History, Rest and Exercise Score (HRE‐S) for assessment of disease severity in horses with trigeminal‐mediated headshaking

Abstract

AbstractBackgroundIn horses with trigeminal‐mediated headshaking (TMHS), clinical signs are likely to be expression of neuropathic facial pain. Currently, subjective assessment of disease severity is used as measure of compromise of animal's welfare.ObjectivesTo develop and validate a precise scoring system for TMHS: History, Rest and Exercise Score (HRE‐S). The HRE‐S consists of three subscores: history score (H‐S), resting score (R‐S) and exercise score (E‐S).Study designRetrospective observational study.MethodsSeven masked observers with different experience used HRE‐S to score 40 video recordings taken during rest and lungeing including five duplicates. Video recordings were taken from nine horses with TMHS and three controls. Inter‐ and intraobserver reliability and practicability of HRE‐S were assessed. For every video recording severity of clinical signs was graded by every observer using an intuitive global‐type‐scale and interobserver reliability was calculated. Convergent validity was evaluated comparing HRE‐S to groups created by an existing score (grade 0–3). Discriminant validity was analysed comparing HRE‐S to groups created by intuitive global‐type‐scale.ResultsReliability for HRE‐S was excellent, irrespective of observers experience: Spearman's Rho = 0.946, p < 0.001 (intraobserver reliability) and intraclass correlation coefficient = 0.98, p < 0.001 (interobserver reliability). Interobserver reliability for intuitive global‐type‐scale was fair to substantial: Fleiss' κappa = 0.48 (R‐S) −0.63 (E‐S). Groups created by intuitive global‐type‐scale had significantly different R‐S and E‐S (p < 0.05), demonstrating discriminant validity. Convergent validity was proven as horses with grade 3/3 had significantly higher average E‐S and total scores compared with an existing score than those with grade 0/3 or 1/3 (p < 0.001).Main limitationsRetrospective nature, video recordings, sample size.ConclusionsHRE‐S is a valid and reliable score evaluating disease severity in TMHS, independent of observers' experience.