title: Development and analytic validation of an electron ionization gas chromatography/mass spectrometry (EI-GC/MS) method for the measurement of 3-bromotyrosine in canine serum.
abstract: BACKGROUND
  The activation of eosinophils causes the release of eosinophil peroxidase and subsequent production of 3-bromotyrosine (3-BrY), a stable byproduct. In people, 3-BrY is used as a biomarker for eosinophil activation. The method for measuring 3-BrY concentrations in biologic samples from dogs has not previously been described.
  
  
  OBJECTIVE
  The objective of this study was to develop and analytically validate an electron ionization gas chromatography/mass spectrometry (EI-GC/MS) method for the measurement of 3-BrY in canine serum samples.
  
  
  METHODS
  Pooled canine serum samples were utilized to validate the assay. Serum samples from healthy control dogs (n = 41) were used to evaluate 3-BrY concentrations and establish a reference interval.
  
  
  RESULTS
  The analytic validation revealed that the limit of blank and limit of detection were 0.33 and 0.63 μmol/L, respectively. The coefficients of variation for precision and reproducibility for 3-BrY were < 13.9% and < 11.0%, respectively. The means ± SD of observed-to-expected ratios for linearity and accuracy were 109.6 ± 17.2% and 98.7 ± 11.3%, respectively. The reference interval was determined as ≤ 1.12 μmol/L (median [range]: ≤ 0.63 μmol/L [≤ 0.63-1.13]).
  
  
  CONCLUSIONS
  The EI-GC/MS assay described here for the measurement of 3-BrY in canine serum samples was precise, reproducible, linear, and accurate. Further studies are underway to determine the diagnostic utilities in canine patients with eosinophilic diseases.
authors.affiliation: Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA. psatta@cvm.tamu.edu.|Department of Companion Animal Clinical Sciences, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand. psatta@cvm.tamu.edu.
authors.forename: Panpicha
authors.identifier: http://orcid.org/0000-0002-9373-6169
authors.initials: P
authors.lastname: Sattasathuchana
authors.affiliation: Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA.
authors.forename: Nora
authors.initials: N
authors.lastname: Berghoff
authors.affiliation: Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA.
authors.forename: Niels
authors.initials: N
authors.lastname: Grützner
authors.affiliation: Department of Companion Animal Clinical Sciences, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand.
authors.forename: Naris
authors.initials: N
authors.lastname: Thengchaisri
authors.affiliation: Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA.
authors.forename: Venkat R
authors.initials: VR
authors.lastname: Rangachari
authors.affiliation: Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA.
authors.forename: Jan S
authors.initials: JS
authors.lastname: Suchodolski
authors.affiliation: Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, USA.
authors.forename: Jörg M
authors.initials: JM
authors.lastname: Steiner
mesh_terms: D000818:Animals; D004285:Dogs / Q000097:blood*; D004583:Electrons; D008401:Gas Chromatography-Mass Spectrometry / Q000662:veterinary*; D015203:Reproducibility of Results; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014443:Tyrosine; C118327:3-bromotyrosine
keywords: 3-bromotyrosine; canine; eosinophil activation; eosinophil peroxidase; serum