Effect of inclusion or exclusion of epithelial cells in equine respiratory cytology analysis.
Authors: Allen K J, Tennant K V, Franklin S H
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Epithelial Cells in Equine Respiratory Cytology Inconsistent methodology across published equine respiratory research has created ambiguity around whether epithelial cells should be included when calculating differential cell counts from tracheal wash and bronchoalveolar lavage samples—a decision that directly impacts clinical interpretation. Allen and colleagues examined 21 horses using standard diagnostic thresholds (>20% neutrophils for tracheal wash abnormality; >10% neutrophils or >5% mast cells for bronchoalveolar lavage abnormality) and compared results when epithelial cells were either included or excluded from the differential count. Excluding epithelial cells from calculations significantly altered case categorisation in a meaningful proportion of horses: 21% of tracheal wash samples shifted from normal to abnormal classification, alongside 4% of bronchoalveolar lavage samples and 8% when using mast cell criteria. For practitioners and researchers alike, this variation in methodology risks both missed diagnoses of genuine airway inflammation and potential false positives, particularly when comparing findings against published reference ranges or making longitudinal assessments. The profession requires standardised reporting conventions—explicitly stating epithelial cell inclusion status—to ensure diagnostic consistency and allow meaningful comparison of cytological findings across studies and clinical cases.
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Practical Takeaways
- •When reviewing equine airway cytology results, always verify whether the laboratory included or excluded epithelial cells, as this significantly affects interpretation—particularly for tracheal wash samples where 21% of cases can be reclassified
- •Request explicit documentation of methodology from your diagnostic laboratory and maintain consistency within your practice to ensure accurate trending and treatment decisions
- •Consider advocating for industry consensus on epithelial cell reporting standards to improve diagnostic reliability across veterinary practices
Key Findings
- •Excluding epithelial cells from differential counts changed categorization from normal to abnormal in 21% of horses using >20% tracheal wash neutrophils criterion
- •Excluding epithelial cells changed categorization in 4% of horses using >10% bronchoalveolar lavage neutrophils criterion
- •Excluding epithelial cells changed categorization in 8% of horses using >5% bronchoalveolar lavage mast cells criterion
- •Published studies lack standardized methodology regarding epithelial cell inclusion/exclusion in equine respiratory cytology analysis