Interpretation of tracheal wash samples in horses

Respiratory tract disease is among the most common diseases in horses causing poor performance and compromising health. Determining a diagnosis can be challenging due to non-specific clinical signs; therefore, due to ease and rapidity, respiratory tract endoscopy and tracheal wash (TW) are often used during initial testing. However, interpretation of tracheal wash fluid (TWF) is complicated by the fact that there is no universally accepted cytological reference range. This article discusses obtaining, processing and interpreting the results of a TW sample to provide the maximum information, so that a diagnosis can be made and an appropriate treatment selected.