title: The inaccuracy of cystatin C and creatinine-based equations in predicting GFR in orthotopic liver transplant recipients.
abstract: BACKGROUND
  As survival with an orthotopic liver transplant (OLT) improves, the incidence of chronic kidney disease in OLT recipients increases. Measurement of kidney function using creatinine-based estimates is often inaccurate, while cystatin C may overcome the biases that effect creatinine. The aim of this study was to assess the accuracy of creatinine- and cystatin C-based equations to estimate kidney function in long-term OLT recipients.
  
  
  METHODS
  This was a cross-sectional study performed on OLT recipients within a single liver transplant centre where creatinine (n = 41) and cystatin C (n = 30) were measured and glomerular filtration rate (GFR) estimated using the Modification of Diet and Renal Disease (MDRD), Cockcroft-Gault (CG), Hoek, Larsson, Filler and Le Bricon equations. Comparison was made with the nuclear GFR (nGFR) (n = 41) measured through 51-Cr EDTA clearance.
  
  
  RESULTS
  The mean age of recipients was 56 +/- 13 years, and they were 6.5 +/- 4.7 years post-OLT. Fifty-six percent of recipients had a nGFR < or =60 mL/min/1.73 m(2). nGFR correlated significantly with all predictive equations (P < 0.001). The MDRD, CG and Le Bricon equations had the smallest degree of bias (-7.6, -7.3 and 3.4 mL/min/1.73 m(2), respectively), with 22%, 22% and 27% of estimates, respectively, being within 10% of nGFR measurements. In OLT recipients with nGFR < or =60 mL/min/1.73 m(2), the degree of bias of both the creatinine-base MDRD and cystatin-based Hoek equations was within 2 mL/min/1.73 m(2) difference between the measured and estimated GFR, but 41% and 36% of estimates were within 10% of the nGFR measurement.
  
  
  CONCLUSIONS
  Therefore, the degree of inaccuracy in cystatin C- and creatinine-based predictive equations brings into question their clinical utility in OLT recipients. We have no evidence that cystatin C is superior to creatinine in this population.
authors.affiliation: University of Western Australia, Australia. neil.boudville@uwa.edu.au
authors.forename: Neil
authors.initials: N
authors.lastname: Boudville
authors.forename: Muna
authors.initials: M
authors.lastname: Salama
authors.forename: Gary P
authors.initials: GP
authors.lastname: Jeffrey
authors.forename: Paolo
authors.initials: P
authors.lastname: Ferrari
mesh_terms: D000328:Adult; D000368:Aged; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007677:Kidney Function Tests / Q000379:methods / Q000706:statistics & numerical data; D016031:Liver Transplantation / Q000009:adverse effects / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D051436:Renal Insufficiency, Chronic / Q000209:etiology / Q000503:physiopathology
chemical_list: C525030:CST3 protein, human; D055316:Cystatin C; D003404:Creatinine