Mild-moderate equine asthma: A scoping review of evidence supporting the consensus definition.
Authors: Kinnison T, McGilvray T A, Couëtil L L, Smith K C, Wylie C E, Bacigalupo S A, Gomez-Grau E, Cardwell J M
Journal: Veterinary journal (London, England : 1997)
Summary
# Mild-Moderate Equine Asthma: Evidence Review and Research Gaps Researchers at multiple institutions conducted a scoping review of peer-reviewed literature to critically evaluate the diagnostic indicators underpinning the current consensus definition of mild-moderate equine asthma (mEA), which replaced the previous term "inflammatory airway disease." Screening over 2,000 articles and analysing 44 studies involving 6,092 horses, the authors assessed how reliably each diagnostic marker—cough, poor performance, tracheobronchial mucus, inflammatory BAL cytology and pulmonary dysfunction—correlates with underlying lung inflammation. The evidence base proved inconsistent: whilst cough and increased tracheobronchial mucus showed reasonably consistent associations, the relationship between BAL cytology findings and objective lung function measures was notably weak, and nearly 50% of reviewed studies carried high risk of bias in study power and blinding protocols. The predominance of Thoroughbred racehorses (58–73% of horses studied) limits generalisability to other breeds and uses, and substantial heterogeneity in how diagnostic variables were measured and reported prevented formal meta-analysis. For equine professionals, this review underscores that current mEA diagnostic criteria, whilst consensus-driven, rest on an incomplete and sometimes contradictory evidence foundation—meaning clinical interpretation of individual diagnostic findings requires caution, and there is urgent need for standardised measurement protocols and clearer diagnostic algorithms to improve both research quality and clinical decision-making.
Read the full abstract on PubMed
Practical Takeaways
- •The consensus definition provides a hierarchical framework for diagnosing mild-moderate asthma in horses, but practitioners should recognise that individual diagnostic indicators do not correlate consistently with each other across published literature.
- •Current evidence is strongest for using cough and tracheobronchial mucus as diagnostic indicators; relationships between BAL cytology findings and lung function testing are more variable and warrant cautious interpretation.
- •Standardised diagnostic protocols and reporting methods are needed to improve clinical decision-making; when possible, use multiple diagnostic approaches rather than relying on single indicators.
Key Findings
- •A scoping review of 45 studies across 6092 horses identified consensus diagnostic criteria for mild-moderate equine asthma including cough, poor performance, increased tracheobronchial mucus, inflammatory BAL cytology, and pulmonary dysfunction.
- •Evidence was more consistent for certain diagnostic relationships (e.g., cough and tracheobronchial mucus) than others (e.g., BAL cytology and lung function).
- •High risk of bias in approximately 50% of articles in domains of study power and masking limited strength of conclusions.
- •Heterogeneity in clinical and laboratory measures across 44 predominantly observational and cross-sectional studies (median 74 horses) precluded meta-analysis and highlighted need for standardisation.