Objective assessment of chronic pain in donkeys using the Donkey Chronic Pain Scale.

Objective To clinically evaluate previously developed pain scales [Donkey Chronic Pain Composite Pain Scale (DCP-CPS), Donkey Chronic Pain Facial Assessment of Pain (DCP-FAP), and combined Donkey Chronic Pain Scale (DCPS)], including behavioural and facial expression related variables, for the assessment of chronic pain in donkeys. Study design Prospective, blinded clinical study. Animal population A group of 77 donkeys (34 patients and 43 healthy control animals) Methods Animals were assessed by two observers that were blinded to the condition of the animals. Results Both DCP composite pain scale (CPS), DCP facial assessment of pain (FAP) and resulting Donkey Chronic Pain Scale (DCPS) scores showed good inter-observer reliability (Intra Class Correlation (ICC) coefficient = 0.91, confidence interval (CI) = 0.86–0.95, p < 0.001; ICC = 0.71, CI = 0.50–0.83, p < 0.001 and ICC = 0.84, CI = 0.72–0.91, p < 0.001 respectively). All scores (DCP-CPS, DCP-FAP and the resulting combined DCPS) were significantly higher for patients compared to controls at all time points (p < 0.001 for all three scales). Sensitivity and specificity for identification of pain (cut-off value > 3) was 73.0 and 65.1% for DCP-CPS, while for DCP-FAP this was 60.9% and 83.3%, respectively. For the combined DCPS, sensitivity was 87.0% and specificity 90.9% (cut-off value > 6). Conclusions and clinical relevance The DCPS, based on behavioural and facial expression-based variables, proved a promising and reproducible tool to assess different types of chronic pain in donkeys. The combination of behavioural and facial expression-based variables showed the best discriminatory characteristics in the current study. Further studies are needed for refinement of these tools.