Pilot study of newborn screening for six lysosomal storage diseases using Tandem Mass Spectrometry

TLDR

Newborn screening programs are expanding to include lysosomal storage disorders because early treatment can improve outcomes. This study evaluates the performance of a multiplex tandem mass spectrometry assay for six lysosomal enzymes to identify newborns at risk for Pompe, MPS‑I, Fabry, Gaucher, Niemann‑Pick A/B, and Krabbe disease. Enzyme activities of GAA, GALC, GBA, GLA, IDUA, and SMPD‑1 were measured on ~43,000 dried blood spot samples in a Washington state NBS laboratory, with screen‑positive specimens sent for DNA sequencing and the assay performed by a single technician on one MS/MS instrument. The assay yielded screen‑positive rates of 4.5–25.0 per 100,000 newborns, demonstrated a 5‑ to 15‑fold higher analytical range than fluorimetric methods, and consistently produced lower detection rates than a digital microfluidics fluorimetric platform, confirming its feasibility and improved performance in NBS.

Abstract

There is current expansion of newborn screening (NBS) programs to include lysosomal storage disorders because of the availability of treatments that produce an optimal clinical outcome when started early in life. To evaluate the performance of a multiplex-tandem mass spectrometry (MS/MS) enzymatic activity assay of 6 lysosomal enzymes in a NBS laboratory for the identification of newborns at risk for developing Pompe, Mucopolysaccharidosis-I (MPS-I), Fabry, Gaucher, Niemann Pick-A/B, and Krabbe diseases. Enzyme activities (acid α-glucosidase (GAA), galactocerebrosidase (GALC), glucocerebrosidase (GBA), α-galactosidase A (GLA), α-iduronidase (IDUA) and sphingomyeline phosphodiesterase-1 (SMPD-1)) were measured on ~ 43,000 de-identified dried blood spot (DBS) punches, and screen positive samples were submitted for DNA sequencing to obtain genotype confirmation of disease risk. The 6-plex assay was efficiently performed in the Washington state NBS laboratory by a single laboratory technician at the bench using a single MS/MS instrument. The number of screen positive samples per 100,000 newborns were as follows: GAA (4.5), IDUA (13.6), GLA (18.2), SMPD1 (11.4), GBA (6.8), and GALC (25.0). A 6-plex MS/MS assay for 6 lysosomal enzymes can be successfully performed in a NBS laboratory. The analytical ranges (enzyme-dependent assay response for the quality control HIGH sample divided by that for all enzyme-independent processes) for the 6-enzymes with the MS/MS is 5- to 15-fold higher than comparable fluorimetric assays using 4-methylumbelliferyl substrates. The rate of screen positive detection is consistently lower for the MS/MS assay compared to the fluorimetric assay using a digital microfluidics platform.