A research group from Kumamoto University, Japan has discovered that cysteinylated albumin (oxidized albumin) in serum can be used as an early diagnostic marker for diabetic kidney disease. Compared with urinary albumin, serum oxidized albumin not only reflects renal pathology at an earlier stage, but can also predict the progression of renal pathology by its degree of elevation. The researchers believe that it can be used as a new diagnostic marker for early diagnosis of diabetic kidney disease.