Feline Grimace Scale (FGS)

Overview

Developer

Evangelista, Watanabe, Leung, Monteiro, O'Toole, Pang, Steagall (Université de Montréal)

Year published

2019

Species

Feline

Domain

Acute pain

Structure and administration

5 facial action units (ear position, orbital tightening, muzzle tension, whisker change, head position) each scored 0-2. Total 0-10; published clinical threshold is normalised >= 0.39 (raw >= 4).

Owner- or clinician-completed via reference-photo matching, 2-3 minutes per assessment.

Psychometric properties

Cronbach α

0.89

Test-retest ICC

0.85

Cut-off and interpretation

Cut-off threshold

5

Source: Evangelista et al. 2019 publishes a normalised threshold of 0.39 (raw >= 4) as analgesia-indicated. Sightline shifts the 'consult vet' band to raw >= 5 to reduce false-positive escalation in owner-completed assessments while preserving the borderline 3-4 range as a re-score prompt.

Citation and validation

Evangelista MC, Watanabe R, Leung VSY, Monteiro BP, O'Toole E, Pang DSJ, Steagall PV. Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale. Sci Rep 2019;9:19128.

DOI: 10.1038/s41598-019-55693-8

Revisions

• v1.0 (Evangelista et al. 2019): original five-unit scale validated against acute clinical and post-procedure pain. Paper and supplementary training manual published in Scientific Reports under CC BY 4.0; the separate felinegrimacescale.com online scoring tool is © Université de Montréal, all rights reserved.
• Cross-cultural validation (Steagall et al., subsequent publications): confirmed psychometric performance across populations and observers.

Target population

Cats with acute or post-procedural pain. Specifically validated for clinical and post-operative pain detection. Brachycephalic breeds (Persian, Himalayan, Exotic Shorthair, British Shorthair, Scottish Fold) can score artificially high because resting facial morphology overlaps the AU patterns the scale flags; Sightline surfaces a warning before the questionnaire starts and recommends cross-referencing with FMPI-SF or asking the vet to score in person.

Available languages

English (UK)

Licence

The Scientific Reports 2019 paper (Sci Rep 9:19128, doi:10.1038/s41598-019-55693-8) is published under Creative Commons Attribution 4.0 International (CC BY 4.0), permitting commercial use of the article and its supplementary appendices with attribution. Reference imagery in this build is sourced from Appendix 1 (the training manual) of that paper. The felinegrimacescale.com website artwork and the FGS app are separately © Université de Montréal, all rights reserved, and are NOT used. Attribution: Reference imagery adapted (cropped) from Evangelista MC, Watanabe R, Leung VSY, Monteiro BP, O'Toole E, Pang DSJ, Steagall PV. Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale. Scientific Reports 9:19128 (2019). doi:10.1038/s41598-019-55693-8. Licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).

Scoring algorithm version

sightline-fgs-v1.0.0

Strengths

• Fast (2-3 minutes), suitable for both owner-side post-procedure tracking and clinician bedside use.
• Strong psychometrics (Cronbach α 0.89, test-retest ICC 0.85) for an observer-rated scale.
• Reference imagery is CC BY 4.0 via the Scientific Reports paper, so Sightline can carry the photos in-app with attribution and no per-deployment licence fee.
• The published clinical cutoff (analgesia indicated at normalised >= 0.39) is one of the few cat-specific pain thresholds with population-validation data.

Limitations

• Brachycephalic cats (flat-faced breeds) are a known false-positive group; Sightline shows a warning and recommends cross-referencing with FMPI-SF.
• The scoring is observer-rated, so inter-rater reliability depends on owner familiarity with the reference photos.
• FGS scores can be elevated by stress, restraint, or unfamiliar environments; in-clinic scoring within 5-10 minutes of a settled cat is more reliable than freshly-handled scoring.
• The reference imagery must be sourced from the Scientific Reports paper (CC BY 4.0) rather than felinegrimacescale.com (separately © all rights reserved); attribution wording must render on every surface that shows the scale.

Why Sightline uses it

FGS is the only widely-validated owner-administered acute pain instrument for cats. Pairing FGS (acute, point-in-time) with CSOM (owner-defined) gives Sightline focused cat-pain coverage on top of the daily Sightline Score. The CC BY 4.0 reference imagery in the Scientific Reports paper means Sightline can ship a fully-functional in-app scoring tool with attribution and no per-deployment licence fees.