational age at screening. The detection rates (DRs), at a false-positive rate (FPR) of 10%, for PE delivering < 32 weeks were 79% and 97% with screening at 12 and 22 weeks, respectively. The DRs for PE delivering at 32 + 0 to 36 + 6 weeks were 57%, 65% and 90% with screening at 12, 22 and 32 weeks. The DRs for PE delivering ≥ 37 weeks were 40%, 37%, 54% and 64% with screening at 12, 22, 32 and 36 weeks, respectively.

CONCLUSIONS

The performance of combined screening with maternal factors, medical history and PlGF is superior in screening for early, compared to late, PE and improves with advancing gestational age at screening. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Maternal serum soluble fms-like tyrosine kinase-1 at 12, 22, 32 and 36 weeks' gestation in screening for pre-eclampsia

OBJECTIVE

To examine the distribution of maternal serum soluble fms-like tyrosine kinase-1 (sFlt-1) at 12, 22, 32 and 36 weeks' gestation in singleton pregnancies that develop pre-eclampsia (PE) and examine the performance of this biomarker in screening for PE.

METHODS

Serum sFlt-1 was measured in 7066 cases at 11-13 weeks, 8079 cases at 19-24 weeks, 8472 at 30-34 weeks and 4043 at 35-37 weeks. Bayes' theorem was used to combine the a-priori risk from maternal characteristics and medical history with serum levels of sFlt-1. The performance of screening for PE in women requiring delivery < 32, between 32 + 0 and 36 + 6 and ≥ 37 weeks' gestation was estimated.

RESULTS

In pregnancies that developed PE, serum sFlt-1 was increased and the separation in multiples of the median (MoM) values from normal was greater with earlier, compared to later, gestational age at which delivery for PE became necessary. In pregnancies that developed PE, the slope of the regression lines of sFlt-1 MoM with gestational age at delivery increased with advancing gestational age at screening. Measurement of sFlt-1 at 11-13 weeks did not improve the prediction of PE achieved by maternal factors alone, sFlt-1 at 19-24 weeks improved the prediction of PE delivering < 37 weeks but not for PE delivering ≥ 37 weeks, sFlt-1 at 30-34 weeks improved the prediction of PE delivering < 37 and PE delivering ≥ 37 weeks and sFlt-1 at 35-37 weeks improved the prediction of PE delivering ≥ 37 weeks. The detection rates (DRs), at a false-positive rate (FPR) of 10%, of PE delivering < 32 weeks were 52% and 65% with screening at 12 and 22 weeks, respectively. The DRs for PE delivering between 32 + 0 and 36 + 6 weeks were 44%, 44% and 93% with screening at 12, 22 and 32 weeks. The DR for PE delivering ≥ 37 weeks were 37%, 37%, 52% and 69% with screening at 12, 22, 32 and 36 weeks, respectively.

CONCLUSIONS

The performance of combined screening with maternal factors, medical history and serum sFlt-1 is superior for detection of early, compared to late, PE and improves with advancing gestational age at screening. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

A comparison of the diagnostic utility of the sFlt-1/PlGF ratio versus PlGF alone for the detection of preeclampsia/HELLP syndrome

OBJECTIVE

The Elecsys(®) immunoassay sFlt-1/PlGF ratio and the Triage(®) PlGF assay were compared (in a prospective, multicenter, case-control study) for diagnosis of preeclampsia/hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome.

METHODS

Women in European perinatal care centers with singleton pregnancies were enrolled: 178 cases had confirmed preeclampsia and 391 controls had normal outcome. Patients in the preeclampsia/HELLP syndrome group were matched pairwise by gestational week to healthy controls (1:2). Maternal blood samples were analyzed using (a) fully automated Elecsys PlGF and Elecsys sFlt-1 immunoassays with two cutoffs (early-onset [<34 weeks] ≤33, ≥85; late-onset [≥34 weeks] ≤33, ≥110), and (b) Triage PlGF immunoassay (single cutoff). Diagnostic performance and utility were assessed.

RESULTS

Respectively, 83 and 95 women had early-onset or late-onset preeclampsia/HELLP syndrome. The overall diagnostic performance of the Elecsys immunoassay sFlt-1/PlGF ratio (area under the curve [AUC] 0.941) was higher than for Triage PlGF (AUC 0.917). The Elecsys immunoassay sFlt-1/PlGF ratio sensitivity and specificity was: 94.0% (95% confidence interval [CI] 86.5-98.0) and 99.4% (95% CI: 96.8-99.9) for early-onset preeclampsia; and 89.5% (95% CI: 81.5-94.8) and 95.4% (95% CI: 91.7-97.8) for late-onset preeclampsia. The Triage assay sensitivity and specificity was: 96.4% (95% CI: 89.8-99.3) and 88.5% (95% CI: 82.8-92.8) (early-onset); and 90.5% (95% CI: 83-96) and 64.5% (95% CI: 57.8-70.9) (late onset).

CONCLUSIONS

The fully automated Elecsys immunoassay sFlt-1/PlGF ratio provides improved diagnostic utility over the Triage PlGF assay with improved specificity for the clinical management of pregnant women with suspected preeclampsia/HELLP syndrome.

Longitudinal changes in maternal serum placental growth factor and soluble fms-like tyrosine kinase-1 in women at increased risk of pre-eclampsia

OBJECTIVES

To investigate longitudinal changes in maternal serum levels of placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) in pregnant women who develop pre-eclampsia (PE) or gestational hypertension (GH).

METHODS

This was a prospective longitudinal study in women with singleton pregnancies identified by screening at 11 + 0 to 13 + 6 weeks' gestation as being at high-risk of PE. Blood samples were taken every 4 weeks until delivery. Values were compared in women who developed preterm PE (requiring delivery before 37 weeks' gestation), term PE or GH and those who remained normotensive.

RESULTS

A total of 1069 samples were analyzed in 234 women, including 172 who remained normotensive, 18 who developed GH, 22 who developed preterm PE and 22 who developed term PE. In the preterm PE group, compared to the normotensive group, sFlt-1 levels were significantly higher from 15 weeks' gestation onward and the difference increased with gestational age (P < 0.001). In the preterm PE group, compared to the normotensive group, PlGF levels were significantly lower from 11 weeks' gestation onward and the difference increased significantly with gestational age (P < 0.001). Similarly, in the term PE and GH groups, PlGF levels were lower from 13 and 27 weeks onward, respectively, and the differences increased significantly with gestational age (P < 0.001 for both groups). In the preterm PE group, compared to the normotensive group, the sFlt-1/PlGF ratio was significantly higher from 11 weeks onward and the difference increased significantly with gestational age (P < 0.001). A random slope model provided a significantly better fit to the data than did a single-level model for sFlt-1 (likelihood ratio (LR) = 516; degrees of freedom (df) = 3; P < 0.001), PlGF (LR = 542; df = 3; P < 0.001) and the sFlt-1/PlGF ratio (LR = 468; df = 3; P < 0.001).

CONCLUSION

Repeat measurements of the biochemical markers used in this study are likely to be better predictors of PE than are measurements at a single time point during pregnancy, as the differences between normotensive and hypertensive pregnancies increase with gestational age. In screening for preterm PE, maternal serum level of PlGF is a useful marker from the first trimester onward, while the level of sFlt-1 is likely to have a predictive value from the second trimester onward. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Predictive Value of the sFlt-1:PlGF Ratio in Women with Suspected Preeclampsia

BACKGROUND

The ratio of soluble fms-like tyrosine kinase 1 (sFlt-1) to placental growth factor (PlGF) is elevated in pregnant women before the clinical onset of preeclampsia, but its predictive value in women with suspected preeclampsia is unclear.

METHODS

We performed a prospective, multicenter, observational study to derive and validate a ratio of serum sFlt-1 to PlGF that would be predictive of the absence or presence of preeclampsia in the short term in women with singleton pregnancies in whom preeclampsia was suspected (24 weeks 0 days to 36 weeks 6 days of gestation). Primary objectives were to assess whether low sFlt-1:PlGF ratios (at or below a derived cutoff) predict the absence of preeclampsia within 1 week after the first visit and whether high ratios (above the cutoff) predict the presence of preeclampsia within 4 weeks.

RESULTS

In the development cohort (500 women), we identified an sFlt-1:PlGF ratio cutoff of 38 as having important predictive value. In a subsequent validation study among an additional 550 women, an sFlt-1:PlGF ratio of 38 or lower had a negative predictive value (i.e., no preeclampsia in the subsequent week) of 99.3% (95% confidence interval [CI], 97.9 to 99.9), with 80.0% sensitivity (95% CI, 51.9 to 95.7) and 78.3% specificity (95% CI, 74.6 to 81.7). The positive predictive value of an sFlt-1:PlGF ratio above 38 for a diagnosis of preeclampsia within 4 weeks was 36.7% (95% CI, 28.4 to 45.7), with 66.2% sensitivity (95% CI, 54.0 to 77.0) and 83.1% specificity (95% CI, 79.4 to 86.3).

CONCLUSIONS

An sFlt-1:PlGF ratio of 38 or lower can be used to predict the short-term absence of preeclampsia in women in whom the syndrome is suspected clinically. (Funded by Roche Diagnostics.).

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

Ischemic placental syndrome--prediction and new disease monitoring

The last decade has seen an improved understanding of the cause of the development of pathologies such as gestational hypertension, preeclampsia, intrauterine growth restriction, intrauterine fetal death or placental abruption. Nowadays, we know that most conditions within this group share the same pathogenesis, the cause of which is placental ischemia. The following review is an attempt to propose a new method for prediction, diagnosis and--above all--appropriate monitoring of pregnant women and fetuses developing the ischemic placental syndrome with the use of tests that are new but yet widely available in clinical diagnosis. They are closely related to the condition's pathogenesis, therefore their elevated levels may predate clinical symptoms, and--most importantly--they correlate with syndrome aggravation and the occurrence of complications. Perhaps, the new look will allow us to improve perinatal results by reducing mortality and severe complications in pregnant women and fetal deaths resulting from sudden intrauterine fetal death or placental abruption.

Angiogenesis-Related Biomarkers (sFlt-1/PLGF) in the Prediction and Diagnosis of Placental Dysfunction: An Approach for Clinical Integration

Placental dysfunction is involved in a group of obstetrical conditions including preeclampsia, intrauterine growth restriction, and placental abruption. Their timely and accurate recognition is often a challenge since diagnostic criteria are still based on nonspecific signs and symptoms. The discovering of the role of angiogenic-related factors (sFlt-1/PlGF) in the underlying pathophysiology of placental dysfunction, taking into account that angiogenesis-related biomarkers are not specific to any particular placental insufficiency-related disease, has marked an important step for improving their early diagnosis and prognosis assessment. However, sFlt-1/PlGF has not been yet established as a part of most guidelines. We will review the current evidence on the clinical utility of sFlt-1/PlGF and propose a new protocol for its clinical integration.

Serum soluble fms-like tyrosine kinase-1 in the three trimesters of pregnancy: effects of maternal characteristics and medical history

OBJECTIVE

To define the contribution of maternal variables which influence the measured level of maternal serum soluble fms-like tyrosine kinase-1 (sFlt-1) in screening for pregnancy complications.

METHODS

Maternal characteristics and medical history were recorded and serum sFlt-1 was measured in women with a singleton pregnancy attending for three routine hospital visits at 11 + 0 to 13 + 6, 19 + 0 to 24 + 6 and 30 + 0 to 34 + 6 or 35 + 0 to 37 + 6 weeks' gestation. For pregnancies delivering phenotypically normal live births or stillbirths ≥ 24 weeks' gestation, variables from maternal demographic characteristics and medical history that are important in the prediction of sFlt-1 were determined from a linear mixed-effects multiple regression.

RESULTS

Serum sFlt-1 was measured in 7066 cases in the first trimester, 8078 in the second trimester and 10,464 in the third trimester. Significant independent contributions to serum sFlt-1 were provided by gestational age, maternal weight, racial origin, cigarette smoking, birth-weight Z-score of the neonate in the previous pregnancy and interpregnancy interval. Random-effects multiple regression analysis was used to define the contribution of maternal variables that influence the measured level of serum sFlt-1 and express the values as multiples of the median (MoMs). The model was shown to provide an adequate fit of MoM values for all covariates, both in pregnancies that developed pre-eclampsia and in those without this pregnancy complication.

CONCLUSIONS

A model was fitted to express measured serum sFlt-1 across the three trimesters of pregnancy as MoMs, after adjusting for variables from maternal characteristics and medical history that affect this measurement.

Serum placental growth factor in the three trimesters of pregnancy: effects of maternal characteristics and medical history

OBJECTIVE

To define the contribution of maternal variables which influence the measured level of maternal serum placental growth factor (PlGF) in screening for pregnancy complications.

METHODS

Maternal characteristics and medical history were recorded and serum levels of PlGF were measured in women with a singleton pregnancy attending for three routine hospital visits at 11 + 0 to 13 + 6, 19 + 0 to 24 + 6 and 30 + 0 to 34 + 6 or 35 + 0 to 37 + 6 weeks' gestation. For women delivering phenotypically normal live births or stillbirths ≥ 24 weeks' gestation, variables from maternal demographic characteristics and medical history important in the prediction of PlGF were determined from a linear mixed-effects multiple regression.

RESULTS

Serum levels of PlGF were measured in 38,002 cases in the first trimester, 10,281 in the second trimester and 12,392 in the third trimester. Significant independent contributions to serum PlGF were provided by gestational age, maternal age, weight and racial origin, cigarette smoking, diabetes mellitus, and gestational age at delivery and birth-weight Z-score of the neonate in the previous pregnancy. The machine used to measure serum PlGF was also found to have a significant effect. Allowing for other factors, the effect of maternal age on PlGF changed over the three trimesters, whereas other variables had constant effects over the three trimesters. Random-effects multiple regression analysis was used to define the contribution of maternal variables that influence the measured serum PlGF and express the values as multiples of the median (MoMs). The model was shown to provide an adequate fit of MoM values for all covariates, both in pregnancies that developed pre-eclampsia and in those without this complication.

CONCLUSIONS

A model was fitted to express the measured level of maternal serum PlGF across the three trimesters of pregnancy as MoMs, after adjusting for variables of maternal characteristics and medical history that affect this measurement.

Modeling risk for severe adverse outcomes using angiogenic factor measurements in women with suspected preterm preeclampsia

INTRODUCTION

Preeclampsia (PE) is a pregnancy-specific syndrome associated with adverse maternal and fetal outcomes. Patient-specific risks based on angiogenic factors might better categorize those who might have a severe adverse outcome.

METHODS

Women evaluated for suspected PE at a tertiary hospital (2009-2012) had pregnancy outcomes categorized as 'referent' or 'severe', based solely on maternal/fetal findings. Outcomes that may have been influenced by a PE diagnosis were considered 'unclassified'. Soluble fms-like tyrosine kinase (sFlt1) and placental growth factor (PlGF) were subjected to bivariate discriminant modeling, allowing patient-specific risks to be assigned for severe outcomes.

RESULTS

Three hundred twenty-eight singleton pregnancies presented at ≤34.0 weeks' gestation. sFlt1 and PlGF levels were adjusted for gestational age. Risks above 5 : 1 (10-fold over background) occurred in 77% of severe (95% CI 66 to 87%) and 0.7% of referent (95% CI <0.1 to 3.8%) outcomes. Positive likelihood ratios for the modeling and validation datasets were 19 (95% CI 6.2-58) and 15 (95% CI 5.8-40) fold, respectively.

CONCLUSIONS

This validated model assigns patient-specific risks of any severe outcome among women attending PE triage. In practice, women with high risks would receive close surveillance with the added potential for reducing unnecessary preterm deliveries among remaining women. © 2015 The Authors. Prenatal Diagnosis published by John Wiley & Sons Ltd.

Early prediction of preeclampsia

Effective screening for the development of early onset preeclampsia (PE) can be provided in the first-trimester of pregnancy. Screening by a combination of maternal risk factors, uterine artery Doppler, mean arterial pressure, maternal serum pregnancy-associated plasma protein-A, and placental growth factor can identify about 95% of cases of early onset PE for a false-positive rate of 10%.

Competing risk model in screening for preeclampsia by mean arterial pressure and uterine artery pulsatility index at 30-33 weeks' gestation

OBJECTIVE

To assess risk for preeclampsia (PE) based on maternal characteristics, mean arterial pressure (MAP) and uterine artery pulsatility index (Ut-PI) at 30-33 weeks' gestation.

METHODS

Screening study in singleton pregnancies including 2,140 that subsequently developed PE and 83,615 that were unaffected by PE, gestational hypertension or delivery of small-for-gestational-age neonates (normal group). We developed a survival time model for the time of delivery for PE by combination of maternal characteristics and history with MAP and Ut-PI multiple of the median (MoM) values (biophysical test). Data on third-trimester MAP and Ut-PI were available in 350 cases of PE and 13,878 of the normal group. The detection rate of PE requiring delivery within 4, 6 and 8 weeks of the visit was estimated.

RESULTS

In pregnancies with PE the log10 MoM values of MAP and Ut-PI were inversely related to gestational age at delivery. Biophysical testing detected 90, 65 and 53% of PE with delivery within 4, 6 and 8 weeks of the visit, at a fixed false-positive rate of 5%.

INTERPRETATION

Testing by maternal characteristics, Ut-PI and MAP at 30-33 weeks could identify 90% of pregnancies developing PE and requiring delivery within the subsequent 4 weeks.

Competing risks model in screening for preeclampsia by biophysical and biochemical markers at 30-33 weeks' gestation

OBJECTIVE

To assess the risk for preeclampsia (PE) by maternal characteristics, uterine artery pulsatility index (Ut-PI), mean arterial pressure (MAP), serum placental growth factor (PlGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) at 30-33 weeks' gestation.

METHODS

This was a screening study in singleton pregnancies including 2,140 that developed PE and 83,615 that were unaffected by PE. We developed a survival time model for the time of delivery for PE by combining maternal characteristics and history with Ut-PI, MAP, PlGF and sFlt-1 multiple of the median (MoM) values (combined test). Data on third-trimester MAP and Ut-PI were available in 350 cases of PE, and 13,878 unaffected pregnancies and data on PlGF and sFlt-1 were available in 118 cases of PE and 3,734 unaffected pregnancies. Modelled detection rate of all PE and PE requiring delivery within 4 and 6 weeks of the visit was estimated.

RESULTS

Screening by the combined test would detect 66, 98 and 86% of all PE and PE requiring delivery within 4 and 6 weeks of the visit, respectively, at a false positive rate of 5%.

INTERPRETATION

Screening by biophysical and biochemical testing at 30-33 weeks could identify most pregnancies developing PE and requiring delivery within the subsequent 4 weeks.