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/beta2-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.