Clinical Chemistry, Vol 29, 16-20, Copyright © 1983 by American Association for Clinical Chemistry

Urinary oxalate determination by use of immobilized oxalate oxidase in a continuous-flow system

N Potezny, R Bais, PD O'Loughlin, JB Edwards, AM Rofe and RA Conyers

In this procedure, oxalate oxidase (EC 1.2.3.4) immobilized in a continuous-flow system is used to determine oxalate in urine. The hydrogen peroxide formed from oxalate is detected by use of a color reaction with peroxidase (EC 1.11.1.7), 3-methyl-2-benzothiazoline hydrazine, and N,N-dimethylalanine. However, urine contains an oxalate oxidase inhibitor, which cannot be removed by heating, ion-exchange resins, or cellulose columns. This makes it necessary to precipitate the oxalate before assay. The overall assay system is accurate (oxalate recovery, 95.9%), sensitive (less than or equal to 5 mumol/L), precise (within-batch CV less than 1.25%, between-batch CV less than 5%), and relatively rapid (60 samples per working day). The assay system has better accuracy than an established chemical method and a gas- chromatographic method, and is considerably less arduous than and correlates well (r = 0.94) with a modified chemical method. The reference interval for urinary oxalate excretion is 0.16-0.56 mmol per day (n = 97). Only nonphysiological concentrations of ascorbate interfere with the assay, by increasing the oxalate result in the overall assay, presumably by post-micturition formation of oxalate from ascorbate in the urine samples.

The following articles in journals at HighWire Press have cited this article:

				P. M. Ladwig, R. R. Liedtke, T. S. Larson, and J. C. Lieske Sensitive Spectrophotometric Assay for Plasma Oxalate Clin. Chem., December 1, 2005; 51(12): 2377 - 2380. [Full Text] [PDF]

				R. A. J. Conyers, R. Bais, and A. M. Rofe Oxalosis and the E-Ferol Toxicity Syndrome JAMA, November 21, 1986; 256(19): 2677 - 2678. [Abstract] [PDF]