Horse Grimace Scale Does Not Detect Pain in Horses with Equine Gastric Ulcer Syndrome.
Authors: Ferlini Agne Gustavo, May Bridget Eileen, Lovett Amy, Simon Olivier, Steel Catherine, Santos Luiz, Guedes do Carmo Laize, Barbosa Bianca, Werner Laís Cristine, Daros Ruan R, Somogyi Andrew A, Sykes Benjamin, Franklin Samantha
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Horse Grimace Scale and Equine Gastric Ulcer Syndrome Equine gastric ulcer syndrome (EGUS) affects a substantial proportion of horses, yet uncertainty remains about the actual pain experience and how we might objectively quantify it. Researchers evaluated whether the Horse Grimace Scale (HGS)—a validated facial coding system assessing six action units—could detect pain-related behavioural changes in 61 horses with and without endoscopically confirmed gastric lesions, whilst excluding confounding variables such as lameness and systemic inflammation (serum amyloid A ≥50 µg/mL). Despite demonstrating excellent inter-observer reliability (ICC 0.75), HGS scores showed no significant difference between ulcerated and non-ulcerated horses (3.36 versus 3.0, p = 0.566), nor any correlation with ulcer severity (mild versus moderate-severe). The findings suggest that facial grimacing may not be a sensitive pain indicator for EGUS specifically, which carries important implications: practitioners cannot currently rely on HGS as a diagnostic or monitoring tool for this condition, and further investigation into alternative pain assessment methods—including behavioural, physiological, or other facial coding approaches—is warranted to better characterise the pain experience in affected horses.
Read the full abstract on PubMed
Practical Takeaways
- •Do not rely on the Horse Grimace Scale alone to identify pain in horses with suspected gastric ulcers; clinical examination and gastroscopy remain essential diagnostic tools
- •Horses with EGUS may experience pain that is not reflected in facial expressions, suggesting pain assessment in this condition requires alternative or complementary methods beyond facial action unit evaluation
- •Further research is needed to identify better pain assessment tools specific to visceral pain conditions like gastric ulcers before implementing them in clinical practice
Key Findings
- •Horse Grimace Scale showed excellent inter-observer reliability (ICC 0.75) but failed to detect differences between horses with and without gastric ulcers (p = 0.566)
- •Mean HGS scores were 3.36 in horses with EGUS versus 3.0 in horses without EGUS, showing no significant difference
- •HGS scores were not influenced by EGUS severity (none, mild, moderate-severe categories)
- •HGS may not be a suitable pain assessment tool for detecting pain associated with gastric ulceration in horses