Bronchoalveolar lavage fluid from both lungs in horses: Diagnostic reliability of cytology from pooled samples.
Authors: Hermange T, Le Corre S, Bizon C, Richard E A, Couroucé A
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Pooled Bronchoalveolar Lavage Fluid Sampling in Horses Obtaining diagnostic samples from both lungs during bronchoalveolar lavage (BAL) is technically demanding and time-consuming in equine practice, raising the question of whether pooling fluid from both lungs produces reliable cytological results representative of each lung individually. Hermange and colleagues examined 51 horses with poor performance and/or respiratory signs, collecting BALF from both lungs separately and then pooling the samples to compare cytological findings and diagnostic classification. Cell counts and proportions showed no significant differences between pooled and individual samples, with strong correlations (r ≥0.9) for neutrophils and haemosiderophages/macrophages—the two most clinically important markers—and moderate correlations for metachromatic cells and eosinophils; diagnostic agreement was excellent for equine asthma classification (κ ≥0.97) and substantial for exercise-induced pulmonary haemorrhage (κ=0.74), with only four horses misclassified across all categories. Practitioners can confidently use pooled BALF cytology as a valid diagnostic tool, substantially simplifying the technical procedure without sacrificing diagnostic accuracy for asthma or haemorrhage assessment. This streamlined approach may improve the uptake and feasibility of BAL sampling in clinical practice, particularly in field or referral settings where procedure time is a limiting factor.
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Practical Takeaways
- •Sampling only one lung with pooled BALF cytology is diagnostically reliable and can confidently diagnose equine asthma, reducing procedural burden and cost compared to bilateral sampling
- •For EIPH diagnosis, pooled sampling remains valid but with slightly lower agreement; practitioners should be aware of the 7.8% misclassification risk in borderline cases
- •Neutrophil proportions and macrophage ratios from pooled samples are highly reliable and should be the primary focus of interpretation in respiratory disease screening
Key Findings
- •Pooled BALF cytology showed no significant difference from individual lung samples for all cell types (P>0.05)
- •Strong correlations (r≥0.9) observed between pooled and individual samples for neutrophil proportions and haemosiderophages/macrophages ratio
- •Pooled BALF samples achieved good categorical agreement (κ≥0.97) for mEA/sEA diagnosis and substantial agreement (κ=0.74) for EIPH diagnosis
- •Only 4 of 51 horses (7.8%) were misclassified using pooled samples: 1 as CTL instead of mEA and 3 as EIPH instead of CTL