Antimitochondrial antibody
Definition
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.
How the Test is Performed
A blood sample is needed. It is usually taken from a vein. The procedure is called a venipuncture.
How to Prepare for the Test
Your health care provider may tell you not to eat or drink anything for up to 6 hours before the test (usually overnight).
How the Test Will Feel
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.
Why the Test is Performed
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.
Normal Results
Normally, there are no antibodies present.
What Abnormal Results Mean
This test is important for diagnosing primary biliary cirrhosis. Up to 94% of patients with this condition are positive for this test. Less than 1% of people without the condition test positive.
Abnormal results may also be found, less often, in people with other kinds of liver disease and some autoimmune diseases.
Risks
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)