Acetylcholine Receptor Antibody (Blood)
Does this test have other names?
Muscle Nicotinic Acetylcholine Receptor (AChR) Binding Antibody, AChR Antibody, Myasthenia
What is this test?
This test measures the concentration of a substance called acetylcholine receptor
(AChR) antibody in your blood.
Acetylcholine is a chemical that helps muscles contract. It acts as a messenger between
nerves and muscles. People who have myasthenia gravis (MG) often make an abnormal
protein called acetylcholine receptor antibody. This protein interferes with how acetylcholine
works. At first, this causes muscle weakness in the eye. You may have double vision
or drooping eyelids. MG is an autoimmune disease because your body makes the protein
that attacks the way acetylcholine normally works.
MG is rare, but it can affect people of any age. It's most common in women younger
than 40 and men older than 60. It's not contagious, although sometimes the newborn
baby of a mother with MG can show symptoms for a few weeks to several months that
disappear with treatment.
Most people with the disorder have a normal life span but need treatment to control
its debilitating symptoms. These often include:
Shortness of breath
Trouble using normal speech
Weakness in the arms, legs, neck, and fingers
Why do I need this test?
You might have this test if your healthcare provider suspects that you have MG. Symptoms
of MG can range from problems with breathing muscles to weakness of muscles throughout
your body. The most common symptoms are weakness in muscles that control:
What other tests might I have along with this test?
Your healthcare provider may also order these tests to check for MG:
Muscle-specific receptor tyrosine kinase (MuSK). The MuSK antibody may be found in 3 in 10 to 2 in 5 people with MG who don't have
Edrophonium chloride. This medicine may temporarily ease muscle weakness caused by MG. So it can be used
to help diagnose MG.
Repetitive nerve stimulation (RNS). This is used to test the strength with which muscles respond to low-frequency nerve
stimulation. People with MG are likely to have a progressively weaker response as
the nerve stimulation continues.
Single fiber electromyography (SFEMG). People with MG and certain other disorders respond to the electrical stimulation of
this test with "muscle jitter." This is an unsteady, jittery contraction. If you have
a normal SFEMG test in a weak muscle, it means that something other than MG is causing
Imaging scans. CT or MRI scans can be used to diagnose thymoma. This is a tumor of the thymus gland
that sometimes develops with MG.
Lung function tests. These measure the strength of the muscles involved in breathing.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
This test can confirm but not completely rule out MG.
If you have a higher concentration of AChR antibody, it means that you may have MG.
Even with a normal level, it's still possible that you have MG. Up to 17 in 20 people
with MG who have general muscle weakness have AChR antibody. In addition, about half
of people with MG around the eyes have the antibody.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight
stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
Timing is important. Having anesthesia or muscle relaxants for surgery within 48 hours
of the test may give a false-positive result.
How do I get ready for this test?
You don't need to prepare for this test.