Rule-in thresholds for DELFIA Xpress PlGF 1-2-3 test for suspected pre-eclampsia

We aimed to establish a rule-in threshold for the DELFIA Xpress placental growth factor (PlGF) 1-2-3 test. Plasma EDTA samples from 305 women presenting with suspected pre-eclampsia before 35 weeks' gestation were analysed using three different PlGF-based tests: PlGF 1-2-3 test (Perkin Elmer); Triage PlGF test (Quidel); Elecsys immunoassay sFlt-1/PlGF ratio (Roche). The rule-in threshold for PlGF 1-2-3 test created with equivalent specificity of the Quidel and Roche tests was 50 pg/ml. This can be used as a rule-in test for diagnosis of preterm pre-eclampsiarequiring delivery within 14 days (specificity 95.0% (95% CI 91.7-97.2%), positive predictive value50 (95% CI 30.6-69.4%), positive likelihood ratio 10.7 (5.8-20).