title: Simplified methods for estimating glomerular filtration rate in cats and for detection of cats with low or borderline glomerular filtration rate.
abstract: OBJECTIVE
  Diagnosis of early feline chronic kidney disease (CKD) is challenging. Glomerular filtration rate (GFR) is the best overall indicator of kidney function, but multisample plasma clearance methods to determine GFR are labour intensive, time consuming and stressful for feline patients. This study aimed to develop simplified methods to detect decreased GFR in cats.
  
  
  METHODS
  Data from a nine-sample combined plasma exogenous creatinine-iohexol clearance test of 73 cats were used. Limited sampling strategies were developed by comparing all sampling time combinations with the complete nine sampling times set and selecting the best sampling time combinations based on maximum relative error. By regression analysis, the ability of routine blood (serum creatinine, serum urea) and urine (urine specific gravity, urinary protein:creatinine ratio) variables to predict GFR or identify cats with low or borderline GFR was examined. Cut-off clearance marker concentrations to predict low or borderline GFR was determined at three time points after marker injection. All procedures were analysed for three clearance markers (exo-iohexol, creatinine, endo-iohexol).
  
  
  RESULTS
  For reliable estimation of GFR, at least three blood samples for clinical purposes and five blood samples for research purposes are required. Regression formulae based on routine variables did not reliably predict GFR, but accurately identified cats with low (sensitivity 96.5-98.2%; specificity 60-91.3%) or borderline (sensitivity 91.1-96%; specificity 76.5-81.8%) GFR. Clearance marker concentrations exceeding given marker cut-off concentrations also identified cats with low or borderline GFR with high sensitivities and specificities.
  
  
  CONCLUSIONS
  These simplified methods will facilitate the detection of early kidney dysfunction in cats. Early diagnosis allows timely therapeutic intervention, and future studies must reveal whether this improves the long-term outcome of cats with CKD.
authors.affiliation: Department of Medicine and Clinical Biology of Small Animals, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium dominique.paepe@ugent.be.
authors.forename: Dominique
authors.initials: D
authors.lastname: Paepe
authors.affiliation: University of Toulouse, INP, National Veterinary School of Toulouse, Clinical Research Unit, Toulouse, France.
authors.forename: Hervé P
authors.initials: HP
authors.lastname: Lefebvre
authors.affiliation: INRA, UMR 1331, Toxalim, National Veterinary School of Toulouse, 23 Chemin des Capelles, Toulouse, France.
authors.forename: Didier
authors.initials: D
authors.lastname: Concordet
authors.affiliation: Department of Medicine and Clinical Biology of Small Animals, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium Current address: Royal Canin SAS, BP 4 - 650, Avenue de la Petite Camargue, 30470, Aimargues, France.
authors.forename: Ingrid
authors.initials: I
authors.lastname: van Hoek
authors.affiliation: Department of Pharmacology, Toxicology and Biochemistry, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Siska
authors.initials: S
authors.lastname: Croubels
authors.affiliation: Department of Medicine and Clinical Biology of Small Animals, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Daminet
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000652:urine; D001806:Blood Urea Nitrogen; D002371:Cat Diseases / Q000175:diagnosis* / Q000652:urine*; D002415:Cats; D003404:Creatinine / Q000652:urine; D005919:Glomerular Filtration Rate / Q000662:veterinary*; D007677:Kidney Function Tests / Q000662:veterinary; D012044:Regression Analysis; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis / Q000662:veterinary*; D013048:Specimen Handling / Q000662:veterinary
chemical_list: D015415:Biomarkers; D003404:Creatinine