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23142 Myasthenia Gravis Evaluation, Adult (MGA1)

Myasthenia Gravis Evaluation, Adult (MGA1)
Test Code: MGADSO
Synonyms/Keywords
Ref Lab Code: 83370, Acetylcholine Receptor (Muscle AChR) Antibodies, AChR (Acetylcholine Receptor), Anti-Skeletal Muscle Antibodies, GAD65 (Glutamic Acid Decarboxylase), Muscle End-Plate Antibodies, Myasthenia Gravis Antibodies, Myoid Antibody, Neuronal Potassium Channel Ab, Striational (Striated Muscle) Antibodies, VGKC, VGPC, Voltage-Gated Potassium Channel Ab, Potassium Channel Antibodies (specify), Glutamate Decarboxylase Antibodies (GAD65)
Test Components
​This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab. The following tests are reflexed and charged when indicated: CRMP-5-IgG Western Blot, AChR Ganglionic Neuronal Ab, Glutamic Acid Decarboxylase Ab (GAD65), and Neuronal Voltage-Gated Potassium Channel (VGKC).
Useful For
​Initial evaluation of patients aged 20 or older with symptoms and signs of acquired myasthenia gravis (MG)
 
Bone marrow transplant recipients with suspected graft-versus-host disease, particularly if weakness has appeared
 
Confirming that a recently acquired neurological disorder has an autoimmune basis (eg, MG)
 
Providing a quantitative baseline for future comparisons in monitoring a patient's clinical course and the response to immunomodulatory treatment
 
Raising likelihood of neoplasia
 
If muscle AChR modulating antibody value is (or exceeds) 90% acetylcholine receptor (AChR) loss and striational antibody is detected, thymoma is likely. Reflexive testing will include CRMP-5-lgG Western blot, ganglionic AChR antibody, GAD65 antibody, and VGKC antibody (which are frequent with thymoma).
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 Saturday
ACh receptor (muscle) modulating antibodies: Monday through Thursday
Striational (striated muscle) antibodies: Monday through Thursday, Sunday
CRMP-5-IgG Western blot: Monday through Friday
AChR ganglionic neuronal antibody: Tuesday, Thursday, Sunday
Neuronal VGKC autoantibody: Tuesday, Thursday, Sunday
GAD65 antibody assay: Monday through Thursday, Sunday​
 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
​The patient's autoantibody profile is more informative than the result of any single test for supporting a diagnosis of myasthenia gravis (MG), and for predicting the likelihood of thymoma (see MGETH/83372 Myasthenia Gravis [MG] Evaluation, Thymoma).
 
Muscle acetylcholine receptor (AChR) and striational autoantibodies are characteristic but not diagnostic of MG. One or both are found in 13% of patients with Lambert-Eaton Syndrome (LES), but P/Q-type calcium channel autoantibodies are very rare in MG.
 
Results are sometimes positive in patients with neoplasia without evidence of neurological impairment.
 
Titers are generally higher in patients with severe weakness, or with thymoma, but severity cannot be predicted by antibody titer.
 
Test results for muscle acetylcholine receptor and striational antibodies may be negative for 6 to 12 months after MG symptom onset. Only 8% of nonimmunosuppressed patients with generalized MG remain seronegative beyond 12 months for all autoantibodies in the adult MG evaluation. Of those patients 38% will have the alternative muscle-specific receptor tyrosine kinase (MuSK)-specific autoantibody.
 
MuSK antibody-positive patients lack thymoma, and have predominantly oculobulbar symptoms that respond to plasmapheresis and immunosuppressant therapy. They do not benefit from thymectomy.
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
83519​ ​ 2​ ACh receptor antibodies​ ​
83520​ ​ ​ Striational antibody​ ​
83519​ ​ ​2  ACh blocking receptor ​If needed
84182​ ​ ​ CRMP-5 Western blot ​If needed
86341​ ​ ​ GAD65 ​If needed
Synonyms/Keywords
Ref Lab Code: 83370, Acetylcholine Receptor (Muscle AChR) Antibodies, AChR (Acetylcholine Receptor), Anti-Skeletal Muscle Antibodies, GAD65 (Glutamic Acid Decarboxylase), Muscle End-Plate Antibodies, Myasthenia Gravis Antibodies, Myoid Antibody, Neuronal Potassium Channel Ab, Striational (Striated Muscle) Antibodies, VGKC, VGPC, Voltage-Gated Potassium Channel Ab, Potassium Channel Antibodies (specify), Glutamate Decarboxylase Antibodies (GAD65)
Test Components
​This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab. The following tests are reflexed and charged when indicated: CRMP-5-IgG Western Blot, AChR Ganglionic Neuronal Ab, Glutamic Acid Decarboxylase Ab (GAD65), and Neuronal Voltage-Gated Potassium Channel (VGKC).
Ordering Applications
Ordering Application Description
​Centricity ​Myasthenia Gravis Eval, Adult
​Cerner ​Myasthenia Gravis Eval, Adult (83370)
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
​Initial evaluation of patients aged 20 or older with symptoms and signs of acquired myasthenia gravis (MG)
 
Bone marrow transplant recipients with suspected graft-versus-host disease, particularly if weakness has appeared
 
Confirming that a recently acquired neurological disorder has an autoimmune basis (eg, MG)
 
Providing a quantitative baseline for future comparisons in monitoring a patient's clinical course and the response to immunomodulatory treatment
 
Raising likelihood of neoplasia
 
If muscle AChR modulating antibody value is (or exceeds) 90% acetylcholine receptor (AChR) loss and striational antibody is detected, thymoma is likely. Reflexive testing will include CRMP-5-lgG Western blot, ganglionic AChR antibody, GAD65 antibody, and VGKC antibody (which are frequent with thymoma).
Test Components
​This test includes: ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab. The following tests are reflexed and charged when indicated: CRMP-5-IgG Western Blot, AChR Ganglionic Neuronal Ab, Glutamic Acid Decarboxylase Ab (GAD65), and Neuronal Voltage-Gated Potassium Channel (VGKC).
Reference Range Information
Interpretive report.
Interpretation
​The patient's autoantibody profile is more informative than the result of any single test for supporting a diagnosis of myasthenia gravis (MG), and for predicting the likelihood of thymoma (see MGETH/83372 Myasthenia Gravis [MG] Evaluation, Thymoma).
 
Muscle acetylcholine receptor (AChR) and striational autoantibodies are characteristic but not diagnostic of MG. One or both are found in 13% of patients with Lambert-Eaton Syndrome (LES), but P/Q-type calcium channel autoantibodies are very rare in MG.
 
Results are sometimes positive in patients with neoplasia without evidence of neurological impairment.
 
Titers are generally higher in patients with severe weakness, or with thymoma, but severity cannot be predicted by antibody titer.
 
Test results for muscle acetylcholine receptor and striational antibodies may be negative for 6 to 12 months after MG symptom onset. Only 8% of nonimmunosuppressed patients with generalized MG remain seronegative beyond 12 months for all autoantibodies in the adult MG evaluation. Of those patients 38% will have the alternative muscle-specific receptor tyrosine kinase (MuSK)-specific autoantibody.
 
MuSK antibody-positive patients lack thymoma, and have predominantly oculobulbar symptoms that respond to plasmapheresis and immunosuppressant therapy. They do not benefit from thymectomy.
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Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
Mayo Medical Laboratories​
ACh receptor (muscle) binding antibody: Monday through Saturday
ACh receptor (muscle) modulating antibodies: Monday through Thursday
Striational (striated muscle) antibodies: Monday through Thursday, Sunday
CRMP-5-IgG Western blot: Monday through Friday
AChR ganglionic neuronal antibody: Tuesday, Thursday, Sunday
Neuronal VGKC autoantibody: Tuesday, Thursday, Sunday
GAD65 antibody assay: Monday through Thursday, Sunday​
 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​ ​ 2​ ACh receptor antibodies​ ​
83520​ ​ ​ Striational antibody​ ​
83519​ ​ ​2  ACh blocking receptor ​If needed
84182​ ​ ​ CRMP-5 Western blot ​If needed
86341​ ​ ​ GAD65 ​If needed
For most current information refer to the Marshfield Laboratory online reference manual.