Pancreatitis is a disease that’s common in both dogs and cats. But despite its prevalence and its potential seriousness, unfortunately, the condition is often not straightforward to diagnose.
There’s no one, single test that can definitely confirm pancreatitis. Instead, it requires looking at the whole picture of clinical symptoms, signalment, history, and different diagnostic tests.
So, where do in-house pancreatic lipase immunoreactivity (PLI) tests fit into this picture? And how useful are they? Here are some things to know…
Which Diagnostic Tests Can Be Used to Help Diagnose Pancreatitis?
Signalment, history, and the physical exam may lead a veterinarian to suspect pancreatitis. And in many cases, supportive care and treatment may be initiated based on this information alone, especially if a pet owner can’t afford diagnostics or if a patient is very ill but results of the tests can’t be obtained right away.
Assuming a client pursues diagnostic testing, the following modalities are commonly used…
Bloodwork and urinalysis. A CBC, chem panel, any other relevant blood panels, and a urine analysis can provide valuable information. But unfortunately, general bloodwork panels (even ones that include serum amylase and lipase) have limited utility for diagnosing pancreatitis.
However, these tests can be crucial for ruling out other conditions that may be causing a patient’s symptoms, evaluating overall health, and determining hydration status and electrolyte balance that must be addressed during treatment.
Radiographs. Like bloodwork/urinalysis, radiographs help rule out other conditions—especially surgical conditions like a GI foreign body obstruction. However, although some radiographic changes can be seen with severe pancreatitis, many times x-rays won’t show appreciable changes specific to the pancreas.
Ultrasound. Ultrasound is more sensitive than x-rays in terms of detecting changes (like inflammation) associated with pancreatitis. However, it’s user-dependent, and even this modality can’t detect pancreatitis 100% of the time.
PLI tests. This is one of the most valuable options for testing specifically for pancreatitis, but limitations of the tests must be recognized. See the next section for more details.
Biopsy. A pancreatic biopsy may be the most accurate way to diagnose the condition. However, this option is often not practical (and may even be harmful) for acutely ill patients.
Which PLI Tests Are Available to Veterinarians?
Serum amylase and lipase are often included on blood chemistry profiles, especially in patients who are exhibiting GI signs. However, many experts agree that these values are not good indicators of pancreatitis unless SIGNIFICANTLY elevated (3-4 times the normal range). That’s because these markers can be elevated with non-pancreatic disease and may be normal in dogs and cats with pancreatitis.
Trypsin-like immunoreactivity (TLI) is also not considered diagnostic for pancreatitis, as it can increase with azotemia, and it doesn’t remain elevated consistently and thus may be normal even in a patient with pancreatitis.
Another test, the PLI test, was designed to be specific for serum concentration of lipase of pancreatic origin. Both canine (cPLI) and feline (fPLI) versions of the test are available.
The PLI test was originally developed at Texas A&M University. Idexx later developed a similar test (SpecPL). These two tests are performed at the respective laboratories, so samples must be sent out.
Idexx also developed a point of care version of the test: the SNAP cPL (canine) and SNAP fPL (feline). And Zoetis offers the VETSCAN cPL rapid test. These tests are available for in-house testing in veterinary practices.
How Well Do PLI Tests Work?
The sensitivity and specificity of any diagnostic test depend on many things, including cut-offs for an abnormal reading, which population of pets are being tested (healthy versus ill), and other factors.
In a nutshell, the cage-side (SNAP cPL and fPL) are considered a sensitive test, which means they’re less likely to have false negatives, but more likely to have false positives. In other words, they’re a good tool for screening symptomatic patients. A negative test means it’s less likely (though not impossible) that a patient has pancreatitis. A positive result helps support a diagnosis but MUST be followed up with additional testing.
The laboratory tests for PLI (the original test at Texas A&M and the SpecPL) have a higher specificity than the in-house tests. Therefore, many veterinarians use these as confirmatory tests after obtaining a positive SNAP test. Even these tests are not 100% diagnostic, and thus results must be interpreted in light of the whole clinical picture. But they are an important piece of the clinical puzzle when it comes to pancreatitis.
Caveats for Testing
Many experts don’t recommend testing for markers of pancreatitis (serum amylase and lipase, or PLI) as a screening test in healthy patients. Statistically speaking, false positives are more likely when doing widespread testing on a healthy population. Instead, testing is most accurate and valuable for symptomatic patients.
Of note, all of these tests may be most accurate for acute, severe pancreatitis. Milder forms of the disease, as well as chronic pancreatitis (especially in cats), may be less likely to show an abnormal result.
Laboratory testing offers the added benefit of a quantitative (number) value. This may be valuable not only for diagnosis, but for monitoring of the condition.
Of note, while PLI (both lab and in-house) tests are more specific to the pancreas than serum amylase and lipase, PLI can be elevated from non-pancreatic conditions.
Details and specifics of these tests may evolve over time. It’s important to check directly with the company for the most up-to-date information before making a purchase.
With all these things in mind, PLI tests can be a valuable addition for many veterinary practices. But they must be used appropriately and interpreted in conjunction with the entire clinical picture.
Disclaimer: This article is for general informational purposes only, and not intended as a guide to the medical treatment of any specific animal.
Written by: Dr. Tammy Powell, DVM
