Bile Acids in Clinical Tests

Although research has shown that bile acids play an important role in liver and intestinal function, and that the metabolism or enterohepatic circulation of bile acids is altered in certain diseases, tests involving bile acids are uncommon in the clinical chemistry laboratory. This is probably because bile acid tests are not absolutely necessary for the diagnosis of any important or well-known disease and they are generally regarded as too specialized for routine use (H12). Thus, at present bile acid tests tend to be confined to gastroenterology units with research interests in bile acid metabolism. However, there is currently much interest in evaluating serum bile acid levels as a liver function test (H19) and bile acid tests have been developed to assess various aspects of intestinal function, as described below. 

In normal, healthy subjects, the fasting level of serum bile acids is low imd is less than 5 p,mol/liter. This level is greatly increased in various hepatobiliary diseases (A9, B6, F2, F3, P9, S34, Til). For example, some liver diseases and their reported range of fasting serum bile acid concentrations (in brackets) are liver cirrhosis (5-100 pmol/liter), viral hepatitis (78—405 p,mol/liter), and extrahepatic biliary obstruction (5-230 p,mol/liter) (P9). An elevated serum bile acid concentration is highly specific for liver disease, but there is no specificity as to the type of liver disease. Determination of the profile of individual bile acids and calculations such as the cholic to che-nodeoxycholic acid ratio have been proposed as useful in the differential diagnosis of liver disease (P9). In practice, however, there is too much overlap between diseases, so that the pattern of serum bile acids does not normally provide useful diagnostic information. 

Serum bile acid concentrations as a test of liver function can be measured either in the fosting state or after a meal when there is a 2- to 6-fold increase 

It is still too early to tell whether serum bile acid determinations will be added to the currently available combination of liver function tests or replace individual tests, such as the measurement of bilirubin (H19). In correctly diagnosing patients with histologically defined liver disease, serum bile acids appear to slightly improve the results from conventional liver tests, if used in combination with these tests (F3). Perhaps when sensitive analytical methods such as bioluminescence, which can be applied to serum bile acid analysis, become available and established in diagnostic laboratories, serious consideration will be given to routine measurement of serum bile acid levels to 

COMPAWSON OF THE SeNSITIVITV OF PASTING SeRUM BiLE ACID LeVEI-S WITH ThaT OF Routine Liver Function Tests in the Diagnosis of Histologically Classified 

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