To help diagnose myasthenia gravis (MG) and to distinguish between MG and other conditions with similar symptoms
Acetylcholine Receptor (AChR) Antibody
Acetylcholine Receptor (AChR) Antibody
Also Known As
AChR Antibody
Muscle nicotinic Acetylcholine Receptor (AChR) Binding Antibody
Myasthenia Gravis Antibodies
Acetylcholine Receptor Binding Antibody
Acetylcholine Receptor Blocking Antibody
Acetylcholine Receptor Modulating Antibody
Formal Name
Myasthenia Gravis (MG) Evaluation, serum
This article was last reviewed
on
This article waslast modified
on July 22, 2020.
At a Glance
Why Get Tested?
When To Get Tested?
When you have symptoms that suggest MG, such as a drooping eyelid, double vision, difficulty chewing or swallowing, and/or weakness in specific voluntary muscles
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
None
Accordion Title
Common Questions
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How is the test used?
An acetylcholine receptor (AChR) antibody test is used to help diagnose myasthenia gravis (MG) and to distinguish it from other conditions that may cause similar symptoms, such as chronic muscle fatigue and weakness.
Three types of AChR antibodies may be tested:
- AChR binding antibodies
- AChR blocking antibodies
- AChR modulating antibodies
The test that measures binding antibodies is most commonly used because it is generally rare for the other two tests to be positive without the binding antibody test being positive as well. These other two tests may be used when a healthcare practitioner strongly suspects myasthenia gravis and the binding antibody test is negative.
One or more of these AChR antibody tests may be ordered as part of a panel of tests that may also include a striated muscle antibody test to help establish a diagnosis. If AChR antibody test results are normal but a healthcare practitioner strongly suspects myasthenia gravis, an anti-MuSK (muscle-specific tyrosine kinase) antibody test may also be ordered.
People with MG often have an enlarged thymus gland and may have thymomas (typically benign tumors of the thymus). Located under the breastbone, the thymus is an active part of the immune system during childhood but normally becomes less active during the teen years. If a thymoma is detected, such as during a chest computed tomography (CT) scan done for a different reason, then an AChR antibody test may sometimes be used to determine whether the person has developed these antibodies.
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When is it ordered?
The AChR antibody test may be ordered when you have signs and symptoms that suggest myasthenia gravis, such as:
- Drooping eyelid
- Double vision
- Decreased eye movement control
- Difficulty swallowing, chewing, with choking, drooling and gagging
- Slurred speech
- Weak neck muscles
- Trouble holding up your head
- Difficulty breathing
- Difficulty walking and an altered gait
- Specific muscle weakness but normal feelings/sensations
- Muscle weakness that worsens with sustained effort and improves with rest
In patients with known myasthenia gravis, repeat AChR antibody tests may be done to monitor response to therapy, to guide disease management, or to assess the risk of AChR antibody transfer from a mother to her unborn child.
An AChR antibody test may sometimes be ordered when a thymoma is detected during an imaging scan.
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What does the test result mean?
AChR antibodies are not normally present in the blood. They are autoantibodies and their presence indicates an autoimmune response.
If you have AChR antibodies and symptoms of myasthenia gravis (MG), then it is likely that you have this condition. The extent to which AChR antibodies are elevated does not predict the severity of the disease at the time of diagnosis. However, changes in AChR antibody concentrations over time may help inform the effectiveness of treatment or predict the recurrence of disease. Therefore, repeat testing of AChR antibodies may be requested in some cases.
AChR antibodies may also be positive with some thymomas, in people who are being treated with drugs such as penicillamine, with some small cell lung cancers, with autoimmune liver disease, with Guillain-Barre syndrome, and with Lambert-Eaton myasthenic syndrome (a condition associated with interference with the release of acetylcholine from the nerve ending).
A negative test result does not rule out MG. Up to 50% of those with ocular MG (affecting only eye-related muscles) and about 10-15% of those with generalized MG will be negative for AChR antibodies. Repeat testing of AChR antibodies in those with initially negative results may be useful as the concentration of antibodies may increase as the disease progresses, resulting in a subsequent positive AChR antibody test result.
Results from other tests for autoantibodies, such as anti-MuSK (muscle-specific kinase) antibody test, anti-LRP4 (LDL-receptor-related protein 4) antibody test, and anti-striated muscle antibody test, may also aid in establishing a diagnosis.
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Can this test be performed in my healthcare provider's office?
No, it is specialized testing that is not offered by every laboratory. Your blood sample will likely need to be sent to a reference laboratory for testing.
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How serious is myasthenia gravis (MG)?
Most people who have it can live a normal or near normal life with treatment and monitoring. One of the most serious complications is a respiratory myasthenic crisis that can occur when muscles that control breathing are weakened. This can be a medical emergency and often requires hospitalization. For additional details, see the article on Myasthenia Gravis.
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Can myasthenia gravis affect my heart?
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Is there anything I can do to prevent getting AChR binding antibodies?
No, the cause of MG is not known and the condition is not preventable.
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Can MG be passed from one person to another?
MG is not contagious, but a pregnant woman with MG can pass some of her AChR antibodies to her fetus. This can cause a newborn to have MG symptoms for several weeks after birth.
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Can MG be inherited?
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Is there anything else I should know?
Use of drugs such as succinylcholine can increase AChR antibodies.
People who have MG are more likely to also have other autoimmune disorders, such as rheumatoid arthritis or lupus.
Recent radioactive treatments can interfere with testing.