Serum sFlt1:PlGF Ratio, PlGF, and Soluble Endoglin Levels in Gestational Proteinuria

Literature Review: The sFlt1/PlGF Ratio and Pregestational Maternal Comorbidities: New Risk Factors to Predict Pre-Eclampsia

One of the main causes of maternal and neonatal morbidity and mortality is pre-eclampsia. It is characterized by a high sFlt1/PlGF ratio, according to prior research. Pregestational diseases in mothers may increase the risk of developing pre-eclampsia. Only a few studies have looked at the connection between maternal comorbidities before conception and the sFlt1/PlGF ratio. The most recent information regarding the association between maternal pregestational diseases and the ratio of sFlt1/PlGF is described in this review. The paper also examines current research suggesting that changes in pregnancy hormones and metabolites are related to a high sFlt1/PlGF ratio. Certain maternal disorders have been found to dramatically raise sFlt-1 and sFlt1/PlGF levels, according to an analysis of the literature. There is still debate about the data on the association between the sFlt1/PlGF ratio and maternal disorders such as HIV, acute coronary syndromes, cardiovascular function in the mother between 19 and 23 weeks of pregnancy, thyroid hormones, diabetes, and cancer. Additional research is needed to confirm these findings.

Clinical usefulness of serum levels of soluble fms-like tyrosine kinase 1/placental growth factor ratio to rule out preeclampsia in women with new-onset lupus nephritis during pregnancy

Measurement of the soluble fms-like tyrosine kinase 1 (sFlt-1)/placental growth factor (PlGF) ratio may be clinically useful to discriminate systemic lupus erythematosus (SLE) from preeclampsia. Here, we present a pregnant woman with new-onset SLE with hypertension, with the measurement of the sFlt-1/PlGF ratio during pregnancy. A 31-year-old Japanese nulliparous woman, who had been diagnosed with idiopathic thrombocytopenic purpura at 10 years, had a systolic blood pressure of 120 mmHg and was negative for proteinuria at 12⁺¹ weeks. Since her blood pressure increased to 159/86 mmHg with 3+ proteinuria at 25⁺⁴ weeks, preeclampsia was suspected. Deterioration of the kidney function (creatinine: 0.58 mg/dL at 24⁺⁶ weeks to 0.83 mg/dL at 33⁺⁶ weeks) necessitated cesarean section at 33⁺⁶ weeks. After delivery, she still showed increased creatinine and proteinuria. Therefore, she was transferred to a nephrology specialist in a tertiary center and was finally diagnosed with SLE with lupus nephritis class IV-G(A) (diffuse lupus nephritis). The serum levels of sFlt-1 and the sFlt-1/PlGF ratio, which are usually elevated in preeclampsia, were within normal reference ranges at 27⁺⁶, 28⁺¹, and 28⁺⁶ weeks of gestation, although the serum levels of PlGF were slightly lower than the normal reference range. In conclusion, measurement of the sFlt-1/PlGF ratio may be clinically useful to discriminate lupus nephritis from preeclampsia.

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.

Placental growth factor and vascular endothelial growth factor serum levels in Tunisian Arab women with suspected preeclampsia

The angiogenic factors vascular endothelial growth factor (VEGF) and placental growth factor (PIGF) play a central role in the process of angiogenesis. We evaluated the association of free PIGF and free VEGF levels and the risk of preeclampsia (PE) among Tunisian Arab women, and established the range of VEGF and PIGF in normal healthy pregnancies, between 24 and 42weeks of gestation. This retrospective case-control study included 345 women with PE, and 289 women with uncomplicated pregnancies. PIGF and VEGF plasma levels were quantitated by commercially-available ELISA. Compared to control women, plasma PIGF concentrations were lower in women with PE at all gestation age intervals (P<0.0001), compared to VEGF levels which were significantly lower in women with PE but only during early gestation age intervals ([29-32[ and [32-35[). High odds for developing PE, and correspondingly higher associations, were associated with low PIGF values (less than the 5(th) percentile), at all gestation age intervals. The only exception was recorded for the [29-32 [interval, which was not statistically significant. PIGF testing, recorded at 29-37weeks of gestation, had a higher specificity (93-100%) than sensitivity, and the positive predictive values ranged from 90% to 100% for 24-37weeks of gestation. This indicates that it mainly detects non-PE healthy women as well, and thus may be useful as a screening test, though currently unreliable for diagnostic purposes. Reduced PIGF levels during different gestation age intervals, and reduced VEGF levels during early gestation age intervals are also associated with subsequent development of PE in our population; the gestational age interval adjusted-5(th) percentiles of PIGF provide reference ranges for this marker in normal pregnancy.

A Role of sFlt-1 in Oxidative Stress and Apoptosis in Human and Mouse Pre-Eclamptic Trophoblasts

Pre-eclampsia (PE) is a hypertensive disorder that occurs during pregnancy, and is a multifactorial disease. The antiangiogenic factor, soluble fms-like tyrosine kinase 1 (sFlt-1), has been reported to be important in the pathogenesis of PE, but the mechanism of its involvement remains unknown. To test the effects of sFlt-1 on pregnancy, we injected pregnant mice with exogenous mouse sFlt-1. After 18 days of gestation, higher blood pressure, proteinuria, and histological differences were observed compared with controls. Mitochondrial swelling inside the trophoblast cells in the placenta of sFlt-1-treated pregnant mice was observed by electron microscopy, which suggested a role of sFlt-1 in oxidative stress in trophoblasts in PE. Furthermore, apoptosis markers were upregulated in sFlt-1-treated mice. In conclusion, sFlt-1 appears to play a role in oxidative stress, which promotes apoptosis of trophoblasts. This may be an important mechanism in the development of PE.

Maternal serum glycosylated fibronectin as a point-of-care biomarker for assessment of preeclampsia

OBJECTIVE

We assessed the association of glycosylated fibronectin (GlyFn) with preeclampsia and its performance in a point-of-care (POC) test.

STUDY DESIGN

GlyFn, placental growth factor (PlGF), and soluble vascular endothelial growth factor receptor 1 (sFlt1) levels were determined in serum samples from 107 pregnant women. In all, 45 were normotensive and 62 were diagnosed with preeclampsia. The ability of GlyFn to assess preeclampsia status and relationships between GlyFn and maternal characteristics and pregnancy outcomes were analyzed.

RESULTS

GlyFn serum levels in the first trimester were significantly higher in women with preeclampsia (P < .01) and remained higher throughout pregnancy (P < .01). GlyFn, sFlt1, PlGF, and the sFlt1/PlGF ratio were significantly associated (P < .01) with preeclampsia status, and the classification performance of these analytes represented by area under the receiver operating characteristic curve was 0.99, 0.96, 0.94, and 0.98, respectively, with 95% confidence intervals of 0.98-1.00, 0.89-1.00, 0.86-1.00, and 0.94-1.00, respectively. Increased GlyFn levels were significantly associated with gestational age at delivery (P < .01), blood pressure (P = .04), and small-for-gestational-age neonates. Repeated-measures analysis of the difference in weekly GlyFn change in the third trimester demonstrated that mild preeclampsia was associated with a weekly change of 81.7 μg/mL (SE 94.1) vs 195.2 μg/mL (SE 88.2) for severe preeclampsia. The GlyFn POC demonstrated similar performance to a plate assay with an area under the receiver operating characteristic curve of 0.93 and 95% confidence interval of 0.85-1.00.

CONCLUSION

GlyFn is a robust biomarker for monitoring of preeclampsia in both a standard and POC format, which supports its utility in diverse settings.

Increased antiangiogenetic factors in severe proteinuria without hypertension in pregnancy: is kidney biopsy necessary?

Acute onset of severe proteinuria during pregnancy obliges physicians to clinically discriminate between gestational proteinuria (GP) and new onset of nephritis. A multiparous woman developed severe proteinuria (5.8 g/day) without hypertension at 32 weeks of gestation. We measured the maternal level of soluble fms-like tyrosine kinase 1 (sFlt-1) and soluble endoglin (sEng), which were extremely high (41.3 and 54.8 ng/ml, respectively), leading us to consider this condition as GP rather than acute onset of nephritis. Thus, we did not perform a kidney biopsy and did not administer a steroid agent. Non-reassuring fetal status required emergency Cesarean section at 33 weeks. Proteinuria decreased to 0.36 g/day at 12 weeks after delivery, and finally disappeared 26 weeks postpartum. Measurement of sFlt-1 and sEng in a pregnant woman with severe proteinuria without hypertension may assist in differential diagnosis of GP from acute onset of nephritis, and thus help to decide whether to perform kidney biopsy during pregnancy.

Automated measurement of sFlt1, PlGF and sFlt1/PlGF ratio in differential diagnosis of hypertensive pregnancy disorders

OBJECTIVES

The utility of angiogenic and antiangiogenic biomarkers as diagnostic tools in preeclampsia (PE) has been shown in previous studies. Our study's aim was to evaluate the use of automated measurement of sFlt1, PlGF and their ratio (sFlt1/PlGF) in differential diagnosis of hypertensive pregnancy disorders.

PATIENTS/METHODS

Sixty-four patients with PE/HELLP, 18 with pregnancy-induced hypertension (PIH), 22 with gestational proteinuria (GP) and 232 controls were investigated. The PE/HELLP group was divided into mild PE (mPE, n=31), severe PE (sevPE, n=20), superimposed PE (supPE, n=7) and HELLP syndrome (n=6). sFlt1 and PlGF were measured in serum samples on an automated platform. Statistical analysis was performed using parametric and non-parametric methods, ROC analysis and logistic regression method.

RESULTS

PE patients showed higher sFlt1 and ratio and lower PlGF than controls (median ± SEM in pg/mL; 10888 ± 878 versus 2456 ± 116; 268 ± 39 versus 16 ± 2 and 68 ± 6 versus 439 ± 37, each p<0.001), subgroups showed similar differences in ratios (median ± SEM; supPE: 202 ± 110; mPE: 137 ± 27; sevPE: 497 ± 91; HELLP syndrome: 254 ± 72 versus controls 16 ± 2, each p<0.001). ROC analysis showed best performance for sFlt1/PlGF (AUC all PE: ratio 96.4%, sFlt1 92.8%, PlGF 92.4%, supPE: ratio 93.6%, mPE: ratio 94.8%, sevPE: ratio 99.4%, HELLP: ratio 98.6%, each versus controls). Patients with PIH and GP showed significant differences compared to controls (p ≤ 0.01, respectively), mPE (p ≤ 0.007), sevPE (p<0.001) and HELLP syndrome (p ≤ 0.003).

CONCLUSION

The automated measurement of sFlt1/PlGF is a reliable diagnostic tool in differential diagnosis of hypertensive pregnancy disorders and gives additional valuable information for clinical management.

Plasma concentrations of angiogenic/anti-angiogenic factors have prognostic value in women presenting with suspected preeclampsia to the obstetrical triage area: a prospective study

OBJECTIVE

To prospectively determine the prognostic value of maternal plasma concentrations of placental growth factor (PlGF), soluble endoglin (sEng) and soluble vascular endothelial growth factor receptors-1 and -2 (sVEGFR-1 and -2) in identifying patients with suspected preeclampsia (PE), who require preterm delivery (PTD) or develop adverse outcomes.

STUDY DESIGN

This prospective cohort study included 85 consecutive patients who presented to the obstetrical triage area at 20-36 weeks with a diagnosis of "rule out PE." Patients were classified as: 1) those who remained stable until term (n = 37); and 2) those who developed severe PE and required PTD (n = 48). Plasma concentrations of PlGF, sEng and sVEGFR-1 and -2 were determined by ELISA.

RESULTS

Patients with PlGF/sVEGFR-1 ≤0.05 multiples of the median (MoM) or PlGF/sEng ≤0.07 MoM were more likely to deliver preterm due to PE [adjusted odd ratio (aOR) 7.4 and 8.8], and to develop maternal (aOR 3.7 and 2.4) or neonatal complications (aOR 10.0 and 10.1). Among patients who presented <34 weeks of gestation, PlGF/sVEGFR-1 ≤ 0.035 MoM or PlGF/sEng ≤0.05 MoM had a sensitivity of 89% (16/18), specificity of 96% (24/25) and likelihood ratio for a positive test of 22 to identify patients who delivered within 2 weeks. The addition of the PlGF/sVEGFR-1 ratio to standard clinical tests improved the sensitivity at a fixed false-positive rate of 3% (p = 0.004) for the identification of patients who were delivered due to PE within 2 weeks. Among patients who had a plasma concentration of PlGF/sVEGFR-1 ratio ≤0.035 MoM, 0.036-0.34 MoM and ≥0.35 MoM, the rates of PTD <34 weeks were 94%, 27% and 7%, respectively.

CONCLUSIONS

The determination of angiogenic/anti-angiogenic factors has prognostic value in patients presenting to the obstetrical triage area with suspected PE for the identification of those requiring preterm delivery and at risk for adverse maternal/neonatal outcomes.

Placental growth factor for the prediction of adverse outcomes in patients with suspected preeclampsia or intrauterine growth restriction

Background

The circulating concentration of PlGF is reported to be lower in patients experiencing preeclampsia and patients delivering a small for gestational age (SGA) neonate. To evaluate the predictive value of circulating PlGF for preeclampsia and adverse outcome in patients with suspected preeclampsia or intrauterine growth restriction (IUGR).

Methodology/Principal Findings

A double blind prospective study. We enrolled 96 women for suspected preeclampsia or IUGR, and measured plasma levels of PlGF (Triage®) at enrolment. We defined adverse outcome as severe preeclampsia, SGA neonate (<10^th centile) or elective delivery for maternal or fetal complication. Severe adverse outcome was studied among patients included <34 weeks gestation (WG) and defined as eclampsia, HELLP syndrome, very SGA (<3^rd centile) or elective delivery <34 WG. The mean logtransformed PlGF level was lower for women who experienced preeclampsia (2.9 vs 3.7, p = 0.02), and was markedly lower for patients who experienced adverse outcome (2.9 vs 4.3, p<0.001). The odds of presenting an adverse outcome were higher for the lowest tertile of PlGF compared to the higher (OR = 13 , 95% CI [3–50]). For severe adverse outcome, odds were respectively for the lowest and intermediate tertile as compared with the higher tertile : OR = 216, 95% CI [18–2571]; and OR = 17, 95% CI [3–94]. When included <34 WG, patients with a PlGF level <12 pg/ml experienced a severe adverse outcome in 96% of cases (24/25), and only 1 of 20 patients with a PlGF level >5^th centile experienced a severe adverse outcome within 15 days (5%).

Conclusions/Significance

Among women with suspected preeclampsia or IUGR, PlGF helps identify women who will experience an adverse outcome and those who will not within a time period of 15 days.

Soluble fms-like tyrosine kinase 1 and soluble endoglin are elevated circulating anti-angiogenic factors in pre-eclampsia

Pre-eclampsia, characterized by hypertension and proteinuria, affects approximately 3-5% of all pregnancies worldwide and is a major cause of maternal and fetal morbidity and mortality. Maternal endothelial dysfunction is associated with disease pathogenesis. Recently, reports have shown that elevated levels of circulating soluble fms-like tyrosine kinase 1 [sFlt1] and soluble endoglin [sEng] are associated with pre-eclampsia. Flt1 is a receptor for vascular endothelial growth factor receptor [VEGF], whereas endoglin [Eng] is an auxiliary receptor for transforming growth factor-β [TGF-β] super-family members. Both signaling pathways modulate angiogenesis and are involved in vascular homeostasis. Increased levels of sFlt1 and sEng dysregulate VEGF and TGF-β signaling respectively, resulting in endothelial dysfunction of maternal blood vessels. This review summarizes our current knowledge of Flt1 and endoglin and soluble forms in pre-eclampsia. Furthermore, it highlights the predictive and early-screening value of circulating levels of sFlt1 and sEng for the risk of developing pre-eclampsia.

Pre-eclampsia: fitting together the placental, immune and cardiovascular pieces

The success of pregnancy is a result of countless ongoing interactions between the placenta and the maternal immune and cardiovascular systems. Pre-eclampsia is a serious pregnancy complication that arises from multiple potential aberrations in these systems. The pathophysiology of pre-eclampsia is established in the first trimester of pregnancy, when a range of deficiencies in placentation affect the key process of spiral artery remodelling. As pregnancy progresses to the third trimester, inadequate spiral artery remodelling along with multiple haemodynamic, placental and maternal factors converge to activate the maternal immune and cardiovascular systems, events which may in part result from increased shedding of placental debris. As we understand more about the pathophysiology of pre-eclampsia, it is becoming clear that the development of early- and late-onset pre-eclampsia, as well as intrauterine growth restriction (IUGR), does not necessarily arise from the same underlying pathology.

Angiogenic imbalances: the obstetric perspective

Clinical and experimental evidence indicates that angiogenic imbalances may participate in the mechanisms of disease of several pregnancy complications, some of which may be life threatening. This article reviews current evidence in support of this view and the possibility that the fetus may play a central role in these imbalances; it also reviews recent experimental observations that modulation of angiogenic imbalances during pregnancy may have prophylactic and/or therapeutic value.

Outcome of pregnancy in patients with isolated proteinuria

PURPOSE OF REVIEW

The outcome of pregnancy in patients with isolated proteinuria is believed to be favorable. However, whether women with isolated proteinuria are at risk for progressing to preeclampsia has not been extensively studied.

RECENT FINDINGS

The amount of proteinuria is thought to increase in the early third trimester, irrespective of whether preeclampsia has been diagnosed. A dipstick urinalysis has a poor sensitivity (ranging from 22 to 86%) for the detection of significant proteinuria (> or = 0.3 g/day). Measurements of the levels of circulating angiogenic factors such as soluble fms-like tyrosine kinase 1, soluble endoglin, vascular endothelial growth factor, and placental growth factor suggest that gestational proteinuria is a mild variant of preeclampsia. In one study, women with isolated proteinuria (> or = 0.3 g/day) were found to be more likely to progress to preeclampsia than women with isolated hypertension. A considerable number of women with eclampsia exhibited proteinuria alone during their last antenatal visit performed within a week prior to their first convulsion.

SUMMARY

The outcome of women with a retrospective diagnosis of gestational proteinuria is generally favorable. However, a considerable number of women with isolated proteinuria develop hypertension and progress to preeclampsia. Therefore, the statement that the 'outcome of pregnancy in patients with isolated proteinuria is favorable' is misleading. Physicians should be aware of this type of preeclampsia when counseling patients. One possible explanation for the difficulty in diagnosing this form of preeclampsia might be the low sensitivity of the dipstick urinalysis technique for the detection of significant proteinuria.

PROTEINURIA IN PREECLAMPSIA: FROM BENCH TO BEDSIDE

Pre-eclampsia (PE) remains the leading cause of maternal and fetal mortality in the developed world and parts of the developing world. Morbidity and mortality from PE is increased in the developing world compared to the developed world, as availability and access to antenatal care and pathology services are limited.