Serum cystatin C as an endogenous marker of renal function in patients with mild to moderate impairment of kidney function

Abstract

Background. Estimation of the glomerular filtration rate (GFR) is essential for the evaluation of patients with chronic kidney disease (CKD). Recently, serum cystatin C was proposed as a new endogenous marker of GFR and in our study its diagnostic accuracy was compared with that of other markers of GFR. Methods. In this study, 164 patients with CKD stages 2–3 (GFR 30–89 ml/min/1.73 m²), who had performed ⁵¹Cr-labelled ethylenediaminetetra-acetic acid clearance, were enrolled. In each patient, serum creatinine and serum cystatin C were determined. Creatinine clearance was calculated using the Cockcroft–Gault (C&G) and the modification of diet in renal disease (MDRD) formulas. Results. The mean ⁵¹CrEDTA clearance was 57 ml/min/1.73 m², the mean serum creatinine 149 μmol/l and the mean serum cystatin C 1.74 mg/l. We found significant correlation between ⁵¹CrEDTA clearance and serum creatinine (R = −0.666), serum cystatin C (R = −0.792), reciprocal of serum creatinine (R = 0.628), reciprocal of serum cystatin C (R = 0.753) and calculated creatinine clearance from the formulas C&G (R = 0.515) and MDRD formulas (R = 0.716). The receiver operating characteristic (ROC) curve analysis (cut-off for GFR 60 ml/min/1.73 m²) showed that serum cystatin C had a significantly higher diagnostic accuracy than serum creatinine (P = 0.04) and calculated creatinine clearance from the C&G formula (PConclusions. Our results indicate that serum cystatin C is a reliable marker of GFR in patients with mildly to moderately impaired kidney function and has a higher diagnostic accuracy than serum creatinine and calculated creatinine clearance from the C&G formula in female patients.