Serum Total Bile Acids Test in Veterinary Clinics

Determination of serum TBA is a common diagnostic test for animal hepatic functions in veterinary laboratories. While there are several different liver-function tests available, serum TBA test is the most sensitive,the easiest to perform and the most liver-specific. TBA testing is also useful in avian medicine because elevated liver enzyme activity in birds, such as increased AST, does not always correlate with the presence of liver disease. Testing for serum TBA bile 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 of animals.

Clinical InterpretationIncreased values:
In the presence of impaired hepatic anion transport, which can be induced by a variety of hepatic diseases, serum TBA levels can be expected to rise markedly from 100 mmole/L to over 350 mmole/L in severe cases. This test has generally replaced the BSP clearance test as the indicator of choice in hepatic anion transport and has been used successfully in many species of animals and birds. Because of the enterohepatic circulation, an evaluation of gut function must be made before interpreting TBA results, as lower than expected concentrations could occur due to impaired re-absorption. The test should compliment standard tests forevidence of liver function/disease rather than act as a replacement. In monogastric animals, the pre- and post- prandial measurement of TBA is a very sensitive measure of hepatic biliary disease due to the normal increase in secretion with eating and subsequent re-absorption into the blood stream. In healthy animals, serum TBA concentrations return to normal baseline levels within two hours after eating. Serum TBA tests have replaced the use of plasma ammonia tests in the detection of hepato-portal shunts.

Low values:
Extremely low values of serum TBA may be seen with intestinal blockage by foreign bodies and stasis.

Reference Ranges
The following series of reference values for serum TBA are currently in use and can be used as an aid to interpretation. It should be noted that these reference values were determined using enzymatic TBA assay method, and should not be compared with the values quoted in literature using radio-immuno assay.

Species Range (µmole/L)

Species Range
(µmole/L)

Sheep

0-50

Cattle

0-50

Goat

0-50

Pig

0-50

Horse

0-15

Dog-fasting

0-30

Dog-postprandial

0-50

Cat-fasting

0-10

Cat-postprandial

0-30

Birds

0-100

Sample handling:
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 im-

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. However, when enzyme cycling based TBA test is used, lipemia and hemolytic samples are more tolerated. A serum sample is preferred for the TBA test. However, when serum is not available, a heparinized plasma sample can also be used, but the recovery of TBA is only 90% of serum TBA.

References
1. M. Sawkat Anwer et al. Liver Disease, 25: 503-517, 1995
2. Norman B. Javitt Clinics in Gastroenterology,6: 219-226, 1977
3. Youichi Kamiyama et al. Chem. Pharm. Bull. 30: 3796-3799, 1982
4. T. Osuga et al. Clin. Chim. Acta, 75: 81-85,1977
5. Toshihide Shima et al. J. Gastroenterologyand hepatology, 15: 294-299, 2000
6. H. Reyes in Bile Acids and Pregnant. Edited by U. Leuschner et al. Kluwer Academic Publishers, Dordrecht/Boston/London, 2002
7. Edward Lebovics et al. Digestive Diseases and Sciences, 42: 1094-1099, 1997
8. Ian A. et al. Gut, 19: 492-496, 1978
9. M. Angelico et al. Digestive Diseases, 22: 941-946, 1977
10. Melvyn G. Korman et al. The New England Journal of Medicine, 290: 1399- 1402, 1974