Study of glycated amino acid elimination reaction for an improved enzymatic glycated albumin measurement method

BACKGROUND: In order to improve enzymatic glycated albumin measurement, we studied the endogenous glycated amino acid elimination reaction and the new bromocresolpurple (BCP) method for albumin measurement. METHODS: In the assay, endogenous glycated amino acids are first eliminated by oxidation by ketoamine oxidase. Second, glycated albumin is hydrolyzed to glycated amino acids by proteinase digestion, and glycated amino acids are oxidized to produce hydrogen peroxide, which is quantitatively measured. Third, albumin is measured by the new BCP method. Finally, glycated albumin value is calculated as the percentage of glycated albumin in total albumin. RESULTS: Glycated amino acid concentrations in prepared total parenteral nutrition products were increased in direct proportion to storage time and temperature. The glycated amino acid elimination reaction using ketoamine oxidase may be able to eliminate more than 15 mmol/l glycated amino acids. The glycated albumin values of samples calculated from the albumin concentrations using the new BCP method accorded with those calculated with the HPLC method. Fundamental performances (linearity, dilution test, analytical recovery, within-run and between-run CVs, interference study) of the present method were good. Detection of glycated albumin by the present method was significantly correlated with detection of glycated albumin by the high-performance liquid chromatography method (r(p) = 0.995). CONCLUSIONS: This new improved method is free of interference by endogenous glycated amino acids and is unaffected by albumin concentration, and enables more accurate analysis of glycated albumin.