Newborn Screening for Mucopolysaccharidoses: Results of a Pilot Study with 100 000 Dried Blood Spots

Objective: To test, in a newborn screening (NBS) laboratory, the performance of liquid chromatography-tandem mass spectrometry (LC-MS/MS) to assay 5 enzymatic activities in dried blood spots (DBS) for NBS of 5 lysosomal storage diseases (mucopolysaccharidosis [MPS]-II, MPS-IIIB, MPS-IVA, MPS-VI, and MPS-VII).

Study design: Three mm punches from de-identified DBS were obtained from the Washington NBS laboratory and submitted to the 5-plex LC-MS/MS assay. Screen cut-offs were established by analyzing the enzymatic activity in patients confirmed to have the MPS disorder. DNA sequencing of the relevant gene was performed on a second DBS punch for all samples with enzyme activity below 10% of the mean daily activity.

Results: (1) For MPS-II, 18 below cut-off samples, 1 pathogenic genotype, and 2 "high risk" genotypes; (2) For MPS-IIIB, no below cut-off samples; (3) For MPS-IVA, 8 below cut-off samples, 4 non-pathogenic genotypes, 4 genotypes unobtainable; (4) For MPS-VI, 4 below cut-off samples and no high-risk genotypes; (5) For MPS-VII, 1 below cut-off sample confirmed by genotype and clinical report to be affected.

Conclusions: These results establish that the number of initial screen positive samples is low and manageable. Thus, population newborn screening for these conditions is feasible in a state newborn screening laboratory.