title: GFR estimation using standardized cystatin C in kidney transplant recipients.
abstract: BACKGROUND
  The utility of serum cystatin C (SCysC) as a filtration marker in kidney transplantation is uncertain. We took advantage of the recent validation of a reference calibrator for SCysC and of newly developed CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equations (2012) expressed for use with standardized SCysC level to reassess the performance of SCysC as a filtration marker in kidney transplant recipients.
  
  
  METHODS
  Study of diagnostic test accuracy.
  
  
  METHODS
  670 kidney transplant recipients from 3 centers undergoing glomerular filtration rate (GFR) measurements from December 2006 to November 2012.
  
  
  METHODS
  Estimated GFR (eGFR) using the 2012 SCysC-based and serum creatinine (SCr)/SCysC-based CKD-EPI equations (eGFR(cys) and eGFR(cr-cys), respectively) and the 2009 SCr-based CKD-EPI equation (eGFR(cr)), with SCysC and SCr measured at a single laboratory between April 2011 and June 2011.
  
  
  METHODS
  Measured GFR (mGFR) using urinary clearance of inulin.
  
  
  RESULTS
  Bias (the difference between mGFR and eGFR) was significantly smaller for eGFR(cys) and eGFR(cr-cys) versus eGFR(cr) (-2.82 and -0.54 vs +4.4 mL/min/1.73 m(2), respectively; P < 0.001). Precision (standard deviation of the mean bias) also was better for eGFR(cys) and eGFR(cr-cys) versus eGFR(cr) (12 and 11 vs 13 mL/min/1.73 m(2) [P < 0.001 for both comparisons]). Accuracy (percentage of GFR estimates within 30% of mGFR) was greater for eGFR(cys) and eGFR(cr-cys) versus eGFR(cr) (81% and 86% vs 75%, respectively [P = 0.004 and P < 0.001]). Net reclassification index with respect to mGFR of 30 mL/min/1.73 m(2) for eGFR(cr-cys) and eGFR(cys) versus eGFR(cr) was 18.8% [95% CI, 8.6%-28.9%] and 22.5% [95% CI, 10.2%-34.9%].
  
  
  CONCLUSIONS
  Patients were exclusively of European descent; association with transplant outcome was not evaluated.
  
  
  CONCLUSIONS
  Our data validate the use of both the newly developed SCysC-based and SCr/SCysC-based CKD-EPI equations (2012) in kidney transplant recipients. Both equations perform better than the SCr-based CKD-EPI equation (2009).
authors.affiliation: Service de Néphrologie Dialyse Transplantation rénale, CHU Hopital Nord, Saint-Etienne, France.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Masson
authors.forename: Nicolas
authors.initials: N
authors.lastname: Maillard
authors.forename: Ivan
authors.initials: I
authors.lastname: Tack
authors.forename: Lise
authors.initials: L
authors.lastname: Thibaudin
authors.forename: Laurence
authors.initials: L
authors.lastname: Dubourg
authors.forename: Pierre
authors.initials: P
authors.lastname: Delanaye
authors.forename: Etienne
authors.initials: E
authors.lastname: Cavalier
authors.forename: Christine
authors.initials: C
authors.lastname: Bonneau
authors.forename: Nassim
authors.initials: N
authors.lastname: Kamar
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Morelon
authors.forename: Olivier
authors.initials: O
authors.lastname: Moranne
authors.forename: Eric
authors.initials: E
authors.lastname: Alamartine
authors.forename: Christophe
authors.initials: C
authors.lastname: Mariat
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D016030:Kidney Transplantation; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D055815:Young Adult
chemical_list: D055316:Cystatin C