Special Edition

New bile acids test for the IDEXX SNAP® Reader

Add bile acids to your in-house testing menu to expand your liver-function testing capabilities.

Only the IDEXX VetLab® system offers you the flexibility to test what you want when you want, and the ability to use the liver-function test best suited to your patients' needs. The IDEXX VetTest® Chemistry Analyzer already provides flexibility in evaluating liver enzymes and the ability to run ammonia to determine liver function. By adding the SNAP® Bile Acids Test to your in-house testing, you will expand your liver-function testing capabilities, giving you the most comprehensive in-house diagnostics for liver testing.

Bile Acids
It is now possible to screen for decreased liver function with the easy-to-use, in-house SNAP Bile Acids Test for the IDEXX SNAP Reader. The IDEXX SNAP Reader test menu is expanding to include bile acids in addition to the T₄ and cortisol testing capabilities that you already have. With quick results, you can begin treatment or rule out impairment during the patient visit.

Ammonia
The VetTest analyzer is the only in-house analyzer that offers ammonia, which can be used for plasma ammonia concentration tests and an ammonia tolerance test. While ammonia concentrations are very unstable after blood collection, the VetTest analyzer allows you to run these tests immediately using plasma, assuring quick and accurate results. Although less sensitive than the bile acids assay for determining liver function, the plasma ammonia concentration test and ammonia tolerance test may be the best choice for a liver-function test in some cases. Moreover, the plasma ammonia concentration test is an excellent assay to screen for early neurologic dysfunction in your patients with liver disease.

For more information on the IDEXX SNAP Bile Acids Test and other IDEXX products, call IDEXX at 1-800-355-2896.

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Why test bile acids?

The liver performs a large number of unique metabolic functions that impact all body systems. Liver-function tests evaluate the ability of the liver to perform specific functions. While there are several different liver-function tests available, the bile acids assay is the most sensitive, the easiest to perform and the most liver-specific. Bile acids are produced in the liver, excreted by the gall bladder, and are critical for the digestion and absorption of fats and fat-soluble vitamins.

Normally, the liver is very efficient at capturing and removing bile acids from hepatic-portal circulation. In healthy animals, circulating bile acid levels are generally low. When liver function is compromised, more bile acids appear in circulation because the liver is not adequately removing them.

Testing for serum bile acids detects liver changes before the development of clinical signs such as icterus. This early sensitivity is extremely important because it allows for the possibility of treatment before the development of extensive and irreversible liver damage.

When evaluating liver function, it is important to understand and differentiate the information provided by the liver enzymes and the bile acids test. Liver enzymes (ALT, AST, LDH, ALKP and GGT) help identify damage to liver cells and serve as indicators of hepatocellular integrity or cholestasis, whereas bile acids are an indicator of liver function, despite the presence or absence of hepatocellular injury.

While certain clinical signs such as icterus are specific for liver disease, other signs are less obvious and can include anorexia, vomiting, lethargy, weight loss, fever, inhibited growth, long anesthesia recovery, ascites, hepatomegaly and hepatic encephalopathy. When confronted with these symptoms, you should consider liver disease and work up the case accordingly.

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Meet Marketing Associate, Jeff Raymond

Jeff has worked at IDEXX for eight years and has held a variety of positions. In his current position as a marketing associate for the SNAP® Reader, he is responsible for coordinating and developing product-related training and reference materials for the instrument and its tests—T₄, cortisol and the new bile acids assay.

As a former senior technical support representative, Jeff knows the importance of providing the highest quality in-house diagnostics available and support you can depend on. Jeff notes, "Adding bile acids to the IDEXX VetLab® suite will allow veterinarians to evaluate liver function in-house. More comprehensive in-house diagnostics help doctors practice better medicine and provide immediate patient care. It's also convenient for pet owners. It's a win-win situation for everyone!"

Jeff enjoys running with his girlfriend and weekend adventures with his son and three adopted rescue dogs—Angel, a black lab mix who had been abandoned at a truck station; Boo, a beagle mix rescued from an abusive home; and Nick, a rottweiler mix who came from a refuge in Florida where he had been tormenting their monkeys!

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did you know? by Michelle Kahn, MS, DVM

Bile Acids Basics
There are many reasons the bile acids test has become the liver-function test of choice in the veterinary community. It is relatively inexpensive and easy to perform (all that is required is a fasted serum sample and a two-hour postprandial sample), and best of all, it is a very sensitive indicator of liver function. To obtain the best results, there are some basics to consider when performing this assay:

• A 12-hour fast must be undertaken prior to the first (preprandial) sample.

• It is very important to perform a postprandial sample, as well as a fasting sample, or the diagnosis may be missed.

• The amount and type of food used with this assay are important. While the amount of food is not known for sure, general recommendations are to feed at least 2 teaspoons of food to animals that weigh less than 5 kg, and approximately 1/4 can of food for larger animals. You don't want to overfeed because lipemia can adversely affect the bile acids results, and you should avoid foods with low-fat and low-protein concentrations.

• Hemolysis can adversely affect your test results. Careful sample handling and a large-gauge needle are useful to avoid hemolysis, which can significantly impact bile acids assay results. If you note hemolysis, you should draw a new sample for testing.

• Sometimes, preprandial levels may be higher than postprandial levels. This may be due to many things, including delayed gastric emptying and interdigestive gall bladder contraction. It is suggested that you retest if this type of result is noted. You should also consider that owner compliance might be a problem and the client may have tried to sneak some breakfast to the dog. It is important to emphasize that the patient must be fasted for the retest!

• The Maltese conundrum: abnormal bile acids test results are commonly seen in this breed when there is no liver function abnormality. This is obviously a concern since this breed is genetically predisposed to portosystemic shunts (PSS). Therefore, an abnormal bile acids test result is inconclusive, but a normal bile acids test can rule out PSS in Maltese puppies. Several other terrier breeds may also produce suspect results.

• Don't test icteric "yellow" dogs. Knowing when not to run can be just as important as knowing when to run the bile acids assay. If an animal is icteric (and not anemic), there is no reason to run a bile acids assay. You already know that liver function is compromised in this patient, and you should move on to finding the cause of the liver disease.

To get the most out of your bile acids testing, you should keep in mind that a complete diagnostic workup is essential to diagnosing liver disease in the cat and dog. You should always perform a complete CBC, a biochemical profile and a urinalysis (including a sediment exam) prior to evaluating liver function. I can think of several cases where I went back and tested for a portosystemic shunt after noting ammonium biurate crystals in the urine. Even though there were no clinical signs and nothing in the history suggested a shunt, it was present. If possible, you should assess the liver with diagnostic imaging as well. An ultrasound can be particularly beneficial, especially in the right hands. The more complete your diagnostic protocol, the better your chance of discovering the underlying pathology and successfully treating your patient.

To contact Dr. Kahn, e-mail
Didyouknow@idexx.com.

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Did you know that the IDEXX SNAP® Reader currently gives you the ability to screen for and monitor the following endocrine disorders?

• Canine hypothyroidism—A T₄ value within the reference range (1.3–2.9 µg/dL) indicates that hypothyroidism is unlikely. However a low T₄ value is not definitively diagnostic for hypothyroidism because outside factors (e.g., nonthyroidal illness and some drugs) can falsely lower T₄ levels. A low total T₄ is only a piece of the puzzle in diagnosing the disease. Other information to take into consideration includes clinical signs, a biochemical profile (hypercholesterolemia) and a hematology analysis (a nonregenerative anemia). However, when the above analysis is inconclusive, experts recommend that the T₄ test be repeated in four weeks. If still inconclusive, additional thyroid diagnostics (TSH or free T₄ by equilibrium dialysis) may be needed.

• Feline hyperthyroidism—Experts agree that a diagnosis can be made from a single high T₄ result. Because euthyroid sick patients have suppressed T₄ and T₃ concentrations, concomitant hyperthyroidism should be considered in any middle- to old-aged cat with a nonthyroidal illness and a high-normal T₄ level, especially if clinical signs are present.

• Hyperadrenocorticism (Cushing's syndrome)—A diagnosis and the decision to treat should not be based solely on laboratory testing, but should include the presence of clinical signs such as polydipsia, polyuria, abdominal enlargement, alopecia, decreased exercise tolerance, calcinosis cutis, hyperpigmentation, panting, lethargy and obesity.

• Hypoadrenocorticism (Addison's disease)—It is important to rule out the presenting signs and symptoms (anorexia, lethargy, depression, vomiting, weakness, weight loss, diarrhea, dehydration, bradycardia, weak femoral pulse, waxing/waning symptoms) as being iatrogenic, and include electrolytes, a physical exam and history when diagnosing Addison's disease. It is crucial that these signs are identified quickly to prevent or correct a potential Addisonian crisis.

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frequently asked question

Where can I find information about interpreting my
SNAP Reader results?

Cortisol and T₄ results provide valuable information to aid in the diagnosis of complex thyroid and adrenal disease. IDEXX provides several sources of complete interpretive information, including package inserts and diagnostic protocol guides for cases of suspected hypothyroidism, hyperthyroidism and Cushing's syndrome. For additional information, call IDEXX Customer Support at 1-800-248-2483.

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