Biochemical assay of serum bile acids: methods and applications

Immunoassays and bioluminescence assays of bile acids in serum have provided relatively simple and sensitive methods for assessing the concentration of selected sub-groups of bile acids. However, these assays do not provide full data for each of the individual bile acids. The recent development of sensitive techniques such as high-performance liquid chromatography (HPLC) and gas-liquid chromatography-mass spectrometry (GLC-MS) have made possible the separation and quantification of free and conjugated bile acids in biological samples. Several studies have demonstrated the value of individual serum bile acid levels and bile acid ratios when assessing the hepatic function of experimental animals treated with various hepatoxic agents, and in humans with various hepatic disorders. Current data show that individual serum bile acids are more sensitive and specific as early predictors of hepatic injury, and are an accurate independent prognostic indicator. These studies have provided further insight into the various determinants of serum bile acid levels in physiological and pathological conditions affecting the liver. Future studies using these techniques and perhaps monoclonal antibodies, fast atom bombardment-mass spectrometry (FAB-MS) and nuclear magnetic resonance (NMR) for bile acid assays may provide both researcher and clinician with a reliable, sensitive and specific indicator of hepatic injury.