title: Urinary corticoid concentrations measured by 5 different immunoassays and gas chromatography-mass spectrometry in healthy dogs and dogs with hypercortisolism at home and in the hospital.
abstract: BACKGROUND
  Determination of the urinary corticoid-to-creatinine ratio (UCCR) is an important screening test in the diagnosis of hypercortisolism (HC). However, urinary cortisol metabolites interfere with cortisol measurement in immunoassays, leading to decreased specificity. Gas chromatography-mass spectrometry (GC-MS) is considered the gold standard for steroid hormone analysis, because it provides a high level of selectivity and accuracy.
  
  
  OBJECTIVE
  To prospectively compare the UCCR of healthy dogs and dogs with HC determined by 5 different immunoassays and by GC-MS and to evaluate the influence of veterinary care on UCCR.
  
  
  METHODS
  Twenty healthy dogs; 18 dogs with HC.
  
  
  METHODS
  Urine was collected in the hospital and again after 6 days at home. Three chemiluminescence immunoassays (Access 2, Beckmann; Immulite 2000, DPC Siemens, with and without trichloromethane extraction) and 2 RIAs (Utrecht in house; Access Beckmann) were used. GC-MS analyses were performed with Agilent 6890N/5973N. Urinary corticoid concentrations were related to urinary creatinine concentrations.
  
  
  RESULTS
  Immunoassay results were significantly higher compared to GC-MS results. Evaluation of bias plots and clinical assessment made on the basis of the assay results of each dog indicated substantial disagreement among the assays. Sensitivity varied from 37.5 to 75% and with selected assays was lower in samples from day 6 compared to day 0. GC-MS was not superior to the immunoassays in discriminating healthy from HC dogs.
  
  
  CONCLUSIONS
  Considerable variation must be anticipated comparing different urinary cortisol assays. Establishing an assay- and laboratory-specific reference range is critical when using UCCR.
authors.affiliation: Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland.
authors.forename: L
authors.initials: L
authors.lastname: Galeandro
authors.forename: N S
authors.initials: NS
authors.lastname: Sieber-Ruckstuhl
authors.forename: B
authors.initials: B
authors.lastname: Riond
authors.forename: S
authors.initials: S
authors.lastname: Hartnack
authors.forename: R
authors.initials: R
authors.lastname: Hofmann-Lehmann
authors.forename: C E
authors.initials: CE
authors.lastname: Reusch
authors.forename: F S
authors.initials: FS
authors.lastname: Boretti
mesh_terms: D000305:Adrenal Cortex Hormones / Q000652:urine*; D000818:Animals; D003404:Creatinine / Q000652:urine; D003480:Cushing Syndrome / Q000652:urine / Q000662:veterinary*; D004283:Dog Diseases / Q000652:urine*; D004285:Dogs / Q000652:urine*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry / Q000662:veterinary*; D007118:Immunoassay / Q000662:veterinary*; D008163:Luminescent Measurements / Q000662:veterinary; D008297:Male; D011446:Prospective Studies; D011863:Radioimmunoassay / Q000662:veterinary
chemical_list: D000305:Adrenal Cortex Hormones; D003404:Creatinine
keywords: Hospital stress; Influence; Reference interval; UCCR; Variation