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Texas GI Panel:
Valuable Diagnostic, Minimal Investment

Private: Dr. Rebekah Mack, Diplomate ACVIM

In both general and specialty practices, one of the most common presenting complaints is gastrointestinal disease. Whether it presents as acute onset diarrhea and vomiting or chronic ongoing signs, the volume of such cases makes diagnosis and appropriate care essential to a successful clinical day.  Because of the wide variance in presentation and causes, noninvasive diagnostics that help better define not only the disease but also a treatment plan are paramount.

The Texas GI panel (Texas A&M Gastrointestinal Lab) has a variety of applications. It helps to confirm disorders of both the small intestine and the pancreas. It focuses on quantifying pancreatic dysfunction or inflammation through the TLI and PLI, and small intestinal health through cobalamin and folate.  Used in combination with clinical suspicion and basic bloodwork, these assays will help provide valuable additional information with minimal investment. All of these assays are run on serum and results are typically available within 3 to 5 business days.

TLI ballTLI: This assay measures the trypsninogen and Trypsin-Like Immunoreactivity. This is primarily a test for exocrine pancreatic insufficiency (EPI).  The TLI is specifically validated for dogs through multiple labs but only for cats through Texas A &M Gastrointestinal Laboratory.  It must be completed after a 12 hour fast. It is highly sensitive and specific making it an excellent diagnostic tool for suspected cases of EPI. There is a grey zone for this test when values fall between 2.5-5.7 ug/L in dogs, in these instances retesting in 1 to 2 months often reveals confirmatory results.

Case Example:
  • Signalment: 6-month-old male neutered Border collie
  • History: Over the dog’s entire life the owners have noted foul smelling, light colored stool, sometimes almost appearing that the stool has undigested food present within it.  He looks to be a “poor doer,” small in stature with a BCS 2/9.
  • Diagnostics: Bloodwork reveals a macrocytic mild non-regenerative anemia and lightly low albumin. The dog has had multiple negative fecals and a negative giardia snap test.
  • Treatments: Unresponsive to deworming, Metronidazole, and a low residue diet.
  • TLI: 0.7ug/L, well below normal limit
  • Outcome: Responsive to Pancreazyme, normal stools, and weight gain.

PLI ballPLI: (Pancreatic Lipase Immunoreactivity)This test measures pancreatic lipase as an ELISA using monoclonal antibodies and recombinant antigen. It is a quantitative test and referred to as a Spec cPL. While the SNAP cPL gauges a response greater than 200 ug/L as moderate and greater than 400 ug/L (5.4 ug/L in cats) as strongly abnormal, the Spec cPL gives an exact quantitative value.  This test is fairly accurate; it can be affected by a recent meal so a fasted sample is important.  Systemic inflammation can cause the SNAP cPL to show strong positives while the Spec cPL allows for a more specific and sensitive test especially at higher values. A PLI of any type should only be done in the face of clinical suspicion of disease.  In the clinical position where no ultrasound is available or for animals with chronic vomiting, anorexia, or cranial abdominal pain this test is helpful in confirming disease.  Recent studies have revealed that using the Spec cPL for following chronic pancreatitis in both dogs and cats may not be accurate. Therefore, clinical response is a better gauge of an animal’s current level of inflammation.

Case Example:
  • Signalment: 5-year-old female spayed DSH
  • History: 6 month history of reduced appetite, picky feeding, and occasional vomiting.
  • Diagnostics: Unremarkable biochemistry, normal T4, a mild neutrophilia has been noted on serial CBC’s; radiographs show good abdominal detail and normal distribution of the small intestine.
  • Treatments: Multiple diets offered, Famotidine at 1mg/kg daily, and Cerenia as needed. The cat has been hospitalized once and responds to supportive care.
  • Spec fPL: 10.4 ug/L, strong positive for pancreatitis
  • Outcome:  Owners are much quicker to provide supportive care. Omeprazole, Cerenia, and Low to Medium-fat diet introduced, and during episodes appropriate pain management is provided.

B12 ballCobalamin: (Vitamin B12) is a water-soluble vitamin which plays a significant role in a multitude of systems as a reaction-dependent enzyme. Deficiencies affect not only gastrointestinal health, but also cardiovascular health, nerve function, and bone marrow red blood cell production.  Low serum cobalamin directly reflects the tissue level of cobalamin. Cobalamin is associated with the ileum specifically. Recent studies show a direct correlation between low cobalamin levels and more severe gastrointestinal disease in cats, as well as dogs with EPI.  Historically in cases of bacterial overgrowth in dogs cobalamin will also be reduced. In most cases cobalamin should be examined in combination with folate. An increase in folate with a drop in cobalamin would be indicative of bacterial overgrowth. Perhaps the most important role of cobalamin is confirming small intestinal dysfunction and malabsorption when diagnostics such as an ultrasound or biopsy are not available.  This test appears to be quite sensitive in cats, and may also suggest the presence of small cell lymphoma in the small intestine where a very low cobalamin is found in conjunction with clinical signs. Cobalamin levels are also reflective of appropriate therapy and can be used to ensure appropriate dosing.

 Case Example:
  • Signalment: 9-year-old female spayed Bengal cat
  • History: Acute anorexia for 5 days, notable weight loss over the last 6 months of 1.5 pounds with a poor hair coat developing
  • Diagnostics: Biochemistry (mild decrease in albumin), Complete Blood Count (Unremarkable), Urinalysis (Quiet Sediment, SG 1.037), Abdominal radiographs (diffuse presence of gas in the small intestine).
  • Treatments: No care has been sought until recent anorexia, unresponsive to Pepcid, Cerenia, and Mirtazapine
  • Cobalamin: 90ng/L (<300ng/L is considered significant)
  • Treatment: Based on the clinical signs and low B12, surgical biopsies are taken, and histopathology reveals small cell lymphoma of the small intestine Prednisolone, B12, and Chlorambucil are instituted and an esophageal feeding tube placed. One week after beginning therapy the cat is eating well.

New supplementation guidelines (Texas A&M):

  • 250ug per cat

Texas AM  supplement chart

  • Give once weekly for 6 weeks, and every 3 weeks after that point. A cobalamin level should be checked at 30 days after last weekly dosing.

B9 ballFolate: (Vitamin B9) is a water-soluble vitamin that is metabolized by the cranial small intestine (duodenum). While important in many functions, it is most commonly used as an indicator for bacterial overgrowth. Folate will often increase in cases of bacterial overgrowth. It is also important to recognize that a low folate level should not be ignored and is indicative of small intestinal dysfunction.

 Case Example:
  • Signalment: 6-year-old male neutered German shorthair pointer
  • History: 2-year history of chronic small bowel diarrhea, somewhat responsive to select protein diet and metronidazole.
  • Diagnostics: Multiple Biochemistries with low albumin, low normal globulins, and low cholesterol; complete blood count showed a mild non-regenerative anemia. No protein is present in the urine. Abdominal radiographs show decreased peritoneal detail. An abdomenocentesis reveals a clear low-protein fluid with a low cellular count.
  • Cobalamin and Folate: B12 120ug/L and Folate 3ug/L (7.7 – 24.4ug/L)
  • Treatment: Hypoallergenic Diet, Prednisone (1mg/kg), Supplementation of B12 and Folate, GI protectants, and low dose aspirin.

The Bottom Line:

This is an easily performed, well researched, and noninvasive diagnostic.  When used with clinical suspicions it can help diagnose small intestinal and pancreatic disease and provide guidelines for therapy. In addition each of these assays can be performed separately as individual tests except Cobalamin and Folate which must be run together. The entire panel can be kept at a reasonable cost for clients.  It should be considered for its daily diagnostic value in appropriate cases.

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