The aims of this study were to determine the diagnostic effectiveness of fasting and postprandial serum bile acid determinations in liver diseases, and to compare results with those of conventional liver function tests.

In 322 patients with biopsy-proved liver disease and 93 healthy subjects, fasting and postprandial (2 hr) serum levels of cholic, chenodeoxycholic, and lithocholic acid conjugates and conventional liver function tests were evaluated. Data were subjected to variance and discriminant and factor analyses.

Fasting serum bile acids were higher in patients when compared to controls and were significantly higher in severe than in mild liver diseases. Determination of cholic plus lithocholic acid provided the highest discrimination capacity.

The percent of correct allocation was 75.4% for conventional liver function tests, 70.1% for fasting serum bile acids and increased to 79.6% when liver function tests plus serum bile acids were considered. Postprandial percentages were always lower than fasting. Factor analysis identified two factors possibly related to cytolysis and protein synthesis. The serum bile acid concentrations highly correlated with both factors.

We conclude that serum bile acid determinations increase the diagnostic and discriminant capacities of liver function tests and are more sensitive and discriminant when obtained in fasting than postprandially.