Scott CR, Elliott S, Hong X, et al. - Three mm punches from de-identified dried blood spots (DBS) were collected from the Washington NBS laboratory and given to the 5-plex LC-MS/MS assay in order to examine, in a newborn screening (NBS) laboratory, the performance of liquid chromatography-tandem mass spectrometry (LC-MS/MS) to assay five enzymatic activities in DBS for NBS of 5 lysosomal storage diseases (mucopolysaccharidosis [MPS]-II, MPS-IIIB, MPS-IVA, MPS-VI, and MPS-VII). For MPS-II, 18 below cut-off samples, one pathogenic genotype, and two “high risk” genotypes, for MPS-IIIB, no below cut-off samples, for MPS-IVA, eight below cut-off samples, four non-pathogenic genotypes, for genotypes unobtainable, for MPS-VI, four below cut-off samples and no high-risk genotypes and, for MPS-VII, one below cut-off sample verified by genotype and clinical report to be impacted. Results authenticated that the number of initial screen-positive samples is low and flexible. Therefore, for these conditions, population newborn screening is achievable in a state newborn screening laboratory.