Measurement of urinary free cortisol using liquid chromatography-tandem mass spectrometry: comparison with the urine adapted ACS:180 serum cortisol chemiluminescent immunoassay and development of a new reference range.

Background: The measurement of urinary free cortisol (UFC) is commonly used in the investigation of possible Cushing's syndrome. With the recent availability of liquid chromatography-tandem mass spectrometry (LC-MS/MS) in hospital laboratories, we wanted to develop a specific UFC LC-MS/MS method and compare it with our current immunoassay method and develop a new LC-MS/MS reference range if required.

Methods: A UFC LC-MS/MS method using deuterated cortisol as an internal standard was optimized using solid-phase extraction as a clean-up procedure.

Measurement of total homocysteine in plasma and blood spots using liquid chromatography-tandem mass spectrometry: comparison with the plasma Abbott IMx method.

Background: Current sampling for total homocysteine (tHcy) is problematic, requiring plasma separation within 15 min. The aim of this study was to develop a liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for the measurement of tHcy in plasma and dried blood spots and to determine whether the dried blood spot concentration could be used to predict plasma concentrations of tHcy.

Methods: LC-MS/MS methodology was optimized to measure tHcy in plasma and dried blood spots.

Assay of teicoplanin in serum: comparison of high-performance liquid chromatography and fluorescence polarization immunoassay.

A simple liquid extraction coupled with reverse-phase HPLC and UV detection was shown to correlate well with fluorescence polarization immunoassay (FPIA) on the Abbott TD(x) analyser for serum teicoplanin analysis, r(2) = 0.974, HPLC = 0.908 TDx + 2.