Abstract
BACKGROUND: Acute phase proteins (APP) may guide treatment of pneumonia in dogs but correlations with radiographic abnormalities are poorly characterized. OBJECTIVES: Develop a thoracic radiographic severity scoring system (TRSS), assess correlation of radiographic changes with APP concentrations, and compare time to APP and radiograph normalization with duration of antimicrobials treatment. ANIMALS: Sixteen client-owned dogs, 12 with aspiration pneumonia, and 4 with community-acquired pneumonia. METHODS: Concentrations of C-reactive protein (CRP), serum amyloid A (SAA), and haptoglobin were measured on days 1, 3, 7, 14, 28, and 60 and orthogonal 2-view thoracic radiographs were obtained on days 1, 7, 14, 28, and 60. Treatment was clinician-guided and blinded to APP concentrations. Radiographic severity scores were assigned by blinded, randomized retrospective review by 2 board-certified radiologists with arbitration by a third radiologist. RESULTS: Median (interquartile range [IQR]) time to normalization of CRP (7 days [7-14]) and SAA concentrations (7 days [7-14]) were shorter than antimicrobial treatment duration (17.5 days [14.5-33.5]; P = .001 and .002, respectively) and TRSS normalization (14 days [8.8-52], P = .02 and .02, respectively). The CRP and SAA concentrations were positively correlated with TRSS (CRP r(s) , 0.643; SAA r(s) , 0.634; both P < .0001). Both CRP and SAA identified normal thoracic radiographs area under the curve (AUC) 0.873 and 0.817, respectively, both P < .0001. Interobserver agreement for TRSS assignment was moderate (κ, .499; P < .0001). CONCLUSION AND CLINICAL IMPORTANCE: Concentrations of CRP and SAA normalized before radiographic resolution and before clinicians discontinued antimicrobial treatment. The CRP and SAA concentrations may guide duration of antimicrobial treatment for dogs with pneumonia.