Associations between clinical signs, endoscopic and cytological findings in equine bronchoalveolar lavage samples

Abstract

Background: Endoscopy, including tracheal mucus score (TMS) and bronchoalveolar lavage (BAL) fluid cytology, are commonly used to diagnose equine asthma (EA). Large-scale studies comparing clinical signs, TMS and BAL cytology are warranted. Objectives: Investigate associations between clinical signs of EA, tracheal mucus score and BAL cytology. Study design: cross-sectional study Methods: Data from 604 horses, each horse having one BAL cytology sample evaluated at the laboratory service at the Large Animal Teaching Hospital in Denmark, with further information provided by an owner questionnaire and veterinarian performing the endoscopy and BAL. Results: Tracheal mucus score increased significantly with EA severity, BAL neutrophilia and owner reported coughing, but not with BAL mastocytosis. Owner complaint of coughing was associated with an increasing amount of BAL neutrophils, but not with an increase in BAL mast cells. Poor performance was not correlated to BAL neutrophils, mast cells or TMS. Percentage of BAL aspirated was found lower in the SEA group compared to the non-asthmatic and MEA groups. Main limitations: Several different veterinarians performed the BAL sampling, BAL samples were shipped and a 24 hour delay in processing of the sample. Not able to adjust for season as these data was not recorded. Conclusion: this large-scale study showed a correlation between TMS and increasing severity of lower airway inflammation, confirming TMS as a reliable diagnostic factor for EA. Owner complaint of coughing, was found to be associated with TMS and BAL neutrophilia, and poor performance without coughing is not a reliable parameter for EA.