Nasopharyngeal and laryngopharyngeal collapse: intra- and interrater agreement supports novel endoscopic scoring classifications in horses.

Abstract

Objective: The contribution of reduced airway patency from heightened inspiratory pressure or active muscular contraction to the pathophysiology of pharyngeal collapse is unknown. Existing classifications refer to the entire pharyngeal region; however, anatomical differences are evident between rostral and caudal collapse. Novel classifications and grading systems are proposed to differentiate 2 pathologies: nasopharyngeal collapse (NPC; collapse of ≥ 1 pharyngeal wall rostral to the tip of the epiglottis; grades 0 through 4), and laryngopharyngeal collapse (LPC; collapse of ≥ 1 pharyngeal wall caudal to the tip of the epiglottis; grades 0 through 3).

Methods: Clinical reports from 99 barrel racing horses in Southern Alberta previously diagnosed with pharyngeal collapse via overground endoscopy (2015 through 2025) were retrospectively analyzed. Horses were referred for respiratory signs and/or poor performance. Two raters independently assessed still images obtained during high-speed exercise in a blinded and randomized fashion. Descriptive statistics and intrarater/interrater agreement for classification (McNemar test) and scoring (weighted κ) were reported.

Results: Similar frequencies of NPC (64.6%) and LPC (67.6%) were observed (32% had both). Intrarater agreement for NPC was χ2 = 7.0 (rater 1) and χ2 = 1.0 (rater 2) for NPC and χ2 = 2.0 (rater 1) and χ2 = 1.6 (rater 2) for LPC. Scoring agreement was good to very good for NPC (κ = 0.69 to 0.81) and moderate to good for LPC (κ = 0.56 to 0.80), indicating reliable performance. Interrater agreement was χ2 = 4.6 (rater 1) and χ2 = 0.7 (rater 2) for NPC and χ2 = 0.2 (rater 1) and 2.0 (rater 2) for LPC.

Conclusions: Intra- and interrater agreement supports the feasibility and practicality of distinguishing NPC from LPC.

Clinical relevance: Novel classifications reflecting functional anatomy may provide insight into the pathophysiology of pharyngeal collapse.