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 modified on June 28, 2021

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Anti-MuSK (muscle-specific kinase) Antibodies

At a Glance

Why Get Tested?

To help diagnose myasthenia gravis (MG) and to distinguish between MG and other conditions with similar symptoms

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

Looking For Test Results?

Looking For Reference Ranges?

You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.

Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

Acetylcholine receptor (AChR) antibodies are autoantibodies produced by the immune system that mistakenly target proteins called acetylcholine receptors that are located on muscles that you can consciously or voluntarily control (known as skeletal muscle fibers). This test detects and measures AChR antibodies in the blood.

Muscle movement starts when an impulse is sent down a nerve to the nerve ending, where it stimulates the release of acetylcholine, a chemical substance (neurotransmitter) that transmits messages between specific types of cells. Acetylcholine travels across the very small gap between the nerve ending and a muscle fiber (this gap is called the “neuromuscular junction”). When acetylcholine reaches the muscle fiber, it binds to one of many acetylcholine receptors or “docking stations” and activates it, initiating muscle contraction.

AChR antibodies impede communication between nerves and skeletal muscles, inhibit muscle contraction, and cause rapid muscle fatigue by preventing activation of the acetylcholine receptors. They do this in three major ways:

Binding antibodies attach to the receptors on nerve cells and may initiate an inflammatory reaction that destroys the receptors.
Blocking antibodies may sit on the receptors, preventing acetylcholine from binding.
Modulating antibodies may cross-link the receptors, causing them to be taken up into the muscle cell and removed from the neuromuscular junction.

The end result of this interference is the development of myasthenia gravis (MG), a chronic autoimmune disorder associated with the presence of these antibodies and with their effects on muscle control.

AChR antibodies may be detected in different ways to determine which mechanism may be the problem, and the antibodies may be referred to as “binding,” “blocking,” or “modulating.” However, the technique that measures “binding” is the most commonly performed and, generally speaking, it is rare for the other two tests to be positive without the “binding” test being positive as well. These other two tests may be useful when a healthcare practitioner strongly suspects myasthenia gravis and the “binding” test is negative.

Common Questions

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.

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.

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.

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.

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.

Can myasthenia gravis affect my heart?

No, the receptors for heart and smooth (digestive) muscles are different from skeletal muscles, so they are not affected by the formation of AChR antibodies.

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.

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.

Can MG be inherited?

As an autoimmune process, no. Some people may inherit a genetic defect that causes congenital myasthenic syndrome, a condition with similar symptoms.

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.

View Sources

Sources Used in Current Review

2020 review performed by Michelle L. Parker, PhD, FCACB, Clinical Chemist, DynaLIFE Medical Labs.

Gilhus, N.E., Tzartos, S., Evoli, A., Palace, J., Burns, T.M. & Verschuuren, J.J.G.M. (2019). Myasthenia gravis. Nat Rev Dis Primers. May 2;5(1):30. doi: 10.1038/s41572-019-0079-y.

Maddison, P., Sadalage, G., Ambrose, P.A., Jacob, S. & Vincent, A. (2019). False-positive acetylcholine receptor antibody results in patients without myasthenia gravis. J Neuroimmunol. Jul 15;332:69-72. doi: 10.1016/j.jneuroim.2019.04.001.

Vincent, A. (2020). Antibodies and receptors: From neuromuscular junction to central nervous system. Neuroscience. Mar 17 Epub ahead of print. doi: 10.1016/j.neuroscience.2020.03.009.

Mantegazza, R., Bernasconi, P. & Cavalcante, P. (2018). Myasthenia gravis: From autoantibodies to therapy. Curr Opin Neurol. Oct;31(5):517-525. doi: 10.1097/WCO.0000000000000596.

Lazaridis, K. & Tzartos, S.J. (2020). Autoantibody specificities in myasthenia gravis: Implications for improved diagnostics and therapeutics. Front Immunol. Feb 14;11:212. doi: 10.3389/fimmu.2020.00212.

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Acetylcholine Receptor (AChR) Antibody