title: Cystatin C is not more sensitive than creatinine for detecting early renal impairment in patients with diabetes.
abstract: This study evaluated serum cystatin C as a potential new marker of glomerular filtration rate (GFR) in 49 patients who had steady-state diabetes with early renal impairment. We determined the correlation between GFR measured by chromium 51-labeled EDTA and levels of serum cystatin C, serum creatinine, serum beta(2)-microglobulin, endogenous creatinine clearance, and Cockcroft formula. Sensitivity and specificity for the diagnosis of renal failure, defined as a GFR less than either 80 or 60 mL/min/1.73 m(2), were calculated by receiver operating characteristic (ROC) curves for creatinine, cystatin C, and beta(2)-microglobulin. Finally, we compared mean values of these three serum parameters in patients grouped according to GFR using the two definitions of renal failure. Correlation coefficients with GFR were -0.77 for serum creatinine level, -0.65 for serum cystatin C level, -0.71 for serum beta(2)-microglobulin level, +0.56 for endogenous creatinine clearance, and +0.69 for Cockcroft formula (all P < 0.001). With a cutoff value of 60 mL/min/1.73 m(2), areas under the ROC curve were 0.972 for beta(2)-microglobulin, 0.925 for cystatin C, and 0.916 for creatinine levels. With a cutoff value of 80 mL/min/1.73 m(2), these were 0.838 for beta(2)-microglobulin, 0.780 for cystatin C, and 0.905 for creatinine levels (P = not significant between parameters). These results were not altered after the exclusion of patients (n = 8) with a serum creatinine level greater than 1.41 mg/dL. When patients were classified into three groups according to GFR (group 1, >80 mL/min/1.73 m(2); group 2, 60 to 80 mL/min/1.73 m(2); group 3, <60 mL/min/1.73 m(2)), mean values of serum parameters in the three groups were statistically different (P < 0.0001) except between groups 1 and 2 for cystatin C and beta(2)-microglobulin. With patients classified into two groups (GFR > or < 80 mL/min/1.73 m(2)), mean values for each parameter were statistically different (P < 0.001). Sensitivity, specificity, and positive and negative predictive values for serum creatinine and serum cystatin C levels were very close for both definitions of renal failure. Serum cystatin C is not better than serum creatinine or serum beta(2)-microglobulin levels for estimating GFR in patients with steady-state diabetes using ROC curves or other validation tests.
authors.affiliation: Laboratoire Central and Centre d'Investigation Clinique, Hôpital Sainte Marguerite.
authors.forename: C
authors.initials: C
authors.lastname: Oddoze
authors.forename: S
authors.initials: S
authors.lastname: Morange
authors.forename: H
authors.initials: H
authors.lastname: Portugal
authors.forename: Y
authors.initials: Y
authors.lastname: Berland
authors.forename: B
authors.initials: B
authors.lastname: Dussol
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D003922:Diabetes Mellitus, Type 1 / Q000150:complications*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D003928:Diabetic Nephropathies / Q000097:blood / Q000175:diagnosis* / Q000209:etiology; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012680:Sensitivity and Specificity; D001613:beta 2-Microglobulin / Q000097:blood
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D001613:beta 2-Microglobulin; D003404:Creatinine