Myasthenia Gravis Evaluation with Muscle-Specific Kinase (MuSK) Reflex, Serum
Use
This test is useful for diagnosing autoimmune myasthenia gravis (MG) in adults and children. It distinguishes autoimmune MG from congenital forms and other acquired neuromuscular junction transmission disorders. The test establishes a quantitative baseline value, allowing comparison with future levels if weakness worsens. Positive results in this antibody evaluation indicate autoimmune MG, and should be interpreted alongside clinical and electrophysiological contexts.
Special Instructions
This test should not be ordered for patients who have recently received radioisotopes due to potential assay interference. Specimens will be screened for radioactivity before analysis. Specimens collected post-administration of immunosuppressant medication may reduce diagnostic sensitivity. A cautionary note is that positive muscle AChR may also occur in autoimmune liver disorders, graft-versus-host disease, and D-penicillamine recipients. Referral to specific neurology specialties and forms are advised for non-electronic ordering.
Limitations
The presence of alpha-bungarotoxin antibodies may interfere with the AChR muscle binding antibody assay, preventing reporting of AChR binding results. Seropositive rates differ across laboratories, so patient results tested at different facilities should not be treated as equivalent. Only 5% of adult patients with generalized MG on immunosuppression remain seronegative for AChR antibodies beyond 12 months. Positive results should be interpreted in the appropriate clinical context and are not diagnostic in isolation.
New York Approved
Methodology
Other
Biomarkers
LOINC Codes
- 53706-8
- 97558-1
- 69048-7
Result Turnaround Time
3-10 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
3 mL
Minimum Volume
2 mL
Container
Plastic vial
Collection Instructions
Centrifuge and aliquot serum into a plastic vial.
Patient Preparation
Specimen collection is recommended prior to the initiation of immunosuppressant medication or intravenous immunoglobulin treatment.
Causes for Rejection
Gross hemolysis, gross lipemia, gross icterus
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 72 hours |
| Refrigerated | 28 days |
| Frozen | 28 days |