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Test ID ASMW Acid Sphingomyelinase, Leukocytes


Shipping Instructions


For optimal isolation of leukocytes, it is recommended the specimen arrive refrigerated within 96 hours of collection to be stabilized. Collect specimen Monday through Thursday only and not the day before a holiday. Specimen should be collected and packaged as close to shipping time as possible.



Specimen Required


Container/Tube:

Preferred: Yellow top (ACD solution B)

Acceptable: Yellow top (ACD solution A) or lavender top (EDTA)

Specimen Volume: 6 mL

Collection Instructions: Send specimen in original tube. Do not transfer blood to other containers.


Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602) in Special Instructions

Useful For

Investigation of possible diagnosis of Niemann-Pick disease types A and B

 

This test is not recommended for carrier detection because of the wide range of enzymatic activities observed in carriers and noncarriers.

Method Name

Flow Injection Analysis-Tandem Mass Spectrometry (FIA-MS/MS)

Reporting Name

Acid Sphingomyelinase, Leukocytes

Specimen Type

Whole Blood ACD

Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood ACD Refrigerated (preferred) 4 days
  Ambient  72 hours

Clinical Information

Niemann-Pick disease (NPD) types A (NPA) and B (NPB) are autosomal recessive lysosomal storage disorders affecting metabolism of specific lipids within cells. NPA and NPB are caused by a deficiency of sphingomyelinase, which results in extensive storage of sphingomyelin and cholesterol in the liver, spleen, lungs, and, to a lesser degree, brain. NPA disease is more severe than NPB and is characterized by early onset with feeding problems, dystrophy, persistent jaundice, development of hepatosplenomegaly, neurological deterioration, deafness, and blindness, leading to death by age 3. NPB disease is limited to visceral symptoms with survival into adulthood. Some patients have been described with intermediary phenotypes. Large lipid-laden foam cells are characteristic of the disease. Approximately 50% of cases have cherry-red spots in the macula. Sphingomyelinase is encoded by the SMPD1 gene.

 

The combined prevalence of NPA and NPB is estimated to be 1 in 250,000. NPA and NPB are inherited in an autosomal recessive manner and are caused by variants in the SMPD1 gene. Although there is a higher frequency of type A among the Ashkenazi Jewish population, both types are panethnic. Individuals with NPD types A and B typically have elevations of lyso-sphingomyelin (LSM) and lyso-sphingomyelin 509 (LSM 509) combined with elevations of the oxysterols cholestane-3 beta, 5 alpha, 6 beta-triol (COT) and 7-ketocholesterol (7-KC). (see OXNP / Oxysterols, Plasma; OXYWB / Oxysterols, Blood; OXYBS / Oxysterols, Blood Spot). Molecular genetic testing for NPA and NPB disease is also available (see NPABZ / Niemann-Pick Disease, Types A and B, Full Gene Analysis, Varies).

Reference Values

≥0.32 nmol/hour/mg protein

An interpretative report will be provided.

Interpretation

Values below the reference range are consistent with a diagnosis for Niemann-Pick types A and B.

 

When abnormal results are detected, a detailed interpretation is given, including an overview of the results and of their significance, a correlation to available clinical information, elements of differential diagnosis, recommendations for additional biochemical testing, and in vitro, confirmatory studies (enzyme assay, molecular analysis), name and phone number of key contacts who may provide these studies, and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Clinical Reference

1. Elliott S, Buroker N, Cournoyer JJ, et al: Pilot study of newborn screening for six lysosomal storage diseases using Tandem Mass Spectrometry. Mol Genet Metab. 2016 Aug;118(4):304-309

2. Matern D, Gavrilov D, Oglesbee D, Raymond K, Rinaldo P, Tortorelli S:  Newborn screening for lysosomal storage disorders. Semin Perinatol. 2015 Apr;39(3):206-216

3. Schuchman EH, Desnick RJ: Niemann-Pick disease types A and B: acid sphingomyelinase deficiencies. In: Valle D, Beaudet AL, Vogelstein B, et al. The Online Metabolic Bases of Inherited Disease. McGraw-Hill. Accessed 2/14/2019. Available at https://ommbid.mhmedical.com/content.aspx?sectionid=225545671&bookid=2709&Resultclick=2

4. Wasserstein MP, Schuchman EH: Acid sphingomyelinase deficiency. In: Pagon RA, Adam MP, Ardinger HH, et al. GeneReviews. [Internet] Updated 2015 June 18. Retrieved 2/14/2019. Available at www.ncbi.nlm.nih.gov/books/NBK1370/

5. Schuchman EH, Desnick, RJ: Types A and B Niemann-Pick disease. Mol Genet Metab. 2017;120(1-2)27-33

Day(s) and Time(s) Performed

Specimens are processed Monday through Sunday.

Assay is performed: Varies

Analytic Time

5 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82657

LOINC Code Information

Test ID Test Order Name Order LOINC Value
ASMW Acid Sphingomyelinase, Leukocytes 24101-8

 

Result ID Test Result Name Result LOINC Value
606264 Acid Sphingomyelinase, Leukocytes 24101-8
606265 Interpretation 59462-2
606266 Reviewed By 18771-6