Effects of collecting serial tracheal aspirate and bronchoalveolar lavage samples on the cytological findings of subsequent fluid samples in healthy Standardbred horses

Objective To evaluate the effect of collecting serial tracheal aspirate (TA) and bronchoalveolar lavage (BAL) samples on the cytological findings of subsequent fluid samples obtained from horses without clinical signs of respiratory disease. Study design Experimental. Study population Six healthy Standardbred horses. Methods Endoscopically‐guided TA samples, and BAL samples collected using the blind field technique were obtained from the six horses on days 1, 2, 3, 4, 5, 12, and 17. On day 17, horses were sampled three times: at baseline and at 2.5 h and 4 h apart. The differential cytology of the fluid samples collected at each time point was expressed as percentages and compared statistically. Results There was a significant increase in neutrophil percentage in the TA samples taken at day 17 (at 2.5 h but not at 4 h apart). There was no significant change in the neutrophil percentages in the TA samples when repeated samples were taken ≥24 h apart. There was no significant change in the neutrophil percentages in the BAL fluid at any collection point. There were inconsistent changes in the percentages of lymphocytes and macrophages in the BAL fluid over time, but these remained within normal reference ranges and were considered clinically insignificant. Conclusions Serial TA and BAL samples can be taken at 24 h intervals without affecting the cytological findings of subsequent fluid samples collected using the techniques described.