title: Chronic kidney disease stage in renal transplantation classification using cystatin C and creatinine-based equations.
abstract: BACKGROUND
  Current clinical guidelines recommend that renal transplant recipients (RTRs) be classified into chronic kidney disease (CKD) stage using a creatinine-based estimate of glomerular filtration rate (GFR). However, creatinine-based equations are inaccurate in RTRs leading to frequent CKD stage misclassification. It is not known whether the classification of CKD stage would be improved using a cystatin C-based estimate of GFR.
  
  
  METHODS
  We measured (99m)Tc-DTPA GFR, cystatin C and creatinine in 198 stable RTRs. GFR was estimated using cystatin C-based equations (Filler, Le Bricon and Rule) and four creatinine-based equations. We determined the proportion, overall and by CKD stage, that were classified correctly by each equation as compared to the (99m)Tc-DTPA GFR.
  
  
  RESULTS
  The Filler equation correctly classified 76% of patients compared to only 65% with the abbreviated modification of diet in renal disease (MDRD) equation and 69% with the Cockcroft-Gault equation. In CKD stages two and four, the Filler equation correctly classified 77% and 60% of patients whereas the abbreviated MDRD equation correctly classified 46% and 93% of patients. The area under the curve by receiver operating curve analysis for overall stage classification was uniformly poor for all equations (0.52-0.56).
  
  
  CONCLUSIONS
  The cystatin C-based Filler and Le Bricon GFR estimates classified slightly more patients into the correct CKD stage than the standard creatinine-based equations in stable RTRs although the overall diagnostic accuracies were similar. The differences are modest and prospective studies will be needed to determine if the adoption of these equations for classification would lead to improved recognition of CKD complications or patient care.
authors.affiliation: Division of Nephrology, Queen's University, Kingston, Ontario, Canada.
authors.forename: Christine
authors.initials: C
authors.lastname: White
authors.forename: Ayub
authors.initials: A
authors.lastname: Akbari
authors.forename: Naser
authors.initials: N
authors.lastname: Hussain
authors.forename: Laurent
authors.initials: L
authors.lastname: Dinh
authors.forename: Guido
authors.initials: G
authors.lastname: Filler
authors.forename: Nathalie
authors.initials: N
authors.lastname: Lepage
authors.forename: Greg A
authors.initials: GA
authors.lastname: Knoll
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D003404:Creatinine / Q000097:blood / Q000378:metabolism*; D055316:Cystatin C; D015891:Cystatins / Q000378:metabolism*; D018450:Disease Progression; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000145:classification* / Q000175:diagnosis*; D016030:Kidney Transplantation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D015203:Reproducibility of Results; D016284:Technetium Tc 99m Pentetate / Q000494:pharmacology; D016896:Treatment Outcome
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D015891:Cystatins; D003404:Creatinine; D016284:Technetium Tc 99m Pentetate