title: Effects of various methods of preservation on the stability of uric acid in frozen canine urine.
abstract: OBJECTIVE
  To evaluate the effects of dilution and alkalinization, separately and together, on the stability of uric acid in canine urine stored at -20 C.
  
  
  METHODS
  Prospective-controlled study.
  
  
  METHODS
  5 dogs with confirmed ammonium urate uroliths, 6 Beagles, and 6 mixed-breed dogs.
  
  
  METHODS
  Dogs were fed a 31.4% protein (dry weight), meat-based diet for 21 days, and urine samples were collected on day 22. Urine samples were preserved, using combinations of dilution and alkalinization, and divided into 1-ml aliquots for storage at -20 C for 1 to 12 weeks. Urine uric acid concentrations were measured, using high-performance liquid chromatography, on day of collection (baseline), and after 1, 2, 4, 8, and 12 weeks.
  
  
  RESULTS
  Alkalinization did not have a significant effect on reproducibility of measurements of uric acid concentrations in urine; however, dilution did have a significant effect. Compared with baseline, uric acid concentrations in urine samples collected from dogs with ammonium urate uroliths and Beagles and diluted 1:10 or 1:20 with deionized water were not different after storage for 1 to 12 weeks. Uric acid concentrations in urine samples collected from mixed-breed dogs did not differ from baseline values during the 12-week storage period whether samples were undiluted or were diluted 1:10 or 1:20 with deionized water.
  
  
  CONCLUSIONS
  Measurements of uric acid concentration are most reproducible in canine urine samples stored at -20 C for 1 to 12 weeks when samples are diluted 1:20 with deionized water.
  
  
  CONCLUSIONS
  To ensure reproducibility of measurements of uric acid concentration in urine samples collected from dogs affected with urate uroliths, urine should be diluted 1:20 with deionized water. Alkalinization is not necessary, and is not recommended because of the additional step in processing and its potential to interfere with measurement of other urinary analytes.
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Bartges
authors.forename: C A
authors.initials: CA
authors.lastname: Osborne
authors.forename: L J
authors.initials: LJ
authors.lastname: Felice
authors.forename: T F
authors.initials: TF
authors.lastname: Fletcher
authors.forename: J P
authors.initials: JP
authors.lastname: Lulich
authors.forename: M
authors.initials: M
authors.lastname: Chen
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000662:veterinary; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D004283:Dog Diseases / Q000652:urine; D004285:Dogs / Q000652:urine*; D011446:Prospective Studies; D015203:Reproducibility of Results; D013696:Temperature; D013997:Time Factors; D014527:Uric Acid / Q000652:urine*; D014545:Urinary Calculi / Q000652:urine / Q000662:veterinary
chemical_list: D014527:Uric Acid