Cytological analysis of equine bronchoalveolar lavage fluid. Part 3: The effect of time, temperature and fixatives.

Bronchoalveolar lavage fluid (BALF) samples are often subject to time delays, possibly with temperature fluctuations, between collection and processing. The aim of this study was to evaluate the effects of time, temperature and 2 different fixatives on equine BALF cytology, in order to develop guidelines for optimal equine BALF storage conditions. Total nucleated cell count (TCC), differential cell counts (DCC), absolute cell counts (ACC), cell viability, cell morphology and bacterial growth of BALF samples stored at 4, 18 (+/- addition of formalin- or alcohol-based fixatives) and 38 degrees C were monitored serially over a 72 h period. The time taken for a significant reduction in TCC and cell viability of unfixed BALF samples decreased as the storage temperature increased. There was no diagnostically significant difference in DCC or ACC over this time-course at any temperature. Unfixed BALF samples showed significant bacterial growth by 24 h at 4 degrees C, and 8 h at 18 and 38 degrees C; and poor morphology by 48 h at 4 degrees C, 24 h at 18 degrees C and 8 h at 38 degrees C. Fixed BALF samples showed poor morphology with Leishman's stain compared to unfixed samples.