Fractional excretion of angiogenic factors in women with severe preeclampsia

OBJECTIVE: We estimated the fractional excretions of soluble fms-like tyrosine kinase 1 (sFIt-1), vascular endothelial growth factor, and placental growth factor of severely preeclamptic women at the time of disease clinical manifestation. METHODS: Levels of free sFIt-1, vascular endothelial growth factor, and placental growth factor were measured by immunoassay from time-matched serum-urine samples from 64 women in the following groups: nonpregnant reproductive aged (n = 9), healthy pregnant controls (n = 13), mildly preeclamptic women (n = 15), and women with severe preeclampsia (n = 27). Urinary concentrations of angiogenic factors were normalized to creatinine and fractional excretions calculated. Correlations were estimated between fractional excretions of angiogenic factors, albuminuria, nonspecific proteinuria and urine protein-to-creatinine ratio. RESULTS: Severely preeclamptic women had more than double urinary vascular endothelial growth factor (P = .01) and fractional excretion of vascular endothelial growth factor compared with mildly preeclamptic women (P = .007) or pregnant controls (P < .001). Serum, urine and fractional excretion levels of sFIt-1 were much higher among severely preeclamptic women compared with all the other pregnant groups (P < .001). Conversely, severely preeclamptic women had lower serum placental growth factor levels compared with healthy pregnant women (P < .05) and mildly preeclamptic groups (P < .05). Severely preeclamptic women had increased fractional excretions of placental growth factor, albumin, proteinuria, and random urine total protein/creatinine ratio. Among severely preeclamptic women there was no correlation between proteinuria and fractional excretion of vascular endothelial growth factor (r = 0.30, P = .127) or sFIt-1 (r = 0.35, P = .07). There was a significant correlation between fractional excretion for placental growth factor, random urine total protein/creatinine ratio (r = 0.60, P = .002), and nonspecific proteinuria (r = 0.50, P = .01). CONCLUSION: Severe preeclampsia is characterized by increased fractional excretion of angiogenic factors and especially of vascular endothelial growth factor, likely reflecting 2 separate phenomena that may have additive effects: "endogenous" renal production and glomerular "leakage."