Guo Z, et al. - Researchers pursued a comparison of aldosterone measurement by radioimmunoassay (RIA) with liquid chromatography-tandem mass spectrometry (LC-MS/MS) as well as assessed performances of proposed LC-MS/MS–specific cutoffs for primary aldosteronism (PA) screening and confirmatory testing. For this investigation, 41 patients had aldosterone/renin ratio (ARR) testing to screen for, and fludrocortisone suppression testing (FST) to confirm or exclude, PA. If plasma aldosterone concentration (PAC) is measured by LC-MS/MS, adjustment of the current cutoffs for PA diagnostic testing is essential. As per preliminary results, the proposed LC-MS/MS cutoffs for ARR and FST perform as well as current RIA cutoffs.