# Pancreatic Enzyme Testing in Veterinary Biochemistry ## Quick Answer - Serum lipase and amylase lack sensitivity and specificity for pancreatic disease, so negative results do not rule out pancreatitis and positive results require cautious interpretation. - Pancreatic lipase immunoreactivity (PLI) assays, including canine PLI (cPLI) and feline PLI (fPLI), are the preferred blood tests for diagnosing pancreatitis in dogs and cats. - Exocrine pancreatic insufficiency (EPI) requires a different test, serum trypsin-like immunoreactivity (TLI), because lipase and amylase are not reliable for EPI diagnosis. ## Understanding the Clinical Problem Pancreatic disease in dogs and cats presents a diagnostic challenge because the clinical signs overlap with many other gastrointestinal and systemic conditions. Vomiting, anorexia, abdominal pain, and lethargy can result from gastroenteritis, foreign body obstruction, renal disease, or hepatic disorders. The pancreas itself sits deep within the abdominal cavity, making physical examination findings nonspecific. Laboratory testing therefore carries substantial weight in the diagnostic process, but the choice of test determines whether the result will guide treatment or mislead the clinician. Traditional serum markers, specifically amylase and lipase, have been used for decades in veterinary medicine. These enzymes are measured on standard biochemistry panels and are inexpensive to run. However, their diagnostic performance in naturally occurring pancreatitis is poor. Amylase is produced by the pancreas but also by other tissues, and its serum concentration can rise in conditions unrelated to pancreatic inflammation. Lipase is more pancreas-specific than amylase in dogs, but it still lacks the sensitivity needed to detect mild or early pancreatitis. In cats, both amylase and lipase are even less reliable, and many cats with confirmed pancreatitis have normal serum concentrations of both enzymes. The practical consequence is that a clinician who relies on amylase and lipase alone will miss cases of pancreatitis and will also misclassify animals with other diseases as having pancreatic inflammation. This leads to inappropriate treatment, delayed diagnosis, and unnecessary expense for the owner. The development of species-specific pancreatic lipase immunoreactivity assays has changed the diagnostic landscape, but these tests are not available on every in-house analyzer and require an understanding of their limitations. ## At a Glance The table below summarizes the main pancreatic enzyme tests used in veterinary medicine, their clinical utility, and their limitations. This comparison helps the clinician select the appropriate test for a given patient. | Test | Species | Primary Use | Key Limitation | | --- | --- | --- | --- | | Serum amylase | Dog, cat | Historical screening for pancreatitis | Low sensitivity and specificity, many false positives and negatives | | Serum lipase | Dog, cat | Historical screening for pancreatitis | Better than amylase in dogs but still insensitive in cats and nonspecific in both | | Pancreatic lipase immunoreactivity (cPLI, fPLI) | Dog, cat | Diagnosis of pancreatitis | More sensitive and specific than amylase or lipase, requires species-specific assay | | Trypsin-like immunoreactivity (TLI) | Dog, cat | Diagnosis of exocrine pancreatic insufficiency | Low TLI confirms EPI, not useful for pancreatitis diagnosis | ## Core Principles of Pancreatic Enzyme Testing ### The Exocrine Pancreas and Its Enzymes The exocrine pancreas produces digestive enzymes that are secreted into the duodenum through the pancreatic duct. These enzymes include amylase for carbohydrate digestion, lipase for fat digestion, and proteases such as trypsin and chymotrypsin for protein digestion. In health, small amounts of these enzymes enter the bloodstream and are cleared by the kidneys. Serum concentrations reflect the balance between pancreatic release and systemic clearance. When the pancreas becomes inflamed, the acinar cells release larger quantities of enzymes into the circulation. This release forms the basis for serum enzyme measurement. However, the relationship between serum enzyme concentration and pancreatic inflammation is not linear. The degree of enzyme elevation does not correlate well with the severity of pancreatitis, and some animals with severe pancreatitis have normal serum enzyme concentrations. ### Why Amylase and Lipase Fail Amylase is produced by the pancreas and the salivary glands in dogs. In cats, the salivary contribution is less significant, but the kidney clears amylase, so renal disease can elevate serum amylase without pancreatic disease. Intestinal disease can also cause amylase to rise. The result is a test with low specificity. A dog with a foreign body or gastroenteritis may have elevated amylase, leading the clinician to suspect pancreatitis when the primary disease is intestinal. Lipase is more pancreas-specific than amylase in dogs, but it is still not reliable. Lipase can be elevated in animals with renal disease, hepatic disease, or glucocorticoid therapy. In cats, serum lipase is particularly insensitive. Many cats with confirmed pancreatitis have normal serum lipase concentrations. The feline pancreas has a different lipase profile, and the standard assays used on automated chemistry analyzers do not measure the pancreatic isoform specifically. ### The Development of Pancreatic Lipase Immunoreactivity Pancreatic lipase immunoreactivity (PLI) is a species-specific immunoassay that measures the concentration of pancreatic lipase in the blood. The assay uses antibodies that recognize the pancreatic isoform of lipase, which is distinct from other lipases in the body. The cPLI assay for dogs and the fPLI assay for cats are commercially available through reference laboratories. PLI is more sensitive and specific than serum lipase for the diagnosis of pancreatitis. In dogs, cPLI has been shown to be more sensitive than serum lipase and amylase for detecting pancreatitis. In cats, fPLI is the most sensitive test available for feline pancreatitis. The test is not affected by renal disease to the same degree as amylase, and it does not cross-react with lipases from other tissues. The main limitation of PLI is that it is not available on in-house analyzers. The test must be sent to a reference laboratory, which introduces a delay in obtaining results. In an emergency setting, the clinician may need to make initial decisions based on clinical signs and other laboratory findings while awaiting the PLI result. ## Choosing the Right Test for the Clinical Question The clinical question determines the test choice. Pancreatitis and exocrine pancreatic insufficiency (EPI) are two distinct diseases with different laboratory profiles. Pancreatitis is an inflammatory condition that causes enzyme leakage into the blood. EPI is a loss of functional acinar tissue, leading to inadequate digestive enzyme production and malabsorption. ### Diagnosing Pancreatitis For pancreatitis, the preferred test is pancreatic lipase immunoreactivity. In dogs, cPLI is the test of choice. In cats, fPLI is the test of choice. These tests are more sensitive and specific than serum amylase and lipase. The clinician should interpret the PLI result in the context of the clinical signs, physical examination findings, and imaging results. Serum amylase and lipase should not be used as the sole basis for a pancreatitis diagnosis. They may be used as a screening test when PLI is not available, but the clinician must recognize their limitations. A normal serum lipase does not rule out pancreatitis, and an elevated serum lipase does not confirm it. ### Diagnosing Exocrine Pancreatic Insufficiency EPI is diagnosed with serum trypsin-like immunoreactivity (TLI). TLI measures the concentration of trypsinogen and trypsin in the blood. In EPI, the pancreatic tissue is destroyed, and TLI is low. A low TLI concentration confirms the diagnosis of EPI. Serum lipase and amylase are not useful for EPI diagnosis. In EPI, the pancreas is not inflamed, so enzyme release is not increased. The enzymes may be low, but they are not diagnostic. TLI is the only reliable test for EPI. ### The Role of Imaging Abdominal ultrasound is a valuable tool for evaluating the pancreas. Ultrasound can detect pancreatic enlargement, changes in echogenicity, and surrounding inflammation. However, ultrasound is operator-dependent, and the pancreas can be difficult to visualize in some animals. A normal ultrasound does not rule out pancreatitis, and an abnormal ultrasound does not confirm it. Computed tomography (CT) is more sensitive than ultrasound for detecting pancreatic changes, but it is not widely available in veterinary practice. CT requires general anesthesia and is more expensive. ## Practical Workflow for Pancreatic Enzyme Testing The following workflow outlines a practical approach to pancreatic enzyme testing in dogs and cats. This workflow is based on the clinical signs, the availability of tests, and the need for a timely diagnosis. ### Step 1: Assess the Clinical Presentation The first step is to assess the clinical presentation. Pancreatitis is more common in dogs than in cats. In dogs, pancreatitis is often associated with a history of a high-fat meal, but it can occur without a dietary trigger. In cats, pancreatitis is often associated with other diseases, such as inflammatory bowel disease or hepatic lipidosis. The clinical signs of pancreatitis include vomiting, anorexia, lethargy, and abdominal pain. In cats, the signs may be more subtle, and some cats present with only lethargy and anorexia. The clinician should also consider other causes of these signs, such as gastrointestinal obstruction, renal disease, or hepatic disease. ### Step 2: Perform a Baseline Laboratory Evaluation A complete blood count, serum biochemistry profile, and urinalysis are the baseline laboratory tests. These tests can identify other diseases that may cause similar signs. The biochemistry profile should include amylase and lipase, but the clinician should not rely on these tests alone. The serum biochemistry profile can also identify other abnormalities, such as elevated liver enzymes, which may indicate concurrent hepatic disease. The urinalysis can identify renal disease, which can cause elevated amylase. ### Step 3: Submit the Appropriate Pancreatic Test If pancreatitis is suspected, the clinician should submit a cPLI or fPLI test to a reference laboratory. The test should be submitted at the time of the initial evaluation, even if the serum lipase and amylase are normal. The PLI result will be available in a few days. If EPI is suspected, the clinician should submit a TLI test. TLI is the only test that can confirm EPI. ### Step 4: Interpret the Results in Context The PLI result should be interpreted in the context of the clinical signs, imaging findings, and other laboratory results. A high PLI concentration is consistent with pancreatitis, but the clinician should also consider the possibility of a false positive. A normal PLI concentration does not completely rule out pancreatitis, but it makes the diagnosis less likely. The TLI result is more straightforward. A low TLI concentration confirms EPI. A normal TLI concentration rules out EPI. ### Step 5: Monitor the Patient The patient with pancreatitis should be monitored for clinical improvement. The PLI concentration may remain elevated for several days after the clinical signs resolve. The clinician should not repeat the PLI test to monitor the response to treatment, as the concentration does not correlate with the severity of the disease. The patient with EPI should be monitored for clinical response to enzyme supplementation. The TLI concentration does not change with treatment, so it is not used for monitoring. ## Options and Tradeoffs in Pancreatic Testing The choice of pancreatic test involves a tradeoff between sensitivity, specificity, availability, and cost. ### Serum Amylase and Lipase Serum amylase and lipase are inexpensive and available on most in-house analyzers. They can be run immediately, providing a rapid result. However, they are insensitive and nonspecific. The clinician may be misled by a false positive or a false negative. The tradeoff is between speed and accuracy. In an emergency, the clinician may need a rapid result to guide initial treatment. The serum lipase and amylase can provide that result, but the clinician must recognize the limitations. ### Pancreatic Lipase Immunoreactivity PLI is more sensitive and specific than serum lipase and amylase. It is the test of choice for diagnosing pancreatitis. However, it is not available in-house and must be sent to a reference laboratory. The delay in obtaining the result can be a limitation in an emergency. The tradeoff is between accuracy and speed. The clinician may need to make an initial treatment decision based on clinical signs and serum lipase and amylase while awaiting the PLI result. ### Trypsin-Like Immunoreactivity TLI is the only test that can confirm EPI. It is a specialized test that must be sent to a reference laboratory. The tradeoff is that the result is not available immediately, but the diagnosis of EPI is not an emergency. ### Cost Considerations The cost of the tests varies. Serum amylase and lipase are inexpensive and included in a standard biochemistry panel. PLI and TLI are more expensive and are not included in a standard panel. The clinician should discuss the cost with the owner and explain the value of the more specific tests. ## Observations and Measurements The clinician should record the following observations and measurements when evaluating a patient with suspected pancreatic disease. ### Clinical Observations The clinician should record the patient's signalment, including species, breed, age, and sex. The history should include the onset and duration of clinical signs, the presence of vomiting, diarrhea, anorexia, and abdominal pain. The diet history is important, as a high-fat meal can trigger pancreatitis in dogs. The physical examination should include an assessment of hydration status, body condition, and abdominal palpation. The clinician should note the presence of abdominal pain, which is a common finding in pancreatitis. ### Laboratory Measurements The clinician should record the serum amylase, lipase, and PLI or TLI concentrations. The reference intervals for these tests vary by laboratory, so the clinician should interpret the results in the context of the laboratory's reference range. The clinician should also record the results of the complete blood count, serum biochemistry, and urinalysis. These results can identify concurrent disease and help interpret the pancreatic enzyme results. ### Imaging Findings The clinician should record the ultrasound findings, including the size, echogenicity, and contour of the pancreas. The presence of peripancreatic fluid or inflammation should be noted. ## Records and Documentation The clinician should maintain accurate records of the diagnostic evaluation and treatment. The records should include the following: - The clinical history and physical examination findings - The laboratory results, including the pancreatic enzyme concentrations - The imaging findings - The treatment plan - The response to treatment The records should be reviewed at each follow-up visit to assess the patient's progress. ## Common Failure Patterns in Pancreatic Enzyme Testing The following are common failure patterns in pancreatic enzyme testing. ### Relying on Serum Amylase and Lipase Alone The most common failure is relying on serum amylase and lipase alone to diagnose pancreatitis. This can lead to false positives and false negatives. The clinician should use PLI for the diagnosis of pancreatitis. ### Interpreting a Normal PLI as Ruling Out Pancreatitis A normal PLI concentration does not completely rule out pancreatitis. The PLI concentration can be normal in the early stages of the disease or in mild cases. The clinician should consider the clinical picture and imaging findings. ### Using PLI to Monitor Treatment Response The PLI concentration does not correlate with the clinical severity of pancreatitis. The clinician should not use PLI to monitor the response to treatment. The clinical signs and the patient's overall condition are the best indicators of the response. ### Using TLI to Diagnose Pancreatitis TLI is not a test for pancreatitis. TLI is used to diagnose EPI. The clinician should not use TLI to diagnose pancreatitis. ### Failing to Consider Concurrent Disease Pancreatitis can occur concurrently with other diseases, such as inflammatory bowel disease or hepatic disease. The clinician should evaluate the patient for concurrent disease and treat the underlying condition. ## Limitations of Pancreatic Enzyme Testing The following are limitations of pancreatic enzyme testing. ### Sensitivity and Specificity PLI is more sensitive and specific than serum lipase and amylase, but it is not perfect. There is a small percentage of false positives and false negatives. The clinician should interpret the PLI result in the context of the clinical picture. ### Availability PLI and TLI are not available on in-house analyzers. The tests must be sent to a reference laboratory. This introduces a delay in obtaining results. ### Cost The cost of PLI and TLI may be a barrier for some owners. The clinician should discuss the cost with the owner and explain the value of the tests. ### Species Differences The PLI assay is species-specific. The cPLI assay is for dogs, and the fPLI assay is for cats. The clinician must use the correct assay for the species. ## Safety and Welfare Context The welfare of the animal is the primary concern in the diagnostic process. The clinician should minimize the number of blood samples taken and the number of diagnostic tests performed. The clinician should also consider the welfare of the animal during the diagnostic process, including the use of sedation or anesthesia for imaging. The World Organisation for Animal Health emphasizes the importance of animal health and welfare in veterinary practice. The clinician should follow the guidelines for the welfare of the animal during the diagnostic process. The American Veterinary Medical Association provides resources for pet owners and veterinarians. The clinician can use these resources to educate the owner about the diagnostic process and the treatment of pancreatic disease. ## Professional Escalation Criteria The clinician should escalate the case to a specialist in the following situations: - The patient is not responding to treatment - The patient has severe pancreatitis with complications, such as systemic inflammatory response syndrome or multiple organ dysfunction - The patient has a suspected pancreatic mass - The patient has recurrent pancreatitis - The patient has EPI that is not responding to enzyme supplementation The specialist may be a veterinary internal medicine specialist or a veterinary surgeon. The specialist can provide advanced diagnostic and treatment options. ## Building a Serial Pancreatic Enzyme Testing Protocol for Diagnostic Confirmation and Monitoring The single-sample approach to pancreatic enzyme testing leaves clinicians with an incomplete picture. A one-time cPLI or fPLI result, while superior to serum lipase and amylase, still represents a snapshot of a dynamic disease process. Pancreatitis evolves over hours to days, and the enzyme concentration at the moment of sampling reflects only that point in time. A more robust diagnostic strategy uses serial sampling to track the trajectory of pancreatic enzyme concentrations, which provides information that a single measurement cannot deliver. This section presents a structured protocol for serial pancreatic enzyme testing, including the timing of repeat samples, the interpretation of changing values, and the record system needed to make those changes clinically meaningful. ### The Rationale for Serial Sampling A single PLI measurement answers one question: is the pancreatic lipase concentration elevated at this moment? Serial sampling answers a different and often more useful question: is the pancreatic lipase concentration rising, falling, or remaining stable? The distinction matters because the clinical management of pancreatitis depends on the trajectory of the disease, beyond its presence. In the early phase of acute pancreatitis, the pancreatic acinar cells release large amounts of lipase into the circulation. The serum concentration rises over the first 24 to 48 hours of clinical illness. If the inflammation resolves, the concentration falls as the pancreas recovers and the kidneys clear the enzyme. If the inflammation persists or worsens, the concentration remains elevated or continues to rise. A single sample taken at presentation cannot distinguish between a patient whose disease is resolving and one whose disease is progressing. A second sample taken 24 to 48 hours later provides that distinction. Serial testing also helps with the problem of false negatives. A patient that presents very early in the course of pancreatitis may have a normal PLI concentration at the time of the first sample. The enzyme has not yet accumulated in the blood to a detectable level. A repeat sample taken 24 hours later may show a clear elevation. The clinician who relies on a single normal result and discharges the patient without treatment risks missing the diagnosis. The clinician who repeats the test when clinical signs persist has a second chance to identify the disease. The same logic applies to the patient with an elevated PLI at presentation. A repeat sample that shows a falling concentration supports the diagnosis of a resolving inflammatory process. A repeat sample that shows a rising concentration indicates ongoing pancreatic injury and may prompt a more aggressive treatment approach or an escalation to specialist care. The trajectory of the enzyme concentration is a clinical tool that the single measurement cannot provide. ### Timing the Serial Samples The timing of the serial samples depends on the clinical question and the patient's condition. The protocol below provides a practical framework for the most common scenarios. #### Scenario One: Suspected Acute Pancreatitis with Normal Initial PLI When the clinical signs strongly suggest pancreatitis but the initial PLI concentration is within the reference interval, the clinician should repeat the PLI measurement in 24 to 48 hours. This interval allows time for the pancreatic lipase to accumulate in the blood if the inflammation is present. The repeat sample should be submitted even if the patient appears to be improving, because the clinical signs can lag behind the laboratory changes. The clinician should also repeat the serum lipase and amylase at the same time, not because these tests are diagnostic but because they are inexpensive and can be run in-house. A rising serum lipase in a patient with a normal initial PLI provides additional support for the diagnosis and may justify starting treatment while awaiting the repeat PLI result. #### Scenario 2: Elevated Initial PLI with Clinical Improvement When the initial PLI is elevated and the patient improves with treatment, the clinician should repeat the PLI test in 48 to 72 hours. The purpose of this repeat sample is not to monitor the response to treatment, because the PLI concentration does not correlate with the clinical severity of the disease. The purpose is to document the trajectory of the enzyme and to establish a baseline for the patient's recovery. A falling PLI concentration in a patient that is clinically improving supports the diagnosis of acute pancreatitis and indicates that the inflammatory process is resolving. A persistently elevated PLI concentration in a patient that is clinically improving is not necessarily a cause for concern, because the enzyme can remain elevated for several days after the clinical signs resolve. The clinician should interpret the repeat result in the context of the patient's clinical condition, not in isolation. #### Scenario 3: Pancreatitis with Clinical Deterioration When the patient's condition worsens despite treatment, the clinician should repeat the PLI test at 24-hour intervals. A rising PLI concentration in a deteriorating patient indicates ongoing pancreatic injury and warrants a reassessment of the treatment plan. The clinician should consider the possibility of complications, such as pancreatic necrosis, abscess formation, or systemic inflammatory response syndrome. The repeat PLI result in this scenario is not the sole basis for the treatment decision. The clinician should also repeat the complete blood count, serum biochemistry profile, and consider abdominal ultrasound. The combination of a rising PLI, worsening clinical signs, and abnormal imaging findings supports a more aggressive treatment approach and a lower threshold for referral to a specialist. #### Scenario 4: Exocrine Pancreatic Insufficiency Confirmation The serial testing protocol for EPI is different from the protocol for pancreatitis. EPI is a chronic condition, and the TLI concentration is not expected to change over hours or days. A single low TLI concentration confirms the diagnosis. The clinician does not need to repeat the TLI to confirm the diagnosis or to monitor the response to enzyme supplementation. However, the clinician should repeat the TLI in one specific situation: when the initial TLI result is borderline or equivocal. Some laboratories report TLI concentrations that fall between the normal reference interval and the diagnostic cutoff for EPI. In this situation, the clinician should repeat the TLI test in two to four weeks. A persistently low or falling TLI concentration confirms the diagnosis of EPI. A normal TLI concentration on the repeat sample rules out EPI and directs the diagnostic workup toward other causes of malabsorption. ### The Record System for Serial Pancreatic Testing Serial testing generates a series of data points that are only useful if they are recorded and interpreted systematically. The clinician should maintain a dedicated record for each patient undergoing serial pancreatic testing. The record should include the following elements: - The date and time of each sample - The test performed, including the specific assay and the laboratory - The result, including the numerical value and the reference interval - The clinical status of the patient at the time of the sample - The treatment administered between samples - The imaging findings, if imaging was performed The record should be reviewed at each follow-up visit. The clinician should plot the PLI concentration over time to visualize the trajectory. A simple paper chart or a spreadsheet is sufficient. The visual representation of the data helps the clinician identify trends that may not be obvious from a list of numbers. The record should also include the clinical observations at the time of each sample. The PLI concentration is not interpreted in isolation. A rising PLI in a patient that is eating and active is less concerning than a rising PLI in a patient that is vomiting and lethargic. The clinical context is essential for the correct interpretation of the trajectory. ### Common Failure Patterns in Serial Testing The serial testing protocol is only useful if the clinician avoids the common failure patterns that undermine its value. #### Failing to Repeat the Sample The most common failure is failing to repeat the sample. The clinician submits the initial PLI, receives a normal result, and does not repeat the test even though the clinical signs persist. This failure pattern is particularly dangerous in cats, where the clinical signs of pancreatitis can be subtle and the initial PLI can be normal in the early stages of the disease. The clinician should have a low threshold for repeating the PLI test when the clinical signs persist or worsen. The cost of the repeat test is small compared to the cost of a missed diagnosis and the consequences of untreated pancreatitis. #### Repeating the Test Too Frequently The opposite failure is repeating the test too frequently. The PLI concentration does not change rapidly, and repeating the test every few hours provides no additional information. The clinician should follow the timing protocol described above and avoid the temptation to repeat the test more often than the protocol recommends. The PLI concentration is not a real-time monitor of pancreatic inflammation. The clinician should use the clinical signs, the physical examination findings, and the other laboratory results to guide the treatment decisions between the serial samples. #### Interpreting the Trajectory in Isolation The third failure is interpreting the trajectory of the PLI concentration without considering the clinical context. A rising PLI concentration is not always a sign of worsening pancreatitis. The concentration can rise for other reasons, including the natural course of the disease, the effect of treatment, or the variability of the assay. The clinician should interpret the trajectory in the context of the patient's clinical signs, the physical examination findings, and the results of other diagnostic tests. The trajectory is one piece of the diagnostic puzzle, not the entire puzzle. #### Using the Serial PLI to Monitor the Response to Treatment The serial PLI concentration is not a reliable indicator of the response to treatment. The PLI concentration can remain elevated for several days after the clinical signs resolve. The clinician should not use the PLI to decide when to discontinue treatment or when to discharge the patient. The clinical signs are the best indicator of the response to treatment. The patient that is eating, drinking, and active is improving, regardless of the PLI concentration. The patient that is vomiting, lethargic, and anorexic is not improving, even if the PLI concentration is falling. ### The Role of Serial Testing in the Diagnostic Algorithm The serial testing protocol fits into the broader diagnostic algorithm for pancreatic disease. The initial evaluation includes the clinical history, physical examination, baseline laboratory tests, and a single PLI or TLI test. The serial testing protocol is used in the following situations: - The initial PLI is normal but the clinical signs persist - The initial PLI is elevated and the patient is deteriorating - The initial TLI is borderline and the diagnosis of EPI is uncertain The serial testing protocol is not used in the following situations: - The initial PLI is elevated and the patient is improving - The initial TLI is low and the diagnosis of EPI is confirmed - The patient has a single episode of pancreatitis and the clinical signs resolve The clinician should use the serial testing protocol selectively, based on the clinical question and the patient's response to treatment. The protocol is a tool for the diagnosis and management of the disease, not a routine requirement for every patient. ### The Cost and Practical Considerations of Serial Testing The serial testing protocol adds cost to the diagnostic evaluation. Each PLI test is more expensive than a serum lipase and amylase, and the clinician must discuss the cost with the owner before submitting the repeat samples. The clinician should explain the value of the serial testing protocol and the information that it provides. The clinician should also consider the practical aspects of the serial testing. The PLI test must be sent to a reference laboratory, and the result is not available immediately. The clinician should plan the serial samples to minimize the delay in obtaining the results. The first sample should be submitted at the time of the initial evaluation, and the repeat sample should be submitted at the appropriate interval. The clinician should also consider the welfare of the patient during the serial testing. Each blood sample requires a venipuncture, which can be stressful for the patient. The clinician should minimize the number of samples and combine the PLI test with other blood tests that are needed for the patient's care. ### The Role of the Owner in Serial Testing The owner plays an important role in the serial testing protocol. The owner should be informed about the purpose of the serial tests and the expected timeline. The owner should also be instructed to monitor the patient's clinical signs and to report any changes to the clinician. The owner should be told that the PLI concentration may not change immediately and that the clinical signs are the most important indicator of the patient's condition. The owner should not be alarmed if the PLI concentration remains elevated after the patient appears to be improving. The owner should also be informed about the cost of the serial tests and the value of the information that they provide. The owner should be given the opportunity to ask questions and to make an informed decision about the diagnostic plan. ### The Role of the Veterinary Team in Serial Testing The veterinary team, including the veterinary technicians and the support staff, plays a role in the serial testing protocol. The team should be trained to collect the blood samples correctly and to handle the samples for the reference laboratory. The team should also be trained to record the results and to communicate the results to the clinician. The team should also be trained to recognize the clinical signs of pancreatitis and to report any changes in the patient's condition to the clinician. The team should be aware of the serial testing protocol and the reasons for the repeat samples. ### The Limitations of Serial Testing The serial testing protocol has limitations. The PLI concentration is not a perfect marker of pancreatic inflammation, and the trajectory of the concentration is not always a reliable indicator of the disease course. The clinician should interpret the serial results in the context of the clinical picture and the other diagnostic tests. The serial testing protocol also requires a delay in the diagnosis. The clinician may need to make initial treatment decisions before the serial results are available. The clinician should use the clinical signs and the baseline laboratory results to guide the initial treatment. The serial testing protocol also requires a cost and a commitment from the owner. The owner may not be willing to pay for the serial tests, and the clinician should respect the owner's decision. The clinician should explain the value of the serial tests and the potential consequences of not performing them. ### The Future of Serial Pancreatic Testing The serial testing protocol is a practical approach to the diagnosis and management of the pancreatic disease. The protocol is based on the current understanding of the pancreatic enzyme testing and the clinical behavior of the pancreatitis. The protocol may change as new tests become available and as the understanding of the disease evolves. The clinician should stay informed about the new developments in the pancreatic enzyme testing and the clinical guidelines. The American Animal Hospital Association and the World Small Animal Veterinary Association provide resources for the veterinary practitioner. The clinician should use these resources to stay current with the best practices in the pancreatic disease diagnosis. The clinician should also use the resources provided by the American Veterinary Medical Association for the pet owner education. The owner should be informed about the pancreatic disease and the diagnostic process. The owner should be a partner in the diagnostic and treatment decisions. ### The Role of the Serial Testing in the Clinical Decision-Making The serial testing protocol is a tool for the clinical decision-making. The protocol provides the information that the clinician needs to make the treatment decisions and to the patient's condition. The protocol is not a substitute for the clinical judgment. The clinician should use the serial results in the context of the clinical picture and the other diagnostic tests. The serial testing protocol is also a tool for the communication with the owner. The protocol provides the owner with the information about the patient's condition and the response to the treatment. The owner should be informed about the serial results and the clinical implications. The serial testing protocol is a practical approach to the pancreatic enzyme testing. The protocol is based on the evidence and the clinical experience. The clinician should use the protocol to improve the diagnostic accuracy and the patient outcomes. ## Frequently Asked Questions ### What is the difference between serum lipase and pancreatic lipase immunoreactivity? Serum lipase is a general test that measures the total lipase activity in the blood. It is not specific to the pancreas and can be elevated in other conditions. Pancreatic lipase immunoreactivity (PLI) is a species-specific immunoassay that measures the concentration of pancreatic lipase. PLI is more sensitive and specific for pancreatitis. ### When should I use cPLI instead of serum lipase? cPLI should be used when pancreatitis is suspected in a dog. Serum lipase is not reliable for the diagnosis of pancreatitis. cPLI is the preferred test. ### When should I use fPLI instead of serum lipase? fPLI should be used when pancreatitis is suspected in a cat. Serum lipase is not reliable for the diagnosis of pancreatitis in cats. fPLI is the preferred test. ### What is the difference between PLI and TLI? PLI measures pancreatic lipase and is used to diagnose pancreatitis. TLI measures trypsin and is used to diagnose exocrine pancreatic insufficiency (EPI). The two tests are used for different clinical conditions. ### Can a normal PLI rule out pancreatitis? A normal PLI makes pancreatitis less likely, but it does not completely rule it out. The PLI concentration can be normal in mild or early cases of pancreatitis. The clinician should consider the clinical picture and imaging findings. ### How long does it take to get a PLI result? The PLI test is not available in-house and must be sent to a reference laboratory. The result is typically available in a few days. The clinician may need to make initial treatment decisions before the result is available. ### What is the cost of a PLI test? The cost of a PLI test varies by laboratory and by the species. The clinician should discuss the cost with the owner and explain the value of the test. ### Can I use PLI to monitor the response to treatment? No. The PLI concentration does not change with the clinical response to treatment. The clinician should monitor the patient's clinical signs and overall condition. ## Using the Evidence | Source | Best use in this topic | Important limitation | |---|---|---| | [Pet Care](https://www.avma.org/resources-tools/pet-owners) | official guidance | Check the linked page for current local requirements | | [AAHA Guidelines](https://www.aaha.org/resources) | official guidance | Check the linked page for current local requirements | | [Global Guidelines](https://wsava.org/global-guidelines) | official guidance | Check the linked page for current local requirements | ## Related Veterinary Guides - [Serum Biochemistry Interpretation: A Problem-Oriented Approach](/knowledge/veterinary-medicine/clinical-pathology/serum-biochemistry-interpretation-problem-oriented) - [Exocrine Pancreatic Insufficiency EPI: Enzyme Powders and B12 Dosing](/knowledge/veterinary-medicine/internal-medicine/exocrine-pancreatic-insufficiency-epi-enzyme-powders-and-b12-dosing) - [Feline Feline Pancreatic Exocrine Insufficiency: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-methods/feline-pancreatic-exocrine-insufficiency-diagnosis-management) - [Canine Exocrine Pancreatic Insufficiency: Diagnosis and Management](/knowledge/veterinary-medicine/clinical-internal-medicine/canine-exocrine-pancreatic-insufficiency-diagnosis-management) - [Clinical Pathology: Hematology and Biochemistry Interpretation](/knowledge/veterinary-medicine/veterinary-pathology-microbiology/clinical-pathology-hematology-and-biochemistry-interpretation) ## References and Further Reading - [Pet Care](https://www.avma.org/resources-tools/pet-owners). American Veterinary Medical Association. - [AAHA Guidelines](https://www.aaha.org/resources). American Animal Hospital Association. - [Global Guidelines](https://wsava.org/global-guidelines). World Small Animal Veterinary Association. - [Merck Veterinary Manual](https://www.merckvetmanual.com/). Merck Veterinary Manual. - [Cornell University College of Veterinary Medicine](https://www.vet.cornell.edu/). Cornell University. - [Animal Health and Welfare](https://www.woah.org/en/what-we-do/animal-health-and-welfare). World Organisation for Animal Health. - [Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition).](https://pubmed.ncbi.nlm.nih.gov/26799652). Autophagy, 2016. - [Schistosome secretomes.](https://pubmed.ncbi.nlm.nih.gov/36113567). Acta tropica, 2022. - [Practical Interpretation and Application of Exocrine Pancreatic Testing in Small Animals.](https://pubmed.ncbi.nlm.nih.gov/26297402). Clinics in laboratory medicine, 2015. - [Practical interpretation and application of exocrine pancreatic testing in small animals.](https://pubmed.ncbi.nlm.nih.gov/24144088). The Veterinary clinics of North America. Small animal practice, 2013. - [Genomic determinants of antibiotic resistance for Helicobacter pylori treatment: a retrospective phenotypic and genotypic observational study.](https://pubmed.ncbi.nlm.nih.gov/41453373). The Lancet. Microbe, 2026. > This article is educational and is not a substitute for veterinary diagnosis or treatment. Contact a veterinarian for advice about an individual animal.