Pancreatic Lipase Testing
It is 1999. You are working in a general practice. Bart, a five-year-old boxer, comes for an appointment. He presents with abdominal pain and vomiting. You pull blood from him and run a chemistry panel. Bart’s lipase and amylase are high, so you do an ultrasound. You identify an enlarged, hypoechoic pancreas. Cue the pancreatitis treatment plan.
Let’s move forward to 2019. It turns out serum lipase and amylase are known to have poor sensitivities and specificities. High levels of the enzymes are not specific to pancreatitis. Other tissues synthesise and secrete them. Ultrasound results need to be interpreted judiciously. Recent studies caution clinicians not to “overinterpret” findings. Early intervention of pancreatitis is essential in preventing systemic complications. On the other hand, maybe Bart did not have pancreatitis after all.
Histopathology is the gold standard in diagnosing pancreatic conditions, but it is not carried out often. Pancreatic surgical pathology is invasive, has limitations and can be cost-prohibitive. Likewise, fine needle aspirates carry the risk of causing further cellular damage. What do you do?
The answer lies in measuring lipase. Lipase is an enzyme that comes in the forms of pancreatic lipase, colipase, and lipoprotein lipase. Pancreatic lipase breaks down triglycerides, the main component of fat, as they cannot be directly absorbed across the intestinal mucosa. When diseases such as pancreatitis, neoplasia or trauma disrupt pancreatic function, corrosive pancreatic juice from the exocrine cells enter the blood by way of the lymphatics or capillaries.
These harsh pancreatic enzymes paint a clinical picture of anorexia, vomiting and abdominal pain. Any patient with these clinical signs benefits from pancreatic screening. Outsourced pancreatic lipase immunoassays (in particular, the clinicopathological benchmark, pancreatic lipase immunoreactivity), which measure the concentration of pancreatic lipase in the serum, have been validated for dogs and cats. Unfortunately, these tests can be cost-prohibitive and may take days for results.
Thankfully, in-house pancreatic lipase testing is available that is considered highly sensitive and specific. Point-of-care testing can be quantitative or qualitative. Both types show a good level of agreement when compared to outsourced testing. However, quantitative methods allow the clinician to objectively and swiftly monitor the patient’s disease progression or retreat over a period of time, as a high result does not always correlate with the severity of the disease. A quickly decreasing assay, together with improvement in your patient’s condition, indicates a good response to treatment. Lipase is cleared rapidly from the body, so values are considered accurate within 24 hours.
Testing’s accuracy rests on proper sample collection and handling. Fasting your patient (if they are actually eating) increases reliability. Most tests can be performed on either serum or heparinized plasma. A small amount of lipemia, bilirubin, and hemolysis will not affect your results. Samples are stable stored in the refrigerator for two days and in the freezer for one year.
Results of any assay alone are insufficient to diagnose pancreatitis. A careful review of clinical signs, abdominal ultrasonography, and sometimes gold-standard testing such as outsourced pancreatic lipase immunoreactivity or histopathology may be necessary. No test is one hundred percent sensitive or specific. However, thanks to in-house pancreatic testing, in 2019 we have better insight into Bart’s clinical signs.
Cornell University College of Veterinary Medicine, Lipase. EClinPath. opens in a new windowhttp://eclinpath.com/chemistry/pancreas/lipase/ Accessed February 2019.
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