Comparison of a Commercial Enzymic Kit for Urinary Oxalate Analysis with a High Performance Liquid Chromatographic Method

Abstract

A new commercial enzymic kit for urinary oxalate determination has been adapted for use on a centrifugal analyser. It has been evaluated and compared with an established high performance liquid chromatographic (HPLC) procedure developed in our laboratory. Mean recovery of oxalate from urine samples augmented with oxalic acid exceeded 97% by both methods. The precision of the HPLC method was superior to that of the enzymic kit but both methods gave between batch precision values better than CV 12% at low (less than 100μmol/L) oxalate concentrations and better than CV 7% at higher concentrations (greater than 270μmol/L) Urinary oxalate values obtained with the new enzymic procedure correlated more closely with HPLC values ( r = 0·84) than did values previously obtained using the forerunner of the kit ( r = 0·62) which was known to be susceptible to ascorbate interference. No significant interference from ascorbic acid or from high urinary calcium concentrations could be demonstrated using either the improved kit or the HPLC procedure. Its easy adaptation to automated analysers available in most laboratories, coupled to its acceptable analytical performance render the enzymic kit a reasonable alternative to HPLC or other more complex procedures for urinary oxalate analysis.