Fractional excretion of total protein in patients with nephrotic syndrome

Abstract

AbstractBackgroundThe urine protein to creatinine ratio (UPCR) correlates well with the 24‐h urine protein test (24‐h UPT) and is a reliable indicator of proteinuria. However, in nephrotic syndrome, the correlation between the UPCR and the 24‐h UPT tends to decrease. To address this, we introduced the fractional excretion of total protein (FETP), which reflects serum total protein and creatinine levels because severe hypoproteinemia and/or elevated serum creatinine levels tend to occur under these conditions. The 24‐h UPT corrected for body surface area (BSA) (24‐h UPT/BSA) was used to take body size into consideration. The correlation coefficients for 24‐h UPT/BSA and FETP and 24‐h UPT/BSA and UPCR were calculated. The statistical significance of the differences between these coefficients was also calculated.MethodsThirty‐six pediatric patients with nephrotic syndrome were included in this study. The FETP was calculated as total protein clearance/creatinine clearance (%). Correlation coefficients were calculated for 24‐h UPT/BSA and FETP and 24‐h UPT/BSA and UPCR. The statistical significance of the differences between these coefficients was also calculated.ResultsThe mean ± standard error of FETP was 0.11% ± 0.013%. The correlation coefficients of FETP and UPCR with 24‐h UPT/BSA were 0.91 and 0.81, respectively. The FETP demonstrated a significantly stronger correlation with 24‐h UPT/BSA than with UPCR (p = 0.01).ConclusionsThe FETP correlated more strongly with 24‐h UPT/BSA than with UPCR in patients with nephrotic syndrome. The FETP is a reliable indicator of proteinuria in nephrotic syndrome, especially in patients with severe hypoproteinemia or elevated serum creatinine levels.