Determination of oxalate concentration in blood.

The methods used for determination of oxalate in blood are reviewed, and the advantages and disadvantages of the two basic approaches--direct methods and in vivo isotope-dilution techniques--are compared. Possible reasons for the previous discrepancies between direct and isotopic methods are discussed, as are the effects of protein binding, sample handling, and storage conditions on oxalate values in plasma. Necessary precautions for obtaining reproducible results are presented. We recommend and critically review several direct methods, and describe the application of a direct method for oxalate determination in some other biological fluids.