Dr. Sonali Yadav is Ph.D. from King George’s Medical University, Lucknow, U.P. (2014). She is National Post Doctoral Fellowship (N-PDF) from SERB, DST, India (2019). She has worked as Senior Demonstrator in the Department of Molecular Medicine & Biotechnology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow. Her area of interest includes Obstetrics (preeclampsia).
Purpose Preeclampsia (PE) affects 5–7% of the pregnancies worldwide, and is one of the most dreaded disorders of pregnancy contributing to maternal and neonatal mortality. PE is mostly presented in the third trimester of pregnancy. Here, we used serum placental growth factor (PIGF) and soluble fms-like tyrosine kinase-1 (sFlt-1) to develop a model for predicting PE in Indian women in early second trimester.
Methods In this case–control study, a total 1452 healthy pregnant women were recruited. Blood samples were collected at the following gestational weeks (GWs), 12–20 (GW1), 21–28 (GW2) and 29-term (GW3), and post-delivery. Body mass index (BMI) was calculated by anthropometric measurements. Serum sFlt-1, PIGF and VEGF were analyzed by ELISA. A predictive model for PE was developed using multivariable logistic regression analysis.
Results In PE cases, serum PlGF and VEGF levels were significantly lower at each GW, while serum sFlt-1 was lower only at GW1, relative to age-matched controls, (n = 132/group). Age-matched comparison between PE cases and controls indicated that sFlt-1 was associated with decreased PE outcome (Odds ratio. OR = 0.988, CI = 0.982–0.993), whereas sFlt-1/PlGF ratio (OR = 1.577, CI = 1.344–1.920) and BMI (OR = 1.334, CI = 1.187–1.520) were associated with increased PE outcome. Logistic regression was used to develop a predictive model for PE at GW1. Using testing dataset, model was externally validated which resulted in 88% accuracy in predicting PE cases at 0.5 probability cutoff.
Conclusion Prediction model using sFlt-1, sFlt-1/PlGF ratio and BMI may be useful to predict PE as early as 12–20 weeks in women with optimal sensitivity and specificity.
Keywords : Preeclampsia · Pregnancy · Placenta · PlGF · VEGF · sFlt-1
Abbreviations
PlGF Placenta growth factor
VEGF Vascular endothelial growth factor
PE Preeclampsia
Preeclampsia (PE) is a life threatening disorder of pregnancy characterized by new-onset hypertension (blood pressure ≥ 140/90 mmHg), along with one or more of following: proteinuria, uteroplacental dysfunction and evidence of other maternal organ dysfunction [1, 2]. In 2015, hypertensive disorder of pregnancy and especially preeclampsia, accounted for 14% of the overall global maternal mortality ratio of 216 per 100,000 live births, with highest proportion of deaths in low and middle income middle countries [1, 3]. Worldwide, the incidence of PE ranges between 2 and 10% of pregnancies, lack of early detection and unavailability of reliable markers for PE makes the situation worse, especially in developing countries [2]. PE is presented mostly in the third trimester of pregnancy. Thus, early prediction of PE would significantly lower the associated morbidity and mortality by timely clinical management.
During pregnancy, angiogenesis is facilitated by angiogenic growth factors such as vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). Conversely, soluble fms-like tyrosine kinase-1 (sFlt-1) acts as an antagonist which binds to VEGF and PlGF and inhibits them from activating cognate receptors to promote vascular homeostasis. An imbalance of these factors plays a key role in pathogenesis of preeclampsia and has been used to predict PE [3]. An elevation in sFlt-1 levels and reduced levels of PlGF and VEGF has been reported to contribute to endothelial dysfunction, hypertension and proteinuria in PE cases [3–5]. Besides, recent cohort studies from western countries further suggest the use of sFlt-1/PlGF ratio (a cutoff level ≤ 38 between gestational weeks 26 to 34) for ruling out PE possibility in patients with suspicion of the disease [4, 6]. However, a clear recommendation for cutoff to predict PE in early second trimester in pregnant women without any suspicion/known risk for PE is still lacking. Besides, ethnicity, geographic and social diversity sociodemographic and socioeconomic characteristics of pregnant women are important to be considered for setting up a universal cutoff range for early PE diagnosis [4, 6–9]. In this longitudinal study, serum sFlt-1, PlGF and VEGF levels were estimated in normotensive Indian women, who showed up at antenatal clinics between gestational weeks 12–20. The aim of the study was to determine the time course regulation of circulating anti-angiogenic (sFlt-1), and angiogenic factors (PlGF, VEGF) during the course of pregnancy, and to develop a model for early prediction of preeclampsia with optimal sensitivity and specificity.The nested case–control study was carried out with the approval of the King George’s Medical University, Uttar Pradesh ethics committee (XLIII ECM/B-P15). Total 1452 healthy women with singleton pregnancy were included with their written consent. Women with history of essential hypertension, renal disease, epilepsy, diabetes or any other chronic or pre-existing disease were excluded from the study. Women with gestational hypertension, missing specimens or data were also excluded. The gestational age of women, at the time of collection, was determined by ultrasonographic examination.
Among 1452 registered, 132 women were diagnosed with PE according to diagnostic criteria of PE (systolic blood pressure at ≥ 140 mmHg and/or the diastolic blood pressure at ≥ 90 mmHg and accompanied by ≥ 1 of the following new-onset conditions at or after 20 weeks’ gestation: (i) proteinuria (i.e., ≥ 30 mg/mol or ≥ 2 + dipstick); (ii) evidence of other maternal organ dysfunction, including: acute kidney injury (creatinine ≥ 90umol/L; 1 mg/dL), liver involvement (elevated transaminases, e.g., alanine aminotransferase or aspartate aminotransferase > 40 IU/L) neurological complications (e.g., eclampsia, altered mental status, blindness, stroke, clonus, severe headaches, and persistent visual scotomata), or hematological complications (thrombocytopenia– platelet count < 150,000/μL) or (iii) uteroplacental dysfunction such as fetal growth restriction, abnormal umbilical artery, Doppler waveform analysis) [10]. From the rest, agematched normotensive women (n = 132) were selected as control group. Peripheral blood samples were collected from these subjects at different gestational weeks (GWs) categorized as GW1: 12–20 weeks, GW2: 21–28 weeks and GW3: 29 weeks-term and 48 h post-delivery. Serum was separated and stored in multiple aliquots at −80 °C for estimation of sFlt-1, VEGF and PlGF. Despite the limited numbers of reports, an imbalance of circulating anti-angiogenic (sFlt1) and angiogenic factors (PlGF, VEGF) levels has been proposed to contribute in the genesis of preeclampsia and therefore, could predict PE [3, 11–13]. Individual levels of one or more of these factors in combination of maternal characteristics and obstetric history were shown to predict PE as early as 11th week of gestation [14–16]. However, in the meta-analysis by Kleinrouweler et al., the test accuracy of angiogenic/anti-angiogenic factors was found too weak for accurate prediction of onset of preeclampsia in the clinical setting [16, 17]. The metaanalysis had several studies from various countries, but did not contain even a single study from India. Nevertheless, the meta-analysis also emphasized that a generalized ‘abnormal’ value of angiogenic/anti-angiogenic factors is too risky to be used for preeclampsia prediction. Since ‘normal’ values for these factors may vary between individuals and with ethnic and socioeconomic variations, a relative change in these factors could be tried as an approach for diagnosis. Here, we report temporal changes in maternal VEGF, PlGF and sFlt-1 levels during pregnancy in a cohort of Indian women. We found lower levels of PlGF and VEGF throughout pregnancy in women who developed PE. These women also showed an excessive increase in sFlt-1 levels compared to pregnant women who remained normaotensive. Besides, an early prediction model for PE, as early as GW 20, has been developed using the following parameters: sFlt-1, sFlt-1/PlGF ratio and BMI data, with ~ 88% accuracy.Conflict of interest Authors declare that there are no conflicts of interest with regard to this manuscript.
Ethical Statement This study has been ethically approved from King George’s Medical University, Uttar Pradesh ethics committee (Approval No. XLIIIECM/B-P15).
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