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HelpTest Code ARBI Acetylcholine Receptor (Muscle AChR) Binding Antibody, Serum
Reporting Name
ACh Receptor (Muscle) Binding AbUseful For
Supporting the diagnosis of 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
An adjunct to the test for P/Q-type calcium channel binding antibodies as a diagnostic aid for Lambert-Eaton myasthenic syndrome
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumOrdering Guidance
Standalone testing (this test) is recommended in certain situations.
This test should not be requested in 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 for 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.
Supplies: Sarstedt Aliquot Tube 5 mL (T914)
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1.5 mL
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 28 days | |
| Frozen | 28 days | ||
| Ambient | 72 hours |
Reference Values
≤0.02 nmol/L
Day(s) Performed
Monday through Sunday
Test 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
Clinical Information
Fatigable weakness due to impaired postsynaptic transmission at the neuromuscular junction is characteristic of myasthenia gravis (MG). A clinical diagnosis should be supported by electrodiagnostic testing (ie, clinical-electrodiagnosis [EDX]). Positive autoimmune serology increases certainty of MG diagnosis but needs to be interpreted in the proper clinical-EDX context with response to anticholinesterase medications supporting the diagnosis. Most cases are autoimmune and are caused by IgG autoantibodies binding to critical postsynaptic membrane molecules (nicotinic muscle acetylcholine receptor [AChR] or its interacting proteins, such as muscle-specific kinase). Serologically, the detection of AChR binding antibody provides the best diagnostic sensitivity. However, the presence of both AChR binding and modulating activity improves diagnostic accuracy. Autoantibody detection frequency is lowest in patients with weakness confined to extraocular muscles (approximately 70% are positive for AChR binding antibodies) and highest in patients with generalized weakness due to MG (approximately 90% are positive for AChR binding antibodies). In adults with MG and AChR antibodies, approximately 20% will have thymoma and, very rarely (<1%), extrathymic cancers. Computed tomography imaging of the chest is considered the standard of care to evaluate for thymoma.
These results should only be interpreted in the appropriate clinical and electrophysiological context and are not diagnostic in isolation.
Note: Single antibody tests may be requested in the follow-up of patients with positive results previously documented in this laboratory.
Report Available
3 to 6 daysReject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
Method Name
Radioimmunoassay (RIA)
Forms
If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.