Cystatin C as an Early Marker of Diabetic Nephropathy in Patients with Type 2 Diabetes

BACKGROUND: Serum cystatin C has been proposed as an endogenous marker of glomerular filtration rate (GFR) because it shows a correlation with the albumin to creatinine ratio (ACR) in diabetic nephropathy. The aim of this study was to examine the usefulness of cystatin C as an early marker of diabetic nephropathy. METHODS: From February 2010 to July 2010, 205 outpatients with normo- or microalbuminuria and chronic kidney disease (CKD) of stage III or less were included in this study. Various renal markers including serum cystatin C and ACR were evaluated. RESULTS: In the ROC curve analysis, cystatin C showed a performance similar to that of serum creatinine. In addition, cystatin C levels increased with increasing CKD stage I to III and from normo- to microalbuminuria and showed a positive correlation with ACR. In a comparison of renal function markers in diabetic patients according to serum cystatin C level, all markers including ACR, serum creatinine, and eGFR showed significant differences between patients with cystatin C level < 1.06 mg/L and those with cystatin C > or = 1.06 mg/L. CONCLUSIONS: Serum cystatin C is a useful marker of early renal impairment in type 2 diabetic patients because it reflects both a decrease in GFR and elevated ACR.