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HelpTest Code Billings Clinic: 4848 Mayo: MGMR Myasthenia Gravis Evaluation with Muscle-Specific Kinase (MuSK) Reflex, Serum
Reporting Name
MG Evaluation MuSK Reflex, SPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Useful For
Diagnosing autoimmune myasthenia gravis (MG) in adults and children
Distinguishing autoimmune from congenital MG in adults and children or other acquired forms of neuromuscular junction transmission disorders
Establishing a quantitative baseline value that allows comparison with future levels if weakness is worsening
Method Name
ARBI, MUSK: Radioimmunoassay (RIA)
ACMFS: Flow Cytometry
MGMRI: Medical Interpretation
Ordering Guidance
This test should not be requested for patients who have recently received radioisotopes, therapeutically or diagnostically, because of potential assay interference. The specific waiting period before specimen collection will depend on the isotope administered, the dose given, and the clearance rate in the individual patient. Specimens will be screened for radioactivity prior to analysis. Radioactive specimens received in the laboratory will be held 1 week and assayed if sufficiently decayed or canceled if radioactivity remains.
Specimen Required
Patient Preparation: For optimal antibody detection, specimen collection is recommended prior to initiation of immunosuppressant medication or intravenous immunoglobulin treatment.
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 3 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Type
SerumSpecimen Minimum Volume
2 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 |
Reference Values
|
Test ID |
Reporting Name |
Methodology |
Reference Value |
|
MGMRI |
MG with MuSK Interpretation, S |
Interpretation |
NA |
|
ARBI |
ACh Receptor (Muscle) Binding Ab |
Radioimmunoassay (RIA) |
≤0.02 nmol/L |
Reflex Information:
|
Test ID |
Reporting Name |
Methodology |
Reference Value |
|
ACMFS |
AChR Modulating Flow Cytometry, S |
Flow Cytometry |
Negative |
|
MUSK |
MuSK Autoantibody, S |
RIA |
≤0.02 nmol/L |
Interpretation
Positive results in this antibody evaluation are indicative of autoimmune myasthenia gravis (MG). These results should be interpreted in the appropriate clinical and electrophysiological context.
In the presence of either acetylcholine receptor antibodies, a paraneoplastic basis should be considered with thymoma being the most frequently associated tumor with myasthenia gravis. Currently, muscle-specific kinase antibody positive MG is not associated with a paraneoplastic etiology.
Negative results do not exclude the diagnosis of an autoimmune neuromuscular junction disorder. If clinical suspicion remains and symptoms persistent or worsen, consider re-testing.
Day(s) Performed
Profile tests: Monday through Sunday; Reflex tests: Varies
Report Available
3 to 10 daysTest Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
86041
86043 (if appropriate)
86366 (if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| MGMR | MG Evaluation MuSK Reflex, S | 53706-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 608981 | MG with MuSK Interpretation, S | 69048-7 |
| 8338 | ACh Receptor (Muscle) Binding Ab | 97558-1 |
Forms
If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| MGMRI | MG with MuSK Interpretation, S | No | Yes |
| ARBI | ACh Receptor (Muscle) Binding Ab | Yes | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| ACMFS | AChR Modulating Flow Cytometry, S | No | No |
| MUSK | MuSK Autoantibody, S | Yes | No |
Testing Algorithm
If acetylcholine receptor (AChR)-binding antibodies are greater than 0.02 nmol/L, then AChR muscle modulating antibody will be performed at an additional charge.
If AChR-binding antibodies are 0.02 nmol/L or less, then muscle-specific kinase (MuSK) autoantibody will be performed at an additional charge.
If unable to report AChR binding antibody due to interfering substances, then AChR muscle modulating antibody will be performed at an additional charge.
If unable to report AChR binding antibody due to interfering substances and AChR muscle modulating antibody is negative, then MuSK autoantibody will be performed at an additional charge.