Serum cystatin C level as a potentially good marker for impaired kidney function

Objectives: To evaluate the diagnostic significance of serum cystatin C levels in clinical practice. Design and methods: Serum 99mTc-DTPA clearance was compared with serum cystatin C, creatinine, β2-microglobulin levels and creatinine clearance in a group of patients aged 42.61 ± 7.55 years with glomerular filtration rates of 10–60 mL/min/1.73 m2 (n = 52) and healthy controls aged 43.90 ± 12.06 years (n = 52). Results: No effect of sex on serum cystatin C levels was observed, but average levels increased with age. No significant difference was evident between the mean cystatin C levels of three blood samples taken at 1 month intervals from healthy subjects. Reference clearance was correlated with creatinine clearance (r = 0.957), cystatin C (r = 0.828), β2-microglobulin (r = 0.767) and creatinine (r = 0.682). 60 mL/min/1.73 m2 was chosen as the borderline for receiver-operating characteristics analysis. The values for the cut-off point, sensitivity, specificity and the area under curve were determined for cystatin C as 1.36 mg/L, 98%, 99% and 0.99 ± 00.1, respectively; for creatinine, the values were 103 μmol/L, 80%, 100% and 0.97 ± 0.01, respectively, and for β2-microglobulin, the values were 2.51 mg/L, 86%, 92% and 0.94 ± 0.02, respectively. Conclusion: Serum cystatin C level can be used as a marker for renal damage.