Evaluation of several creatinine methods in search of a suitable secondary reference method: Report from the subcommittee on reference method for creatinine, Nordic Society for Clinical Chemistry

Abstract

Several methods for creatinine have been examined by the subcommittee on reference method for creatinine. These include the use of picric acid to precipitate proteins followed by alkalization, or the use of alkaline picrate after protein precipitation and adsorption to Fuller's earth. The first approach was not found to be suitable as a reference method since it was susceptible to matrix effects, fluctuations in temperature and wavelengths. The second approach was less sensitive to these effects but showed variations with different batches of Fuller's earth. The method using high performance liquid chromatography (HPLC) had poor precision, probably because endogenous compounds co-eluted either with creatinine or with the internal standard. The enzymatic method based on the determination of hydrogen peroxide had good accuracy and precision. However, the main disadvantage is that the method is sold as a kit and detailed specifications concerning all the ingredients are not available to permit independent studies using the basic components.

Key Words:

• creatinine
• enzymatic method
• HPLC
• Jaffé reaction
• secondary reference method
• subcommittee report
• Nordic Society for Clinical Chemistry