Analysis of acid sphingomyelinase activity in dried blood spots using tandem mass spectrometry

Elisa Legnini, Joe J. Orsini, Adolf Mühl, Britt Johnson, Angela Dajnoki, Olaf A. Bodamer

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Background: Niemann Pick disease (NP) is a rare, lysosomal storage disorder due to defciency of the intra-lysosomal enzyme acid sphingomyelinase (ASM) resulting in intracellular accumulation of sphingomyelin. We evaluated a tandem mass spectrometry (MS/MS) method to analyze ASM activity in dried blood spots (DBS) that may be suitable for laboratory diagnosis of NP including high throughput screening of at-risk populations and potentially for newborn screening. Methods: ASM activity was measured in 3.2 mm punches from DBS. The eluate was incubated with the ASM substrate (N-Hexanoyl-D-erythro- sphingosylphosphorylcholine [C6-sphingomyelin (C29H 59N2O6P)]) and an internal standard (N-butyroyl-D-erythro-sphingosine [C4-ceramide (C22H 43NO3)]). ASM product and IS were analyzed using MS/MS in multiple reaction monitoring mode for transitions m/z 370.6>264.3 (ASM internal standard) and m/z 398.6>264.3 (ASM product). Results: ASM activities were stable for up to 2 months at or below 4°C. Position of the punch in the DBS and/or hematocrit of the DBS had a limited effect on ASM activities. Both intraand inter-assay variability were below 10%. There was no carry-over. The median ASM activity in 2,085 newborn infants was 9.5 μmol/h/L (mean 10.6) with a SD of 5.06 μmol/h/L. Six of 2,085 (0.3%) infants were found to have ASM activities below the cut-off of 2.5 μmol/h/L. ASM activities were below the cut-off level in all 10 previously diagnosed cases with NP (range: 0.16 to 2.08 μmol/h/L). Conclusions: This MS/MS method for the measurement of ASM activity in DBS is robust and suitable for laboratory diagnosis of N P.

Original languageEnglish (US)
Pages (from-to)319-323
Number of pages5
JournalAnnals of Laboratory Medicine
Volume32
Issue number5
DOIs
StatePublished - Sep 2012

Keywords

  • Acid sphingomyelinase
  • Dried blood spot
  • Lysosomal enzyme
  • Tandem mass spectrometry

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Biochemistry, medical

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    Legnini, E., Orsini, J. J., Mühl, A., Johnson, B., Dajnoki, A., & Bodamer, O. A. (2012). Analysis of acid sphingomyelinase activity in dried blood spots using tandem mass spectrometry. Annals of Laboratory Medicine, 32(5), 319-323. https://doi.org/10.3343/alm.2012.32.5.319