title: Impact of creatinine production on the agreement between glomerular filtration rate estimates using cystatin C-derived, and 4- and 6-variable Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations.
abstract: BACKGROUND
  It has recently been reported that patient selection has a strong impact on the agreement between glomerular filtration rate (GFR) estimates from serum cystatin C and creatinine. The aim of our study was to evaluate the effect of creatinine production rate (CPR) on this subject.
  
  
  METHODS
  GFR was estimated from serum cystatin C and from creatinine using the 4- and 6-variable Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations in 50 healthy subjects, 43 patients with renal failure, 794 kidney and 104 liver transplant recipients, 61 patients with heart failure, 59 patients with biliary obstruction, and 113 critically ill patients.
  
  
  RESULTS
  In the 295 patients with impaired CPR (< 900 mg/24 h/1.73 m(2)), discordances of more than 40% between GFR(MDRD4) and GFR(cystatinC) were observed in 38% of cases, between GFR(MDRD6) and GFR(cystatinC) in 22%, and between GFR(CKD-EPI) and GFR(cystatinC) in 27% (in all cases due to GFR overestimation from creatinine). In the 929 patients with maintained CPR (> 900 mg/24 h/1.73 m(2)), greater discordances than 40% between GFR(MDRD4) and GFR(cystatinC) were observed in 8% of cases, between GFR(MDRD6) and GFR(cystatinC) in 9%, and between GFR(CKD-EPI) and GFR(cystatinC) in 7% (in the major part of cases due to GFR overestimation from cystatin C).
  
  
  CONCLUSIONS
  The main source of differences of more than 40% between GFR estimates from serum creatinine and cystatin C is a GFR overestimation in patients with low CPR and GFR underestimation in patients with high CPR by the creatinine-derived equations.
authors: Unidad Monitorización Fármacos, Laboratorio Central, Hospital Clínico Universitario, Instituto de Investigación Sanitaria (IDIS), 15706 Santiago de Compostela, Spain.
authors: Esperanza F
authors: EF
authors: Hermida-Cadahia
authors: Natalia
authors: N
authors: Lampon
authors: J Carlos
authors: JC
authors: Tutor
mesh_terms: D016022:Case-Control Studies; D003404:Creatinine / Q000378:metabolism*; D055316:Cystatin C / Q000378:metabolism*; D004032:Diet; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000178:diet therapy* / Q000503:physiopathology; D007676:Kidney Failure, Chronic / Q000178:diet therapy* / Q000453:epidemiology / Q000503:physiopathology
chemical_list: D055316:Cystatin C; D003404:Creatinine