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Reliability of the Mouse Grimace Scale in C57BL/6JRj Mice
Katharina Hohlbaum1, Giuliano Mario Corte2, Melanie Humpenöder1
1Institute of Animal Welfare, Animal Behavior and Laboratory Animal Science, Department of Veterinary Medicine, Freie Universität Berlin, 14163 Berlin, Germany.
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.
Insights
The Mouse Grimace Scale (MGS) shows good overall reliability for assessing laboratory mouse welfare. However, scoring consistency varies, with experienced observers and early post-anesthesia periods demonstrating higher agreement.
Area of Science:
- Veterinary Science
- Animal Welfare Science
- Laboratory Animal Science
Background:
- Reliable welfare assessment tools are crucial for laboratory animals.
- The Mouse Grimace Scale (MGS) analyzes facial expressions to gauge pain or distress.
- Concerns exist regarding the objectivity and consistency of MGS scoring.
Purpose of the Study:
- To investigate the interrater reliability of the Mouse Grimace Scale (MGS).
- To assess how observer experience and time post-anesthesia affect MGS reliability.
Main Methods:
- Four observers (two experienced, two inexperienced) scored 188 images of mice.
- Images were captured at baseline, 150 minutes, and two days post-ketamine/xylazine anesthesia.
- Intraclass correlation coefficients (ICCs) were calculated to determine agreement.
Main Results:
- Overall MGS scoring showed good agreement (ICC = 0.851).
- Interrater reliability was highest early post-anesthesia (ICC = 0.799) and lowest on day 2 (ICC = 0.329).
- Orbital tightening showed the best agreement; nose and cheek bulge showed the poorest.
Conclusions:
- The Mouse Grimace Scale demonstrates acceptable overall reliability for assessing mouse welfare.
- Observer experience significantly impacts MGS scoring consistency.
- Anesthesia and time elapsed influence the reliability of MGS assessments, necessitating careful consideration of these factors.
