Comparison of three commercially available placental growth factor-based tests in women with suspected preterm pre-eclampsia: the COMPARE study

To compare the performance of three placental growth factor (PlGF)-based tests in predicting delivery within 14 days from testing in women with suspected preterm pre-eclampsia before 35 weeks' gestation. Methods: This was a retrospective analysis of samples collected from three prospective pregnancy cohort studies. Participants were pregnant women with suspected preterm pre-eclampsia recruited in tertiary maternity units in the UK and Ireland. Samples were analyzed simultaneously according to the manufacturers' directions. The tests compared were the DELFIA Xpress PlGF 1-2-3 test, the Triage PlGF test and the Elecsys immunoassay soluble fms-like tyrosine kinase-1 (sFlt-1)/PlGF ratio. Areas under receiver–operating characteristics curves (AUCs) were compared. The main outcome measure was detection of a difference of 0.05 in AUC between tests for delivery within 14 days of testing. Results Plasma samples from 396 women and serum samples from 244 women were assayed. In predicting delivery within 14 days secondary to suspected pre-eclampsia prior to 35 weeks' gestation, no significant differences were observed in AUCs (P = 0.795), sensitivities (P = 0.249), positive predictive values (P = 0.765) or negative predictive values (P = 0.920) between the three tests. The specificity of the Elecsys sFlt-1/PlGF ratio test was higher than that of the other two tests (P < 0.001). Conclusions: The tests perform similarly in their prediction of need for delivery within 14 days in women with suspected pre-eclampsia. The high negative predictive values support the role of PlGF-based tests as ‘rule-out’ tests for pre-eclampsia