Serum cystatin C may predict the early prognostic stages of patients with type 2 diabetic nephropathy

We determined the relationship between levels of serum cystatin C or serum creatinine (s-Cr) and prognostic stages of type 2 diabetic nephropathy. Serum samples from 174 patients with type 2 diabetes were obtained from Juntendo University Hospital, Tokyo and Juntendo Urayasu Hospital, Chiba, Japan. They were classified into four groups according to the Report of the Ministry of Health and Welfare of Japan as follows: Stage I (normoalbuminuric stage), Stage II (microalburninuric stage), Stage IIIA (macroalbuminuric stage without renal dysfunction), Stage IIIB (macroalbuminuric stage with renal dysfunction), and Stage IV (renal failure stage). Among these patients, 68 were Stage I, 29 Stage II, 32 Stage IIIA, 17 Stage IIIB, and 28 Stage IV. The levels of serum cystatin C were measured using the Dade Behring Cystatin C assay with automated Dade Behring Nephelometer II (BNII) (Dade Behring Marburg GmbH, Germany). The mean levels of serum cystatin C in Stage IIIA were significantly higher than those in Stage I or II (P<0.00001, P<0.0005, respectively). The mean levels of serum cystatin C in Stage IIIB and Stage IV were also significantly higher than those in Stage I (P<0.00001). However, the mean levels of serum creatinine (s-Cr) in Stage IIIA were not significantly higher than those in Stage I or II. The levels of s-Cr in Stage IIIB and Stage IV were significantly higher than those in Stage I (P<0.00001). Receiver operating characteristic (ROC) plots demonstrated that the area under the curve (AUC) of cystatin C (0.76) was greater than that of s-Cr (0.66). As an early prognostic marker of type 2 diabetic nephropathy, serum cystatin C was better than s-Cr in terms of sensitivity and specificity. It appears that the levels of serum cystatin C may predict early prognostic stages of patients with type 2 diabetic nephropathy.