Gestational Age-Specific Reference Ranges for the sFlt-1/PlGF Immunoassay Ratio in Twin Pregnancies

Significance of the sFlt-1/PlGF Ratio in Certain Cohorts - What Needs to be Considered?

The sFlt-1/PlGF ratio is an established tool in clinical practice, where it is part of a diagnostic algorithm and informs the prognosis of preeclampsia (PE). Maternal and gestational comorbidities can affect the performance of the sFlt-1/PlGF ratio and its constituent elements, and a good understanding of the potential pitfalls is required. The objective of this paper was to provide a current narrative review of the literature on the diagnostic and predictive performance of the sFlt-1/PlGF ratio in specific patient cohorts. Potential factors which can negatively affect the clinical interpretability and applicability of the sFlt-1/PlGF ratio include chronic kidney disease, twin pregnancy, and maternal obesity. Pathophysiological mechanisms related to these factors and disorders can result in different concentrations of sFlt-1 and/or PlGF in maternal blood, meaning that the use of standard cut-off values in specific cohorts can lead to errors. To what extent the cut-off values should be adapted in certain patient cohorts can only be clarified in large prospective cohort studies. This applies to the use of the ratio both for diagnosis and prognosis.

The addition of the sFlt-1/PlGF ratio to the protein/creatinine ratio in multiple pregnancy: Post-hoc analysis of the PREPARE cohort study

OBJECTIVE

To assess the predictive accuracy of the sFlt-1/PlGF ratio cut-off 38 in addition to the standard-of-care spot urine protein/creatinine ratio (PCr) for multiple pregnancies in women with suspected pre-eclampsia.

STUDY DESIGN

Post-hoc analysis of a prospective cohort study.

MAIN OUTCOME MEASURES

Primary outcome was the occurrence of pre-eclampsia in one and four weeks after presentation with suspected pre-eclampsia. Test characteristics with 95% confidence intervals (CI) were calculated on pre-eclampsia development in one and four weeks.

RESULTS

Twenty-three multiple pregnancies with suspected pre-eclampsia between 20 and 37 weeks gestation were included for analysis. Women who eventually developed pre-eclampsia had a significantly higher PCr (34.0 vs. 16.5, p = 0.015), sFlt-1 (17033 vs. 5270 pg/ml, p = 0.047) and sFlt-1/PlGF ratio (99 vs. 25, p = 0.033) at baseline. Furthermore, PCr ≥ 30 and sFlt-1/PlGF ratio > 38 was respectively seen in 1/16 (6.3 %) and 3/16 (18.8 %) of the women who did not develop pre-eclampsia. For predicting pre-eclampsia within one week the sFlt-1/PlGF ratio sensitivity was 75.0 % [95 % CI 19.4-99.4] and the negative predictive value 93.8 % [73.0-98.8], while no pre-eclampsia developed when PCr was < 30. Consequently, the combination of these tests did not lead to an improvement in test characteristics, with non-significant differences in positive predictive value (50.0 % [29.5-70.5] versus 80.0 % [37.3-96.4]) compared to PCr alone for pre-eclampsia development in one week.

CONCLUSIONS

In addition to standard-of-care spot urine PCr measurements, this study has not been able to demonstrate that the sFlt-1/PlGF ratio cut-off 38 is of added value in the prediction of pre-eclampsia in multiple pregnancy.

TRIAL REGISTRATION

Netherlands Trial Register (NL8308).

Biomarkers for Early Prediction and Management of Preeclampsia: A Comprehensive Review

Preeclampsia is a common complication of pregnancy. It is a multi-organ disorder that remains one of the main causes of maternal morbidity and mortality. Additionally, preeclampsia leads to many complications that can occur in the fetus or newborn. Preeclampsia occurs in about 1 in 20 pregnant women. This review focuses on the prediction of preeclampsia in women, using various biomarkers, in particular, a factor combining the use of soluble FMS-like tyrosinokinase-1 (sFlt-1) and placental growth factor (PlGF). A low value of the sFlt-1/PlGF ratio rules out the occurrence of preeclampsia within 4 weeks of the test result, and its high value predicts the occurrence of preeclampsia within even 1 week. The review also highlights other factors, such as pregnancy-associated plasma protein A, placental protein 13, disintegrin and metalloprotease 12, ß-human chorionic gonadotropin, inhibin-A, soluble endoglin, nitric oxide, and growth differentiation factor 15. Biomarker testing offers reliable and cost-effective screening methods for early detection, prognosis, and monitoring of preeclampsia. Early diagnosis in groups of women at high risk for preeclampsia allows for quick intervention, preventing the undesirable effects of preeclampsia. However, further research is needed to validate and optimize the use of biomarkers for more accurate prediction and diagnosis. This article aims to review the role of biomarkers, including the sFlt1/PlGF ratio, in the prognosis and management of preeclampsia.

Predictive value of the soluble fms-like tyrosine kinase 1 to placental growth factor ratio for preeclampsia in twin pregnancies: a systematic review and meta-analysis

OBJECTIVE

In recent years, the ratio of soluble fms-like tyrosine kinase 1 to placental growth factor for use in predicting preeclampsia has been explored extensively. Despite extensive research, available data on its effectiveness in predicting preeclampsia in twin pregnancies are limited and conflicting. This meta-analysis aimed to assess the diagnostic accuracy of the soluble fms-like tyrosine kinase 1 to placental growth factor ratio in distinguishing cases with preeclampsia in twin pregnancies from healthy controls.

DATA SOURCES

Studies that evaluated the use of the soluble fms-like tyrosine kinase 1 to placental growth factor ratio in predicting preeclampsia were searched in PubMed, Embase, and Cochrane databases from inception to August 6, 2023, without language restriction.

STUDY ELIGIBILITY CRITERIA

The following population, exposure, comparators, outcomes, and study designs were included: women with twin pregnancies; an increased soluble fms-like tyrosine kinase 1 to placental growth factor ratio with preeclampsia as the outcome; women without preeclampsia; a 2 × 2 diagnostic table, diagnostic accuracy data, and the incidence of preeclampsia; and prospective cohort studies and observational comparative studies, respectively.

STUDY APPRAISAL AND SYNTHESIS METHODS

The quality of the included studies was evaluated. Key parameters, including the specificity, sensitivity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio, were calculated using the random- and fixed-effects models. In addition, the area under the receiver operating characteristic curve and the summary receiver operating characteristic curve were evaluated.

RESULTS

A total of 7 studies were included, including 442 women with twin pregnancies (115 patients with preeclampsia and 327 controls without preeclampsia). The results highlighted the promising effectiveness of the soluble fms-like tyrosine kinase 1 to placental growth factor ratio in predicting preeclampsia in twin pregnancies with a pooled specificity of 0.89 (95% confidence interval, 0.80-0.95), a sensitivity of 0.84 (95% confidence interval, 0.73-0.93), a positive likelihood ratio of 32.76 (95% confidence interval, 12.82-83.74), and a negative likelihood ratio of 0.03 (95% confidence interval, 0.01-0.08). The combined diagnostic odds ratio was 35.72 (95% confidence interval, 12.92-98.76), and the area under the receiver operating characteristic curve was 0.92.

CONCLUSION

These collective findings underscore the potential of the soluble fms-like tyrosine kinase 1 to placental growth factor ratio as an accurate marker for identifying preeclampsia among women with twin pregnancies.

sFlt-1 Levels as a Predicting Tool in Placental Dysfunction Complications in Multiple Pregnancies

BACKGROUND

several studies have demonstrated that angiogenic markers can improve the clinical management of hypertensive disorders (HDs) and fetal growth restriction (FGR) in singleton pregnancies, but few studies have evaluated the performance of these tests in multiple pregnancies. Our aim was to investigate the role of soluble fms-like tyrosine kinase 1 (sFlt-1) in predicting adverse obstetric outcomes in hospitalized multiple pregnancies with HD (preeclampsia/gestational hypertension/uncontrolled chronic hypertension) and/or FGR in one or more fetuses.

METHODS

A retrospective analysis of multiple pregnancies with HD/FGR occurring after the 20th gestational week. Pregnant women were divided into two groups: women with high levels of sFlt-1 and those with low levels of sFlt-1. A value of sFlt-1 greater than or equal to 15,802 pg/mL was considered arbitrarily high, as it is equivalent to two times the 90th percentile expected in an uncomplicated full-term singleton pregnancy based on data from a prospective multicenter study (7901 pg/mL).

RESULTS

The cohort included 39 multiple pregnancies. There were no cases of birth <34 weeks, HELLP syndrome, ICU admission, and urgent cesarean sections for HD/FGR complications reported among women with low levels of sFlt-1.

CONCLUSIONS

A cut-off value of sFlt-1 ≥ 15,802 pg/mL could represent a valuable tool for predicting adverse obstetric outcomes in multiple pregnancies hospitalized for HD/FGR disorders, regardless of gestational age and chorionicity.

Advances in preeclampsia testing

Preeclampsia is a multisystem hypertensive disorder and one of the leading causes of maternal and fetal morbidity and mortality. The clinical hallmarks such as hypertension and proteinuria, and additional laboratory tests currently available including liver enzyme testing, are neither specific nor sufficiently sensitive. Therefore, biomarkers for timely and accurate identification of patients at risk of developing preeclampsia are extremely valuable to improve patient outcomes and safety. In this chapter, we will first discuss the clinical characteristics of preeclampsia and current evidence of the role of angiogenic factors, such as placental growth factor (PlGF) and soluble FMS like tyrosine kinase 1 (sFlt-1) in the pathogenesis of preeclampsia. Second, we will review the clinical practice guidelines for preeclampsia diagnostic criteria and their recommendations on laboratory testing. Third, we will review the currently available PlGF and sFlt-1 assays in terms of their methodologies, analytical performance, and clinical diagnostic values. Finally, we will discuss the future research needs from both an analytical and clinical perspective.

sFLT1, PlGF, the sFLT1/PlGF Ratio and Their Association with Pre-Eclampsia in Twin Pregnancies-A Review of the Literature

Twin pregnancies demonstrate a 2-3-fold higher chance of developing PE compared to singletons, and recent evidence has demonstrated that the sFLT1/PIGF ratio is strongly associated with PE, adverse pregnancy outcomes, as well as imminent deliveries due to PE complications. The primary objective of this systematic review was to summarise the available data on the levels of sFLT1, PlGF and their ratios in twin pregnancies and to investigate their association with the development of PE, adverse pregnancy outcomes and the timing of the delivery. A systematic search of Ovid Embase, Web of Science, Science Direct, PubMed, Ovid Medline, Google Scholar and CINAHL was carried out. sFLT1 levels and the sFLT1/PIGF ratio appeared higher in twins compared to singleton pregnancies, especially in the third trimester, while PlGF levels appeared higher up until the third trimester, with their values showing no difference or being even lower than in singletons thereafter. The sFLT1/PIGF ratio has been reported to be an independent marker of adverse outcomes related to pre-eclampsia and is associated with the mean time until delivery in an inverse manner. Further research is required in order to establish the optimal sFLT1/PIGF cut-off values and to stratify the risk of adverse outcomes in twin pregnancies.

Prediction of Early- and Late-Onset Pre-Eclampsia in the Preclinical Stage via Placenta-Specific Extracellular miRNA Profiling

Pre-eclampsia (PE) is one of the severe complications of pregnancy in 3-8% of all cases and is one of the leading causes of maternal and perinatal mortality. The fundamental role in the pathogenesis of PE is assigned to maternal and/or placental factors, whereby the combination and manifestation of which determines the time of onset of the clinical symptoms of PE (before or after 34 weeks of gestation) and their severity. It is known that the expression level of miRNAs, the regulators of signaling cascades in the cell, depends on gestational age. In the present study, we focused on the identification of the placenta-specific miRNAs that differentiate between early- and late-onset pre-eclampsia (ePE and lPE) throughout pregnancy, from the first to the third trimester. A total of 67 patients were analyzed using small RNA deep sequencing and real-time quantitative PCR, which resulted in a core list of miRNAs (let-7b-5p, let-7d-3p, let-7f-5p, let-7i-5p, miR-22-5p, miR-451a, miR-1246, miR-30e-5p, miR-20a-5p, miR-1307-3p, and miR-320e), which in certain combinations can predict ePE or lPE with 100% sensitivity and 84-100% specificity in the 1st trimester of pregnancy. According to the literature data, these miRNA predictors of PE control trophoblast proliferation, invasion, migration, syncytialization, the endoplasmic reticulum unfolded protein response, immune tolerance, angiogenesis, and vascular integrity. The simultaneous detection of let-7d-3p, miR-451a, and miR-1307-3p, resistant to the repeated freezing/thawing of blood serum samples, in combination with biochemical (b-hCG and PAPP-A) and ultrasound (UAPI) parameters, allowed us to develop a universal model for the prediction of ePE and lPE onset (FPR = 15.7% and FNR = 9.5%), which was validated using a test cohort of 48 patients and demonstrated false-positive results in 26.7% of cases and false negatives in 5.6% of cases. For comparison, the use of the generally accepted Astraia program in the analysis of the test cohort of patients led to worse results: FPR = 62.1% and FNR = 33.3%.

Alterations in Vessel Hemodynamics Across Uncomplicated Pregnancy

Pregnancy is marked by the onset of rapid hemodynamic alterations in order to accommodate the needs of the developing fetus. Arterial stiffness is an independent predictor of cardiovascular events and mortality, and its measurement in clinical practice has been recommended. It follows a U-shaped curve in uncomplicated pregnancy, decreasing to a nadir in mid-pregnancy and rising at term. Systemic vasodilation occurs due to elevated nitric oxide, prostacyclin, endothelium-derived hyperpolarizing factor, estrogen, progesterone, and relaxin. Vascular resistance decreases to a nadir in mid-pregnancy, while endothelial function is enhanced starting in the first trimester. Plasma volume increases by about 50%, and total red blood cell mass increases by up to 40%. Cardiac output increases by up to 45%, at first due primarily to elevated stroke volume, then mainly due to increased heart rate. Along with echocardiography, cardiac magnetic resonance imaging is safe for use in pregnancy. It may assess cardiac function more accurately than echocardiography, and may be indicated in specific clinical cases. Moreover, blood pressure decreases to a nadir in mid-pregnancy and rises to near preconception values postpartum. An appreciation of the vascular changes occurring in healthy pregnancy can aid in the prediction and diagnosis of pregnancy complications, such as preeclampsia and other hypertensive disorders of pregnancy, and inform treatment. In particular, noninvasive arterial stiffness/hemodynamics assessment provides unique clinical information beyond blood pressure and traditional maternal characteristics, and can signal a need for further testing, or be used in combination with other tests to predict or diagnose complications of pregnancy.

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.

Clinical utility of sFlt-1 and PlGF in screening, prediction, diagnosis and monitoring of pre-eclampsia and fetal growth restriction

Pre-eclampsia (PE) is characterized by placental and maternal endothelial dysfunction, and associated with fetal growth restriction (FGR), placental abruption, preterm delivery and stillbirth. The angiogenic factors soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) are altered in pregnancies complicated by placenta-related disorders. In this Review, we summarize the existing knowledge, examining the performance of maternal PlGF, sFlt-1 and the sFlt-1/PlGF ratio for screening PE, predicting development of PE in the short term, diagnosing PE, monitoring established PE and predicting other placenta-related disorders in singleton pregnancy. We also discuss the performance of PlGF and the sFlt-1/PlGF ratio for predicting PE in twin pregnancy. For first-trimester screening in singleton pregnancy, a more accurate way of identifying high-risk women than current practice is to combine maternal PlGF levels with clinical risk factors and ultrasound markers. Later in pregnancy, the sFlt-1/PlGF ratio has advantages over PlGF because it has a higher pooled sensitivity and specificity for diagnosing and monitoring PE. It has clinical value because it can rule out the development of PE in the 1-4-week period after the test. Once a diagnosis of PE is established, repeat measurement of sFlt-1 and PlGF can help monitor progression of the condition and may inform clinical decision-making regarding the optimal time for delivery. The sFlt-1/PlGF ratio is useful for predicting FGR and preterm delivery, but the association between stillbirth and the angiogenic factors is unclear. The sFlt-1/PlGF ratio can be used to predict PE in twin pregnancy, although different sFlt-1/PlGF ratio cut-offs from those for singleton pregnancy should be applied for optimal performance. In summary, PlGF, sFlt-1 and the sFlt-1/PlGF ratio are useful for screening, diagnosing, predicting and monitoring placenta-related disorders in singleton and twin pregnancy. We propose that tests for these angiogenic factors are integrated more fully into clinical practice.© 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Clinical interpretation and implementation of the sFlt-1/PlGF ratio in the prediction, diagnosis and management of preeclampsia

Preeclampsia is associated with significant morbidity and mortality for mother and baby. Although around 30% of all pregnancies are evaluated for preeclampsia, diagnosis is difficult, especially in patients who have overlying symptoms from other diseases. Discovery of circulating angiogenic factors in the pathogenesis of preeclampsia has been a major advance for both diagnosis and prognosis. The anti-angiogenic factor, soluble fms-like tyrosine kinase 1 (sFlt-1) and the pro-angiogenic factor, placental growth factor (PlGF), can be measured in plasma and serum and are usually reported as a ratio, which specifically relates to the onset and severity of preeclampsia. The sFlt-1/PlGF ratio has a very high negative predictive value in ruling out the development of preeclampsia within 7 days among women with suspected preeclampsia. Currently, there is no clear consensus on the practical use of angiogenic biomarkers in the detection and management of preeclampsia in routine clinical practice. While major international clinical guidelines exist, they do not define which specific parameters signal patient admission, or outpatient evaluation of suspected preeclampsia, and most clinicians follow local practices. Better guidance is needed on risk stratification among women with suspected preeclampsia, as well as among women at high risk for preeclampsia. Prediction of adverse outcomes in women, after the clinical diagnosis of preeclampsia, is also important. This report has been developed following a meeting of international experts and aims to guide clinicians in the management of pregnant women at risk of preeclampsia using the sFlt-1/PlGF ratio test.

Predictive value of the sFlt-1/PlGF ratio for preeclampsia in twin pregnancies: a retrospective study

Objective: This study aimed to investigate the efficiency of the soluble Fms-like tyrosine kinase 1 (sFlt-1)/placental growth factor (PlGF) ratio in predicting preeclampsia (PE) within 4 weeks in twin pregnancies.Methods: Seventy-eight women with serum angiogenic markers measured at 28 + 0 to 30 + 6 weeks of gestation were enrolled. A receiver-operating characteristic curve was used to determine the sFlt-1/PlGF ratio threshold to predict PE.Results: A cutoff value for the sFlt-1/PlGF ratio of 22.2 predicted PE presence within 4 weeks.Conclusion: An sFlt-1/PlGF ratio of ≤22.2 is potentially indicative of PE absence within 4 weeks in twin pregnancies.