Objectives: The aim of the study was to determine the effects of training on inter-rater reliability and agreement of Feline Grimace Scale (FGS) scoring by small animal practitioners.
Methods: Seven small animal veterinarians were asked to score a total of 50 images of cats in varying degrees of pain before and after training in FGS scoring. Participant scores were compared with those of an expert rater. Inter-rater reliability was analyzed using the intraclass correlation coefficient (ICC) before and after training (ICC <0.50 = poor reliability, 0.50-0.75 = moderate reliability, 0.76-0.90 = good reliability and >0.90 = excellent reliability). The Bland-Altman method was used to analyze the limits of agreement (LoAs) and bias between participants and the expert rater.
Results: After training, the ICC classification improved for each action unit (ear position, orbital tightening, muzzle tension, whiskers change and head position). The inter-rater reliability for the total FGS ratio scores before and after the FGS training session was moderate (ICC = 0.75; 95% confidence interval [CI] 0.66-0.83) and good (ICC = 0.80; 95% CI 0.73-0.87), respectively. Before training, LoAs were -0.277 to 0.310 with a bias of 0.016. After training, LoAs were -0.237 to 0.255 with a bias of 0.008. The bias was low (<0.1) both before and after training and LoAs did not span the FGS analgesic threshold (0.39).
Conclusions and relevance: Training in FGS scoring improved inter-rater reliability and agreement among seven small animal veterinarians and the veterinarians' skills in pain assessment.
Keywords: Feline Grimace Scale; analgesia; facial expressions; pain; pain assessment.