Antenatal risk stratification for preeclampsia with sFlt-1/PlGF ratio: Which is the best time to test?

OBJECTIVE: To find out the predictive value of sFlt-1/PlGF ratio for antenatal risk stratification (ARS) of women at high risk of preeclampsia (PE). METHODS: Antenatal women at high risk of PE underwent sFlt-1/PlGF ratio at 20-22, 28-30 and 34-36 weeks and were followed till delivery. Those who developed PE were cases those who had normal outcome were controls, the cases and controls were compared. RESULTS: Hypertension in pregnancy was seen in 116/287 (40.4 %), 46/287(16.0 %) had PE and 21(7.3 %) had early onset PE. Mean arterial pressure at 20-22 weeks was the high in those who developed early onset PE (109.08 ± 9.74 mmHg). The sFlt-1/PlGF ratio of 38 or more at 20-22 weeks resulted in either PE or adverse fetal outcome in all cases. Whereas, the ratio of less than 38 ruled out PE in all cases up to 29 + 6 weeks. At 28-30 weeks, the ratio less than 38 predicted no PE up to 34 weeks and no complication up to 29+6 weeks. The sensitivity for the detection at later gestation further decreased as the gestation advanced however the specificity was above 98 % at all gestations. The positive predictive value of the test increased with the advancing gestation, the negative predictive value was 93 % or higher at all gestations. CONCLUSION: The usefulness of sFlt-1/PlGF ratio ≥38 for risk stratification was validated in the study, the testing at 28-30 weeks appeared to be the best time to test for PE prediction in high risk women.