Serum cystatin C in diabetic patients. Not only an indicator for renal dysfunction in patients with overt nephropathy but also a predictor for cardiovascular events in patients without nephropathy.

Serum cystatin C (CysC) has been proposed as a potentially superior marker for the evaluation of renal function because it was more sensitive and accurate for the estimation of glomerular filtration rate (GFR) than other markers. We evaluated the clinical usefulness of CysC in diabetic nephropathy. The study was performed on 414 Japanese diabetic patients. We compared serum CysC levels with serum creatinine levels, urinary concentrations of albumin, transferrin and type IV collagen, and creatinine clearance (Ccr). Then, the correlation between serum CysC levels and high-sensitivity C-reactive protein (H-CRP) levels were examined. When the patients were classified by renal function, 19% of the patients were free from nephropathy, 49% had microalbuminuria, 28% had persistent proteinuria, and 4% had end stage renal disease. The serum CysC levels increased with the progression of nephropathy, and significantly higher in overt nephropathy, but not significant in early nephropathy. Serum CysC levels were well-correlated with H-CRP levels in the patients without nephropathy. These results indicate that serum CysC would be practical for the evaluation of renal function in diabetic patients with overt nephropathy but not early nephropathy and might be related with a risk for cardiovascular events in patients without nephropathy.