Serum cystatin C concentration as a marker of glomerular filtration rate in patients with various renal diseases.

Objective: The present study was undertaken to evaluate clinical application of serum cystatin C as a new marker of glomerular filtration rate (GFR) in patients with various renal diseases.
Patients and Methods: A total of 140 patients were enrolled in the study. We measured the serum cystatin C levels and compared them with creatinine clearance (Ccr) and inulin clearance (Cin) as an indicator of GFR.
Results: There was a significant positive correlation between serum cystatin C and creatinine levels (r=0.928). Serum cystatin C was inversely correlated with creatinine clearance. Moreover, the reciprocal serum cystatin C level was positively correlated with Cin (r=0.882). The receiver-operating characteristic curve of serum cystatin C and creatinine demonstrated that the diagnostic accuracy of the serum cystatin C level is superior to that of creatinine in identifying individuals with reduced GFR.
Conclusion: These results indicated that measurement of serum cystatin C is useful to estimate GFR, and in particular, to detect a mild reduction of GFR in patients with renal diseases.