title: Simple cystatin C formula compared to serum creatinine-based formulas for estimation of glomerular filtration rate in patients with mildly to moderately impaired kidney function.
abstract: BACKGROUND
  Serum cystatin C (SCC)-based formulas and the newer creatinine formula (the Chronic Kidney Disease Epidemiology Collaboration formula (CKD-EPI)) were proposed as improved glomerular filtration rate (GFR) markers. The aim of our study was to compare serum creatinine (SCr)-based and SCC-based equations against (51)Cr-EDTA clearance in patients with mildly to moderately impaired kidney function.
  
  
  METHODS
  255 adult Caucasian patients with chronic kidney disease (GFR 89-30 ml/min/1.73 m(2)) were enrolled. In each patient, (51)Cr-EDTA clearance, SCr and SCC were determined. GFR was calculated using the Cockcroft-Gault (C&G), Modification of Diet in Renal Disease (MDRD), CKD-EPI formulas and simple cystatin C formula (SCCF) (100/SCC).
  
  
  RESULTS
  The receiver-operating characteristic curve analysis (cut-off for GFR 60 ml/min/1.73 m(2)) showed that the SCCF had a higher diagnostic accuracy than C&G but not than MDRD or CKD-EPI formulas. The Bland-Altman analysis for the same cut-off value showed that creatinine formulas underestimated and SCCF overestimated the measured GFR. Analysis of ability to correctly predict a patient's GFR <60 or >60 ml/min/1.73 m(2) showed the higher ability for the SCCF compared to all creatinine-based formulas.
  
  
  CONCLUSIONS
  Our results indicate that the SCCF is a reliable marker of GFR and comparable to creatinine formulas including the CKD-EPI formula.
authors.affiliation: Department of Nephrology, Clinic of Internal Medicine, Maribor, Slovenia. sebastjanbevc @ yahoo.com
authors.forename: Sebastjan
authors.initials: S
authors.lastname: Bevc
authors.forename: Radovan
authors.initials: R
authors.lastname: Hojs
authors.forename: Robert
authors.initials: R
authors.lastname: Ekart
authors.forename: Maksimiljan
authors.initials: M
authors.lastname: Gorenjak
authors.forename: Ludvik
authors.initials: L
authors.lastname: Puklavec
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007668:Kidney / Q000473:pathology / Q000502:physiology*; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology; D007677:Kidney Function Tests / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine