Cytological analysis of equine bronchoalveolar lavage fluid. Part 3: The effect of time, temperature and fixatives.
Authors: Pickles K, Pirie R S, Rhind S, Dixon P M, McGorum B C
Journal: Equine veterinary journal
Summary
# Editorial Summary Bronchoalveolar lavage fluid (BALF) samples frequently experience delays and temperature fluctuations between collection and laboratory analysis, yet the impact of these variables on diagnostic accuracy remains poorly characterised in equine medicine. Pickles and colleagues systematically exposed BALF samples to three storage temperatures (4°C, 18°C and 38°C) over 72 hours, with and without formalin or alcohol-based fixatives, monitoring total nucleated cell counts, differential cell counts, cell viability, morphology and bacterial contamination at serial intervals. Whilst differential and absolute cell counts remained diagnostically stable across all conditions, total cell counts and viability declined progressively as temperature increased—unfixed samples deteriorated most rapidly at 38°C, with significant bacterial overgrowth evident within 8 hours at room temperature and above, and unacceptable cellular morphology appearing by 24 hours at 18°C. Importantly, fixatives compromised cell morphology under light microscopy compared to unfixed samples, limiting their utility despite reducing bacterial growth. For practitioners, these findings emphasise the critical importance of refrigerating BALF at 4°C immediately after collection and processing samples within 24 hours when unfixed, particularly in warm climates or ambulatory situations where delays are unavoidable.
Read the full abstract on PubMed
Practical Takeaways
- •Store BALF samples at 4°C (refrigeration) to maintain cell morphology and minimize bacterial growth compared to room or body temperature
- •Process unfixed samples within 8-24 hours depending on storage temperature; do not delay processing at room or higher temperatures
- •Consider using fixatives with caution as they compromise cell morphology with Leishman's staining compared to unfixed samples
Key Findings
- •Unfixed BALF samples showed significant bacterial growth by 24 h at 4°C and by 8 h at 18-38°C
- •Cell morphology deterioration occurred within 8 h at 38°C, 24 h at 18°C, and 48 h at 4°C in unfixed samples
- •Time to significant reduction in total nucleated cell count and viability decreased with increasing storage temperature
- •Differential and absolute cell counts showed no diagnostically significant changes over 72 h at any temperature