Inter-Rater Reliability of the Feline Grimace Scale in Cats Undergoing Dental Extractions

Abstract

This study aimed to evaluate the inter-rater reliability of the Feline Grimace Scale (FGS) in cats undergoing dental extractions and the effects of the caregiver's presence on the FGS scores. Twenty-four cats (6 ± 3.3 years old; 4.9 ± 1.7 kg) undergoing oral treatment were included in a prospective, blinded, randomized, clinical study. They underwent treatment under general anesthesia (acepromazine-hydromorphone-propofol-isoflurane-meloxicam-local anesthetic blocks) at day 1 and were discharged at day 6. Images of cat faces were captured from video recordings with or without the caregiver's presence at 6 h postoperatively (day 1), day 6, and before and after rescue analgesia. Images were randomized and independently evaluated by four raters using the FGS [five action units (AU): ear position, orbital tightening, muzzle tension, whiskers change, and head position; score 0-2 for each]. Inter-rater reliability and the effects of the caregiver's presence were analyzed with intraclass correlation coefficient [single measures (95% confidence interval)] and the Wilcoxon signed-rank test, respectively (p < 0.05). A total of 91 images were scored. Total FGS scores showed good inter-rater reliability [0.84 (0.77-0.89)]. Reliability for each AU was: ears [0.68 (0.55-0.78)], orbital tightening [0.76 (0.65-0.84)], muzzle [0.56 (0.43-0.69)], whiskers [0.64 (0.50-0.76)], and head position [0.74 (0.63-0.82)]. The FGS scores were not different with [0.075 (0-0.325)] or without [0.088 (0-0.525)] the caregivers' presence (p = 0.12). The FGS is a reliable tool for pain assessment in cats undergoing dental extractions. The caregiver's presence did not affect FGS scores.

Reliability of the Mouse Grimace Scale in C57BL/6JRj Mice

“…Probably due to the difficulty in clearly recognizing and evaluating certain FAU, some working groups excluded nose and cheek bulge [19] or whisker change [38,39] from facial expression analysis in mice. Similar observations were made in cats: the highest ICC value was found for orbital tightening and the lowest for muzzle tension as well as whisker change [31]. Considering these challenges of scoring certain FAU, grimace scales that were developed more recently often comprise less parameters than earlier grimace scales.…”

“…Our interrater reliability of mean MGS scores in C57BL/6JRj mice (ICC = 0.845 over all time points) was similar to that found by the MGS inventors (ICC = 0.90) in CD-1 mice [5] and other working groups in CD-1 mice (ICC = 0.8405) [28], BALB/c mice (ICC ranging from 0.75 to 0.84) [29], or BALB/cAnNCrl mice (ICC ranging from 0.7 to 0.84) [30]. In cats, the ICC between four persons applying the Feline Grimace Scale was 0.84 [31].…”

“…In contrast to ears, eyes, and whiskers, the cheeks and nose bridge have the same color as the faces of the mice. In other species such as cats and horses, it has also been reported that the identification of some FAU is difficult in black-furred animals [8,14,31].…”

2022 ISFM Consensus Guidelines on the Management of Acute Pain in Cats

“…Facial expressions are incorporated into all three of these acute pain assessment tools; the Feline Grimace Scale (felinegrimacescale.com) is based entirely on facial 'action units' (Figure 6). 8,29,30,33 These scales provide a cut-off/intervention score that suggests administration of analgesia is required (Table 2). Guidance to assist the veterinary nurse or technician in advocating for their patient, and the clinician with decision-making, is a clear benefit of using pain assessment tools.…”

Closing an Eye for the Reliability of Orbital Tightening in Pain Detection: A Model-Specific Simplification of the Mouse Grimace Scale

“…The pain face, or, so-called grimace scale, which was originally developed in humans for the recognition of pain in children or other patients who depend on non-verbal communication 4 , is scaling the pain sensation based on the expression of different facial features. Meanwhile, the Mouse Grimace Scale (MGS) 5 was developed and transferred to different animal species as well [6][7][8][9][10][11] . Numerous studies were able to demonstrate and verify the applicability and utilization of the grimace scale for pain recognition 12,13 .…”