Serum cystatin C reliably detects renal dysfunction in patients with various renal diseases

A clinical investigation was conducted to clarify the reliability and efficacy of serum cystatin C measurement for estimation of the glomerular filtration rate (GFR). Two hundred twelve patients with various renal diseases enrolled in the study. All patients were evaluated for 24-hour creatinine clearance (24 h C-Cr) and the standard sodium thiosulfate clearance test (C-Thio) within a week of blood sample collection. Serum cystatin C concentration was determined by a particle-enhanced immunonephelometry method. C-Thio and 1/cystatin C, 24 h C-Cr, 1/beta(2)-microglobulin and 1/creatinine were well correlated. The correlation coefficients for C-Thio obtained by 24 h C-Cr and 1/cystatin C were comparable to each other (0.701 vs. 0.679). Receiver-operated characteristic (ROC) analysis revealed that 24 h C-Cr showed the highest area under the curve when C-Thio = 60 ml/min or C-Thio = 100 ml/min were applied as the discrimination point. However, the ROC value obtained by cystatin C was slightly greater than 24 h C-Cr when C-Thio = 80 ml/min was used as the discrimination point. Patient age, gender, glucose tolerance, presence of proteinuria, systemic inflammation, lupus, or systemic use of steroids did not interfere in the relationship between C-Thio and 1/cystatin C. In conclusion, serum cystatin C measurement is an excellent diagnostic test for detecting patients with subclinical renal dysfunction. Copyright (C) 2002 S. Karger AG, Basel.