US Patent 7871789 Method for assaying glycated albumin

An albumin denaturing agent for digesting an albumin by a protease efficiently is provided. The albumin denaturing agent contains quaternary ammonium having a hydrocarbon group with a carbon number of 12 or more, or a salt of the quaternary ammonium. The albumin in a sample is digested by the protease in the presence of the albumin denaturing agent, a glycated part of the thus obtained albumin digestion product and a FAOD effect a reaction, and a redox reaction between the glycated part and the FAOD is measured, thereby determining a ratio (GA (%)) of the glycated albumin of the glycated albumin with respect to the albumin.