sFlt‐1 - Soluble fms‐like tyrosine kinase‐1
The sFlt‐1 assay is used in combination with the PlGF assay to determine the sFlt‐1/PlGF ratio. The sFlt‐1/PlGF ratio is intended for use as an aid in the diagnosis of preeclampsia in conjunction with other diagnostic and clinical information. In addition the sFlt‐1/PlGF ratio is intended for use as an aid in short-term prediction of preeclampsia (rule-out and rule-in) in pregnant women with suspicion of preeclampsia in conjunction with other diagnostic and clinical information.
Preeclampsia (PE) is a serious complication of pregnancy characterized by hypertension and proteinuria after 20 weeks of gestation. Preeclampsia occurs in 3‐5 % of pregnancies and results in substantial maternal and fetal or neonatal mortality and morbidity. Clinical manifestations can vary from mild to severe forms; preeclampsia is still one of the leading causes of fetal and maternal morbidity and mortality.
Preeclampsia appears to be due to the release of angiogenic factors from the placenta that induce endothelial dysfunction. Serum levels of PlGF (placental growth factor) and sFlt‐1 (soluble fms‐like tyrosine kinase‐1, also known as VEGF receptor‐1) are altered in women with preeclampsia. Moreover, circulating levels of PlGF and sFlt‐1 can discriminate normal pregnancy from preeclampsia even before clinical symptoms occur. In normal pregnancy, the pro‐angiogenic factor PlGF increases during the first two trimesters and decreases as pregnancy progresses to term. In contrast, levels of the anti-angiogenic factor sFlt‐1 remain stable during the early and middle stages of gestation and increase steadily until term. In women who develop preeclampsia, sFlt‐1 levels have been found to be higher and PlGF levels have been found to be lower than in normal pregnancy.
The ratio of sFlt‐1 to PlGF has been shown to be a better predictor of preeclampsia than either measure alone. The sFlt‐1/PlGF ratio seems a reliable tool for discriminating between different types of pregnancy-related hypertensive disorders. In addition, sFlt‐1/PlGF has potential relevance as a prognostic parameter in PE and may be useful in prediction of preeclampsia and related adverse outcomes, risk stratification and management.
The level of anti-angiogenic factor sFlt‐1 seems correlated with sub-clinical cardiac dysfunction and elevated in women with peri-partum cardiomyopathy. Removal of sFlt‐1 may benefit women with very preterm PE: in a pilot study, apheresis with dextran sulfate cellulose (DSC) columns reduced circulating sFlt‐1 levels and allowed prolonged pregnancy without maternal/fetal adverse outcomes.
In summary, PlGF and sFlt‐1 concentrations measured by immunoassay in maternal blood improve the diagnostic possibilities in preeclampsia which comprise clinical symptoms, proteinuria and uterine artery Doppler velocimetry.
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