Background: Thymus and activation-regulated chemokine (TARC/CCL17) has been implicated in the pathogenesis of canine atopic dermatitis (cAD). Serum TARC concentrations are a reliable biomarker for human atopic dermatitis; however, their potential as a biomarker for cAD has not been investigated. Hypothesis/Objectives: To investigate whether serum TARC concentrations correlate with disease severity and therapeutic responses for cAD. Animals: Thirty-nine dogs with cAD and 42 healthy dogs were recruited. Methods and materials: Serum TARC concentrations in dogs with cAD and healthy dogs were measured by sandwich ELISA with anti-canine TARC antibodies. The clinical severity of cAD was scored using the validated Canine Atopic Dermatitis Extent and Severity Index, 4th iteration (CADESI-04). Serum TARC concentrations were compared between dogs with cAD and healthy controls, and their relationship with CADESI-04 was examined. Serum TARC concentrations also were measured in 20 dogs with cAD treated with prednisolone or oclacitinib for four weeks. Results: Serum TARC concentrations were significantly higher in dogs with cAD than in healthy dogs (P < 0.001). In dogs with cAD, serum TARC concentrations correlated with CADESI-04 scores (ρ = 0.457, P < 0.01). Furthermore, serum TARC concentrations significantly decreased in treated dogs with the attenuation of clinical signs (P < 0.001). Changes in serum TARC concentrations before and after treatment correlated with those in CADESI-04 scores (ρ = 0.746, P < 0.001). Conclusions and clinical relevance: Serum TARC concentrations have potential as a clinical and research tool for the objective evaluation of disease severity and therapeutic responses for cAD.
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