TLI in Brief

  • To confirm EPI, schedule a TLI Blood Test
    (Updated website link)  http://vetmed.tamu.edu/gilab/service/assays/tli  
    (Previous website link)  http://www.cvm.tamu.edu/gilab/assays/TLI.shtml
  • Fast the patient for 12-15 hours prior to test
  • Do test on Mon, Tue or Wed ONLY, especially when also doing recommended B12 assay at the same time.
  • 2.5 or less = clinical EPI
  • 3.5 thru 5.7 = not clinical EPI but possible pancreatic acinar cell destruction (EPI) developing. Re-test in the near future.

The TLI Test 

The gold-standard test to  confirm EPI is with a TLI (Trypsin-Like Immunoreactivity) blood test. If your dog is a newly diagnosed puppy with EPI, although not necessary, but if possible, talk to your vet about re-testing in a few months with another TLI test to eliminate any rare false-positive reads and confirm EPI. The only reason why this is mentioned here is because although almost all dogs that test positive for EPI do indeed have EPI- - there have been extremely rare cases of a false read. Out of over 1,000 dogs...I know of only two that this happened with.

The following is from Texas A&M University (TAMU) GI Laboratory explaining the TLI test:   Serum Trypsin-Like Immunoreactivity  (TLI)  

Control Ranges: (normal ranges)

Canine5.7 - 45.2 µg/L
Feline12.0 - 82.0 µg/L

*** To see assay schedule, testing and shipping instructions please directly visit TAMU's GI website as noted above***


In dogs, values below 2.5 µg/L are diagnostic for EPI. Values between 3.5 and 5.7 µg/L are rarely if ever associated with signs of EPI but may reflect subclinical pancreatic disease such as subtotal pancreatic acinar cell destruction secondary to on-going immune-mediated lymphocytic pancreatitis. Progression of the disease in such patients may ultimately lead to EPI. Values between 2.5 and 3.5 µg/L are sometimes (but rarely) associated with clinical signs due to EPI. In these cases the TLI assay should be repeated after one month paying particular attention to ensuring that food is withheld for 12 to 15 hours before the blood sample is collected.
In cats, values equal to or below 8.0 µg/L are diagnostic for EPI, with values between 8.0 and 12.0 being equivocal. As in the dog, repeating the assay one month later should be considered.
Serum TLI values above 50.0 µg/L (dogs) and 100.0 ug/L (cats) are consistent with either acute or chronic pancreatitis or decreased renal excretion due to severe renal insufficiency, although our experience suggests that serum TLI is often minimally increased even in severe renal failure. Elevated serum TLI concentrations are also seen in some malnourished patients (dogs usually) without evidence of pancreatitis, and in some cats with patchy pancreatic hypertrophy/atrophy (generally considered to be a benign age-related change). Serum TLI is increased in approximately 30-40% of cats and dogs with pancreatitis; it is important to recognize that normal test results do not rule out the possibility of pancreatic inflammation. We believe that in acute pancreatitis testing of samples obtained as soon as possible after the onset of clinical signs is most likely to yield an abnormal test result. If pancreatitis is suspected, a PLI test should be performed. In cats increased serum TLI is often also observed with small intestinal disease. In these cases serum concentrations of cobalamin and folate should be determined for evaluation of the small intestine.


0.5 ml fasting (12-18 hours) non-hemolyzed serum for canines
0.2 ml fasting (12-18 hours) non-hemolyzed serum for felines  
Serum TLI is extremely stable and serum can be shipped at ambient temperatures. 
Exocrine pancreatic insufficiency (EPI) occurs as a consequence of insufficient synthesis and secretion of digestive enzymes by the pancreatic acinar tissue. The functional reserve of the pancreas is considerable, however, and EPI only develops when the exocrine secretory capacity is reduced to less than 10 - 15% of normal. At this point residual pancreatic function together with extra-pancreatic mechanisms of digestion cannot support adequate nutrient digestion and so weight loss, diarrhea, and other clinical signs ensue. 
Small quantities of zymogens (inactive precursor molecules) of pancreatic proteases are present in the blood of normal animals. Trypsinogen is synthesized exclusively by the acinar cells pancreas, and measurement of this zymogen by assay of TLI provides an excellent indirect index of pancreatic function. This assay detects both trypsinogen and trypsin (hence the use of the term TLI to describe the total concentration of these two immunoreactive species), but the active enzyme (trypsin) is only present in the serum when there is pancreatic inflammation.


Administration of oral pancreatic extracts does not affect serum TLI concentrations in either normal dogs or cats with EPI, so withdrawal of enzyme supplementation prior to testing of dogs and cats that are already receiving supplementation is unnecessary.

Additionally, assays of serum cobalamin (vitamin B12) and folate are strongly recommended whenever serum TLI is assayed. Serum vitamin abnormalities are common in dogs and especially cats with EPI. Therapeutic supplementation may be essential before an optimal response to enzyme supplementation is obtained. 
EXPLANATION FOR POSSIBLE TLI VARIANCE:  Dr. David A. Williams, developer of the TLI test, said was that there are no absolutes. There is inherent variability in the TLI assay (as with any assay) and this variability is not the same across all values ? indeed the variation in the numerical value is greatest for low (especially within the ?EPI range?) and high values. So do not over-interpret the absolute values in the ?EPI range?. Anything that is reported as less than 2.0 should just be regarded as essentially undetectable. A dog with a reported value of 0.6 is no sicker than one with a value of 1.6, and by the same token, there is no reason to believe that it will need more enzymes or do less well.

Regarding the variability in reported values, the way Dr. Williams explained it to me was that if you took one vial of blood and tested it (for example) on Tuesday at 1:00 and got one numeric value of 1.5? you can take more blood from that same vial and test it on the same equipment on the same Tuesday at 2:00 and get a different numeric value of maybe 1.0. Indeed, if you tested the same sample twice at the same time you still might get the same difference of 0.5 between the two sets of results! The more you did this; took an average of all the values you got from that one vial of blood tested on the same day on the same equipment would yield a more accurate value, but it still would not be all absolute. This is why, he explained, there is variability that does not reflect any significant difference, and both values are diagnostically low and indicative of EPI. Differences between test results of approximately 2.0 and approximately 3.0 are generally reproducible however, and of diagnostic and functional significance. While both are abnormally low values, the former is almost always associated with clinical signs while the latter almost never is. Fortunately, the vast majority of test results are usually clearly diagnostically low (less than 2.5) or clearly normal (greater than 5.0) so these niceties regarding the assay are of no practical consequence.  I hope this helps clarify why TLI values may somewhat fluctuate within the EPI range. 


  1. Williams DA. The Pancreas. In: Strombeck DR, Guilford WG, Center SA, Williams DA, Meyer DJ, eds. Small Animal Gastroenterology. Philadelphia: W.B. Saunders 1996:381-410.
  2. Williams DA, Batt RM. Sensitivity and specificity of radioimmunoassay of serum trypsin-like immunoreactivity for the diagnosis of canine exocrine pancreatic insufficiency. J.Am.Vet.Med.Assoc. 1988;192:195-201.
  3. Steiner JM, Williams DA. Feline exocrine pancreatic disorders. The Veterinary Clinics of North America 1999;29:551-75.
  4. Steiner JM, Williams DA, Moeller EM, Melgarejo TL. Development and validation of an enzyme-linked immuno sorbent assay (ELISA) for feline trypsin-like immunoreactivity (fTLI). Am.J.Vet.Res. 2000;61:620-3.
  5. Bruner JM, Steiner JM, Williams DA, Van Alstine WG, Blevins W. High feline trypsin-like immunoreactivity in a cat with pancreatitis and hepatic lipidosis. J Am.Vet.Med.Assoc. 1997;210:1757-60.
  6. Parent C, Washabau RJ, Williams DA et al. Serum trypsin-like immunoreactivity, amylase and lipase in the diagnosis of feline acute pancreatitis. J.Vet.Int.Med. 1995;9:194 (abstr).
  7. Swift NC, Marks SL, MacLachlan NJ, Norris CR. Evaluation of serum feline trypsin-like immunoreactivity for the diagnosis of pancreatitis in cats. Journal of American Veterinary Medical Association 2000;217:37-42.
  8. Steiner JM, Williams DA. Disagrees with criteria for diagnosing pancreatitis in cats. J.Am.Vet.Med.Assoc. 2000;217:816-7.
  9. Steiner JM, Williams DA. Serum feline trypsin-like immunoreactivity in cats with exocrine pancreatic insufficiency. J.Vet.Intern.Med. 2000;14:627-9.




TLI testing can be done at the Texas A&M Gastrointestinal lab (recommended), Antech labs, or Idexx labs)

When a TLI test results comes back between 2.6 and 5.6... explained!


A cTLI test value less than 2.5ug/L is the current “gold standard” for a diagnosis of EPI. However, there is an “equivocal” range between 2.6 and 5.6 ug/L in which the ability of the test to confirm or rule out EPI is less certain. While dogs with cTLI values in this “equivocal” range do not meet the criteria for a diagnosis of EPI, some (especially at the low end of the range) may still benefit from pancreatic enzyme supplementation. There are at least three potential explanations for this observation. 


·         First, it is possible for the cTLI value of a dog with EPI to be above the diagnostic cut-off value of 2.5 ug/L at any single sampling time based on natural fluctuations in the patient (if tested on repeated days the cTLI will not be exactly the same). Normally this makes no difference to interpretation of the result, since for example if a patient’s results vary between 1 and 2 ug/L they are still low and consistent with EPI. Similarly, normal results will always be normal. 


·         A second cause of variation is the inherent limits of precision of the cTLI test itself (or any similar laboratory test) - if you test the same sample repeatedly on the same day or different days you will not get exactly the same result. Again, this unavoidable variation usually is of no clinical significance – the results always indicate EPI (or normal). However, when the result is at the upper level of the diagnostically low range or the lower end of the equivocal range, there is inherent uncertainty. This means that a dog with a cTLI value of 3.2 may not be that different from one with a cTLI of 2.4 and may still have a severe enough deficiency in pancreatic enzyme production to warrant enzyme supplementation. Veterinarians often consult with us regarding management of these patients, and we make individualized recommendations based upon all the clinical information available.


·         Third, it is also possible that some dogs with a cTLI at the lower end of the 2.6-5.6 ug/L range may respond to pancreatic enzyme supplementation due to individual variability in the production of digestive enzymes from other parts of the body. For example, normal dogs digest about 20% of the fat in their food using a gastric lipase made in the stomach). This is quite a different enzyme than the pancreatic lipase made by the pancreas, that digests most of the food in the diet, and that is deficient in dogs with EPI. However, some dogs produce far more gastric lipase, and some far less, than the average. If a dog with normally low production of lipase from the stomach develops a more mild degree of exocrine pancreatic damage than a typical dog with EPI, they may benefit from pancreatic enzyme supplementation because they are very dependent on pancreatic digestive enzymes and have much more limited ability to compensate with gastric lipase. 


If your dog’s health has improved with the addition of pancreatic enzymes, it may be prudent to continue this therapy.

If your dog has persistent clinical signs of gastrointestinal disease (weight loss, changes in appetite, vomiting, soft stool/diarrhea), despite enzyme supplementation, we recommend that you discuss other diagnostic and treatment options with your primary care veterinarian, as EPI may not be the primary, or only, cause of your pet’s illness.


In the overwhelming majority of cases results of serum cTLI testing are absolutely clear-cut and interpretation is unequivocal. Very few tests in medicine give such “black and white” results. Nonetheless, after decades of experience interpreting serum cTLI test results, there are certainly rare individual patients whose cTLI values are unexpected and perhaps even seemingly inexplicable, especially on repeat testing. Simplified interpretation algorithms cannot cover all these eventualities, but after consultation with a specialist and discussions with the owner, veterinarians can usually come up with a logical plan to help manage the patient’s clinical problems most effectively.



Patrick Barko, DVM 

David Williams, MA VetMB PhD DACVIM ECVIM-CA

TLI testing in India

For those in India struggling with a dog that they suspect has EPI..... there is now a place in India that DOES perform the TLI test ....

Cessna Lifeline Veterinary Hospital

Address: #148, HBCS, Amar Jyothi Layout, KGA Road, Off Intermediate Ring Road, Domlur, Bengaluru, Karnataka 560071, India

Phone:+91 80 3016 1324 

as of April 2016, the estimated cost is 2000 Indian Rupees (which is about $30 in USA dollars)

 There is also a vet, Dr. Srikanth : Address: No.38/27, 1st A Cross, 5th Block, 3rd Phase, Near Kamakya Theatre,, Banashankari 3rd Stage, Bengaluru, Karnataka 560085, India that understands and has a good reputations working with EPI dogs.

Phone:+91 98440 57919


Schebo *new* Pancreas Elastase 1 Quick™ Canine test

 If money is tight, there is an 'INDICATION" option..... although not the gold-standard like the TLI... the Schebo can be done and then confirmed with a TLI at a later date when one has the resources.


ScheBo® • Pancreas Elastase 1 Quick™ Canine Test

Epi4Dogs would like to offer a new / revised Fecal Elastase test produced by Schebo (a German Bio-Tech company established 1989)http://www.schebo.com/products/veterinary-diagnostics/veterinary-diagnostics-rapid-test/ that you can purchase as an individual and test your dog (via feces) in your own home for an “indication” whether or not your dog may be dealing with EPI.  The specificity of this test has a 93% accuracy….. not 99.9% like the TLI … BUT…. well worth doing as an in-home test kit…. to get an indication of possible EPI.


Too many times, people, shelters or rescue organizations are not immediately able to financially afford the accurate $125+ gold-standard TLI blood test to positively confirm EPI ….. and although you can readily treat for EPI based on the physical signs ….. EPI physical signs can also mimic many other conditions….and sometimes not be EPI.  


Although treating without testing often comes about from good intentions………. some dogs are then mis-diagnosed and consequently mis-treated putting them at risk, sometimes with dire consequences.  If you are or know someone who would benefit from testing for an indication of EPI, please consider trying the Schebo Pancreas Elastase 1 Quick Canine test kit for an indication that your dog is most likely dealing with EPI.   IF the results are positive, then talk to your vet about treating for EPI and make plans to confirm diagnosis with a follow-up TLI test when you can afford it. The benefit of this test is that it positively rules out some of the more serious other conditions that may mimic EPI.


Because Epi4Dogs is a Non-Profit Organization, we will not sell this product but do want to offer it to our EPI community.  Epi4Dogs has partnered with Schebohttp://www.schebo.com/products/veterinary-diagnostics/veterinary-diagnostics-rapid-test/ and Schebo’s  NA distributor, Catachem http://www.catacheminc.com/news/  with regards to working on the specifics on how to best distribute the Schebo product at the best price for the EPI community. 

We are very pleased and thankful to announce that EnzymeDiane is working with Schebo's NA distributor and will now carry this test kit.



The cost of the kit is $38 plus shipping. 

This test is specific for Exocrine Pancreatic Insufficiency and showed a 95.3% sensitivity and a 92% specificity in a clinical trial of 331 dogs of which 43 had known clinical EPI. I have requested from Schebo the clinical trial research results for your review… and have posted below the original product 2000 research below.

 (new) ScheBo® • Pancreas Elastase 1 Quick™ Canine Test is a rapid stool test kit that quickly and conveniently excludes or diagnoses possible canine EPI in your own home or vet’s office.

Any dog presenting with the following symptoms could have Exocrine Pancreatic Insufficiency:

  • Steatorrhoea (greasy/oily stools)
  • Diarrhea (loose/watery stools)
  • Vomiting
  • Cow-pat stool, frequent stools
  • Polyphagia (ravenous appetite)
  • Rapid weight loss, failure to thrive
  • Gas, abdominal discomfort
  • Borborygmus (tummy sounds)
  • Coprophagia (eating feces)
  • Poor coat condition (dry, dull, brittle)

The test is simple to perform:

A single small stool sample is sufficient.

  • Absolutely pancreas-specific
  • No additional equipment required
  • Results available 10 minutes after adding the stool extract
  • No starvation periods needed
  • No blood sampling
  • Intestinal inflammation does not affect the test result
  • Uses monoclonal antibodies - substitution therapy does not influence the test result
  • Store kit at 4 - 27 C (Does not require refrigeration)
We have had a question come up about this test:
QUESTION: If the line in the test region, but it was pale/light/faded - not nearly as beefy, bright or solid as the control line. What does this mean??? 
ANSWERThe Elastase 1 levels are fine if you are able to see two lines after waiting exactly ten minutes to read the test results. The test line must be recognizable as a line, although it may be weaker than that of the control.  

 Catachem   has designed this informative (and easy to understand) "How-To" brochure explaining the testing process:   Schebo Pancreas Elastase brochure


Schebo Test kit available in Australia

The Schebo Fecal Pancreas test kit is now available in Australia at the following Schebo distributor:


Kelvin Chan  |  Product Specialist

Mobile:  +61 458 844 550  
Email:  [email protected]
Free Call:  1800 222 287  Free Fax:  1800 287 222

ABN:  63 126 255 990   www.abacus-als.com 

The Schebo "original" fecal test research (with flaws)

Please feel free to read PDF link of the "original" Schebo Pancreas Elastase Fecal (cE1) research, published in 2000 in the European Journal of Comparative Gastroenterology, Vol 5, No. 2, December 2000

schebo.co.uk_img_pdf_vet-Spillmann-EurJrnlCompGstro 2000.pdf

and thank you Jack for submitting this! 



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