LC-MS/MS progress in newborn screening

Newborn screening programs detect treatable disorders in infants before they become symptomatic. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has greatly increased the screening possibilities by monitoring levels of amino acids and acylcarnitines. After the initial screening step, LC-MS/MS can also be used in screening positive samples as a second tier test to differentiate between true and false positive samples. As the list of disorders screened for by LC-tandem MS increases, questions arise about screening for untreatable disorders, such as some lysosomal storage diseases (LSDs). For LSDs screening methods are being developed and tested more quickly than treatments are becoming available. This goes against one of the main tenets of newborn screening which requires that a treatment be available. LC-MS/MS can detect several disorders with a single injection, which is important in high throughput laboratories. Measuring different amino acids and acylcarnitines can be used to detect up to 45 different inherited disorders depending on how diseases are counted. The LSD assays are designed in a similar way to detect multiple disorders with common sample preparation and a single injection. The clinical implications of applying this technology to NBS on a large scale in many jurisdictions across the world are discussed.