title: Serum cystatin C-based formulas for prediction of glomerular filtration rate in patients with chronic kidney disease.
abstract: BACKGROUND
  The present study, involving a large group of patients with chronic kidney disease (CKD), compares different serum cystatin C-based equations for prediction of the glomerular filtration rate (GFR).
  
  
  METHODS
  A total of 592 adult patients with CKD were enrolled in the study. Serum cystatin C was determined in each patient by an immunonephelometric method. Their GFR was estimated using 5 equations based on serum cystatin C: (1) the Larsson formula, (2) the Hoek formula, (3) the Grubb formula, (4) the simple cystatin C formula (GFR = 100/cystatin C) and (5) our own cystatin C formula (GFR = 90.63 x cystatin C(-1.192)). The actual GFR was measured using (51)CrEDTA clearance.
  
  
  RESULTS
  The mean (51)CrEDTA clearance was 47 ml/min/1.73 m(2); the mean serum cystatin C concentration was 2.68 mg/l. Receiver operating characteristic curve analysis (cutoff for GFR: 60 ml/min/ 1.73 m(2)) showed no difference between the cystatin C formulas with regard to diagnostic accuracy. All equations underestimated the measured GFR except the simple cystatin C formula, which slightly overestimated the measured GFR. All equations lacked precision. The ability to correctly estimate the patient's GFR was high for all equations (87.3-91.9%), except for the Larsson formula, with which 29.2% of subjects were misclassified.
  
  
  CONCLUSIONS
  Our results indicate that all serum cystatin C-based equations, excluding the Larsson formula, are reliable markers of the GFR in patients with CKD, and for daily clinical practice the simplest formula (100/cystatin C) could be accurate enough for GFR estimation.
authors.affiliation: Department of Nephrology, Clinic of Internal Medicine, University Medical Center Maribor, Maribor, Slovenia.
authors.forename: Radovan
authors.initials: R
authors.lastname: Hojs
authors.forename: Sebastjan
authors.initials: S
authors.lastname: Bevc
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; D055316:Cystatin C / Q000097:blood*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017524:Slovenia / Q000453:epidemiology; D055815:Young Adult
chemical_list: D055316:Cystatin C