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Test Code MGT1 Myasthenia Gravis (MG) Evaluation, Thymoma, Serum

Useful For

Investigating patients with suspected or proven thymoma, whether or not symptoms or signs of myasthenia gravis (MG) are present

 

Serially monitoring patients for recurrence or metastasis after removal of thymoma

 

Providing a quantitative autoantibody baseline for future comparisons in monitoring a patient's clinical course and the response to thymectomy and immunomodulatory treatment

 

Assessing the likelihood of occult thymoma in a patient with an acquired disorder of neuromuscular or autonomic transmission

 

Evaluating bone marrow transplant recipients with suspected graft-versus-host disease, particularly if there is evidence of weakness

 

Confirming that a recently acquired neurological disorder has an autoimmune basis (eg, MG or dysautonomia)

Profile Information

Test ID Reporting Name Available Separately Always Performed
MGETI MG Thymoma Interpretation, S No Yes
ARBI ACh Receptor (Muscle) Binding Ab Yes Yes
ARMO ACh Receptor (Muscle) Modulating Ab No Yes
STR Striational (Striated Muscle) Ab, S Yes Yes
CRMWS CRMP-5-IgG Western Blot, S Yes Yes
GANG AChR Ganglionic Neuronal Ab, S No Yes
VGKC Neuronal (V-G) K+ Channel Ab, S No Yes
GD65S GAD65 Ab Assay, S Yes Yes

Testing Algorithm

Recommended for investigation of: 1) a patient with suspected or proven thymoma, whether or not symptoms or signs of myasthenia gravis (MG) are present (also of value for serially monitoring patients after removal of thymoma; a rising autoantibody titer may herald tumor persistence or recurrence), or emergence of an unrelated neoplasm and 2) a bone marrow transplant recipient with suspected graft-versus-host disease, particularly if there is evidence of weakness.

 

See Myasthenia Gravis: Thymoma Diagnostic Algorithm in Special Instructions.

Method Name

ARBI, ARMO, GANG, GD65S, VGKC: Radioimmunoassay (RIA)

STR: Enzyme Immunoassay (EIA)

CRMWS: Western Blot

Reporting Name

MG Evaluation, Thymoma

Specimen Type

Serum


Specimen Required


Container/Tube: 

Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 3 mL

Additional Information: Patient should have no general anesthetic or muscle-relaxant drugs in the previous 24 hours.


Specimen Minimum Volume

2 mL

Specimen Stability Information

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

Reference Values

ACh RECEPTOR (MUSCLE) BINDING ANTIBODY

≤0.02 nmol/L

 

ACh RECEPTOR (MUSCLE) MODULATING ANTIBODIES

0-20% (reported as __% loss of AChR)

 

STRIATIONAL (STRIATED MUSCLE) ANTIBODIES

<1:120

 

CRMP-5-IgG WESTERN BLOT

Negative

 

AChR GANGLIONIC NEURONAL ANTIBODY

≤0.02 nmol/L

 

NEURONAL (V-G) K+ CHANNEL AUTOANTIBODY

≤0.02 nmol/L

 

GAD65 ANTIBODY ASSAY

≤0.02 nmol/L

Day(s) and Time(s) Performed

ACh receptor (muscle) binding antibody:

Monday through Friday; 11 a.m., 6 p.m., 10 p.m.

Saturday; 6 a.m.

Sunday; 6 a.m., 10 a.m.

 

ACh receptor (muscle) modulating antibodies:

Monday through Thursday; 2 p.m.

Saturday; 8 a.m.

 

Striational (striated muscle) antibodies:

Monday through Friday; 4 a.m., 3 p.m.

Saturday; 6 a.m.

 

CRMP-5-IgG Western blot:

Monday, Wednesday, Friday; 8 a.m.

 

AChR ganglionic neuronal antibody:

Monday through Friday; 11 a.m., 6 p.m.

Saturday; 6 a.m.

Sunday; 6 a.m.

 

Neuronal (V-G) K+ channel autoantibody:

Monday through Friday; 11 a.m., 6 p.m.

Saturday; 6 a.m.

Sunday; 6 a.m.

 

GAD65 antibody assay:

Monday through Friday; 6 a.m., 4 p.m.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

LOINC Code Information

Test ID Test Order Name Order LOINC Value
MGT1 MG Evaluation, Thymoma 90231-2

 

Result ID Test Result Name Result LOINC Value
8338 ACh Receptor (Muscle) Binding Ab 11034-6
8879 ACh Receptor (Muscle) Modulating Ab 30192-9
83107 CRMP-5-IgG Western Blot, S 47401-5
84321 AChR Ganglionic Neuronal Ab, S 94694-7
81596 GAD65 Ab Assay, S 94345-6
8746 Striational (Striated Muscle) Ab, S 94817-4
89165 Neuronal (V-G) K+ Channel Ab, S 94816-6
34274 MG Thymoma Interpretation, S 69048-7

CPT Code Information

83519 x 4-ACh receptor (muscle) binding antibody

83520

84182

86341

Forms

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