Canine EPI diagnosis gets a new cTLI cutoff
Bottom line
Diagnosis of canine exocrine pancreatic insufficiency should now use a higher reference interval and a higher diagnostic cutoff for serum canine trypsin-like immunoreactivity, according to a new JAVMA study by Wei-Hsiu Chuang, Yuan Wu, and Jonathan A. Lidbury. The change reflects a documented shift in the commercially available cTLI assay used in practice. Texas A&M’s GI Lab, a major reference laboratory for these tests, has already updated its interpretive guidance: values of 10.9 to 50.0 µg/L are now considered within the reference interval, ≤ 5.5 µg/L is considered diagnostic for EPI, 5.6 to 7.5 µg/L is an equivocal range where EPI cannot be excluded, and 7.6 to 10.8 µg/L is subnormal but considered less likely to represent EPI. The study itself evaluated 102 clinically healthy dogs to reset the lower limit of the reference interval and reviewed low-cTLI clinical cases with blinded internist assessment to establish the revised cutoff. (vetmed.tamu.edu)
Why it matters: For veterinarians, this is a practical diagnostic update, not just a statistical one. Dogs that might previously have been labeled normal or only borderline under the older framework may now fall into a range that warrants closer follow-up, repeat fasted testing, or a therapeutic trial if clinical signs fit EPI. The Texas A&M GI Lab notes that dogs in the 5.6 to 7.5 µg/L range with compatible signs may merit pancreatic enzyme replacement and monitoring, while repeat cTLI in 1 to 2 months can help clarify equivocal cases. The lab also cautions that some dogs with small-intestinal disease can partially respond to enzyme therapy, so cTLI still needs to be interpreted alongside history, body condition, stool quality, cobalamin status, and competing GI differentials. (vetmed.tamu.edu)
What to watch: Expect updated laboratory reports, teaching materials, and clinical workflows to increasingly adopt the ≤ 5.5 µg/L cutoff and the new gray-zone interpretation for dogs with suspected EPI. (vetmed.tamu.edu)
Key facts
- Topic
- Diagnosis of canine exocrine pancreatic insufficiency (EPI) should use a newly adjusted serum canine trypsin-like immunoreactivity (cTLI) reference interval and cutoff.
- Study
- JAVMA study by Wei-Hsiu Chuang, Yuan Wu, and Jonathan A. Lidbury.
- Sample size
- 102 clinically healthy dogs.
- Method
- Lower reference limit set from the fifth percentile of cTLI concentrations; low-cTLI cases were reviewed by five board-certified small animal internists, blinded to cTLI results.
- New reference interval
- 10.9 to 50.0 µg/L.
- Diagnostic cutoff
- ≤ 5.5 µg/L is diagnostic for EPI.
- Equivocal range
- 5.6 to 7.5 µg/L, where EPI cannot be excluded.
- Subnormal range
- 7.6 to 10.8 µg/L, subnormal but less likely to represent EPI.
- Lab guidance
- Texas A&M’s GI Lab has updated its interpretive guidance for cTLI testing.
A new JAVMA study is telling clinicians to recalibrate how they diagnose exocrine pancreatic insufficiency in dogs. The paper concludes that interpretation of serum canine trypsin-like immunoreactivity should use a newly adjusted reference interval and a new diagnostic cutoff, reflecting a shift in the commercially available cTLI assay rather than a change in the disease itself. (pmc.ncbi.nlm.nih.gov)
That shift had already been surfacing in referral-lab communications. Texas A&M’s GI Lab, one of the best-known centers for pancreatic and GI testing in small animals, reported that some dogs with clinical EPI appeared to have cTLI values above the historic diagnostic threshold of ≤ 2.5 µg/L. In response, the lab revised its interpretation framework, raising the lower end of the reference interval to 10.9 µg/L and the diagnostic cutoff to ≤ 5.5 µg/L. Older veterinary references, including prior review material and manuals, commonly cited a canine cTLI reference interval around 5.7 to 45.2 µg/L and an EPI cutoff of ≤ 2.5 µg/L, underscoring how meaningful this change is for day-to-day case interpretation. (vetmed.tamu.edu)
In the JAVMA study, investigators calculated the new lower reference limit from the fifth percentile of cTLI concentrations in 102 clinically healthy dogs. They also sent questionnaires to clinicians managing dogs with serum cTLI concentrations ≤ 10 µg/L, then had five board-certified small animal internists, blinded to the cTLI results, review the cases to help determine the most appropriate diagnostic cutoff for EPI. That design matters because it ties the revised threshold to clinical reality, not just assay analytics. (pmc.ncbi.nlm.nih.gov)
The resulting interpretive scheme is more nuanced than the old binary model. Texas A&M now considers 0 to 5.5 µg/L diagnostic for EPI, 5.6 to 7.5 µg/L a subnormal range where EPI cannot be excluded, 7.6 to 10.8 µg/L subnormal but less suggestive of EPI, and 10.9 to 50.0 µg/L within the reference interval. The lab recommends that dogs in the 5.6 to 7.5 µg/L range with compatible signs can be considered for a pancreatic enzyme replacement trial and close monitoring, with repeat cTLI testing in 1 to 2 months on a fasted sample if needed. The lab also notes that enzyme therapy itself will not interfere with repeat cTLI testing. (vetmed.tamu.edu)
There appears to be early downstream adoption of the revised cutoff beyond the original lab guidance. A 2026 study of dogs and cats with diabetes mellitus used ≤ 5.5 µg/L as the threshold indicating EPI in dogs, suggesting the new decision point is already influencing related clinical research and interpretation. (pubmed.ncbi.nlm.nih.gov)
Expert reaction, at least from the testing side, has been practical rather than dramatic: interpret the number in context, and do not overread borderline results. Texas A&M’s GI Lab specifically warns that some dogs with small-intestinal disease but not EPI can partially improve on pancreatic enzymes, which means response to treatment alone is not definitive. The lab’s longstanding guidance also emphasizes pairing cTLI with broader GI workups, including cobalamin and folate in dogs with chronic diarrhea and weight loss. (vetmed.tamu.edu)
Why it matters: For veterinary professionals, the biggest risk is diagnostic drift if clinics continue using older cutoffs embedded in memory, handouts, software comments, or legacy reference sheets. A dog with classic signs, weight loss, poor stool quality, or hypocobalaminemia could now fall into a clinically meaningful gray zone rather than being dismissed as normal under older thresholds. That has implications for when to repeat testing, when to broaden differentials toward enteropathy, and when to discuss an enzyme trial with the pet parent. It also reinforces the importance of fasting sample collection, because the GI Lab recommends withholding food before cTLI testing and especially in equivocal cases. (vetmed.tamu.edu)
What to watch: Watch for broader harmonization across commercial labs, textbooks, continuing education, and practice-management reference materials, as well as future validation studies that test how the new cTLI ranges perform in primary-care populations and in dogs with overlapping GI disease. (vetmed.tamu.edu)