Fecal bile acids were measured by which method?

• A. High-performance liquid chromatography (HPLC)
• B. Nuclear magnetic resonance (NMR) spectroscopy
• C. Gas chromatography-mass spectrometry (GC/MS)
• D. Enzyme-linked immunosorbent assay (ELISA)

Answer: (C)

Measuring fecal bile acids relies on separating the diverse bile acid molecules present in the sample and accurately identifying them. Gas chromatography–mass spectrometry (GC-MS) excels here because, after proper extraction and derivatization to make the molecules volatile, GC separates the individual bile acids, and the mass spectrometer provides highly specific molecular fingerprints. This combination allows both precise quantification and differentiation between conjugated and unconjugated forms, as well as among different bile acid species, within the complex fecal matrix.

Other methods lack the same breadth and specificity. High-performance liquid chromatography can quantify bile acids but often offers less detailed separation of individual species and may rely on less definitive detectors. ELISA targets specific analytes and isn’t practical for broad bile acid profiling. NMR is less sensitive and struggles to resolve the many overlapping signals in fecal samples. Therefore GC-MS is the best choice for comprehensive, accurate fecal bile acid measurement.