Total hemosiderin score in the tracheal wash fluid when assessing exercise-induced pulmonary hemorrhage in thoroughbred racehorses

Exercise-induced pulmonary hemorrhage (EIPH) is one of the main respiratory conditions that requires clinical follow-up in equine sports medicine. Post exertional airway endoscopy is the reference standard for diagnosing EIPH, however the severity score is based on the amount of blood that ascends the tracheobronchial tree, which might not accurately reflect lung injury. Although the total hemosiderin score (THS) in the bronchoalveolar lavage fluid (BALF) has been shown to have a good sensitivity to diagnose EIPH, racehorse owners and trainers are often reluctant to allow this procedure. The use of the tracheal wash fluid (TWF) to assess EIPH through THS has been demonstrated as an alternative diagnostic approach. The present study evaluated the sensitivity and specificity of THS when applied in TWF samples of Thoroughbred racehorses to establish diagnostic cut-off values. Horses were grouped according to their athletic development, EIPH endoscopic grade, and use of furosemide. Differential cell counts and mean THS by group and by endoscopic grade were compared bythe Median Test. Sensitivity and specificitywere assessed with a contingencytable, and the receiver operating characteristic curve was used to define optimal cut-off values. The cut-off values 30, 138, and 246 were established to interpret THS results according to clinical history. ATHS score of >= 246 can be interpreted as evidence of past bleeding and provides unequivocal confirmation of EIPH in healthy animals. This study demonstrates how defining appropriate cut-off values for THS in TWF samples can aid in the diagnosis and monitoring of EIPH in clinical practice.