Use of the sFlt-1/PlGF ratio to rule out preeclampsia requiring delivery in women with suspected disease. Is the evidence reproducible?

BACKGROUND: Soluble fms-like tyrosine kinase 1 (sFlt-1) to placental growth factor (PlGF) ratio has been proven to predict preeclampsia occurrence.

METHODS: Blood samples from 195 pregnant women with suspected preeclampsia were obtained at obstetric triage admission or from the high-risk pregnancy outpatient office. Serum PlGF and sFlt-1 were measured by an electrochemiluminescence immunoassay (ECLIA) on the immunoanalyser Cobas e601 (Roche Diagnostics) and the corresponding ratio was calculated. Final outcomes were reviewed by an independent obstetrician. Only the first determination was considered.

RESULTS: A sFlt-1/PlGF ratio of 38 or lower ruled out the need for pregnancy termination due to preeclampsia in the subsequent week with a negative predictive value (NPV) of 99.1% (sensitivity 97.1% and specificity 67.5%). None of the 76 pregnancies with first determination of an sFlt-1/PlGF ratio of 38 or lower between 24 and 34 weeks of gestation delivered due to early-onset preeclampsia. Positive likelihood ratio (PLR) of an sFlt-1/PlGF ratio above 38 for prediction of pregnancy termination due to preeclampsia within 4 weeks is analogous to published evidence.

CONCLUSIONS: Between 24 and 34 weeks of gestation, no subsequent determination was needed to completely rule out early-onset preeclampsia when the first sFlt-1/PlGF ratio determination was 38 or lower in singleton pregnancies with signs or symptoms of this syndrome. These findings, if confirmed, will reduce costs and facilitate the implementation of the sFlt-1/PlGF ratio in women with clinical suspicion of preeclampsia in the third trimester.