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
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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. OBJECTIVES: 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.
author list (cited authors)
Sattasathuchana, P., Berghoff, N., Grützner, N., Thengchaisri, N., Rangachari, V. R., Suchodolski, J. S., & Steiner, J. M.