The determination of humane endpoints in an animal study is a core part of harm-benefit assessment. In addition, it is of vital importance in giving those responsible for the research animals adequate guidance in how to tackle critical situations which may occur outside normal working hours. Studies likely to cause pain, distress or harm to the animals may necessitate increased staffing levels to ensure adequate monitoring throughout the 24-hour period. If possible, studies should be designed so that the high-risk period occurs during normal working hours.

There is extensive advice available on how to construct humane endpoints. The criteria for measuring the animals’ status in relation to the endpoints should be as objective as possible, for example based on body weight, tumour volume or other physical parameters, to avoid ambiguity and individual differences in practice. Scientists should indicate whether pilot studies are needed to explore and define these endpoints. If death is to be an endpoint, scientists must explain why this is unavoidable and what measures can be taken to minimise suffering.

Dialogue with local animal welfare and ethics committees is likely to be an important part of this step.

References

• A collection of papers on Score Sheets, Severity Assessment and Humane Endpoints from the Laboratory Animals
• Humane endpoints (NC3Rs website)
• Humane-endpoints.info
• Nunamaker et al. (2021): Developing Recommendations for Cumulative Endpoints and Lifetime Use for Research Animals
• Dudis et al. (2023): Longitudinal temperature measurement can determine humane endpoints in BALB/c mice models of ESKAPEE infection
• Refining Humane Endpoints in Mouse Models of Disease by Systematic Review and Machine Learning-Based Endpoint Definition (Mei et al., 2019)
• A Systematic Approach for Establishing Humane Endpoints (Morton, 2000)
• OECD Guidance Document on the Recognition, Assessment, and Use of Clinical Signs as Humane Endpoints for Experimental Animals Used in Safety Evaluation
• Ellis T & Katsiadaki I (2020): Clarification of early end-points for refinement of animal experiments, with specific reference to fish
• Guidance on a common education and training framework, issued by the EU Commission mentions humane endpoints
• Defining body-weight reduction as a humane endpoint: a critical appraisal (Talbot et al., 2019)