The predictive value of the sFlt-1/PlGF ratio in suspected preeclampsia in a New Zealand population: A prospective cohort study

Background Internationally, placental growth factor (PlGF)-based tests are used as prognostic markers in suspected preeclampsia. However, Ministry of Health guidelines do not currently endorse PlGF-based tests in New Zealand (NZ). Aims To investigate the predictive value of soluble fms-like tyrosine kinase 1 (sFlt-1)/PlGF ratio in suspected preeclampsia in a NZ population. Materials and Methods A prospective cohort study of singleton pregnancies at 20(+0)-36(+6) weeks gestation with suspected preeclampsia as defined by Society of Obstetric Medicine Australia and NZ (SOMANZ) criteria. Primary objective: to evaluate a sFlt-1/PlGF ratio >38 at <= 35(+0) weeks gestation to predict birth <= 14 days. Secondary objectives: to assess a sFlt-1/PlGF ratio cut-off of 38 at <= 37(+0) weeks gestation, to rule out preeclampsia <= 1 week, rule in preeclampsia <= 4 weeks, and to predict perinatal outcome. Clinicians were blinded to sFlt-1/PlGF ratio results. Results Included were 222 participants, 19.4% Maori and 10.4% Pasifika. A sFlt-1/PlGF >38 predicted birth <= 14 days, positive predictive value (PPV) 51.4% (95% CI, 39.6-63.0) and negative predictive value (NPV) 95.9% (95% CI, 91.4-98.1), median (interquartile range) days to birth 14 (2-27) vs 49 (33-70), P < 0.000. A sFlt-1/PlGF cut-off of 38 ruled out preeclampsia <= 1 week (NPV 96.2% (95% CI, 92.3-98.2)) and ruled in preeclampsia <= 4 weeks (PPV 75.0% (95% CI, 65.0-82.9)). A sFlt-1/PlGF >38 was associated with greater perinatal morbidity. Conclusions The predictive value of the sFlt-1/PlGF ratio in NZ is comparable to that reported in international trials. Used in clinical practice the sFlt-1/PlGF ratio may aid risk stratification in suspected preeclampsia, directing limited resources to those pregnancies at highest risk.