Meta-analysis evaluating resting laryngeal endoscopy as a diagnostic tool for recurrent laryngeal neuropathy in the equine athlete.
Authors: Elliott S, Cheetham J
Journal: Equine veterinary journal
Summary
Elliott and Cheetham's 2019 meta-analysis synthesised data from 12 studies encompassing 1,827 horses to establish the diagnostic accuracy of resting laryngeal endoscopy for predicting recurrent laryngeal neuropathy (RLN) during exercise. Whilst resting grades 1 and 2 demonstrated good negative predictive value (with only 3.5–11.9% showing abnormal function at exercise), grade 3 resting findings proved highly variable at exercise: 16% achieved normal dynamic function (grade A), whilst 57.6% exhibited complete or partial paralysis (grade C). Overall sensitivity and specificity were 74.4% and 95.1% respectively, with positive and negative predictive values of 85.6% and 90.5%, confirming resting endoscopy as a reliable screening tool for RLN. For clinical practice, these findings underscore the importance of dynamic endoscopy in horses presenting with grade 3 lesions at rest, as static assessment alone cannot reliably differentiate functional capacity during athletic work—a critical distinction for prognostic counselling and return-to-sport decisions. Practitioners should interpret normal or mildly abnormal resting grades with confidence but recognise that borderline findings warrant exercise endoscopy to fully characterise airway dynamics and exclude alternative causes of respiratory compromise.
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Practical Takeaways
- •Resting endoscopy is a reliable screening tool—normal results (grades 1-2) effectively rule out laryngeal dysfunction in most cases, avoiding unnecessary exercise testing
- •Grade 3 resting findings warrant dynamic endoscopy, as this intermediate grade shows high variability in exercise performance and cannot reliably predict outcome
- •Dynamic endoscopy remains essential because resting exams miss ~9-10% of clinically affected horses and cannot identify other causes of airway obstruction
Key Findings
- •Resting endoscopy demonstrated 74.4% sensitivity and 95.1% specificity for predicting abnormal laryngeal function at exercise
- •Only 3.5% of horses with grade 1 and 11.9% with grade 2 resting laryngeal function showed abnormal function at exercise
- •Among horses with grade 3 resting function, 57.6% demonstrated complete or partial paralysis (grade C) at exercise
- •Negative predictive value was 90.5%, indicating good reliability for ruling out disease when resting endoscopy appears normal