To track for the presence of pain or distress in mice over time, the baseline should be based on:

• A. The signs observed on normal, untreated animals
• B. The signs observed after treatment
• C. Post-procedure pain scores
• D. Historical literature values

Answer: (A)

Establishing a baseline from normal, untreated mice provides a neutral reference for what typical behavior and physiology look like in that specific strain, age, and housing. This baseline is essential because it captures the animal’s true, pre-manipulation state, allowing you to detect real changes in pain or distress over time. By comparing each animal’s future observations to its own baseline, you account for individual variability and accurately assess onset, duration, and severity of discomfort.

Using signs observed after treatment or post-procedure can reflect the effects of the intervention, analgesia, or surgical impact rather than the true baseline state, so they’re not suitable as the baseline reference. Historical literature values may not match your current population or conditions, which can mislead interpretation due to differences in strain, environment, age, or measurement methods.