Initial validation of the LSPain scale: a behaviour-based clinical tool for canine lumbosacral pain.

Introduction: This study aimed to validate the LSPain Scale, a novel 4-point ordinal instrument for assessing lumbosacral pain in dogs based on behavioural responses to palpation of the lumbosacral region. Methods: A preliminary analysis was conducted using clinical data to inform sample size estimation and to explore the scale's convergent validity and responsiveness. Subsequently, a prospective validation was performed using 50 anonymised clinical videos retrospectively collected from client-owned dogs evaluated for suspected lumbosacral pain. Dogs represented a broad clinical spectrum and were graded using the LSPain Scale, where scores range from 0 (no pain) to 3 (severe pain). Trained observers, including pain specialists and general practitioners, independently scored the videos while blinded to clinical data. Results: Psychometric evaluation demonstrated strong convergent and discriminant validity, responsiveness to treatment, inter- and intra-rater reliability, and usability across experience levels. Discussion: The findings support the LSPain Scale as a valid and reliable clinician-based tool for standardised assessment and monitoring of lumbosacral pain in dogs.