Influence of bronchoalveolar lavage volume on cytological profiles and subsequent diagnosis of inflammatory airway disease in horses.
Authors: Orard Marie, Depecker Marianne, Hue Erika, Pitel Pierre-Hugues, Couroucé-Malblanc Anne, Richard Eric A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Bronchoalveolar Lavage Volume and Equine Airway Cytology Diagnostic consistency in inflammatory airway disease (IAD) depends partly on standardised sampling protocols, yet variation in bronchoalveolar lavage (BAL) fluid recovery rates could confound cytological interpretation. This study examined whether instilling 250 mL or 500 mL of saline during BAL produced systematically different cellular profiles in 30 Standardbred racehorses, with each animal sampled bilaterally using both volumes and the procedure repeated 72 hours later with volumes reversed. The larger 500 mL instillation yielded significantly higher fluid recovery rates but paradoxically lower neutrophil percentages, whilst poor diagnostic agreement was observed between the two methodologies when applying the standard threshold of >10% neutrophils from at least one lung. Since volume substantially altered cytological outcomes despite both falling within currently recommended ranges, establishing lung-specific reference intervals and standardising BAL technique become essential to prevent misclassification of IAD status and ensure reproducible diagnosis across equine practice. Practitioners should recognise that switching between 250 mL and 500 mL protocols on the same horse may yield incomparable results and potentially obscure or falsely trigger IAD diagnoses.
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Practical Takeaways
- •BAL volume standardization is critical for consistent IAD diagnosis in racehorses—using 250 mL versus 500 mL can change diagnostic conclusions in the same horse
- •Current reference values for neutrophil thresholds (>10%) may not be reliable across different BAL volumes; practitioners should establish consistent protocols within their practice
- •When comparing BAL results across horses or over time, ensure identical instillation volumes are used to avoid false-negative or false-positive IAD diagnoses
Key Findings
- •Larger BAL volume (500 mL) recovered significantly higher proportions of fluid compared to 250 mL instillation
- •Neutrophil percentages were significantly lower with 500 mL volume compared to 250 mL
- •Poor agreement found between 250 mL and 500 mL methodologies for IAD diagnosis when using >10% neutrophil threshold
- •Within the recommended 250-500 mL range, instilled volume significantly influenced cytological profiles and diagnostic outcomes