Blood test misses the mark for equine gastric ulcer pain
Bottom line
A blood-based pain test for equine gastric ulcers didn’t pan out in a new University of Adelaide study, adding to the long-running challenge of finding objective, field-friendly ways to assess pain in horses with Equine Gastric Ulcer Syndrome, or EGUS. In the study, published August 26, 2026, in The Veterinary Journal, researchers tested whether peripheral blood immune cells would release interleukin-1 beta after ex vivo stimulation in a way that tracked with gastric lesions seen on gastroscopy. Among 64 horses included in the final analysis, 59 had gastric lesions, but the assay showed no meaningful diagnostic value for distinguishing horses with or without EGUS, including squamous or glandular disease. Adelaide’s summary said only 25% of horses showed a measurable response, and that response was not significantly associated with EGUS status. (adelaide.edu.au)
Why it matters: For veterinary professionals, the result is negative, but still useful. EGUS is common, especially in performance horses, yet lesion presence doesn’t cleanly map to pain, clinical signs, or welfare impact. This study suggests circulating blood-cell immune responses may be too blunt a tool for localized gastric inflammation, reinforcing that gastroscopy remains the reference standard and that clinicians still don’t have a reliable biomarker for EGUS-associated pain. That fits with broader recent reviews showing mixed performance from proposed biomarkers, including blood sucrose, serum proteins, cortisol-related measures, and salivary analytes. Prior Adelaide work also found the Horse Grimace Scale did not reliably separate horses with EGUS from controls, underlining how difficult pain assessment remains in this condition. (beva.onlinelibrary.wiley.com)
What to watch: Expect more work on multimodal pain assessment, alternative biomarkers, and tools that may help distinguish ulcer presence from clinically meaningful pain and treatment response. (beva.onlinelibrary.wiley.com)
Key facts
- Study type
- University of Adelaide study
- Published
- August 26, 2026, in The Veterinary Journal
- Sample size
- 64 horses in the final analysis
- Initial cohort
- 77 horses were blood-sampled
- Main finding
- PBMC IL-1β response did not reliably identify EGUS
- Diagnostic performance
- AUROC 0.39 for overall EGUS, 0.30 for squamous disease, and 0.56 for glandular disease
- Lesions in cohort
- 59 horses had gastric lesions; Adelaide said 92.2% of the final cohort had lesions
- Assay response rate
- Only 25% of horses showed a measurable blood-cell response
- Reference standard
- Gastroscopy
A new equine gastric ulcer pain biomarker has fallen short in early testing. Researchers at the University of Adelaide reported that a blood-based assay built around interleukin-1 beta release from stimulated immune cells could not reliably identify horses with Equine Gastric Ulcer Syndrome, despite hopes that it might offer a more objective way to detect pain linked to gastric lesions. The study was published August 26, 2026, in The Veterinary Journal, and the university publicized the findings on September 23, 2026. (pubmed.ncbi.nlm.nih.gov)
The work sits in a familiar clinical gap. EGUS is common in adult horses, particularly those in training and competition, but veterinarians still lack a dependable way to tell which horses are actually painful, how much lesions matter clinically, or whether behavior and performance changes are truly ulcer-related. Current guidance continues to emphasize that EGUS can’t be diagnosed from “characteristic” clinical signs alone and should be confirmed with gastroscopy. At the same time, newer reviews note that many proposed biomarkers have produced inconsistent or only preliminary results. (thehorse.com)
In the Adelaide study, investigators collected blood from 77 horses, then evaluated 64 in the final analysis. They isolated peripheral blood mononuclear cells and stimulated toll-like receptors 2 and 4 ex vivo to see whether IL-1β release could serve as a biomarker for EGUS status, using gastric lesions as a proxy for presumed ulcer-associated pain. The test did not perform well: the PubMed summary reported AUROC values of 0.39 for overall EGUS, 0.30 for equine squamous gastric disease, and 0.56 for equine glandular gastric disease, all of which indicate poor discrimination. Adelaide’s release added that 92.2% of horses in the final cohort had gastric lesions, and only 25% showed a measurable response in the blood-cell assay. (pubmed.ncbi.nlm.nih.gov)
That negative result is notable because IL-1β had some biological plausibility going in. Earlier Adelaide-linked work had suggested an association between severe squamous ulceration and heightened IL-1β, while a separate study from the same group found the Horse Grimace Scale also failed to detect EGUS-associated pain. Taken together, those studies suggest the problem may be less about any single failed test and more about the complexity of linking ulceration, inflammation, behavior, and pain in horses. A 2026 review in Equine Veterinary Education reached a similar conclusion, describing a broad but still unsettled biomarker landscape that includes serum proteins, oxidative stress markers, cortisol-related measures, and salivary analytes. (digital.library.adelaide.edu.au)
Public expert reaction has been measured rather than dismissive. In Adelaide’s announcement, lead researcher Gustavo Ferlini Agne said the findings show how difficult it is to identify pain in animals that can’t localize or verbalize discomfort, and that the failed assay still helps clarify where researchers should look next. Broader equine pain discussions are also moving toward multimodal assessment rather than single-test answers. A 2026 Havemeyer Working Group consensus report and BEVA’s growing education around equine chronic pain both point to a field that increasingly sees pain assessment as multidimensional, not something likely to be solved by one biomarker alone. (adelaide.edu.au)
Why it matters: For equine practitioners, this is a reminder to be cautious about overinterpreting ulcers, clinical signs, or emerging diagnostics in isolation. A simple blood test that could flag ulcer-associated pain would be valuable for screening, welfare assessment, treatment decisions, and follow-up, especially when gastroscopy is impractical. But this study suggests PBMC IL-1β response isn’t ready for that role. In practice, veterinarians will likely need to keep relying on a combination of history, management review, gastroscopy, response to treatment, and careful interpretation of behavior and performance changes. It also reinforces a broader research lesson: biomarkers for localized gastric disease may need to be more specific, or combined into panels, to be clinically useful. (pubmed.ncbi.nlm.nih.gov)
What to watch: The next phase will likely focus on validating other candidate biomarkers, testing multimodal pain frameworks, and separating ulcer presence from true pain burden and welfare impact. Reviews published in 2026 suggest the pipeline is still active, but most candidates remain exploratory, meaning clinicians shouldn’t expect a near-term replacement for gastroscopy just yet. (beva.onlinelibrary.wiley.com)