Soluble Flt-1 as a diagnostic marker of pre-eclampsia

BACKGROUND: Serum levels of soluble fms-like tyrosine kinase (sFlt-1) increase in pre-eclampsia (PE). Aims: To determine whether concentrations of serum sFlt-1 can differentiate PE or superimposed PE (SPE) from gestational hypertension (GH) or chronic hypertension (CH). METHODS: Blood was collected from pregnant women being investigated for hypertension (blood pressure of > 140 and/or 90 mmHg). Normotensive (NP) and pre-eclamptic (PE-C) control ranges were measured. RESULTS: Patients with evolving hypertension in pregnancy eventually fell into four groups: GH (n = 14), PE (n = 7), CH (n = 9) and SPE (n = 9). Patients who later developed pre-eclampsia had a higher sFlt-1 (PE: 2.61 ng/mL and SPE: 2.77 ng/mL, respectively) than GH (P < 0.001) or CH (1.05 ng/mL, P = 0.11). Women with established PE at recruitment (PE-C; (n = 18) (3.13 ng/mL; interquartile range (IQR): 2.14-4.17 ng/mL) had a median sFlt-1 higher than NP (n = 18) (0.47 ng/mL; IQR: 0.11-0.89) (P < 0.0008). Patients with GH compared to NP had a slight increase (1.33 ng/mL, P < 0.003). Using a sFlt-1 cut-off of > or = 1.9 ng/mL yielded a sensitivity of 94% (95% confidence interval (CI) 73-100%) and specificity of 78% (95% CI 64-82%). CONCLUSIONS: sFlt-1 was elevated in women with PE compared to NP. The sFlt-1 also differentiated women destined to develop PE among those who presented with a diagnostic rise in maternal blood pressure. The sFlt-1 test is a useful diagnostic test for PE.