Construct validity, responsiveness and reliability of the Feline Grimace. Scale in kittens

This study aimed to investigate construct validity, responsiveness, and reliability of the Feline Grimace Scale (FGS) in kittens.

Following ethics committee approval, thirty-six healthy kittens (aged 10 weeks to 6 months) were included in a prospective, randomized, blinded study. Video-recordings of kittens were performed before, and 1 and 2 hours after ovariohysterectomy using an opioid-free injectable aneasthetic protocol with or without multimodal analgesia, as well as before and 1 hour after administration of rescue analgesia (buprenorphine 0.02 mg kg^-1 IM). Screenshots of facial images were collected from video-recordings for FGS scoring. Four observers unaware of time-points scored 111 randomized images independently and twice within a 5-week interval. Five action units (AU) were scored (ear position, orbital tightening, muzzle tension, whiskers position, and head position; 0-2 each). Construct validity, responsiveness, and inter- and intra-rater reliability were evaluated using linear models with Benjamini-Hochberg corrections, Wilcoxon signed rank test, and intra-class correlation coefficients (ICC), respectively (p < 0.05).