Grimace Scores: Tools to Support the Identification of Pain in Mammals Used in Research
Office of Research, Ethics, and Integrity, University of Melbourne, Melbourne 3010, Australia
Anesthesia and Veterinary Clinical Sciences, University of Melbourne, Melbourne 3010, Australia
Author to whom correspondence should be addressed.
Received: 16 August 2020 / Revised: 15 September 2020 / Accepted: 16 September 2020 / Published: 23 September 2020
The ability to identify and assess pain is paramount in animal research to address the ‘refinement’ principle of the 3Rs (Reduction, Refinement, Replacement), satisfy public acceptability of animal use in research and address ethical and legal obligations. Many physiological, behavioural and physical pain assessments are commonly used, but all have their limitations. Grimace scales are a promising adjunctive behavioural pain assessment technique in some mammalian species used in research. This paper reviews the extant literature studying pain assessment techniques in general, and grimace scales specifically, in animal research. The results indicate that the grimace scale technique is simple and able to be used spontaneously at the ‘cage side’, is non-invasive in its application, highly repeatable, reliable between interobserver and intraobserver applications and easy to train and use. The use of grimace scales should be more frequently considered as an important parameter of interest in research and animal wellbeing. Further research into the use of grimace scales is required to develop scales for a wider range of animal species, increase applicability in studies specifically related to pain assessment and for further validation of the technique.