Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale

Abstract

Grimace scales have been used for pain assessment in different species. This study aimed to develop and validate the Feline Grimace Scale (FGS) to detect naturally-occurring acute pain. Thirty-five client-owned and twenty control cats were video-recorded undisturbed in their cages in a prospective, case-control study. Painful cats received analgesic treatment and videos were repeated one hour later. Five action units (AU) were identified: ear position, orbital tightening, muzzle tension, whiskers change and head position. Four observers independently scored (0–2 for each AU) 110 images of control and painful cats. The FGS scores were higher in painful than in control cats; a very strong correlation with another validated instrument for pain assessment in cats was observed (rho = 0.86, p < 0.001) as well as good overall inter-rater reliability [ICC = 0.89 (95% CI: 0.85–0.92)], excellent intra-rater reliability (ICC > 0.91), and excellent internal consistency (Cronbach’s alpha = 0.89). The FGS detected response to analgesic treatment (scores after analgesia were lower than before) and a cut-off score was determined (total pain score > 0.39 out of 1.0). The FGS is a valid and reliable tool for acute pain assessment in cats.

Clinical applicability of the Feline Grimace Scale: real-time versus image scoring and the influence of sedation and surgery

“…Additionally, responsiveness should also be assessed using FGS-RT. Both methods of pain assessment (FGS-RT and FGS-IMG) detected changes in pain scores corroborating our previous findings (Evangelista et al, 2019). Decreases in pain scores were also observed with the SF-UBCPS.…”

“…Alternatively, the evaluation of the LOA in relation to the analgesic threshold has been proposed (Leung, Zhang & Pang, 2016). The LOA observed in the present study, although narrow (LOA final score : −0.351 to 0.237), spans the analgesic threshold of 0.39 out of 1.0 previously determined for the FGS (Evangelista et al, 2019). This would mean that FGS-RT scores that are close to the analgesic threshold (slightly lower or higher than 0.39) should be interpreted with caution since this threshold is a suggestion for the administration of rescue analgesia based on the probability of being painful above that score.…”

“…Recently, a facial expression-based scoring system has been proposed for assessing acute pain in cats, namely the Feline Grimace Scale (FGS). This instrument has been developed and validated in cats with different sources and intensities of pain produced by naturally-occurring conditions; additionally, its reliability, criterion and construct validity (including responsiveness) were assessed using image scoring (Evangelista et al, 2019).…”

Peer Review #3 of "Clinical applicability of the Feline Grimace Scale: real-time versus image scoring and the influence of sedation and surgery (v0.3)"

“…Manuscript to be reviewed scores corroborating our previous findings (Evangelista et al 2019). Decreases in pain scores were also observed with the SF-UBCPS.…”

“…Alternatively, the evaluation of the LOA in relation to the analgesic threshold has been proposed (Leung et al 2016). The LOA observed in the present study, although narrow (LOA final score : -0.351 to 0.237), spans the analgesic threshold of 0.39 out of 1.0 previously determined for the FGS (Evangelista et al 2019). This would mean that FGS-RT scores that are close to the analgesic threshold (slightly lower or higher than 0.39) should be interpreted with caution since this threshold is a suggestion for the administration of rescue analgesia based on the probability of being painful above that score.…”