Mass spectrometry in the clinical laboratory: how have we done, and where do we need to be?

Mass spectrometry has long been used in clinical laboratories. The first important applications were the use of gas chromatography–mass spectrometry (GC-MS) for drug screening and the diagnosis of organic acid metabolic disorders. More recently liquid chromatography–mass spectrometry [LC-MS; liquid chromatography–tandem mass spectrometry (LC-MS/MS)] has been introduced successfully into clinical laboratories, where it has become the gold standard for newborn screening. The prices for basic LC-MS/MS systems have decreased, and these systems are adequate for many clinical applications. At the higher end, LCMS/MS systems with enhanced capabilities now permit the analysis of clinically important compounds that are present in very low concentrations in biological fluids.