Cytological analysis of equine bronchoalveolar lavage fluid. Part 1: Comparison of sequential and pooled aliquots.
Authors: Pickles K, Pirie R S, Rhind S, Dixon P M, McGorum B C
Journal: Equine veterinary journal
Summary
# Editorial Summary: Sequential versus Pooled Bronchoalveolar Lavage Samples in Horses When performing bronchoalveolar lavage (BAL) in horses, clinicians typically collect fluid in sequential aliquots, with the first representing more proximal airway material and later fractions coming from deeper lung tissue. Pickles and colleagues set out to determine whether all collected aliquots were equally diagnostic, or whether only initial samples should be analysed—a question with practical implications when total fluid recovery is limited. Comparing cytological profiles across three sequential BALF samples and a pooled fourth aliquot from 10 horses (5 healthy and 5 with heaves), they found significant variations in differential cell counts (particularly macrophages and lymphocytes) between individual aliquots, with mast cell percentages notably declining from first to third samples in control horses. Despite these fluctuations in individual aliquots, total nucleated cell counts, absolute cell counts, and cell viability remained consistent across samples, and critically, no diagnostically meaningful differences emerged between sequential and pooled preparations. For practitioners, this finding carries important implications: submitting fluid from any aliquot—or pooled material—yields equally valid cytological results, which is reassuring when BAL yields are poor or when clinical circumstances limit sample collection to early fractions.
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Practical Takeaways
- •All bronchoalveolar lavage fluid aliquots collected during the procedure represent the lavaged lung segment equally well, so cytological analysis remains diagnostically valuable even with low fluid recovery
- •Pooling aliquots is not necessary for accurate cytological interpretation; individual aliquots can be analysed separately without compromising diagnostic value
- •Low-yield bronchoalveolar lavage procedures should not be abandoned as non-diagnostic, as the samples obtained will still provide reliable information about lung cytology
Key Findings
- •No diagnostically significant differences in total nucleated cell count, differential cell count, absolute cell counts, or cell viability among sequential and pooled bronchoalveolar lavage fluid aliquots
- •Nonsignificant trends of increasing total cell count and absolute macrophage count from first to third aliquot
- •Significant differences in macrophage (P<0.05) and lymphocyte (P<0.01) differential cell counts among aliquots without linear trend patterns
- •Mast cell differential count showed significant decrease (P<0.01) from first to third aliquot in control horses only