Serum cystatin C as an endogenous marker of renal function in patients with mild to moderate impairment of kidney function.
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 micromol/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 (P < 0.0001), though only in female patients. No difference in diagnostic accuracy was found between serum cystatin C and creatinine clearance calculated from the MDRD formula.


CONCLUSIONS
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.
Hojs
Radovan
R
Department of Nephrology, Clinical Department of Internal Medicine, Teaching Hospital Maribor, Maribor, Slovenia. Radovan.Hojs@sb-mb.si
Bevc
Sebastjan
S
Ekart
Robert
R
Gorenjak
Maksimiljan
M
Puklavec
Ludvik
L
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002860:Chromium Radioisotopes / Q000378:metabolism; D003404:Creatinine / Q000378:metabolism; D055316:Cystatin C; D015891:Cystatins / Q000097:blood* / Q000378:metabolism; D004492:Edetic Acid / Q000737:chemistry; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis* / Q000378:metabolism; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged
C525030:CST3 protein, human; D002860:Chromium Radioisotopes; D055316:Cystatin C; D015891:Cystatins; D004492:Edetic Acid; D003404:Creatinine