Bronchoscopy is commonly used for to evaluate dogs with acute and chronic coughs. Our aim was to evaluate the diagnostic accuracy of the macroscopic endoscopic exam of the bronchial mucosa for the diagnosis of eosinophilic bronchitis. A retrospective multi-institutional diagnostic accuracy study was performed including all the dogs presenting with acute or chronic coughs and that underwent bronchial endoscopy by the Endovet Italian Group between January 2014 and December 2016. The reference standard was the cytological evaluation of the bronchoalveolar lavage. The primary outcome was sensitivity, specificity, positive predictive value, and negative predictive value of endoscopic visualization of nodules for the diagnosis of eosinophilic bronchitis. Of the 845 cases studied, a total of 781 dogs fulfilled the inclusion criteria with cytological evaluation of the bronchoalveolar lavage. The dogs ranged in age from 0.4 to 16 years (8.0 median, 4.0 SD), in body weight from 1.5 to 45 kg (13.0 median, 9.5 SD), and 325 (41.6%) were females. A final diagnosis of eosinophilic bronchitis was given for 113 (15.6%) cases, and 99 (13.6%) presented nodules during macroscopic endoscopy. In the final logistic regression model, detection of nodules during endoscopy, higher age, and lower body weight were associated with a diagnosis of eosinophilic bronchitis. Odds of having eosinophilic bronchitis were 34.4% (18.9 to 62.6; p<0.001) greater in dogs presenting nodules during endoscopy. The risk of eosinophilic bronchitis increased by 23% (14 to 32%; p<0.001) for a one-year increase in age, and by 3% (0 to 5%; p=0.048) for each kilogram decrease in body weight. Visualization of nodules during endoscopy had a sensitivity of 56.6% (47.0 to 65.9%), specificity of 94.3% (92.3 to 95.9%), positive predictive value of 62.7% (54.3 to 70.5%), and negative predictive value of 92.8% (91.2 to 94.1%). Based on the high specificity and high negative predictive value, visualization of nodules during endoscopy is highly indicative of eosinophilic bronchitis. However, the lack of visualization of nodules during endoscopy does not exclude the presence of eosinophilic bronchitis.

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