Performance of commercially available placental growth factor tests in women with suspected preterm pre-eclampsia; the COMPARE study

OBJECTIVE: To compare the performance of three PlGF-based kits in prediction of time to delivery within 14 days in women with suspected preterm pre-eclampsia prior to 35 weeks' gestation.

METHODS: We conducted 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 analysed simultaneously according to manufacturer's directions. Tests compared were DELFIA Xpress PlGF 1-2-3 test, Triage PlGF test and Elecsys immunoassay sFlt-1/PlGF ratio. Areas under the receiver operating curve (AUROC) were compared. The main outcome measure was detection of a difference of 0.05 in AUROC between tests for time to delivery within 14 days of testing.

RESULTS: Plasma samples from 396 women and serum samples from 244 women were assayed. No significant difference was observed in prediction of delivery within 14 days secondary to suspected pre-eclampsia prior to 35 weeks' gestation in AUROC (p= 0.795), sensitivities (p= 0.249), positive predictive values (p= 0.765) or negative predictive values (p= 0.920).

CONCLUSION: The tests compare similarly in their prediction of need for delivery within 14 days. The negative predictive values support the role of PlGF based tests as a 'rule-out' test for pre-eclampsia.