Is serum CRP level a reliable inflammatory marker in pediatric nephrotic syndrome?

BACKGROUND

This study tested the hypothesis that during massive proteinuria, C-reactive protein (CRP) may be lost into the urine along with other proteins, making serum CRP (sCRP) level an unreliable marker of infection severity in nephrotic syndrome (NS).

METHODS

Children with active NS (n = 23) were compared with two matched control groups: patients with febrile non-renal infectious disease (n = 30) and healthy subjects (n = 16). Laboratory measurements included sCRP, urine protein, creatinine, IgG, and protein electrophoresis. Urinary CRP (uCRP) was measured by ELISA.

RESULTS

Sixty-nine patients were enrolled: 23 patients with NS, 30 patients with non-renal febrile infectious diseases, and 16 healthy children. Median uCRP concentrations were 0 mcg/gCr (0-189.7) in NS, 11 mcg/gCr (0-286) in the febrile group, and 0 mcg/gCr (0-1.8) in the healthy group. The uCRP/creatinine ratio was similar in the NS and healthy groups (p > 0.1) and significantly higher in the febrile group than the other two groups (p < 0.0001). There was no association of uCRP concentration with severity of proteinuria or IgG excretion.

CONCLUSIONS

NS in children is not characterized by significant loss of CRP into the urine. Therefore, sCRP may serve as a reliable marker of inflammation in this setting. The significant urinary excretion of CRP in children with transient non-renal infectious disease might be attributable to CRP synthesis in renal epithelial cells.