title: Increased urinary cystatin C reflects structural and functional renal tubular impairment independent of glomerular filtration rate.
abstract: OBJECTIVE
  The ratio of the urinary mass concentrations of cystatin C and creatinine (UcysC/Ucrea)>/=11.3 mg/mmol has recently been proposed as an accurate marker for the detection of GFR</=60 mL/min/1.73 m(2).
  
  
  METHODS
  We prospectively evaluated the diagnostic performance of UcysC/Ucrea>/=11.3 mg/mmol and factors associated with increased UcysC/Ucrea in 72 children and adults with a wide variety of renal disorders. UcysC/Ucrea was calculated, and GFR wad estimated from serum creatinine and cystatin C by equations.
  
  
  RESULTS
  UcysC/Ucrea>/=11.3 mg/mmol had a low diagnostic value to detect GFR values</=60 mL/min/1.73 m(2) estimated by creatinine or cystatin-C-based equations with sensitivities of 72% and 63%, and specificities of 42% and 34%. ROC curves for UcysC/Ucrea to detect GFR</=60 mL/min/1.73 m(2) confirmed this with AUCs of 0.59 for creatinine and 0.57 for cystatin-C-based equations. Multivariate analysis identified tubular proteinuria, tubulointerstitial disease and heavy proteinuria, but not GFR</=60 mL/min/1.73 m(2), as factors independently associated with increased UcysC/Ucrea.
  
  
  CONCLUSIONS
  UcysC/Ucrea>/=11.3 mg/mmol is not an accurate marker to detect GFR</=60 mL/min/1.73 m(2), but reflects tubular dysfunction and proteinuria due to heavy proteinuria and tubulointerstitial disease.
authors.affiliation: Department of Nephrology, University Hospital, Essen, University Duisburg-Essen, Germany. stefan.herget-rosenthal@uni-due.de
authors.forename: Stefan
authors.initials: S
authors.lastname: Herget-Rosenthal
authors.forename: Joanna A E
authors.initials: JA
authors.lastname: van Wijk
authors.forename: Martina
authors.initials: M
authors.lastname: Bröcker-Preuss
authors.forename: Arend
authors.initials: A
authors.lastname: Bökenkamp
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000652:urine; D055316:Cystatin C; D015891:Cystatins / Q000652:urine*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000503:physiopathology / Q000652:urine*; D007684:Kidney Tubules / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D012372:ROC Curve
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D003404:Creatinine