Onset threshold of the plasma levels of soluble fms-like tyrosine kinase 1/placental growth factor ratio for predicting the imminent onset of preeclampsia within 4 weeks after blood sampling at 19–31 weeks of gestation

HIV Associated Preeclampsia: A Multifactorial Appraisal

Introduction: This review explores angiogenesis, vascular dysfunction, the complement system, RAAS, apoptosis and NETosis as potential pathways that are dysregulated during preeclampsia, HIV infection and ART usage. Results: HIV-1 accessory and matrix proteins are protagonists for the elevation of oxidative stress, apoptosis, angiogenesis, and elevation of adhesion markers. Despite the immunodeficiency during HIV-1 infection, HIV-1 exploits our cellular defence arsenal by escaping cell-mediated lysis, yet HIV-1 infectivity is enhanced via C5a release of TNF-α and IL-6. This review demonstrates that PE is an oxidatively stressed microenvironment associated with increased apoptosis and NETosis, but with a decline in angiogenesis. Immune reconstitution in the duality of HIV-1 and PE by protease inhibitors, HAART and nucleoside reverse transcriptase, affect similar cellular pathways that eventuate in loss of endothelial cell integrity and, hence, its dysfunction. Conclusions: HIV-1 infection, preeclampsia and ARTs differentially affect endothelial cell function. In the synergy of both conditions, endothelial dysfunction predominates. This knowledge will help us to understand the effect of HIV infection and ART on immune reconstitution in preeclampsia.

Short-term prediction of preeclampsia using the sFlt-1/PlGF ratio: a subanalysis of pregnant Japanese women from the PROGNOSIS Asia study

Two prospective multicenter studies demonstrated that a soluble fms-like tyrosine kinase 1 (sFlt-1)/placental growth factor (PlGF) ratio cutoff of ≤38 can rule out preeclampsia within 1 week with a negative predictive value (NPV) of 99.3% (PROGNOSIS) and 98.6% (PROGNOSIS Asia). We report a subanalysis of the Japanese cohort from the PROGNOSIS Asia study. Pregnant women with suspected preeclampsia between gestational weeks 18 + 0 days and 36 + 6 days were enrolled at eight Japanese sites. Primary objectives: Assess the performance of the Elecsys^® sFlt-1/PlGF ratio cutoff ≤38 to rule out preeclampsia within 1 week and of the cutoff >38 to rule in preeclampsia within 4 weeks. Key secondary objectives: Prediction of maternal and fetal adverse outcomes (MAOs/FAOs) and their relationship with duration of pregnancy. Of 192 women enrolled, 180 (93.8%)/175 (91.1%) were evaluable for primary/combined endpoint analyses. Overall preeclampsia prevalence was 13.3%. A sFlt-1/PlGF ratio of ≤38 provided an NPV of 100% (95% confidence interval [CI], 97.5–100) for ruling out preeclampsia within 1 week, and a ratio of >38 provided a positive predictive value of 32.4% (95% CI, 18.0–49.8) for ruling in preeclampsia within 4 weeks. The area under the curve for the prediction of preeclampsia/maternal/fetal adverse outcomes within 1 week was 94.2% (95% CI, 89.3–97.8). After adjusting for gestational age and final preeclampsia status, Cox regression indicated a 2.8-fold greater risk of imminent delivery for women with a sFlt-1/PlGF ratio >38 versus ≤38. This subanalysis of Japanese women with suspicion of preeclampsia showed high predictive value for a Elecsys sFlt-1/PlGF ratio cutoff of 38 for short-term prediction of preeclampsia.

Low placental growth factor levels and high soluble endoglin levels at 26-31 weeks of gestation precede light placenta with and without relatively heavy infant, respectively: A retrospective cohort study

AIM

Our aim was to examine whether serum levels of placental growth factor (PlGF) and soluble endoglin (sEng) at 19-25 and 26-31 weeks of gestation were associated with the occurrence of the 9-block categorization of placenta weight (PW) and fetal/placenta ratio (F/P ratio).

METHODS

We performed a retrospective cohort study in 1391 women with singleton pregnancy. Serum levels of PlGF and sEng were measured by enzyme immunosorbent assay. A light placenta was defined as PW ZS < -1.28 SD. Based on the PW (light, normal, and heavy) and F/P ratio (relatively heavy, balanced growth, and relatively small), 9-block categorization were performed. Multivariable logistic regression analyses were performed.

RESULTS

Low PlGF at 26-31 weeks was an independent risk factor for the birth of infants belonging to Block A (light placenta and relatively heavy infant), after adjusting for prepregnancy body mass index and serum levels of sEng. High sEng at 26-31 weeks was an independent risk factor for the birth of infants belonging to Block D (light placenta and balanced growth of infant), after adjusting for past history of either preeclampsia or gestational hypertension, high pulsatility index of uterine artery flow velocity waveforms in the second trimester, and serum level of PlGF.

CONCLUSIONS

Low PlGF levels at 26-31 weeks of gestation may precede a light placenta and relatively heavy infant (Block A), and high sEng levels at 26-31 weeks of gestation may precede a light placenta and balanced growth of infant (Block D).

Comparative risks and predictors of preeclamptic pregnancy in the Eastern, Western and developing world

Preeclampsia (PE) is a complication of pregnancy characterized by hypertension (HTN-Preg), and often proteinuria. If not managed promptly, PE could lead to eclampsia and seizures. PE could also lead to intrauterine growth restriction (IUGR) and prematurity at birth. Although PE is a major cause of maternal and fetal morbidity and mortality, the underlying mechanisms are unclear. Also, there is a wide variability in the incidence of PE, ranging between 2 and 8% of pregnancies in the Eastern, Western and Developing world, suggesting regional differences in the risk factors and predictors of the pregnancy-related disorder. Several demographic, genetic, dietary and environmental factors, as well as maternal circulating biomarkers have been associated with PE. Demographic factors such as maternal race and ethnicity could play a role in PE. Specific genetic polymorphisms have been identified in PE. Maternal age, parity, education and socioeconomic status could be involved in PE. Dietary fat, protein, calcium and vitamins, body weight, and environmental factors including climate changes and air pollutants could also play a role in PE. Several circulating cytoactive factors including anti-angiogenic factors and cytokines have also been associated with PE. Traditional midwifery care is a common practice in local maternity care units, while advanced perinatal care and new diagnostic tools such as uterine artery Doppler velocimetry have been useful in predicting early PE in major medical centers. These PE risk factors, early predictors and diagnostic tools vary vastly in different regions of the Eastern, Western and Developing world. Further understanding of the differences in the demographic, genetic, dietary and environmental factors among pregnant women in different world regions should help in designing a region-specific cluster of risk factors and predictors of PE, and in turn provide better guidance for region-specific tools for early detection and management of PE.

Cerebrospinal beta-amyloid peptides(1-40) and (1-42) in severe preeclampsia and HELLP syndrome - a pilot study

During pregnancy, substantial alterations in cerebral plasticity, vascular remodeling and neuronal growth occur in the maternal brain. We investigated whether concentrations of selected neurodiagnostic biomarkers in the cerebrospinal fluid of women with preeclampsia/HELLP syndrome differ from those in healthy controls using enzyme-linked immunosorbent assay technique. We found that tau protein concentrations (p = 0.016) and phospho-tau/tau ratio (p < 0.001) in cerebrospinal fluid were significantly lower in 39 preeclamptic women compared to 44 healthy controls during third trimester of pregnancy. Beta-amyloid(1-40)/(1-42) ratio was significantly higher in HELLP syndrome than in severe preeclampsia (8.49 + 2.73 vs. 4.71 + 1.65; p = 0.007). We conclude that beta-amyloid(1-40)/(1-42) ratio in cerebrospinal fluid can discriminate severe preeclampsia and HELLP syndrome. High beta-amyloid peptide and low tau protein concentrations are associated with impaired development of the materno-feto-placental unit and correlate with placental dysfunction.

The need for implementation of first trimester screening for preeclampsia and fetal growth restriction in low resource settings

Background: Preeclampsia [PE] and fetal growth restriction [FGR] is a major cause of perinatal morbidity in both developed and developing countries but the disease leaves a severe impact in developing countries, due to the late presentation of cases where prevention and treatment becomes impossible. Routine antenatal ultrasound and health checkups in periphery are usually done in first trimester for dating and viability scan, in midtrimester for anomaly scan and in third trimester for safe confinement. Underlying disorder of deep placentation which is unidentified can lead to increased maternal morbidity and fetal compromise between 26 to 34 weeks of gestation The complications present at an irreversible stage where there is no sufficient time even for referral to tertiary care center. Frequent antenatal visits as suggested by WHO would definitely bring down maternal mortality but this increased surveillance when offered to all might be a huge burden to health care providers in low resource settings. An acceptable screening test should help in triaging the high risk group in first trimester itself targeting about only one third of the population for prophylactic therapy and increased antenatal surveillance.The objective of this study is to evaluate the performance and feasibility of different screening protocols in low resource settings.Methodology: Screening for PE and FGR was done at the 11-14 weeks aneuploidy scan as per FMF guidelines. Group I included 6289 women whose risk prediction was done with maternal characteristics [MC], mean arterial pressure [MAP] and Uterine artery Doppler [UAD]. Group II included 2067 women whose risk was predicted with MC, MAP, UAD and PAPP-A. Group III included 576 women whose risk prediction included all parameters with PLGF.Results: Two thousand five hundred fifty-seven cases were screen positive in group I and 602 were screen positive in group II. In group III which included PLGF, 24 were positive for early onset PE and 36 for late onset PE. The number needed to treat [NNT] was 35.9, 29.1 and 10% in Group I, II and III respectively. The detection rate [DR] for PE and FGR was 60% in Group I and DR for FGR in Group II was 85%. In Group III, for early onset PE the DR was 98% and 68% for late onset PE.Conclusion: Screening for PE with available resources in the periphery needs to be implemented to avoid its grave complications. Traditional screening for PE by NICE guidelines can be adopted but may have a detection rate of only 30-40%. Though screening by ACOG criteria may have good detection rates but more than two thirds of the population would become screen positive which nullifies this approach as a good screening methodology in low resource settings. Multiparametric approach for screening in first trimester serves as a better screening tool to enable higher detection rate of disease with least false positive rates. Uterine artery Doppler when combined with maternal characteristics and mean arterial pressure could achieve a detection rate of about 60% and would still target only one third of the population for increased antenatal surveillance. This requires training healthcare professionals in the periphery for this approach and this should be our prime focus in the current scenario. Inclusion of serum biochemistry would still bring down the target population to 10% and increase the DR and can be considered as an additional test in economically feasible population. In low resource settings a better screening approach to PE would be a combination of maternal history, biophysical or biochemical parameters whichever is feasible considering the economy and availability of resources.

Difficulty of predicting early-onset super-imposed preeclampsia in pregnant women with hemodialysis due to diabetic nephropathy by serum levels of sFlt-1, PlGF, and sEng

There are few case reports in which circulating levels of soluble fms-like tyrosine kinase 1 (sFlt-1), placental growth factor (PlGF), and soluble endoglin (sEng) were measured before the onset of super-imposed preeclampsia in women with hemodialysis. A 40-year-old Japanese nulliparous women with hemodialysis due to diabetic nephropathy became pregnant by frozen embryo transfer. Intensive hemodialysis was started at 5 weeks of gestation. Her blood pressure (BP) in the first trimester was around 130/80 mmHg. At 20⁺³ weeks, she was admitted for close monitoring; her BP was 137/75 mmHg. Her BP increased to 157/88 mmHg at 31⁺² weeks, and nifedipine at 20 mg/day was started at 31⁺⁶ weeks. However, the serial longitudinal measurements of sFlt-1, PlGF, and sEng did not predict the onset of super-imposed preeclampsia. Cesarean section was performed at 33⁺⁶ weeks due to uncontrollable hypertension. A healthy female infant weighing 2138 g was delivered. As for the changes of biomarkers between just before and just after hemodialysis, sFlt-1 was significantly higher just after compared with just before hemodialysis (5774 ± 1875 pg/mL vs. 2960 ± 905 pg/mL, respectively, p < 0.001). PlGF was also significantly higher just after compared with just before hemodialysis (2227 ± 1038 pg/mL vs. 1377 ± 614 pg/mL, respectively, p < 0.001). However, the sFlt-1/PlGF ratio and sEng levels were not significantly different between just before and just after hemodialysis (p = 0.115, p = 0.672, respectively). In conclusion, prediction of early-onset super-imposed preeclampsia using angiogenic and anti-angiogenic markers in pregnant women with hemodialysis might be difficult.

Effect of Low-Dose Aspirin on Soluble FMS-Like Tyrosine Kinase 1/Placental Growth Factor (sFlt-1/PlGF Ratio) in Pregnancies at High Risk for the Development of Preeclampsia

BACKGROUND

Soluble FMS-like Tyrosine Kinase 1 (sFlt-1) and placental growth factor (PlGF) have been reported to be highly predictive several weeks before the onset of preeclampsia.

OBJECTIVE

To investigate longitudinal changes of serum levels sFlt-1 and PlGF in pregnant women at high risk for the development of preeclampsia and to reveal an impact of aspirin on maternal serum concentrations of sFlt-1 and PlGF.

METHODS

This was a prospective longitudinal study in 394 women with various risk factors for the development of preeclampsia (chronic hypertension, antiphospholipid syndrome/APS or systemic lupus erythematosus/SLE, thrombophilia, women with a history of preeclampsia, pathologic first trimester screening for preeclampsia) and 68 healthy women. Serum levels of sFlt-1 and PlGF were measured prospectively at 4-week intervals (from gestational weeks 12 until postpartum).

RESULTS

The sFlt-1/PlGF ratio was significantly higher in women with an adverse obstetric outcome compared to women with a normal pregnancy, starting between 20 and 24 weeks of gestation. There was no effect of aspirin on sFlt-1/PlGF ratio in women with chronic hypertension, APS/SLE, thrombophilia and controls. The use of aspirin showed a trend towards an improvement of the sFlt-1/PlGF ratio in women with preeclampsia in a previous pregnancy and a significant effect on the sFlt-1/PlGF ratio in women with a pathologic first trimester screening for preeclampsia.

CONCLUSIONS

Our findings reveal an impact of aspirin on sFlt-1/PlGF ratio in women with a pathologic first trimester screening for preeclampsia, strongly supporting its prophylactic use.

Placental Elasticity as a New Non-invasive Predictive Marker of Pre-eclampsia

Point shear wave elastography is an ultrasonography technique used to evaluate tissue elasticity. We examined whether placental elasticity is useful for predicting the onset of pre-eclampsia. Two hundred twenty-one participants were divided into two groups: one group at low risk (n = 185) and the other at high risk (n = 36) for pre-eclampsia. The two groups were compared with respect to shear wave velocity (SWV) of the placenta. Use of SWV as a predictor of pre-eclampsia was also investigated by creating a receiver operating characteristic (ROC) curve. The ROC curve was used to set a cutoff SWV value for predicting pre-eclampsia. The SWV of the high-risk group was significantly higher than that of the low-risk group (p < 0.001). Thirteen participants developed pre-eclampsia after SWV measurements, and the SWVs of these participants were significantly higher than those of participants in who pre-eclampsia did not develop. The cutoff value and area under the ROC curve were 1.188 m/s and 0.9118, respectively. Placental elasticity was significantly increased even before the onset of pre-eclampsia onset and, thus, may be a parameter used to predict the onset of pre-eclampsia.

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.

Proposed clinical management of pregnancies after combined screening for pre-eclampsia at 30-34 weeks' gestation

OBJECTIVE

To estimate the patient-specific risk of pre-eclampsia (PE) at 30-34 weeks' gestation by a combination of maternal characteristics and medical history with multiples of the median (MoM) values of mean arterial pressure (MAP), uterine artery pulsatility index (UtA-PI), serum placental growth factor (PlGF) and serum soluble fms-like tyrosine kinase-1 (sFlt-1), and stratify women into high-, intermediate- and low-risk management groups.

METHODS

This was a prospective observational study in women attending a third-trimester ultrasound scan at 30-34 weeks as part of routine pregnancy care. Patient-specific risks of delivery with PE at < 4 weeks from assessment and at < 40 weeks' gestation were calculated using the competing-risks model to combine the prior risk from maternal characteristics and medical history with MoM values of MAP, UtA-PI, PlGF and sFlt-1. On the basis of these risks, the population was stratified into high-, intermediate- and low-risk groups. Different risk cut-offs were used to vary the proportion of the population stratified into each risk category and the performance of screening for delivery with PE at < 4 weeks from assessment and delivery with PE from 4 weeks after assessment and up to 40 weeks' gestation was estimated.

RESULTS

The study population of 8128 singleton pregnancies included 234 (2.9%) that subsequently developed PE. Using a risk cut-off of 1 in 50 for PE delivering at < 4 weeks and a risk cut-off of 1 in 150 for PE delivering at < 40 weeks' gestation, the proportion of the population stratified into high, intermediate and low risk was about 3%, 26% and 71%, respectively. The high-risk group contained 90% of pregnancies with PE at < 4 weeks and 40% of those with PE at 4 weeks from assessment to 40 weeks' gestation. The intermediate-risk group contained a further 49% of women with PE at 4 weeks from assessment to 40 gestational weeks. In the low-risk group, none of the women developed PE at < 4 weeks and only 0.3% developed PE at 4 weeks to 40 gestational weeks.

CONCLUSION

The study presents risk stratification of PE by the combined test at 30-34 weeks, aiming to identify a high-risk group in need of intensive monitoring from the time of the initial assessment and up to 40 weeks' gestation and an intermediate-risk group in need of monitoring from 4 weeks after the initial assessment and up to 40 weeks' gestation. All pregnancies would need to be reassessed at 40 weeks' gestation. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

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.

Second-trimester urine nephrin:creatinine ratio versus soluble fms-like tyrosine kinase-1:placental growth factor ratio for prediction of preeclampsia among asymptomatic women

This prospective observational study compare urine nephrin:creatinine ratio (NCR, ng/mg) with serum soluble fms-like tyrosine kinase-1:placental growth factor ratio (FPR, pg/pg) for preeclampsia (PE) prediction among unselected asymptomatic pregnant women in 2^nd trimester. NCR and FPR were determined in 254 paired urine/blood samples collected simultaneously from 254 women at median gestational week (GW) 24 (range, 22–27) without hypertension or significant proteinuria in pregnancy (SPIP). Fifteen (5.9%) developed SPIP and hypertension at GW 34.0 (26.0–38.6) and 35.3 (27.6–38.6), respectively, and were diagnosed with PE at GW 35.7 (27.6–38.6). The 90^th percentile level determined in 239 women normotensive throughout pregnancy gave NCR (139) sensitivity and positive predictive values (PPV) of 60% (9/15) and 27% (9/33), while those for serum FPR (4.85) were 40% (6/15) and 20% (6/30), respectively. Relative risks (95%CI) of later PE were 10.0 (3.82–26.4; 27% [9/33] vs. 2.7% [6/221]) and 4.98 (1.91–13.0; 20% [6/30] vs. 4.0% [9/224]) for NCR-positive and FPR-positive women, respectively. Cut-offs suggested by ROC gave NCR (86.6) sensitivity and PPV of 87% (13/15) and 17% (13/79), and FPR (8.8) values of 40% (6/15) and 40% (6/15), respectively. Thus, 2^nd trimester NCR was superior to FPR for PE prediction.

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.

Prediction and prevention of hypertensive disorders of pregnancy

The most common classifications of hypertensive disorders of pregnancy consist of chronic hypertension, gestational hypertension, preeclampsia (PE) and superimposed PE. A common final pathophysiology of PE is endothelial dysfunction. The most successful translational research model for explaining the cause-effect relationship in the genesis of PE is the angiogenic/angiostatic balance theory, involving soluble fms-like tyrosine kinase 1 (sFlt-1), placental growth factor (PlGF) and soluble endoglin (sEng). In a systematic review of articles on the prediction of early-onset PE using angiogenesis-related factors, we revealed that the prediction of early-onset PE in the first trimester is clinically possible, but the prediction of early-onset PE in the early third trimester might be ideal. In addition, an onset threshold or a serial approach appeared to be clinically useful for predicting the imminent onset of PE, with onset at <4 weeks after blood sampling in the second and early third trimesters, because the positive likelihood ratio was >10 and the positive predictive value was >20%. The National Institute for Health and Care Excellence guidelines state that the Triage PlGF testing and Elecsys immunoassay for the sFlt-1/PlGF ratio could help to exclude PE in women with suspected PE at 20-34 weeks of gestation. Until now, we have not found any effective therapies to prevent PE. However, low-dose aspirin treatment starting at ⩽16 weeks of gestation might be associated with a marked reduction in PE. In addition, early statin treatment might prevent the occurrence of PE. Currently, a clinical trial using pravastatin for the prevention of PE is ongoing.

Competing-risks model in screening for pre-eclampsia by maternal factors and biomarkers at 35-37 weeks' gestation

OBJECTIVE

To develop a model for prediction of term pre-eclampsia (PE) based on a combination of maternal factors and late third-trimester biomarkers.

METHODS

Data were derived from prospective screening for adverse obstetric outcomes in women attending their routine hospital visit at 35-37 weeks' gestation in two maternity hospitals in the UK. Uterine artery pulsatility index (UtA-PI) was measured in 5362 pregnancies, mean arterial pressure (MAP) in 5386 and serum placental growth factor (PlGF) and serum soluble fms-like tyrosine kinase-1 (sFlt-1) in 3920. Bayes' theorem was used to combine the a-priori risk of PE from maternal factors with various combinations of biomarkers, expressed as multiples of the median (MoM). Five-fold cross-validation was used to estimate the performance of screening for PE, requiring delivery at some stage after assessment. The empirical performance of screening was compared to model predictions.

RESULTS

In pregnancies that developed PE, the values of MAP, UtA-PI and sFlt-1 were increased and PlGF was decreased compared to unaffected pregnancies. For all biomarkers evaluated, the deviation from normal was inversely related to the gestational age at which delivery became necessary for maternal or fetal indications. Screening by maternal factors and by a combination of maternal factors with all biomarkers predicted 35% and 84% of PE, respectively, at a 10% false-positive rate.

CONCLUSION

A combination of maternal factors and biomarkers at 35-37 weeks' gestation can provide effective screening for term PE. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

Competing risks model in screening for preeclampsia by maternal factors and biomarkers at 30-34 weeks' gestation

BACKGROUND

Preeclampsia (PE) affects 2-3% of all pregnancies and is a major cause of maternal and perinatal morbidity and mortality. We have proposed a 2-stage strategy for the identification of pregnancies at high risk of developing PE. The objective of the first stage, at 11-13 weeks' gestation, is a reduction in the prevalence of the disease through pharmacological intervention in the high-risk group. The objective of the second stage, during the second and/or third trimesters, is to improve perinatal outcome through close monitoring of the high-risk group for earlier diagnosis of the clinical signs of the disease and selection of the appropriate, time, place, and method of delivery.

OBJECTIVE

The objective of the study was to examine the performance of screening for PE by a combination of maternal factors with early third-trimester biomarkers.

STUDY DESIGN

This was a cohort study and data were derived from consecutive women with singleton pregnancies attending for their routine hospital visit at 30-34 weeks' gestation in 3 maternity hospitals in England between March 2011 and December 2014. In the first phase of the study, only uterine artery pulsatility index (UTPI) was measured and then measurement of mean arterial pressure (MAP) was added, and in the final phase, the serum concentration of placental growth factor (PLGF) was measured and then soluble fms-like tyrosine kinase-1 (SFLT) was added. We had data on UTPI, MAP, PLGF, and SFLT from 30,935, 29,042, 10,123, and 8,264 pregnancies, respectively. The Bayes theorem was used to combine the a priori risk from maternal factors with various combinations of biomarker multiple of the median values. Ten-fold cross-validation was used to estimate the performance of screening for PE requiring delivery at < 37 weeks' gestation (preterm-PE) and those delivering at ≥ 37 weeks (term-PE). The empirical performance was compared with model predictions.

RESULTS

In pregnancies that developed PE, the values of MAP, UTPI, and SFLT were increased and PLGF was decreased. For all biomarkers the deviation from normal was greater for preterm-PE than term-PE, and therefore, the performance of screening was inversely related to the gestational age at which delivery become necessary for maternal and/or fetal indications. Combined screening by maternal factors, MAP, UTPI, PLGF, and SFLT predicted 98% (95% confidence interval, 88-100%) of preterm-PE and 49% (95% confidence interval, 42-57%) of term-PE, at a false-positive rate of 5%. These empirical detection rates are compatible with the respective model-based rates of 98% and 54%, but the latter were optimistically biased.

CONCLUSION

Combination of maternal factors and biomarkers in the early third trimester could predict nearly all cases of preterm-PE and half of those with term-PE, at 5% false-positive rate.

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.

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.

Decreased circulating anandamide levels in preeclampsia

The endocannabinoid system has a key role in female reproduction, including implantation, decidualization and placentation. A growing number of studies indicate that placental and peripheral blood anandamide levels correlate closely with both spontaneous miscarriage and ectopic pregnancy. Anandamide has also been implicated in blood pressure regulation. In this study, we aimed to determine circulating anandamide levels in preeclampsia for the first time in the literature. Forty-three preeclamptic patients and 71 healthy pregnant women were involved in this case-control study. Serum anandamide concentrations were determined by high-performance liquid chromatography-mass spectrometry technique. Serum total soluble fms-like tyrosine kinase-1 (sFlt-1) and biologically active placental growth factor (PlGF) levels were measured by electrochemiluminescence immunoassay. For statistical analyses, nonparametric methods were applied. Serum levels of anandamide were significantly lower in preeclamptic patients than in healthy pregnant women (0.75 (0.44-1.03) ng ml(-1) vs. 1.30 (0.76-2.0) ng ml(-1), P<0.001). Preeclamptic patients had significantly higher sFlt-1 levels (12,121 (7963-18,316) pg ml(-1) vs. 2299 (1393-3179) pg ml(-1), P<0.001) and significantly lower PlGF concentrations (71.2 (39.2-86.4) pg ml(-1) vs. 256.8 (181.1-421.0) pg ml(-1), P<0.001) as compared with healthy pregnant women. Serum anandamide concentrations did not correlate with serum levels of sFlt-1 and PlGF in our healthy pregnant and preeclamptic groups. In conclusion, we demonstrated for the first time in the literature that serum anandamide concentrations are decreased in women with preeclampsia. However, the cause and consequence of this observation remain to be determined.

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 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.