Measurement of urinary free cortisol by tandem mass spectrometry and comparison with results obtained by gas chromatography-mass spectrometry and two commercial immunoassays.

Background: Determination of urinary free cortisol (UFC) is an important adjunct for the assessment of adrenal function. In this study, we have analysed cortisol concentrations in urine samples by gas chromatography-mass spectrometry (GC-MS), liquid chromatography-tandem mass spectrometry (LC-MS/MS) and two immunoassays. The results were compared with GC-MS.