Use of serum cystatin C to detect early decline of glomerular filtration rate in type 2 diabetes

Object: The estimation of serum cystatin C and its practical use for the estimation of the glomerular filtration rate (GFR) in diabetic patients has been previously demonstrated, however, those studies did not use the chronic kidney disease GFR staging. Therefore, we performed this study in type 2 diabetic patients with the aim to examine the usefulness of serum cystatin C to detect early decline of GFR using the staging of chronic kidney disease defined by the National Kidney Foundation. Methods: A total of 102 Taiwanese type 2 diabetic patients were recruited from the Chung-Shan Medical University Hospital. Morning fasting blood and urine samples were obtained for basal metabolic parameters, serum creatinine, serum cystatin C, and albumin-creatinine ratio. GFR was determined by Cockcroft-Gault equation creatinine clearance (CG-CCr). Results: Of the 102 type 2 diabetic patients, 67, 25, and 10 had normo-, micro-, and macroalbuminuria, respectively. Serum cystatin C was superior to serum creatinine in detecting early decline of GFR. The diagnostic accuracy of serum cystatin C was better than serum creatinine for stage 1 and 2 chronic kidney disease (CG-CCr cut-off value of 90 ml/ min and 60 ml/min). Furthermore, serum cystatin C was also correlated with urine albumin excretion, which was not true with serum creatinine. Conclusions: These results suggest that serum cystatin C may be an alternative serum marker for the early identification of subjects with a slight reduction of renal function, and also it may be a marker for early glomerular dysfunction in type 2 diabetes.