Enzymatic Determination of Oxalates

Abstract

An assay for oxalate, based on oxalate oxidase, was studied. It is relatively simple, rapid and reproducible and may be semi-automated and is accurate in the range 10- 140 mg/l, has a coefficient of variation of 4.2% in the healthy range (10-19 mg/l serum). Samples may be stored at -20 °C for as long as 2 weeks. It cannot be used for the determination of urinary oxalate because of the presence of variable amounts of low molecular weight inhibitor(s).

Rapid Oxalate Determination in Blood and Synthetic Urine Using a Newly Developed Oxometer

“…Even as recent as the 1980s, the reported normal range of plasma oxalate varied anywhere from 1 lmol/L to 200 lmol/L, depending on the laboratory. 16,17 Explanations for these differences start just after the blood draw; several authors describe increased sample oxalate (oxalalogenesis) from the breakdown of glyoxalate or ascorbate if blood is allowed to stand more than a few minutes or if the samples are frozen and stored. 15,18 Moreover, oxalate stored in an acidified environment can bind to plasma proteins, resulting in up to a 70% oxalate underestimation for some ultrafiltration assay protocols.…”