Cytological analysis of equine bronchoalveolar lavage fluid. Part 2: Comparison of smear and cytocentrifuged preparations.
Authors: Pickles K, Pirie R S, Rhind S, Dixon P M, McGorum B C
Journal: Equine veterinary journal
Summary
# Editorial Summary When diagnosing equine lower airway disease, bronchoalveolar lavage (BAL) cytology is invaluable, but practitioners have traditionally relied on sending fluid samples to laboratories for cytocentrifuge processing—a time-consuming and costly approach. Pickles and colleagues compared smear preparations (enhanced with serum addition) against standard cytocentrifuged methods across 21 BAL samples from control and heaves-affected horses, evaluating cell morphology, differential counts, and counting repeatability. Cytocentrifuged preparations yielded superior cell morphology and significantly higher macrophage, mast cell, and eosinophil counts, whilst smears showed artificially elevated lymphocyte percentages; notably, however, smear preparations reliably identified neutrophilic pulmonary disease, the most clinically relevant finding in suspected equine airway inflammation. For practitioners seeking a practical in-house alternative for screening cases of suspected recurrent airway obstruction or other neutrophil-driven lower airway conditions, smear preparations offer diagnostic utility despite their technical limitations, though cases requiring precise differential cell profiling may still warrant formal laboratory processing.
Read the full abstract on PubMed
Practical Takeaways
- •Smear preparations with serum addition can be performed in-practice for rapid diagnosis of neutrophilic airway disease, eliminating delays from laboratory submission
- •Cytocentrifuge preparations remain superior for detailed differential cell counting and identification of mast cells and eosinophils, so consider laboratory submission when these cell types are diagnostically important
- •Practitioners should be aware that smear preparations may underestimate macrophage, mast cell and eosinophil counts compared to cytocentrifuge methods when making clinical decisions
Key Findings
- •Smear preparations produced smaller, darker-staining cells making cytological identification more difficult than cytocentrifuged preparations
- •Cytocentrifuged preparations showed significantly higher macrophage differential cell counts (P<0.01) and lower lymphocyte counts compared to smear preparations
- •Mast cell and eosinophil counts were significantly higher (P<0.05) on cytocentrifuged compared to smear preparations
- •Smear preparations were reliable for cytological diagnosis of equine neutrophilic pulmonary disease and offer practitioners a practical in-practice alternative to laboratory submission