Acetylcholine receptor antibody is a substance found in the blood of people with myasthenia gravis. The antibody attacks receptors for a chemical called acetylcholine, which sends signals from nerves to muscles and between nerves in the brain.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

No special preparation is required.

There may be a slight stinging or pricking sensation when blood is drawn, but this is usually mild and brief.

This test is used to diagnose myasthenia gravis.

No acetylcholine receptor antibody (or less than .05 nmol) in the bloodstream is normal.

Note: nmol = nanomole

Presence of acetylcholinesterase antibody in the blood of persons who have symptoms of myasthenia gravis supports the diagnosis. However, a lack of these antibodies does not rule out this condition. About 10-15% of people with myasthenia gravis do not have signs of this antibody in their blood.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)