How accurate is chest CT for diagnosing chronic bronchitis in dogs

Abstract

OBJECTIVE To characterize CT findings in dogs with a presumptive diagnosis of chronic bronchitis, estimate the accuracy of thoracic CT for the diagnosis of chronic bronchitis in dogs, and determine interobserver agreement for this method. DESIGN Retrospective case-control and cross-sectional study. ANIMALS 26 dogs with confirmed chronic bronchitis and 20 control dogs with unremarkable results of thoracic CT and no recorded history of cough. PROCEDURES Thoracic CT images of all dogs were interpreted for signs of chronic bronchitis by 2 observers who used specific criteria; observers also used the images to compute the bronchial wall thickness-to-pulmonary artery diameter (BWPA) ratio of the cranial lung lobes. Interobserver agreement was assessed for both diagnostic approaches. Performance of thoracic CT and the BWPA ratio specifically in the diagnosis of chronic bronchitis were evaluated, with the final diagnosis made by the attending internist as the reference standard. Associations between independent variables and the BWPA ratio for all dogs were assessed by linear regression. RESULTS Accuracy of thoracic CT examination for the diagnosis of chronic bronchitis was 57%, sensitivity was 46%, and specificity was 90%. Interobserver agreement was moderate (κ = 0.50). The BWPA ratio had poor accuracy for discriminating dogs with chronic bronchitis from control dogs. Linear regression revealed that as dog body weight increased, BWPA ratios for the left and right cranial lung lobes decreased slightly but significantly. CONCLUSIONS AND CLINICAL RELEVANCE These results suggested that thoracic CT and the associated BWPA ratio have limited value in the diagnosis of chronic bronchitis in dogs.