Relationship between tracheobronchoscopic score and bronchoalveolar lavage red blood cell numbers in the diagnosis of exercise-induced pulmonary hemorrhage in horses.

Abstract

BACKGROUND: Exercise-induced pulmonary hemorrhage (EIPH) is diagnosed and its severity assessed by post-exercise tracheobronchoscopy, and enumeration of bronchoalveolar lavage fluid red blood cells (BALFRBC). Minimal information is available regarding the relationship of tracheobronchoscopy score to BALFRBC number. OBJECTIVE: Evaluate the relationship between BALFRBC number and tracheobronchoscopy scores and determine their diagnostic sensitivities. ANIMALS: Nine sedentary horses, 21 fit Thoroughbreds, 129 Barrel Racers. METHODS: Normal BALFRBC number and the effect of bronchoalveolar lavage (BAL) on it were evaluated by performing 2 BALs 24&#x2009;hours apart in sedentary horses. Tracheobronchoscopy followed by BAL was performed 247 times on 150 horses after treadmill, racetrack, or barrel racing exercise. Lastly, a BALFRBC diagnostic threshold number that optimized the geometric mean of the sensitivity and precision (F1-score) was determined using Bayesian analysis. RESULTS: No increase in BALFRBC occurred after the second BAL (mean&#x2009;&#xb1;&#x2009;SD, 304&#x2009;&#xb1; 173/&#x3bc;L). Tracheobronchoscopy scores ranged from 0 (n = 112) to 4 (n = 4) and BALFRBC ranged from 102 to 4605268/&#x3bc;L. Spearman correlation between tracheobronchoscopy score and BALFRBC was weak (P&#x2009;<&#x2009;.001; rs = 0.42) with large ranges of BALFRBC associated with each tracheobronchoscopy score. The highest F1-score occurred for a BALFRBC threshold number = 992/&#x3bc;L. Seventy-five tracheobronchoscopy scores equaled 0 although BALFRBC number was &#x2265;992/&#x3bc;L. Sensitivity of tracheobronchoscopy for diagnosing EIPH was poor (0.59; 95% confidence intervals [CI], 0.49-0.68), compared to BALFRBC number &#x2265;992/&#x3bc;L (0.93; 95% CI, 0.88-0.96). CONCLUSIONS AND CLINICAL IMPORTANCE: False negatives are common with tracheobronchoscopy. Follow-up determination of BALFRBC may be indicated for tracheobronchoscopy scores = 0 before EIPH can be ruled out.