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23141 Myasthenia Gravis/Lambert Syndrome Evaluation (MGL1)

Myasthenia Gravis/Lambert Syndrome Evaluation (MGL1)
Test Code: MGSYNSO
Synonyms/Keywords
​Ref Lab Code: 83369, Acetylcholine Receptor (Muscle AChR) Antibodies, AChR (Acetylcholine Receptor), Anti-skeletal Muscle Antibodies, Calcium Channel Blockers, Conotoxin (Receptor) Antibodies, Lambert-Eaton Myasthenic Syndrome (LEMS) Antibodies, Motor End-Plate Antibody, Motor Nerve Terminal Antibodies, Muscle Culture Antibodies, Muscle End-Plate Antibodies, Myasthenia Gravis Antibodies, Myoid Antibody, Striational (Striated Muscle) Antibodies, Voltage Gated Calcium Channel (VGCC) Antibodies
Test Components
​This test includes: Calcium Channel Binding Ab, P/Q type; Calcium Channel Binding Ab, N-Type; ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab. The following tests are reflexed when indicated: CRMP-5-IgG Western Blot, and AchR Ganglionic Ab.
Useful For
​
Confirming the autoimmune basis of a defect in neuromuscular transmission (eg, myasthenia gravis [MG], Lambert-Eaton syndrome [LES])
 
Distinguishing LES from 2 recognized autoimmune forms of MG
 
Raising the index of suspicion for cancer, particularly primary lung carcinoma (N-type calcium channel antibody)
 
Providing a quantitative autoantibody baseline for future comparisons in monitoring a patient's clinical course and response to immunomodulatory treatment
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
P/Q-type calcium channel antibody: Monday, Wednesday, Friday; 6 a.m.
N-type calcium channel antibody: Monday, Wednesday, Friday; 6 a.m..
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.​
 3 days​
CCN/81184, CCPQ/81185, ARBI/8338, ARMO/83378, GANG/84321: 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 supporting a diagnosis of Myasthenia Gravis (MG) or Lambert-Eaton syndrome (LES), and for predicting the likelihood of lung carcinoma. Muscle acetylcholine receptor (AChR) and striational antibodies are characteristic but not diagnostic of MG. One or both are found in 13% of patients with LES, but calcium channel antibodies are not found in MG (with exception of rare non-thymomatous paraneoplastic cases).
 
Muscle AChR binding antibody is found in 90% of nonimmunosuppressed MG patients who have thymoma, and 80% have a striational antibody. Calcium channel antibodies have not been encountered with thymoma. The likelihood of thymoma is greatest when striational antibody is accompanied by a high muscle AChR modulating antibody value (> or =90% AChR loss). Detection of CRMP-5-IgG also is consistent with thymoma in patients not at risk for lung carcinoma.
 
N-type calcium channel antibodies are more highly associated with primary lung cancer than P/Q-type. One or all of the autoantibodies in the MG/LES evaluation can occur with neoplasia without evidence of neurological impairment. Calcium channel antibodies may disappear soon after commencing immunosuppressant therapy. Other serological markers of lung cancer also may disappear.
 
One or both calcium channel antibodies (P/Q and N) can occur with paraneoplastic and idiopathic cerebellar ataxia, encephalomyeloneuropathies, and autonomic neuropathy.
 
Titers are generally higher in patients with severe weakness, but severity cannot be predicted by antibody titer.
 
AChR and striational antibodies may be undetectable for 6 to 12 months after MG symptom onset and similarly P/Q-type calcium channel antibody may be undetectable for 6 to 12 months after LES onset. Only about 5% of nonimmunosuppressed adult patients with generalized MG remain seronegative for muscle AChR and striational autoantibodies beyond 12 months.
 
The alternative muscle autoantigen, MuSK, accounts for approximately 1/3 of seronegative MG cases with predominantly oculobulbar symptoms.
Outreach CPTs
CPT Modifier
(if needed)		 Quantity Description Comments
83519 ​ ​ 2​ AchR (binding/blocking) antibodies​ ​
83520 ​ ​ ​ Striational antibody​ ​
83519 ​ ​ 2​ P/Q & N type Ca channel antibodies​ ​
83519 ​ ​ ​ AchR antibody (if needed)​ ​
84182 ​ ​ ​ CRMP-5 Western blot (if needed)​ ​
Synonyms/Keywords
​Ref Lab Code: 83369, Acetylcholine Receptor (Muscle AChR) Antibodies, AChR (Acetylcholine Receptor), Anti-skeletal Muscle Antibodies, Calcium Channel Blockers, Conotoxin (Receptor) Antibodies, Lambert-Eaton Myasthenic Syndrome (LEMS) Antibodies, Motor End-Plate Antibody, Motor Nerve Terminal Antibodies, Muscle Culture Antibodies, Muscle End-Plate Antibodies, Myasthenia Gravis Antibodies, Myoid Antibody, Striational (Striated Muscle) Antibodies, Voltage Gated Calcium Channel (VGCC) Antibodies
Test Components
​This test includes: Calcium Channel Binding Ab, P/Q type; Calcium Channel Binding Ab, N-Type; ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab. The following tests are reflexed when indicated: CRMP-5-IgG Western Blot, and AchR Ganglionic Ab.
Ordering Applications
Ordering Application Description
​Centricity Myasthenia Gravis/Lamb-Eaton
​Cerner ​Myasthenia Gravis/Lambert Syndrome Evaluation (83369)
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
​
Confirming the autoimmune basis of a defect in neuromuscular transmission (eg, myasthenia gravis [MG], Lambert-Eaton syndrome [LES])
 
Distinguishing LES from 2 recognized autoimmune forms of MG
 
Raising the index of suspicion for cancer, particularly primary lung carcinoma (N-type calcium channel antibody)
 
Providing a quantitative autoantibody baseline for future comparisons in monitoring a patient's clinical course and response to immunomodulatory treatment
Test Components
​This test includes: Calcium Channel Binding Ab, P/Q type; Calcium Channel Binding Ab, N-Type; ACh Receptor (Muscle) Binding Ab; ACh Receptor (Muscle) Modulating Ab; Striational (Striated Muscle) Ab. The following tests are reflexed when indicated: CRMP-5-IgG Western Blot, and AchR Ganglionic Ab.
Reference Range Information
​Interpretive report.
Interpretation
​
A patient's autoantibody profile is more informative than the result of any single test for supporting a diagnosis of Myasthenia Gravis (MG) or Lambert-Eaton syndrome (LES), and for predicting the likelihood of lung carcinoma. Muscle acetylcholine receptor (AChR) and striational antibodies are characteristic but not diagnostic of MG. One or both are found in 13% of patients with LES, but calcium channel antibodies are not found in MG (with exception of rare non-thymomatous paraneoplastic cases).
 
Muscle AChR binding antibody is found in 90% of nonimmunosuppressed MG patients who have thymoma, and 80% have a striational antibody. Calcium channel antibodies have not been encountered with thymoma. The likelihood of thymoma is greatest when striational antibody is accompanied by a high muscle AChR modulating antibody value (> or =90% AChR loss). Detection of CRMP-5-IgG also is consistent with thymoma in patients not at risk for lung carcinoma.
 
N-type calcium channel antibodies are more highly associated with primary lung cancer than P/Q-type. One or all of the autoantibodies in the MG/LES evaluation can occur with neoplasia without evidence of neurological impairment. Calcium channel antibodies may disappear soon after commencing immunosuppressant therapy. Other serological markers of lung cancer also may disappear.
 
One or both calcium channel antibodies (P/Q and N) can occur with paraneoplastic and idiopathic cerebellar ataxia, encephalomyeloneuropathies, and autonomic neuropathy.
 
Titers are generally higher in patients with severe weakness, but severity cannot be predicted by antibody titer.
 
AChR and striational antibodies may be undetectable for 6 to 12 months after MG symptom onset and similarly P/Q-type calcium channel antibody may be undetectable for 6 to 12 months after LES onset. Only about 5% of nonimmunosuppressed adult patients with generalized MG remain seronegative for muscle AChR and striational autoantibodies beyond 12 months.
 
The alternative muscle autoantigen, MuSK, accounts for approximately 1/3 of seronegative MG cases with predominantly oculobulbar symptoms.
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Performing Laboratory Information
Performing Location Day(s) Test Performed Analytical Time Methodology/Instrumentation
​Mayo Medical Laboratories
P/Q-type calcium channel antibody: Monday, Wednesday, Friday; 6 a.m.
N-type calcium channel antibody: Monday, Wednesday, Friday; 6 a.m..
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.​
 3 days​
CCN/81184, CCPQ/81185, ARBI/8338, ARMO/83378, GANG/84321: 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​ AchR (binding/blocking) antibodies​ ​
83520 ​ ​ ​ Striational antibody​ ​
83519 ​ ​ 2​ P/Q & N type Ca channel antibodies​ ​
83519 ​ ​ ​ AchR antibody (if needed)​ ​
84182 ​ ​ ​ CRMP-5 Western blot (if needed)​ ​
For most current information refer to the Marshfield Laboratory online reference manual.