Abstract
Simple SummaryThe recognition of pain in equine practice is highly dependent on the assessors’ reliability in using pain assessment tools. The Horse Grimace Scale (HGS) is one such tool, a facial-expression-based pain coding system able to identify a range of acute painful conditions in horses. This study aimed at evaluating the efficacy of a standardised HGS training program at improving the agreement of assessors without horse experience by comparison with an expert. The results suggest that 30-minute face-to-face training may not be sufficient to allow observers without horse experience to effectively learn about HGS and its consentient facial action units to then be able to effectively apply this scale. The training method applied could represent a starting point for a more comprehensive training program for assessors with no experience.The Horse Grimace Scale (HGS) is a facial-expression-based pain coding system that enables a range of acute painful conditions in horses to be effectively identified. Using valid assessment methods to identify pain in horses is of a clear importance; however, the reliability of the assessment is highly dependent on the assessors’ ability to use it. Training of new assessors plays a critical role in underpinning reliability. The aim of the study was to evaluate whether a 30-minute standardised training program on HGS is effective at improving the agreement between observers with no horse experience and when compared to an HGS expert. Two hundred and six undergraduate students with no horse experience were recruited. Prior to any training, observers were asked to score 10 pictures of horse faces using the six Facial Action Units (FAUs) of the HGS. Then, an HGS expert provided a 30-minute face-to-face training session, including detailed descriptions and example pictures of each FAU. After training, observers scored 10 different pictures. Cohen’s k coefficient was used to determine inter-observer reliability between each observer and the expert; a paired-sample t-test was conducted to determine differences in agreement pre- and post-training. Pre-training, Cohen’s k ranged from 0.20 for tension above the eye area to 0.68 for stiffly backwards ears. Post-training, the reliability for stiffly backwards ears and orbital tightening significantly increased, reaching Cohen’s k values of 0.90 and 0.91 respectively (paired-sample t-test; p < 0.001). The results suggest that this 30-minute face-to-face training session was not sufficient to allow observers without horse experience to effectively apply HGS. However, this standardised training program could represent a starting point for a more comprehensive training program for those without horse experience in order to increase their reliably in applying HGS.
Highlights
Using valid assessment methods to identify pain in horses as a consequence of husbandry practices or in a clinical setting is of a clear importance [1,2]
This study did not evaluate the agreement between observers with no horse experience with that of an expert, which is critical for determining the efficacy of training naive observers [16,20]
The results of the present study showed a high variability of agreement between naïve observers and the expert for the different facial action units comprising the Horse Grimace Scale (HGS): ranging from 0.20 for tension above the eye area to 0.68 for stiffly backwards ears (Figure 2)
Summary
Using valid assessment methods to identify pain in horses as a consequence of husbandry practices or in a clinical setting is of a clear importance [1,2]. Several factors can complicate the recognition of pain in horses They are a prey species and may hide their pain [4]; individual temperament has been shown to influence the intensity that pain-related behaviours are exhibited [5]. A training program aiming to improve the accuracy of pain evaluation by new assessors should be developed in order to improve their inter-observer reliability [6,7]. This would guarantee that the use of pain indicators by multiple individuals will provide reliable results, more consistently reflecting pain levels observed, and be applicable in daily clinical practice [8,9]. Well-designed training programs are especially important for equine pain assessment, given the diversity observed in the horse industry, in terms of breeds, different housing systems, various disciplines, different professional levels [10]
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