title: Comparison of cystatin C versus creatinine for detection of mild renal failure.
abstract: OBJECTIVE
  Serum cystatin C (SCyst) has been proposed as a novel indicator of GFR.
  
  
  METHODS
  We compared SCyst, serum creatinine (SCreat) and Cockcroft and Gault's estimated clearance (CCG) using inulin clearance (Cin) as gold standard. 140 subjects (161 samples; aged 39 +/- 14; male/female: 79/82) underwent simultaneous measurements.
  
  
  RESULTS
  A highly significant correlation r = 0.70, 0.74, 0.77 (p < 0.0001) was found between 1/SCyst, 1/SCreat, C(CG), respectively, and Cin. Receiver-operating characteristic (ROC) analysis was performed on SCyst, SCreat and C(CG) using a Cin cut-off of 90 ml/min/1.73 m2. Best fit for SCyst was 0.90 mg/l with a sensitivity of 75% and a specificity of 92%. The area under the ROC curve was not significantly greater for SCreat or C(CG) than for SCyst (p = 0.91,0.13, respectively). When relationship between Cin and SCyst was plotted, experimental data deviated from the theoretical model, suggesting that cystatin C may not be solely filtered. Additional patients were selected in our database on the basis of discordant SCreat/GFR values: false negative (n = 46 samples, 31 patients) and false positive (n = 16 samples, 9 patients). In this highly selected subgroup, 38% of the SCreat false positive had normal SCyst values and 48% of the false negative SCreat had abnormally elevated SCyst.
  
  
  CONCLUSIONS
  This study suggests that SCyst is not more sensitive than SCreat or C(CG) for detecting renal failure, however, SCyst could be proposed as a confirmatory test for patients with elevated SCreat.
authors: Service de Néphrologie et d'Hémodialyse, Hôpitaux Universitaires, Strasbourg, France.
authors: F
authors: F
authors: Chantrel
authors: A
authors: A
authors: Agin
authors: M
authors: M
authors: Offner
authors: C
authors: C
authors: Koehl
authors: B
authors: B
authors: Moulin
authors: T
authors: T
authors: Hannedouche
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood*; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C; D015891:Cystatins / Q000097:blood*; D015853:Cysteine Proteinase Inhibitors / Q000097:blood*; D005260:Female; D006801:Humans; D007444:Inulin; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D051437:Renal Insufficiency / Q000175:diagnosis*
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D007444:Inulin; D003404:Creatinine