title: Glomerular filtration rate estimation by use of a correction formula for slope-intercept plasma iohexol clearance in cats.
abstract: OBJECTIVE
  To develop a formula for correcting slope-intercept plasma iohexol clearance in cats and to compare clearance of total iohexol (TIox), endo-iohexol (EnIox), and exo-iohexol (ExIox).
  
  
  METHODS
  20 client-owned, healthy adult and geriatric cats.
  
  
  METHODS
  Plasma clearance of TIox was determined via multisample and slope-intercept methods. A multisample method was used to determine clearance for EnIox and ExIox. A second-order polynomial correction factor was derived by performing regression analysis of the multisample data with the slope-intercept data and forcing the regression line though the origin. Clearance corrected by use of the derived formula was compared with clearance corrected by use of Brochner-Mortensen human and Heiene canine formulae. Statistical testing was applied, and Bland-Altman plots were created to assess the degree of agreement between TIox, EnIox, and ExIox clearance.
  
  
  RESULTS
  Mean ± SD iohexol clearance estimated via multisample and corrected slope-intercept methods was 2.16 ± 0.35 mL/min/kg and 2.14 ± 0.34 mL/min/kg, respectively. The derived feline correction formula was Cl(corrected) = (1.036 × Cl(uncorrected)) - (0.062 × Cl(uncorrected)(2)), in which Cl represents clearance. Results obtained by use of the 2 methods were in excellent agreement. Clearance corrected by use of the Heiene formula had a linear relationship with clearance corrected by use of the feline formula; however, the relationship of the feline formula with the Brochner-Mortensen formula was nonlinear. Agreement between TIox, EnIox, and ExIox clearance was excellent.
  
  
  CONCLUSIONS
  The derived feline correction formula applied to slope-intercept plasma iohexol clearance accurately predicted multisample clearance in cats. Use of this technique offers an important advantage by reducing stress to cats associated with repeated blood sample collection and decreasing the costs of analysis.
authors: Royal Veterinary College, University of London, London NW1 0TU, England. natalie.finch@bristol.ac.uk
authors: Natalie C
authors: NC
authors: Finch
authors: Harriet M
authors: HM
authors: Syme
authors: Jonathan
authors: J
authors: Elliott
authors: Adrien M
authors: AM
authors: Peters
authors: Robert
authors: R
authors: Gerritsen
authors: Siska
authors: S
authors: Croubels
authors: Reidun
authors: R
authors: Heiene
mesh_terms: D000818:Animals; D002415:Cats / Q000378:metabolism*; D003287:Contrast Media / Q000737:chemistry / Q000493:pharmacokinetics*; D003404:Creatinine / Q000097:blood / Q000493:pharmacokinetics*; D005919:Glomerular Filtration Rate / Q000662:veterinary; D007472:Iohexol / Q000737:chemistry / Q000493:pharmacokinetics*; D007677:Kidney Function Tests / Q000379:methods* / Q000662:veterinary; D008657:Metabolic Clearance Rate; D012044:Regression Analysis
chemical_list: D003287:Contrast Media; D007472:Iohexol; D003404:Creatinine