Endoscopically assessed mucus parameters in equine asthma: Relationship to clinical history and cytological findings data.

Abstract

Background: Mucus parameters are hallmark diagnostic features of equine asthma (EA).

Objectives: To investigate the relationship between mucus quantity score and mucus viscosity score with signalment, history, clinical findings and cytological parameters.

Study design: Retrospective cross-sectional study.

Methods: Mucus quantity and viscosity scores, signalment, history and clinical findings recorded for diagnostic purposes from up to 1599 samples, and cytological values of the corresponding bronchoalveolar lavage fluid (BALF) and tracheobronchial secretions were analysed. The cut-off value of a mucus quantity score >2 for the diagnosis of mild to moderate EA (MEA) was used to calculate the odds ratios for MEA and severe EA (SEA). Associations were tested via a multivariate Kruskal-Wallis test. The mucus scores were analysed pairwise with cytological characteristics, anamnestic data and clinical signs by testing for independence using the chi-square test. Correlations were evaluated using the non-parametric Spearman's rank correlation coefficient.

Results: A mucus quantity score >2 was associated with increased odds of diagnosing SEA (odds ratio 3.6, 95% confidence interval 1.75, 7.17, p < 0.001), but not for MEA. A weak positive correlation was found between neutrophil granulocytes in BALF and mucus quantity score (rho: 0.353, p < 0.001) as well as mucus viscosity score (rho: 0.225, p < 0.001). The mucus scores for quantity and viscosity were significantly associated (p < 0.001) with age, respiratory rate and arterial oxygen partial pressure values, and significantly associated (p < 0.001) with season, type of nasal discharge and respiratory pattern. However, no associations were found with body condition score (BCS), sex and breed.

Main limitations: This was a convenience sample with a cytologically unremarkable control group, but no healthy control group.

Conclusions: Mucus quantity score is a diagnostic parameter for the diagnosis of SEA. Associations between mucus scores and neutrophilic influx and with some clinical parameters were identified, while there was no confirmed relationship to BCS.