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Acetylcholine Receptor (AChR) Antibody

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Also known as: Muscle nicotinic Acetylcholine Receptor (AChR) Binding Antibody; AChR Antibody; Myasthenia Gravis Antibodies
Formal name: Acetylcholine Receptor Binding Antibody; Acetylcholine Receptor Blocking Antibody; Acetylcholine Receptor Modulating Antibody
Related tests: Anti-MuSK (muscle-specific kinase) Antibody, Striated Muscle Antibody, Rheumatoid Factor, Thyroid Panel, Antinuclear Antibody (ANA), Autoantibodies

At a Glance

Why Get Tested?

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

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 muscles 

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

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 skeletal muscle fibers. This test detects and measures AChR antibodies in the blood.

Acetylcholine receptors function as "docking stations" for acetylcholine, a chemical substance (neurotransmitter) that transmits messages between nerve cells. Muscle movement starts when an impulse is sent down a nerve to the nerve ending, where it stimulates the release of acetylcholine. Acetylcholine travels across a microscopic gap between the nerve ending and a muscle fiber at the "neuromuscular junction." When it reaches the muscle fiber, it binds to one of many acetylcholine receptors 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:

  • When they bind to the receptors, the antibodies may initiate an inflammatory reaction that destroys them.
  • The antibodies may sit on the receptors, preventing acetylcholine from binding.
  • The 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 in a particular individual, 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 approaches may be useful when the doctor strongly suspects myasthenia gravis and the "binding" test is negative.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

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(© 1995–2013). Acetylcholine Receptor (Muscle AChR) Binding Antibody, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/8338 through http://www.mayomedicallaboratories.com. Accessed April 2013.

Haven, T. et. al. (2010) An Algorithm for Acetylcholine Receptor Antibody Testing in Patients with Suspected Myasthenia Gravis. Clinical Chemistry v 56 (6) 1028–1040 [On-line information]. Available online at http://www.clinchem.org/content/56/6/1028.full through http://www.clinchem.org. Accessed April 2013.

Sheth, K. (Updated 2011 June 18). Myasthenia gravis. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000712.htm. Accessed April 2013.

Sheth, K. (Updated 2011 April 30). Acetylcholine receptor antibody. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003576.htm. Accessed April 2013.

Hill, H. and Haven, T. (2012 August). Acetylcholine Receptor Antibody Testing, For confirmation and monitoring of autoantibodies in patients with myasthenia gravis. ARUP Technical Information [On-line information]. PDF available for download at http://www.aruplab.com/guides/ug/tests/iconpdf_127.pdf through http://www.aruplab.com. Accessed April 2013.

(2009 December). Facts About Myasthenia Gravis, Lambert-Eaton Myasthenic Syndrome & Congenital Myasthenic Syndromes. Muscular Dystrophy Association [On-line information]. Available online at http://mda.org/publications/facts-about-myasthenia-gravis through http://mda.org. Accessed April 2013.

(Updated 2012 August 29). Neurology Myasthenia Gravis Reflexive Panel. The University of Iowa (UIHC) Department of Pathology Laboratory Services Handbook [On-line information]. Available online at http://www.healthcare.uiowa.edu/path_handbook/handbook/test3101.html through http://www.healthcare.uiowa.edu. Accessed April 2013.

(2013 April 21). Nuromuscular Junction: Myasthenia Gravis. Muscular Dystrophy Australia [On-line information]. Available online at http://www.mda.org.au/Disorders/NMJ/MG.asp through http://www.mda.org.au. Accessed April 2013.

(© 2012). Acetylcholine Receptor Antibodies. NHS Greater Glasgow and Clyde Information [On-line information]. Available online at http://www.nhsggc.org.uk/content/default.asp?page=s1470_1_2 through http://www.nhsggc.org.uk. Accessed April 2013.

(Reviewed 2011 December) Myasthenia Gravis and Acetylcholine Receptor Autoantibodies. Quest Diagnostics Technical Information [On-line information]. Available online at http://www.questdiagnostics.com/testcenter/testguide.action?dc=WP_MyastheniaGravis through http://www.questdiagnostics.com. Accessed April 2013.

(© 2012). Caring for Children and Supporting Adolescents with Myasthenia Gravis. Myasthenia Gravis Foundation of America [On-line information]. Available online at http://www.myasthenia.org/LinkClick.aspx?fileticket=ygJC0SZLVZ4%3d&tabid=84 through http://www.myasthenia.org. Accessed April 2013.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pg 6.

Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL eds, (2005) Harrison's Principles of Internal Medicine, 16th Edition, McGraw Hill, Pp 2518-2521.

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