Comparison of Urinary Proteins in Calcium Stone Formers and Healthy Individuals: A Case-Control Study

Abstract

Objective: This study aimed at comparing the urinary protein levels in calcium stone formers with those of healthy individuals. Patients and Methods: From January 2002 until June 2004, 100 calcium stone formers (mean age 38.6 ± 10.3 years), who had at least two episodes of calcium stone formation, were compared with 100 healthy individuals (mean age 33.8 ± 9.7 years). Their 24-hour urinary protein levels, using SDS-PAGE, were measured. Results: The mean 24-hour urinary Tamm-Horsfall protein (THP) levels were 3.3 ± 0.8 mg in the case group and 4.6 ± 1.9 mg in the controls, and the difference was not statistically significant (p = 0.53). However, the THP levels in individuals with and without bacteriuria were significantly different (15.8 ± 3.3 mg vs. 2.6 ± 1.0 mg, p = 0.0001). The mean 24-hour urinary albumin concentrations were 163.31 ± 15.1 mg in the case group and 74.26 ± 4.6 mg in the controls. The mean 24-hour urinary transferrin levels were 8.09 ± 2.7 mg in the case group and 0.40 ± 0.3 mg in the controls. The differences were statistically significant for both albumin and transferrin (p < 0.0001 and p = 0.0063, respectively). There were no significant differences in any other mean urinary protein concentrations between cases and controls. Conclusions: The THP level in the urine of stone formers is not quantitatively different from that of healthy individuals, but it increases in association with bacteriuria. Albumin and transferrin may play a presumptive role in stone formation.