The sFlt-1/PlGF ratio has high sensitivity and specificity to diagnose preeclampsia (PE) and to predict pregnancy outcome. Especially in patients with preexisting hypertension and/or proteinuria, diagnosis and management of PE is challenging. We studied the predictive value of the sFlt-1/PlGF ratio for the occurrence of adverse outcome in patients with a high prevalence of preexisting hypertension or proteinuria, clinically suspected of having PE.
A sFlt-1/PlGF ratio >= 85 was considered to be a positive test. Adverse pregnancy outcome was defined as HELPP syndrome, intra-uterine growth restriction, or perinatal death. The predictive value of adverse pregnancy outcome of preeclampsia based on clinical grounds (clinical PE) or of a positive ratio was compared using a logistic regression model corrected for gestational age at testing.
Results: So far 64 patients with a gestational age (GA) of 29.3 wks (range 20-37 wks) were included. 19 had preexisting hypertension, 5 had preexisting proteinuria and 6 had both conditions. At time of measurement 23 patients had clinical PE (4 with a negative ratio) and 30 patients had a positive sFlt-1/PlGF test (11 without clinical PE at testing of whom 7 developed clinical PE within 2 wks).
27% of patients had an adverse outcome of pregnancy. GA between patients with clinical PE or a positive test did not differ. Patients with clinical PE at the time of testing had an odds ratio of 2.5 (95% CI: 0.75 - 7.8) and patients with a positive test had an odds ratio of 6.8 (95% CI;2.1 - 33.9) for an adverse outcome. Patients with clinical PE had an absolute risk for an adverse outcome of 39% (9/23) compared to 46%(14/30) for patients with a positive sFlt-1/PlGF test (p=.075)
In patients where the diagnosis of PE is challenging because of preexisting hypertension and/or proteinuria a positive sFlt-1/PlGF is a stronger determinant for poor pregnancy outcome than the clinical diagnosis of PE. An explanation could be that a positive ratio can select patients that will develop PE in the near future and because of misclassification of patients with preexisting hypertension and/or proteinuria.