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23144 Myasthenia Gravis Evaluation, Thymoma (MGT1)

Myasthenia Gravis Evaluation, Thymoma (MGT1)
Test Code: MGTHYSO
Synonyms/Keywords
​Ref Lab Code: 83372,
Acetylcholine Receptor (Muscle AChR) Antibodies, AChR (Acetylcholine Receptor), Anti-Skeletal Muscle Antibodies, Muscle End-Plate Antibodies, Myasthenia Gravis Antibodies, Myoid Antibody, Striational (Striated Muscle) Antibodies
Test Components
​This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab, CRMP-5-IgG Western Blot, AChR Ganglionic Neuronal Ab, Glutamic Acid Decarboxylase (GAD65), and Neuronal Voltage-Gated Potassium Channel (VGKC).
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)
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Serum​ Red Top Tube (RTT)​ Serum Separator Tube (SST)​ 3 mL​ 2 mL​ ​
Collection Processing Instructions
​Patient should have no general anesthetic or muscle-relaxant drugs in the previous 24 hours.
Specimen Stability Information
Specimen Type Temperature Time
Serum​ Refrigerated (preferred)​ 28 days​
​ Ambient ​ 72 hours​
​ Frozen ​ ​28 days
Rejection Criteria
Gross hemolysis
​Gross lipemia
​Gross icterus
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Medical Laboratories​
ACh receptor (muscle) binding antibody: Monday through Thursday; 6 p.m., Saturday; 10 a.m.
ACh receptor (muscle) modulating antibodies: Monday through Thursday; 11 a.m.
Striational (striated muscle) antibodies: Monday through Thursday, Sunday; 10:30 p.m.
CRMP-5-IgG Western blot: Monday through Friday, 6 a.m.
AChR ganglionic neuronal antibody: Tuesday, Thursday, Sunday; 6 a.m.
Neuronal (V-G) K+ channel autoantibody: Tuesday, Thursday, Sunday; a.m.
GAD65 antibody assay: Monday through Thursday, Sunday; 8 a.m. ​
 3 days​
ARBI/8338, ARMO/83378, GANG/84321, GD65S/81596, VGKC/89165: Radioimmunoassay (RIA)
STR/8746: Enzyme Immunoassay (EIA)
CRMWS/83107: Western Blot​
Reference Lab
Mayo Clinic Laboratories
Reference Range Information
Interpretive report.
Interpretation
​A patient's autoantibody profile is more informative than the result of any single test for predicting the likelihood of thymoma, and for supporting a diagnosis of MG or other paraneoplastic neurological complication.
 
Muscle acetylcholine receptor (AChR) and striational autoantibodies are characteristic but not diagnostic of myasthenia gravis (MG) in the context of thymoma. One or more antibodies in the MG/thymoma evaluation are positive in more than 60% of nonimmunosuppressed patients who have thymoma without evidence of any neurological disorder.
 
Titers of muscle AChR and striational antibodies are generally higher in MG patients who have thymoma, but severity of weakness cannot be predicted by antibody titer. A rising antibody titer (or appearance of a new antibody specificity) following thymoma ablation suggests thymoma recurrence or metastasis, or development of an unrelated neoplasm.
 
Antibodies specific for the alternative muscle autoantigen of MG, muscle-specific receptor tyrosine kinase, are not associated with thymoma.
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
83519​ ​ 4​ ACh R binding / modulating antibodies​ ​
83520​ ​ ​ Striational antibody​ ​
84182​ ​ ​ CRMP Western blot​ ​
86341 ​ ​ ​ GAD65 antibody​ ​
Synonyms/Keywords
​Ref Lab Code: 83372,
Acetylcholine Receptor (Muscle AChR) Antibodies, AChR (Acetylcholine Receptor), Anti-Skeletal Muscle Antibodies, Muscle End-Plate Antibodies, Myasthenia Gravis Antibodies, Myoid Antibody, Striational (Striated Muscle) Antibodies
Test Components
​This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab, CRMP-5-IgG Western Blot, AChR Ganglionic Neuronal Ab, Glutamic Acid Decarboxylase (GAD65), and Neuronal Voltage-Gated Potassium Channel (VGKC).
Ordering Applications
Ordering Application Description
​Centricity ​Myasthenia Gravis Eval, Thymoma
​Cerner ​Myasthenia Gravis Eval, Thymoma (83372)
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)		 Pediatric Minimum Volume
(no repeat)
Serum​ Red Top Tube (RTT)​ Serum Separator Tube (SST)​ 3 mL​ 2 mL​ ​
Collection Processing
​Patient should have no general anesthetic or muscle-relaxant drugs in the previous 24 hours.
Specimen Stability Information
Specimen Type Temperature Time
Serum​ Refrigerated (preferred)​ 28 days​
​ Ambient ​ 72 hours​
​ Frozen ​ ​28 days
Rejection Criteria
Gross hemolysis
​Gross lipemia
​Gross icterus
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)
Test Components
​This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab, CRMP-5-IgG Western Blot, AChR Ganglionic Neuronal Ab, Glutamic Acid Decarboxylase (GAD65), and Neuronal Voltage-Gated Potassium Channel (VGKC).
Reference Range Information
Interpretive report.
Interpretation
​A patient's autoantibody profile is more informative than the result of any single test for predicting the likelihood of thymoma, and for supporting a diagnosis of MG or other paraneoplastic neurological complication.
 
Muscle acetylcholine receptor (AChR) and striational autoantibodies are characteristic but not diagnostic of myasthenia gravis (MG) in the context of thymoma. One or more antibodies in the MG/thymoma evaluation are positive in more than 60% of nonimmunosuppressed patients who have thymoma without evidence of any neurological disorder.
 
Titers of muscle AChR and striational antibodies are generally higher in MG patients who have thymoma, but severity of weakness cannot be predicted by antibody titer. A rising antibody titer (or appearance of a new antibody specificity) following thymoma ablation suggests thymoma recurrence or metastasis, or development of an unrelated neoplasm.
 
Antibodies specific for the alternative muscle autoantigen of MG, muscle-specific receptor tyrosine kinase, are not associated with thymoma.
For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Medical Laboratories​
ACh receptor (muscle) binding antibody: Monday through Thursday; 6 p.m., Saturday; 10 a.m.
ACh receptor (muscle) modulating antibodies: Monday through Thursday; 11 a.m.
Striational (striated muscle) antibodies: Monday through Thursday, Sunday; 10:30 p.m.
CRMP-5-IgG Western blot: Monday through Friday, 6 a.m.
AChR ganglionic neuronal antibody: Tuesday, Thursday, Sunday; 6 a.m.
Neuronal (V-G) K+ channel autoantibody: Tuesday, Thursday, Sunday; a.m.
GAD65 antibody assay: Monday through Thursday, Sunday; 8 a.m. ​
 3 days​
ARBI/8338, ARMO/83378, GANG/84321, GD65S/81596, VGKC/89165: Radioimmunoassay (RIA)
STR/8746: Enzyme Immunoassay (EIA)
CRMWS/83107: Western Blot​
Reference Lab
Mayo Clinic Laboratories
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
83519​ ​ 4​ ACh R binding / modulating antibodies​ ​
83520​ ​ ​ Striational antibody​ ​
84182​ ​ ​ CRMP Western blot​ ​
86341 ​ ​ ​ GAD65 antibody​ ​
For most current information refer to the Marshfield Laboratory online reference manual.