The evaluation of methods for determinations of urinary oxalate

Abstract

Estimation of urinary oxalate is one of important tools for the diagnosis and treatment of urolithiasis. And more precise, simple and inexpensive method is desirable. In the present study, we evaluated three methods which were clinically well-used. From October 1996 to June 1997, 146 acidified urine samples were collected for 24 hours from 144 urolithiasis patients. We determined the urinary oxalates by three methods; the colorimetric method, the enzymic method and the ion chromatography (IC method). And we evaluated the correlations of these methods. Correlation coefficients in the urine oxalate concentration were, 0.86 with the colorimetric method and the IC method, 0.91 with the enzymic method and the IC method, 0.90 with the colorimetric method and the enzymic method. The coefficients in the 24 hours-urinary excretion of oxalate (0.76, 0.87, 0.82) were lower than those in the urine oxalate concentration. The correlation coefficients with the colorimetric method and the IC method were, 0.58 in hyperoxaluric group, 0.34 in normooxaluric group. The coefficients with the enzymic method and the IC method, 0.93 in hyperoxaluric group, 0.71 in normooxaluric group. The colorimetric method is least expensive, but is less useful. The enzymic method is less expensive, and is as useful as the IC method.