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HelpTest Code ARBI Acetylcholine Receptor (Muscle AChR) Binding Antibody, Serum
Additional Codes
Aliases:
Acetylcholine Receptor (Muscle AChR) Antibodies
AChR (Acetylcholine Receptor)
Anti -Neuromuscular Junction Receptor Antibodies
Myasthenia Gravis Antibodies
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
Testing Algorithm
This is the primary diagnostic test for myasthenia gravis.
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
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| ARBI | ACh Receptor (Muscle) Binding Ab | 97558-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 8338 | ACh Receptor (Muscle) Binding Ab | 97558-1 |
Interpretation
Positive results (>0.02 nmol/L) are indicative of autoimmune myasthenia gravis (MG). These results should be interpreted in the appropriate clinical and electrophysiological context.
With a diagnosis of MG, a paraneoplastic basis should be considered with thymoma being the most frequently associated tumor with MG.
The clinical sensitivity of this assay is approximately 90% in nonimmunosuppressed patients with generalized MG. The frequency of antibody detection is lower in MG patients with weakness clinically restricted to ocular muscles (71%), and antibody titers are generally low in ocular MG (eg, 0.03-1.0 nmol/L).
Negative results do not exclude the diagnosis of MG. If clinical suspicion remains and symptoms persist or worsen consider retesting. Results may be negative in the first 12 months after symptoms of MG appear or during immunosuppressant therapy. Note: In follow up of seronegative patients with adult-acquired generalized MG, 17.4% seroconvert to positive at 12 months (ie, seronegativity rate at 12 months is 8.4%). A subset of MG patients that are persistently negative for acetylcholine receptor binding antibodies will have muscle-specific kinase (MuSK) antibodies, and therefore, it is recommended to test for MuSK antibodies in seronegative patients with high clinical suspicion of MG.
In general, there is not a close correlation between antibody titer and severity of weakness, but in individual patients, clinical improvement may be accompanied by a decrease in titer.
Clinical Reference
1. Lennon VA. Serological profile of myasthenia gravis and distinction from the Lambert-Eaton myasthenic syndrome. Neurology. 1997;48(Suppl 5):S23-S27. doi:10.1212/WNL.48.Suppl_5.23S
2. Lachance DH, Lennon VA. Paraneoplastic neurological autoimmunity. In: Kalman B, Brannagan III T, eds. Neuroimmunology in Clinical Practice. Blackwell Publishing Ltd; 2008:210-217
3. Gilhus NE. Myasthenia gravis. N Engl J Med. 2016;375(26):2570-2581. doi:10.1056/NEJMra1602678
4. Nicolle MW. Myasthenia gravis and Lambert-Eaton myasthenic syndrome. Continuum (Minneap Minn). 2016;22(6, Muscle and Neuromuscular Junction Disorders):1978-2005. doi:10.1212/CON.0000000000000415
5. Shelly S, Paul P, Bi H, et al. Improving accuracy of myasthenia gravis autoantibody testing by reflex algorithm. Neurology. 2020;95(22):e3002-e3011. doi:10.1212/WNL.0000000000010910
Report Available
3 to 6 daysMethod Name
Radioimmunoassay (RIA)
Forms
If not ordering electronically, complete, print, and send a Neurology Specialty Testing Client Test Request (T732) with the specimen.