Comparison Between Tracheal Wash and Bronchoalveolar Lavage Cytology for the Assessment of Airway Inflammation in Racehorses Affected by Exercise-Induced Pulmonary Hemorrhage

Exercise-Induced Pulmonary Hemorrhage (EIPH) results from alveolar capillary stress failure after strenuous exercise, leading to bleeding and pulmonary inflammation. Bronchoalveolar lavage fluid (BALF) cytology is considered the gold standard for the assessment of airway inflammation; however, it is often considered more invasive compared to tracheal wash (TW). It has been demonstrated that TW is a reliable diagnostic tool that may substitute BALF to diagnose and grade the severity of EIPH in racehorses; however, no information about airway inflammation in EIPH-affected horses has been reported. This retrospective study aimed to verify the agreement between TW and BALF in assessing lower airway inflammation in racehorses with EIPH. Cytological data from 123 poorly performing racehorses regarding neutrophils, eosinophils, and mast cells percentages were reviewed. Non-parametric statistical tests were used to assess the difference and the correlation between TW and BALF, and the distribution of inflammatory patterns in BALF. A strong correlation between TW and BALF was found for neutrophils (ρ = 0.817, p < 0.001) and eosinophils percentage (ρ = 0.806, p < 0.001); while a moderate correlation was found for mast cells percentage (ρ = 0.584, p < 0.001). The eosinophilic-mastocytic inflammation was the prevalent pattern observed in our population. Based on our findings, TW cannot be considered an alternative to BALF cytology for fully characterizing lower airway inflammation in racehorses with EIPH.