Associations Between Otic Cytological Findings and Clinical Severity by Pathogen Group in Canine Otitis Externa: A Retrospective Study of 318 Cases.

BACKGROUND

Otic cytological assessment is routinely used in canine otitis externa (OE) to assess microbial burden and inflammation. Evidence that cytological findings are associated with clinical severity, particularly by pathogen group, remains limited.

OBJECTIVES

To evaluate associations between otic cytological findings and clinical severity in canine OE, overall and by pathogen group.

ANIMALS: Three hundred and eighteen client-owned dogs with OE presented to a referral dermatological service.

MATERIALS AND

METHODS

Clinical severity was scored using the Otitis Index Score 3 (OTIS3; 0-12). Cytological findings were evaluated using a semiquantitative 0-3 scale for cocci, rods and Malassezia, based on predefined institutional criteria. A total cytological score (0-9) was calculated as the sum of the scores for the three groups. Neutrophil presence was also recorded.

RESULTS

OTIS3 scores showed a moderate correlation with total cytological score (p < 0.0001; Spearman's r = 0.45). Scores increased significantly with higher cocci and rod cytological scores (Kruskal-Wallis, p < 0.0001), while Malassezia scores were not. OTIS3 scores also were significantly higher when neutrophils were present.

CONCLUSIONS AND CLINICAL RELEVANCE: Associations between otic cytological findings and clinical severity of OE varied by pathogen group. Greater clinical severity was associated with neutrophil presence and bacterial burden. These findings support the interpretation of cytological findings combined with OTIS3 for assessment and monitoring of canine OE.