sFlt-1:PlGF Ratio in Diagnosing Superimposed Preeclampsia

Preeclampsia: associated with poor placentation, incomplete uteroplacental spiral arteries remodeling. Result: ischemia, re-perfusion injury, oxidative stress. A low-grade systemic inflammatory response is more pronounced in preeclampsia. This results in an imbalance between maternal circulating pro-angiogenic (PlGF \& VEGF) \& anti-angiogenic factors (sFlt-1). PlGF \& VEGF function as vasodilators \& preserve structure \& function of glomerular endothelium. sFlt-1 blocks these actions, resulting in hypertension, endothelial dysfunction \& nephropathy. Various stressors, including hypoxia, villous crowding, angiotensin II, \& oxidative stress are associated with preeclampsia \& mediate secretion of soluble vascular growth factor 1 (sVEGFR-1 or sFlt-1) by GADD45 (Growth Arrest and DNA Damage-45). GADD45 is one of a family of stress-induced genes sFlt-1 releases into maternal circulation. Excess sFlt-1 leads to endothelial dysfunction, hypertension \& proteinuria. Exogenously administered sFlt-1 results in syndrome of nephrotic range proteinuria, hypertension, and glomerular endotheliosis in animal models. Women with preeclampsia tend to have higher sFlt-1 \& lower PlGF, resulting in an increased ratio (sFlt-1:PlGF). The difference is greater in women who develop early-onset preeclampsia (before 34 wks gestation). Verlohren, et al., showed an increased sFlt-1/PlGF ratio in patients with preeclampsia as compared to controls \& patients with chronic/gestational hypertension. Other work has examined the longitudinal changes in the individual values of sFlt-1 \& PlGF over the course of the pregnancy, as well as the ratio. Given the low prevalence of preeclampsia in the population, the positive predictive value remained low, however the negative predictive value approached 97% late in gestation. This suggests that the utility of the sFlt-1/PlGF may be in its ability to rule out preeclampsia. More recently the PROGNOSIS study was designed to investigate the value of the sFlt-1/PlGF ratio for the prediction of the presence or absence of preeclampsia in the short term \& found that a cutoff point of 38 for the sFlt-1/PlGF ratio is useful for predicting the short-term absence of preeclampsia in women with suspected disease (Negative predictive value 99.3% for ruling out preeclampsia within 1 week). Hypothesis: In women with chronic hypertension, the sFlt-1/PlGF ratio will better predict the development of superimposed preeclampsia than clinical criteria alone.