Analysis of Acid Sphingomyelinase Activity in Dried Blood Spots Using Tandem Mass Spectrometry
Annals of Laboratory Medicine
; : 319-323, 2012.
Article
in En
| WPRIM
| ID: wpr-132349
Responsible library:
WPRO
ABSTRACT
BACKGROUND:
Niemann Pick disease (NP) is a rare, lysosomal storage disorder due to deficiency 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 (C29H59N2O6P)]) and an internal standard (N-butyroyl-D-erythro-sphingosine [C4-ceramide (C22H43NO3)]). 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 4degrees C. Position of the punch in the DBS and/or hematocrit of the DBS had a limited effect on ASM activities. Both intra- and inter-assay variability were below 10%. There was no carry-over. The median ASM activity in 2,085 newborn infants was 9.5 micromol/h/L (mean 10.6) with a SD of 5.06 micromol/h/L. Six of 2,085 (0.3%) infants were found to have ASM activities below the cut-off of 2.5 micromol/h/L. ASM activities were below the cut-off level in all 10 previously diagnosed cases with NP (range 0.16 to 2.08 micromol/h/L).CONCLUSIONS:
This MS/MS method for the measurement of ASM activity in DBS is robust and suitable for laboratory diagnosis of NP.Key words
Full text:
1
Database:
WPRIM
Main subject:
Reference Standards
/
Sphingomyelin Phosphodiesterase
/
Sphingomyelins
/
Substrate Specificity
/
Tandem Mass Spectrometry
/
Dried Blood Spot Testing
/
Hematocrit
Limits:
Humans
/
Newborn
Language:
En
Journal:
Annals of Laboratory Medicine
Year:
2012
Document type:
Article