Refinement and revalidation of the Equine Acute Abdominal Pain Scale (EAAPS)

Assessment of pain is vital for colic treatment. The purpose of this study was to revalidate a refined version of the behaviour-based Equine Acute Abdominal Pain Scale (EAAPS). Based on an earlier study, behaviours in the scale were removed or replaced. Ten behaviours remained. For revalidation, forty films of horses with colic were presented by computer-generated random order to two randomly-assigned groups of equine veterinarians. One group (n=8) scored the severity of pain demonstrated in the films by utilizing a numerical rating scale (NRS) and one group (n=7) with the refined version of the EAAPS. Intra-rater reliabilities of the EAAPS and of the NRS were comparable based on Limits of Agreement. The inter-rater reliability of the EAAPS was significantly improved compared to the NRS (NRS; Intraclass correlation (ICC) = 0.6 (95% Confidence Interval (CI); 0.5-0.8) and EAAPS; ICC = 0.88 (95%CI: 0.8-0.9)). Face validity was 71% (95% CI; 29-96) in support of the EAAPS. The two scales showed substantial convergent validity (weighted kappa of 0.73 (95%CI; 0.58-0.88). The predictive validity of the EAAPS scale was similar to the NRS (AUC of EAAPS; 0.75 versus NRS; 0.78 for mortality; AUC of EAAPS 0.76 versus NRS of 0.83 for treatment modality) and the ability to discriminate between extreme groups of either control horses versus cases or by extreme groups defined by NRS scores of 0-2 versus 3-5 was excellent (AUC 0.99 and 0.955, respectively). In summary, revalidation of the refined EAAPS was necessary and was found to be highly reliable and comparatively valid.