Hypertension is the most common medical problem encountered during pregnancy, complicating 2-3% of pregnancies. The cause of preeclampsia is not yet fully understood, but the disorder is thought to be due to placental malperfusion resulting from abnormal remodelling of maternal spiral arteries(1,2). Abnormal remodelling of maternal spiral arteries is observed in women with subsequent preeclampsia, leading to placental hypoperfusion and systemic endothelial dysfunction(3). Angiogenic factors are associated with the pathophysiology of preeclampsia. More evidence supports a role for angiogenic factors in the pathogenesis of preeclampsia, and sFlt-1 levels are strongly correlated with the severity of the syndrome(4).
preeclampsia, angiogenic factors, sFlt/PLGF ratio
Hipertensiunea arterială este cea mai frecventă problemă medicală întâlnită în timpul sarcinii, complicând 2-3% din sarcini. Patogeneza preeclampsiei este multifactorială şi nu este pe deplin înţeleasă. Cu toate acestea, remodelarea anormală a arterelor spirale materne este observată la femeile cu preeclampsie ulterior(1,2), ducând la hipoperfuzie placentară şi la disfuncţie endotelială sistemică(3). Factorii angiogenici sunt asociaţi cu patofiziologia preeclampsiei. Mai multe dovezi susţin un rol al acestora în patogeneza preeclampsiei, iar nivelurile sFlt-1 sunt puternic corelate cu severitatea sindromului(4).
Among hypertensive disorders, preeclampsia (PE) is one of the major life-threatening conditions for mothers and infants alike, with a worldwide mortality of 10-15% of the 500,000 maternal deaths each year(5,6).
Up until recently, the molecular pathogenesis of phenotypic preeclampsia was mostly unknown; however, recent observations support the hypothesis that the altered expression of placental anti-angiogenic factors is responsible for the clinical manifestations of the disease.
Angiogenic factors are assumed to play an important role in regulating the placental vascular development. Soluble FMS-like tyrosine kinase-1 (sFlt-1), the vascular endothelial cell growth factor (VEGF-1), VEGF-2, the placental growth factor (PlGF) and sEndoglin are essential for normal vascular development. Therefore, the loss of endothelial control of vascular development leads to hypertension, while increased vascular permeability causes proteinuria and disturbed endothelial expression of coagulation factors, resulting in coagulopathy(7). Increasing evidence suggests that an imbalance between angiogenic and anti-angiogenic factors may be responsible for the physiopathological effects seen in PE(8,9), which occur prior to clinical signs becoming apparent(10).
Levine et al.(11) showed that, five weeks before the development of clinical symptoms of PE, serum concentrations of sFlt-1 are increased, while PlGF concentrations are low, resulting in an increased sFlt-1/PlGF ratio. Increased sFlt-1 levels and reduced PlGF levels can be used to predict the subsequent development of PE.
A prospective study was carried out to validate the sFlt-1/PlGF ratio for PE management. The PROGNOSIS study (“Prediction of short-term outcome in pregnant women with suspected preeclampsia”) clearly demonstrated that an sFlt-1/PlGF ratio of 38 and below can be used to rule out the onset of PE within the next week, irrespective of gestational age(12). The negative predictive value was 99.3(12). Additionally, an sFlt-1/PlGF ratio higher than 85 (for early-onset PE; <34 weeks of gestation) or 110 (for late-onset PE; >34 weeks) is indicative of an increased risk of a PE or placenta-related diagnosis, requiring strict clinical and biological monitoring. For women with an sFlt-1/PlGF ratio between 35 and 85 or between 38 and 110, current PE can be ruled out; however, these women are still at high risk of developing PE within four weeks(13).
Materials and methodology
The aim of this study was to monitor 106 pregnant women undergoing obstetric examination who showed risk factors for developing PE, alongside a control group with characteristics similar to the study group. A database was established from the charts created in compliance with the protocol, with the patients’ consent, which were then subjected to dynamic monitoring throughout their pregnancy, including serial ultrasound investigations consisting of Doppler examinations of the uterine and foetal middle cerebral and umbilical arteries performed for all patients. The parameters under observation were IR, IP and S/D. Also, the sFlt-1/PlGF ratio was calculated by using the Elecsys immunoassay sFlt-1/PlGF from Roche Diagnostics GmbH for pregnant women with a gestational age between 20 and 32 weeks. The goal of this research was to assess the importance of immunological dosing of some angiogenic factors and of maternal and foetal Doppler examination with a view to assess the foetuses of preeclamptic pregnancies in order to improve the prenatal diagnosis and optimise the obstetric approach.
SFlt-1 above the 95th percentile was observed in 70.83% of cases in the control group, in 71.43% of the women with GHBP and in 67.21% of the pregnant women with PE. No statistically significant difference (p=0.911) was found, with respect to the distribution of sFlt-1 percentiles and the severity of GHBP/PE (Figure 1).
PlGF below the 5th percentile was recorded in 38% of the PE cases. A statistically significant difference (p<0.001) was noted with regard to the distribution of the PlGF percentiles and the severity of GHBP/PE (Figure 2).
The sFlt-1/PlGF ratio below the 38th percentile was observed in all women in the control group, in 19.05% of the women with GHBP, and in 19.67% of the women with PE. In 57.14% of the women with GHBP and in 49.18% of the women with PE, the sFlt-1/PIGF ratio ranged between the 38th percentile to the 85th percentile. An sFlt-1/PIGF ratio above the 85th percentile was seen in 23.81% of women with GHBP and in 31.15% of those with PE. In terms of the percentile distribution of the sFlt-1/PIGF ratio and the severity of GHBP/PE, a statistically significant difference was observed (p<0.001) – Figure 3.
There is no statistically significant correlation between sFlt-1 and the presence of GHBP and PE. PlGF shows no statistically significant correlation with the presence of GHBP, but it is correlated with the presence of PE (p<0.001) and the severity of PE (p<0.001). The sFlt-1/PlGF ratio shows no statistically significant correlation with the presence of GHBP, but is correlated with the presence of PE (p=0.001) and the severity of PE (p<0.001). Preeclampsia markers show no statistically significant correlation with PE onset after collection (Table 1).
For the purpose of determining the threshold values of preeclampsia markers, the ROC curves were studied for each of them. The AUC for sFlt-1 was 0.513, which indicated a very poor accuracy of the test (Figure 4).
For sFlt-1 values above 790.15, the sensitivity was 72% and the specificity was 16.7%. Values above 1078 determined a sensitivity of 52.4% and a specificity of 33.3% (Table 2).
The AUC for PlGF is 0.199, which suggests a random performance of the test (Figure 5). For PlGF values above 321.75, the sensitivity was 52.4% and the specificity was 8.3%. PlGF values above 444.55 determined a sensitivity of 32.9% and a specificity of 20.8% (Table 2).
The AUC for the sFlt-1/PlGF ratio was 0.982, which indicated an excellent accuracy of the test (Figure 6).
For values of the sFlt-1/PlGF ratio above 22.5, the sensitivity was 98.8% and the specificity was 62.5%. Values of the sFlt-1/PlGF ratio above 27 determined a sensitivity of 96.3% and a specificity of 95.8%. If we raise the threshold of the sFlt-1/PlGF ratio to 30.5%, the sensitivity reaches 95.1%, and the specificity is 100% (Table 2).
Table 3 shows the validity and prediction of preeclampsia markers based on threshold values and using percentiles.
An “anti-angiogenic status” has been thought to constitute a mechanism in preeclampsia, in the HELLP syndrome, and in small-for-gestational-age births. This condition appears to be the result of an imbalance in the production and circulating concentrations of angiogenic factors, such as the placental growth factor (PlGF) and the vascular endothelial cell growth factor (VEGF-1), VEGF-2 (VEGF), as well as anti-angiogenic factors, such as the soluble VEGF receptor-1 (sVEGFR-1 or sFlt1); soluble endoglin (s-Eng) should also be mentioned among these factors. A total of 106 women were included in the study. All women had at least one risk factor. The Doppler result of abnormal uterine artery (notch and/or increased pulsatility) was the most frequent risk factor. Our study shows that the sFlt-1/PlGF ratio can be used to rule out PE in a specific population of patients at high risk, with an excellent negative predictive value, as the results obtained indicate that the sFlt-1/PlGF ratio below the 38th percentile was found in all women in the control group, in 19.05% of the women with GHBP and in 19.67% of the women with PE, results which coincide with those reported in a major observational study validated for the sFlt-1/PlGF ratio in the management of PE. The PROGNOSIS study clearly demonstrated that an sFlt-1/PlGF ratio of 38 and below can be used to rule out the onset of PE within the next week, irrespective of gestational age(12). The negative predictive value was 99.3(12).
No statistically significant correlation was found between sFlt-1 and the presence of GHBP and PE. There is no statistically significant correlation between PlGF and the presence of GHBP, however PlGF is correlated with the presence of PE (p<0.001) and the severity of PE (p<0.001) – Figure 1 and Figure 2, indicating low specificity and sensitivity. These findings are consistent with the results reported by Levine et al.(11), showing that, five weeks before the development of clinical symptoms of PE, serum concentrations of sFlt-1 are elevated, while the PlGF concentrations are decreased.
The AUC curve created for the threshold values of markers is 0.982 for the sFlt-1/PlGF ratio, which indicates excellent test accuracy (Figure 6).
The sFlt-1/PlGF ratio can serve as a predictive marker to rule out PE. The use of these biomarkers in the routine management of PE could lead to better clinical care and avoid unnecessary hospitalization, which has a significant economic impact.
Conflict of interests: The authors declare no conflict of interests.
Staff AC, Benton SJ, von Dadelszen P, et al. Redefining preeclampsia using placenta-derived biomarkers. Hypertension. 2013; 61:932-942.
Chaiworapongsa T, Chaemsaithong P, Yeo L, Romero R. Pre-eclampsia. Part 1. Current understanding of its pathophysiology. Nat Rev Nephrol. 2014; 10:466-480.
Wang A, Rana S, Karumanchi SA. Preeclampsia: the role of angiogenic factors in its pathogenesis. Physiology (Bethesda). 2009; 24:147–158.
Mutter WP, Wang A. Molecular mechanisms of preeclampsia. Microvasc Res. 2008; 75:1–8.
Kar M. Role of biomarkers in early detection of preeclampsia. J Clin Diagn Res. 2014; 8: BE01BE04. doi:10.7860/jcdr/2014/7969.4261.
Khan KS, Wojdyla D, Say L, Gulmezoglu AM, Van Look PF. WHO analysis of causes of maternal death: a systematic review. Lancet. 2006; 367:1066–1074. doi:10.1016/S0140-6736(06)68397-9.
Wang A, Rana S, Karumanchi SA. Preeclampsia: the role of angiogenic factors in its pathogenesis. Physiology (Bethesda). 2009; 24:147–58.
Bdolah Y, Sukhatme VP, Karumanchi SA. Angiogenic imbalance in the pathophysiology of preeclampsia: newer insights. Seminars Nephrol. 2004; 24(6):548–556.
Maynard SE, Karumanchi SA. Angiogenic factors and preeclampsia. Seminars Nephrol. 2011; 31(1): 33–46.
Cîrstoiu M, Gunescu DC, Bodean OM, Munteanu O, Vlădăreanu S. Rolul determinării factorilor angiogenici placentari în evaluarea periodică a riscului de preeclampsie. Ginecologia.ro. 2015; nr VIII, 2.
Levine RJ, Maynard SE, Qian C, Lim KH, England LJ, Yu KF, et al. Circulating angiogenic factors and the risk of preeclampsia. N Engl J Med. 2004; 350:672–683.
Zeisler H, Llurba E, Chantraine F, Vatish M, Staff AC, Sennstrom M, et al. Predictive Value of the sFlt-1: PlGF Ratio in Women with Suspected Preeclampsia. N Engl J Med. 2016; 374:13–22.
Stepan H, Herraiz I, Schlembach D, Verlohren S, Brennecke S, Chantraine F, et al. Implementation of the sFlt-1/PlGF ratio for prediction and diagnosis of pre-eclampsia in singleton pregnancy: implications for clinical practice. Ultrasound Obstet Gynecol. 2015; 45:241–246.