Diagnostic Value of Tracheal Wash Cytology for Monitoring Exercise-Induced Pulmonary Hemorrhage in Thoroughbred Racehorses.
Authors: Cascardo Bianca, Bernardes Camila, de Souza Guilherme N, Silva Katia M, Pires Natália R, de Alencar Nayro Xavier, Lessa Daniel A B
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Tracheal Wash for Monitoring Exercise-Induced Pulmonary Hemorrhage Exercise-induced pulmonary haemorrhage (EIPH) remains a significant concern in Thoroughbred racehorses, yet current diagnostic methods present practical challenges: bronchoalveolar lavage, the gold standard for lower airway cytology, requires sedation and is highly invasive, making it unsuitable for monitoring active competition horses. Cascardo and colleagues investigated whether tracheal wash (TW)—a simpler, less invasive alternative—could reliably identify and grade EIPH severity using Total Hemosiderin Score (THS) analysis in 47 Thoroughbreds evaluated endoscopically for EIPH within 60 minutes of racing, with tracheal fluid samples collected 24–30 hours later for cytological examination. Whilst the researchers could not establish a reliable THS cut-off value to discriminate between EIPH-positive and EIPH-negative horses, they found that haemosiderophages (iron-laden macrophages indicating previous bleeding) were detectable even in first-time runners with no clinical EIPH history, suggesting TW can identify subclinical lung bleeding that endoscopy alone might miss. For practitioners, this indicates tracheal wash has genuine diagnostic potential as a low-cost, field-friendly screening tool, though the current evidence suggests it functions better as a sensitive indicator of pulmonary bleeding rather than a quantitative severity assessment—meaning positive results warrant further investigation but negative results cannot yet confidently exclude EIPH.
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Practical Takeaways
- •Tracheal wash cytology can be used for non-invasive monitoring of EIPH in racing Thoroughbreds without sedation, making it practical for in-training horses
- •Evidence of hemosiderophages may be present even in horses without visible EIPH on endoscopy, suggesting the technique detects subclinical bleeding not apparent clinically
- •While promising as a screening tool, tracheal wash analysis cannot yet replace endoscopy for definitive EIPH grading, as no reliable cut-off point has been established
Key Findings
- •Tracheal wash cytology detected hemosiderophages even in EIPH-negative horses, indicating subclinical lung bleeding
- •No statistically significant differences in Total Hemosiderin Score (THS) between EIPH grades despite clinical differences on endoscopy
- •Tracheal wash successfully identified evidence of pulmonary hemorrhage in a first-time runner with no EIPH history
- •Tracheal wash is a less invasive, low-cost alternative to bronchoalveolar lavage that does not require sedation in active racehorses