Antimitochondrial antibodies (AMA) are substances (antibodies) that form against mitochondria, an important part of cells. Mitochondria are the energy source inside all of the body's cells. Mitochondria help cells work properly.

This article discusses the blood test used to measure the amount of AMA in the blood.

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.

Your health care provider may tell you not to eat or drink anything for up to 6 hours before the test (usually overnight).

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Your doctor may order this test if you have signs of liver damage. This test is most often used to diagnose primary biliary cirrhosis (PBC).

The test may also be used to tell the difference between bile system-related cirrhosis and liver problems due to a blockage, viral hepatitis, or alcoholic cirrhosis.

Normally, there are no antibodies present.

A positive test may indicate:

• Autoimmune hepatitis
• Cirrhosis
• Liver blockage
• Primary biliary cirrhosis
• Rheumatoid arthritis (this disease may occur along with PBC in some patients)
• Systemic lupus erythematosus
• Thyroiditis

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:

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