Background: The pathogenesis of nephrotic syndrome is thought to be due to a decrease in protein sieving function in the glomerular capillary wall. However, no research has been conducted on the renal sieving coefficient of serum protein in nephrotic patients. We investigated the renal protein sieving coefficient in pediatric patients with severe nephrotic syndrome.
Methods: Thirty pediatric patients (age: 3−20, mean: 9.3, years; 18 male and 12 female) with severe nephrotic syndrome: hypoproteinemia (TP (Total Protein) ≤ 5.0 g/dL), heavy proteinuria (UTP/Cr (Creatinine) >2 g/gCr), and a normal GFR(glomerular filtration rate) (creatinine clearance ≥ 90 mL/min), were studied. The sieving coefficient of the serum total protein (SCTP) was calculated using a simple formula: Total protein clearance/creatinine clearance (%). The correlation with a twenty-four-hour (24hr) urinary protein test corrected by body surface area (24hrUPT/BSA) was analyzed to assess the accuracy of SCTP. For reference, the correlation between 24hrUPT/BSA and UTP/Cr with SCTP was also analyzed, and the differences between these correlation coefficients were statistically examined.
Results: The mean ± standard error of SCTP was 0.13 ± 0.017%. The correlation coefficients of SCTP and U-TP/Cr with 24hrUPT/BSA were 0.90 and 0.78, respectively. SCTP had a significantly stronger correlation with 24hrUPT/BSA than U-TP/Cr (p < 0.05).
Conclusion: We found that only 0.13% of sieving coefficient dysfunction causes severe nephrotic syndrome. SCTP has a stronger correlation with 24hrUPT/BSA than with UTP/Cr. If nephrotic syndrome is defined as a protein-sieving dysfunction of the glomerular capillary wall, SCTP can be considered a conceptually correct indicator.