Plasma sFlt-1/PlGF ratio of 11.5 multiples of median predicts preeclampsia with severe features within two weeks of testing

Background Angiogenic imbalances, characterized by an excess of antiangiogenic factors (soluble fms-like tyrosine kinase 1 [sFlt-1]) and reduced angiogenic factors (VEGF and placental growth factor [PlGF]), contribute to the mechanisms of disease in preeclampsia. The ratio of sFlt-1 to PlGF has been used as a biomarker for preeclampsia, but cut-off values may vary with gestational age and assay platform. Objectives To compare multiples of the median (MoM) of maternal plasma sFlt-1/PlGF ratio, sFlt-1, PlGF, and conventional clinical and laboratory values to predict preeclampsia with severe features. Study Design We conducted a cohort study across 18 U.S. centers involving hospitalized hypertensive individuals between 23-35 weeks' gestation. Receiver operating characteristic curve (ROC) analyses of maternal plasma biomarkers, highest systolic or diastolic blood pressures, and laboratory values at enrollment were performed for the prediction of preeclampsia with severe features. Their areas under the curve (AUC) were compared, and quasi-Poisson regression models were fitted to estimate relative risks. The primary outcome was preeclampsia with severe features within two weeks of enrollment. Secondary outcomes were a composite of severe adverse maternal outcomes (elevated liver enzymes, low platelets count, placental abruption, eclampsia, disseminated intravascular coagulation, and pulmonary edema) and a composite of severe adverse perinatal outcomes (birthweight <3rd percentile, very preterm birth [<32 weeks] and fetal/neonatal death). Results Out of 543 individuals included in the study, preeclampsia with severe features within two weeks was observed in 33.1% (n=180) of them. A ROC-derived cut-off of 11.5 MoM for sFlt-1/PlGF plasma ratio provided sensitivity (90.6%), specificity (76.9%), positive predictive value (66.0%), negative predictive value (94.3%), positive likelihood ratio (3.91), negative likelihood ratio (0.12), and accuracy (81.4%) for preeclampsia with severe features within two weeks. This cut-off was used to compare test positive cases (≥ cut-off) and test negative cases (< cut-off). Preeclampsia with severe features (66.0% vs. 5.7%; <0.001), and composites of severe adverse maternal (8.11% vs. 2.7%; p=0.006) or perinatal outcomes (41.3% vs. 10.14%; p=0.001) within two weeks were more frequent in test positive cases than test negative cases. sFlt-1/PlGF plasma ratio ≥11.5 MoM was independently associated with preeclampsia with severe features (adjusted incidence rate ratio [aIRR]: 9.08, 95% CI: 6.11 to 14.06; p<0.001) and a composite of severe adverse perinatal outcomes (aIRR: 9.42, 95% CI: 6.36 to 14.53; p<0.001), but not with a composite of severe adverse maternal outcomes (aIRR: 2.20, 95% CI: 0.95 to 5.54; p=0.08).The AUC of sFlt-1/PlGF plasma ratio in MoM (0.91; 95% CI: 0.89-0.94) for preeclampsia with severe features within two weeks was significantly higher (p<0.001 for all comparisons) than either plasma biomarker alone or any other parameter, with the exception of absolute sFlt-1/PlGF plasma ratio values. Conclusions SFlt-1/PlGF plasma ratio ≥11.5 MoM among hospitalized, hypertensive patients between 23- and 35-week’s gestation predicts progression to preeclampsia with severe features and severe adverse perinatal outcomes within two weeks.