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

Abstract

To maintain and foster the welfare of laboratory mice, tools that reliably measure the current state of the animals are applied in clinical assessment. One of these is the Mouse Grimace Scale (MGS), a coding system for facial expression analysis. Since there are concerns about the objectivity of the MGS, we further investigated its reliability. Four observers (two experienced and two inexperienced in use of the MGS) scored 188 images of 33 female and 31 male C57BL/6JRj mice. Images were generated prior to, 150 min, and two days after ketamine/xylazine anesthesia. The intraclass correlations coefficient (ICC = 0.851) indicated good agreement on total MGS scores between all observers when all three time points were included in the analysis. However, interrater reliability was higher in the early post-anesthetic period (ICC = 0.799) than at baseline (ICC = 0.556) and on day 2 after anesthesia (ICC = 0.329). The best agreement was achieved for orbital tightening, and the poorest agreement for nose and cheek bulge, depending on the observers’ experience levels. In general, experienced observers produced scores of higher consistency when compared to inexperienced. Against this background, we critically discuss factors that potentially influence the reliability of MGS scoring.

Supplementation with >Your< Iron Syrup Corrects Iron Status in a Mouse Model of Diet-Induced Iron Deficiency

“…Upon completion of the experiment, the average final body mass or total diet consumed did not differ significantly among groups of the same sex regardless of the diet type. Additionally, no differences in behaviour or health-pain assessment were detected between mice in the Iron deficient and Control diet groups according to regular inspections to recognise pain and assess its severity by the mouse grimace scale method [ 31 , 32 ]. The significant differences between males and females were in parameters known to be sexually dimorphic, such as body mass ( p < 0.0001), amount of consumed diet ( p = 0.0189), mass of liver ( p < 0.0001), percentage liver per body mass ( p < 0.0001) and percentage spleen per body mass ( p < 0.0001), but not in the mass of spleen ( p = 0.1386) [ 33 , 34 ].…”

Methods Used and Application of the Mouse Grimace Scale in Biomedical Research 10 Years on: A Scoping Review

“…However, this proposition is not supported by our synthesis, which implies that whiskers are excluded from scoring at similar rates independent of coat colour (although study numbers are low). There may also be an impact of inexperience in scoring on the ability to accurately identify action units; for instance, Hohlbaum et al, 2020 [ 44 ], demonstrated that cheek and nose bulge scoring had reduced inter-observer agreement compared with orbital tightening, with inexperienced scorers having even reduced accuracy.…”

“…Based on the limited evidence available, inter-rater agreement generally ranges from good to excellent. However, a recent study [ 44 ] did suggest that this may change over time, with differences potentially being obscured by the assimilation of all data. This is a factor that should be considered in future studies.…”

“…Few studies have specifically examined this, and detailed information on training was rarely provided in the included studies. Evidence for a training effect is currently conflicting, with one study [ 44 ] suggesting greater consistency if scorers were experienced, whilst another study [ 64 ] finding good correlation between novice and expert scorers. The impact of and type/frequency of training needed to produce reliable grimace scores is an area that needs further research, especially if the technique is going to gain more widespread acceptance as a pain assessment tool.…”

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

“…Our research aimed at the evaluation of the different MGS criteria and the potential simpli cation of its application, mainly to achieve a faster and more widespread implementation. In evaluating the MGS method, various criticisms of its use are repeatedly raised 13,20 . Overall, the OT-MGS model shows a high residual variance.…”