Evaluation of Serum 3‐Bromotyrosine Concentrations in Dogs with Steroid‐Responsive Diarrhea and Food‐Responsive Diarrhea

BACKGROUND The clinical usefulness of serum 3-BrY concentrations for subclassifying dogs with food-responsive diarrhea (FRD) and steroid-responsive diarrhea (SRD) has not been studied. HYPOTHESIS/OBJECTIVES To compare serum 3-BrY concentrations in dogs with FRD, dogs with SRD, and healthy control dogs. ANIMALS 38 dogs with FRD, 14 dogs with SRD, and 46 healthy dogs. METHODS Prospective study. Measurement of 3-BrY concentration in serum samples was performed by gas chromatography/mass spectrometry. RESULTS There was no association of peripheral eosinophilia in dogs with FRD, SRD, and healthy control dogs (P = 0.069). There was no significant correlation between peripheral eosinophil counts and serum 3-BrY concentrations (ρ = -0.15, P = 0.13). Serum 3-BrY concentrations in dogs with SRD (median [range] = 3.27, 0.9-26.23 μmol/L) were significantly higher than in dogs with FRD (median [range] = 0.99, 0.62-8.82 μmol/L; P = 0.007) or in healthy dogs (median [range] = 0.62, 0.62-1.79 μmol/L; P < 0.001). Also, serum 3-BrY concentrations in dogs with FRD were significantly higher than in healthy dogs (P = 0.025). There was no significant correlation between the canine chronic enteropathy clinical activity index and serum 3-BrY concentrations (ρ = 0.17, P = 0.23). CONCLUSIONS AND CLINICAL IMPORTANCE Measurement of serum 3-BrY concentrations, but not the peripheral eosinophil count, is helpful for detecting dogs with SRD and FRD.