A behaviour-based pain scale for horses with acute colic: scale construction.

A validated tool for assessing the severity of acute abdominal pain is needed for the effective management of colic in horses. Two behaviour-based colic pain scales were constructed by combining together mathematical and judgemental approaches. The mathematical approach identified easily-recognised pain behaviours to select as items. The judgemental approach further modified the items and weighted them based on expert-opinion. Thirty equine practitioners assessed the level of pain demonstrated in 23 film clips of clinical cases exhibiting signs of acute abdominal pain prospectively using a 10cm visual analogue scale (VAS). The practitioners also identified behaviours noted in each clip from a checklist of 23 behaviours identified from the literature. Nine behaviours had insignificant bias and moderate-to-excellent inter-observer agreement (multirater kappas: 0.5-0.95). Six experienced veterinarians then completed questionnaires in an iterative Delphi process to independently judge 15 items that best reflected severity of pain out of 42 items generated from the literature. Two behaviours were generated by the process. Subsequently, an advisory panel of three equine practitioners constructed two clinimetric-type scales based on the results of both approaches. The two resulting equine acute abdominal pain scales (EAAPS) included 12 behaviours. One weight was assigned to each behaviour in the EAAPS-1. In the EAAPS-2, gradations of weights were assigned, based on the frequency of the behaviour being demonstrated. The EAAPS scales are the first pain severity scales designed specifically for clinical use in cases of acute colic utilising the clinimetric approach to scale construction. Further studies are underway to validate the scales.