Diagnosis of preeclampsia with soluble Fms–like tyrosine kinase 1/placental growth factor ratio: an inter–assay comparison

•The KRYPTOR automated assay for soluble Fms-like kinase 1 (sFlt-1) and placental growth factor (PlGF) performed equally or better than an established automated assay in diagnosing preeclampsia.•The sFlt-1/PlGF ratio was most accurate in early onset preeclampsia, and preeclampsia complicated by HELLP or preterm birth. The ratio was less accurate in late onset preeclampsia, especially among obese women.

The angiogenic factor ratio soluble Fms–kinase 1 (sFlt–1)/placental growth factor (PlGF) is a novel diagnostic tool for preeclampsia. We compared the efficacy of the KRYPTOR (BRAHMS) automated assays for sFlt–1 and PlGF with the Elecsys (Roche) assays in a routine clinical setting. Preeclamptic women (n = 39) were included shortly after the time of diagnosis. Normotensive control pregnancies were matched by gestational age (n = 76). The KRYPTOR assays performed comparably or superior to Elecsys (sFlt–1/PlGF area under the curve 0.746 versus 0.735; P = .09; for non–obese 0.820 versus 0.805, P = .047). For early–onset preeclampsia, KRYPTOR area under the curve increased to 0.929 with a 100% specificity for preeclampsia at cut–off 85 and an 88.9% sensitivity for preeclampsia at cut–off 33. For women with preeclampsia and preterm delivery or Hemolysis, Elevated Liver enzymes, Low Platelet count (HELLP) syndrome, the KRYPTOR sFlt–1/PlGF ratio was manifold increased (P < .01). The sFlt–1/PlGF ratio proved especially useful in early–onset preeclampsia, preeclampsia with preterm delivery or HELLP, and among non–obese women.