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 296 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.