Value of serous and urinary cystatin C for the diagnosis of early kidney injury in diabetic patients

Abstract

Objective To detect the changes of serous and urinary cystatin C concentration compared with clinic general renal function indexs, and to evaluate the value of cystatin C for the diagnosis of early kidney injuryin diabetic patients. Methods Eighty-two patients preliminayily diagnosed as diabetes were divided into three groups according to the degree of 24 hours urinary microalbumin quantitation. Twenty-eight healthy volunteers were selected as control. Serous cystatin C, serous creatinine, urinary cystatin C, urinary N-acetyl-β-d-glucosaminidase (NAG), urinary α1-microglobulin(α1-MG), 99mTc-DTPA glomerular filtration rate (99mTc-GFR) and creatinine clearance rate resulted from Cockcroft-Gault equation (Ccr-GFR) were measured and statistical analysis was performed. Results The concentration and abnormal rate of urinary cystatin C increased before those of serous cystatin C were higher. Correlation between serous cystatin C and 99mTc-GFB was superior to that between Ccr-GFR and 99mTc-GFR (r=-0.88 vs r=0.84, P 0.05). Likelihood ratio (LR) of urinary cystatin C was superior to that of serous cystatin C. Conclusion Serous and urinary cystatin C concentration can diagnose early diabetic kidney injury, which can earlier reflect impairment of kidney tubule than that of glomerulum. Key words: Cysteine proteinase inhibitors; Diabetes; Kidney function tests; ROC curve; Kidney tubules