Definition

Acetylcholine receptor antibody is a protein found in the blood of many people with myasthenia gravis. The antibody affects the part of nerve cells that send signals from nerves to muscles.

This article discusses the blood test for acetylcholine receptor antibody.

How the Test is Performed

A blood sample is needed. Most of the time, blood is drawn from a vein located on the inside of the elbow or the back of the hand.

How to Prepare for the Test

Most of the time you do not need to take special steps before this test.

How the Test will Feel

You may feel slight pain or a sting when the needle is inserted. You may also feel some throbbing at the site after the blood is drawn.

Why the Test is Performed

This test is used to help diagnose myasthenia gravis.

Normal Results

Normally, there is no acetylcholine receptor antibody (or less than 0.05 nmol/L) in the bloodstream.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

The example above shows the common measurement for results for these tests. Some laboratories use different measurements or may test different specimens.

What Abnormal Results Mean

An abnormal result means acetylcholine receptor antibody has been found in your blood. It confirms the diagnosis of myasthenia gravis in people who have symptoms. Nearly one half of people with myasthenia gravis that is limited to their eye muscles (ocular myasthenia gravis) have this antibody in their blood. This antibody can also be present in the blood of people who have a thymoma, with or without myasthenia gravis.

However, the lack of this antibody does not rule out myasthenia gravis. About 1 in 5 people with myasthenia gravis do not have signs of this antibody in their blood. Your health care provider may also consider testing you for the muscle specific kinase (MuSK) or other antibodies.

References

Evoli A, Vincent A. Disorders of neuromuscular transmission. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 394.

Guptill JT, Sanders DB. Disorders of neuromuscular transmission. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 108.