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Epic Code LAB12308395 Myelin-Associated Glycoprotein Autoantibodies, IgM, Serum

Additional Codes

Mayo Code: MAGES

Reporting Name

MAG IgM, S

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Clinical Information

Autoantibodies directed against myelin-associated glycoprotein (MAG) are associated with sensory motor demyelinating peripheral neuropathy. A distal acquired demyelinating symmetric (DADS) neuropathy phenotype is the most commonly associated presentation. Patients typically have a slowly progressive symmetric sensory ataxia with/without distal weakness and an IgM monoclonal gammopathy of undetermined significance. Nerve conductions studies typically demonstrate a characteristic progressive sensory predominant mixed axonal and demyelinating neuropathy with reduced distal conduction velocities that are greater distally. In general, patients with a DADS neuropathy show limited treatment responses to intravenous immunoglobulin and more aggressive immunotherapy may be needed. MAG antibody titers do not correlate with disease severity nor treatment responses. The presence of MAG antibodies is not exclusively diagnostic of an acquired neuropathy and results must be interpreted in the correct clinical and electrophysiological context. MAG antibodies are present in approximately 50% to 70% of those with an IgM M-protein and a DADS neuropathy phenotype. However, MAG antibodies may also be identified in those with an IgM M-protein and a chronic inflammatory demyelinating polyneuropathy (CIDP) presentation as well as in other IgM paraproteinemic disorders that present with neuropathy including in myeloma, lymphoplasmacytic lymphoma (Waldenstrom macroglobulinemia) and amyloid light chain (AL)-IgM primary amyloidosis. Higher MAG antibody titers (>10,000 Buhlmann titer unit) are better predictors of an electrophysiological DADS phenotype whereas low titer MAG antibodies may be associated with a more diverse group of neuropathies. Detection of MAG IgM antibody by enzyme-linked immunosorbent assay based on human MAG (100 kDa) antigen is significantly more sensitive and specific than MAG western blot and immunofluorescence assays using primate antigen.

Useful For

Evaluating peripheral neuropathy

 

Evaluating paraproteinemic neuropathy

Specimen Type

Serum


Specimen Required


Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL


Laboratory Test Directory Note:

COLLECTION NOTE: Volumes listed are in serum or plasma, draw approximately 2 1/2 times the requested volume in whole blood.

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
  Frozen  28 days
  Ambient  72 hours

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Day(s) Performed

Tuesday, Friday

Reference Values

<1500 Buhlmann Titer Unit

Interpretation

A positive result is consistent with anti-myelin-associated glycoprotein neuropathy.

Cautions

This test is not diagnostic and should be interpreted in the correct clinical context. Myelin-associated glycoprotein antibodies may be found in those without neuropathy, IgM M-protein, or paraproteinemic neuropathy.

Clinical Reference

1. Kuijf ML, Eurelings M, Tio-Gillen AP, et al: Detection of anti-MAG antibodies in polyneuropathy associated with IgM monoclonal gammopathy. Neurology. 2009 Sep;73(9):688-695. doi: 10.1212/WNL.0b013e3181b59a80

2. Katz JS, Saperstein DS, Gronseth G, Amato AA, Barohn RJ: Distal acquired demyelinating symmetric neuropathy. Neurology. 2000 Feb;54(3):615-620. doi: 10.1212/wnl.54.3.615

3. Magy L, Kabore R, Mathis S, et al: Heterogeneity of polyneuropathy associated with anti-MAG antibodies. J Immunol Res. 2015;2015:450391. doi: 10.1155/2015/450391

Method Name

Enzyme-Linked Immunosorbent Assay (ELISA)

Method Description

Microwells are precoated with human myelin-associated glycoprotein (MAG) antigen. The calibrators, controls, and diluted patient samples are added to the wells, and autoantibodies recognizing the MAG antigen bind during the first incubation. After washing the wells to remove all unbound proteins, purified horseradish peroxidase-labeled anti-human IgM conjugate is added. The conjugate binds to the captured human autoantibody, and the excess unbound conjugate is removed by a further wash step. The bound conjugate is visualized with 3,3',5,5'-tetramethylbenzidine substrate, which gives a blue reaction product, the intensity of which is proportional to a concentration of autoantibody in the sample. Acid is added to each well to stop the reaction. This produces a yellow end-point color, which is read at 450 nm.(Package insert: anti-MAG Autoantibodies ELISA. Buhlmann Laboratories AG; 10/2018)

Report Available

2 to 6 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 US Food and Drug Administration.

CPT Code Information

83520

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MAGES MAG IgM, S 39087-2

 

Result ID Test Result Name Result LOINC Value
607034 MAG IgM, S 39087-2

Forms

If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.

Laboratory Test Directory Additional Information:

Replaces test LAB1230061