Clinical Implication of Cystatin C and β2-Microglobulin in Early Detection of Diabetic Nephropathy

BACKGROUND: Diabetic nephropathy (DN) is one of the major late complications of type 2 diabetes mellitus (T2DM). The aim of this study was to evaluate the efficiency of cystatin C (cysC) and β2-microglobulin (β2-MG) in diagnosing early DN and to identify the optimal threshold in the Chinese patients. METHODS: T2DM patients were divided into 102 non-DN subjects, 60 early DN subjects, and 38 clinical DN subjects. Blood and urine measurements were compared among the groups. Receiver-operating characteristic (ROC) curves and areas under the curve (AUC) were calculated to demonstrate the prediction values of the variables. RESULTS: Stepwise regression analysis showed that the levels of cysC and β2-MG were associated with early DN. The AUC was 0.874 for cysC and 0.792 for β2-MG. The threshold based on the ROC curve had the best diagnostic performance compared with the threshold with respect to mean + SD (standard deviation) and parallel tests. A high sensitivity of 91.67% was achieved at the cysC threshold of 0.91 mg/L with a moderate specificity of 76.47% and a sensitivity of 80.00% for the β2-MG threshold of 1.86 mg/L with a specificity of 67.65%. CONCLUSIONS: The findings suggest that the cysC threshold of 0.91 mg/L may be acceptable as a diagnostic criterion for early DN in the Chinese patients. The results also suggest that for T2DM patients the normal reference range of cysC should be set lower in favor of early DN screening.