What Is an Antimitochondrial Antibody Test?
The mitochondria are the energy factory cells. They are critical to the normal functioning of all cells.
Antimitochondrial antibodies (AMAs) are the autoimmune response that occurs when the body turns against its own cells, tissues, and organs. When this happens, the immune system attacks the body as though it were an infection. AMAs attack the mitochondria.
The AMA test looks for autoimmune disorders affecting the mitochondria. It is most often used to detect an autoimmune condition known as primary biliary cirrhosis (PBC).
Why Is the AMA Test Ordered?
AMA testing is primarily used to detect PBC. This autoimmune disease destroys the mitochondria in the small bile ducts of the liver. Damaged bile ducts affect the liver’s ability to get rid of toxins. This can cause scarring, or cirrhosis of the liver.
Symptoms of PBC include:
- yellowing of the skin (jaundice)
- pain in the upper right abdomen
- swelling (edema) of the hands and feet
- a buildup of fluid in the abdomen
- dry mouth and eyes
- itchy skin
An AMA test is used to help confirm a doctor’s clinical diagnosis of PBC. An abnormal AMA test alone is not enough to diagnose PBC. Your doctor may also order the following tests:
- antinuclear antibodies (ANA)
- immunoglobulin (IgM)
- c-reactive protein
- smooth muscle antibodies (SMA)
AMA testing can also be used to rule out PBC after elevated levels of alkaline phosphatase (ALP) are found during routine blood testing. Elevated ALP levels may be a sign of liver damage.
How Is the AMA Test Administered?
The AMA test is a blood test. A nurse or technician will draw your blood from a vein near your elbow or hand. This blood will be collected in a tube. It will then be sent to a lab for analysis.
Your doctor will contact you to explain your results when they become available.
What Are the Risks of the AMA Test?
You may experience some discomfort when the blood sample is drawn. There can be pain at the puncture site during or after the test.
In general, the risks of a blood draw are minimal. Potential risks include:
- difficulty obtaining a sample, resulting in multiple needle sticks
- excessive bleeding at the needle site
- fainting as a result of blood loss
- accumulation of blood under the skin, known as a hematoma
- infection at the puncture site
No preparation is needed for this test.
Understanding Your AMA Test Results
Normal test results are negative for AMA. A positive AMA test means that antibodies are being made that are attacking the mitochondria of cells. In the majority of cases, these are cells of the small bile ducts. A positive AMA test typically means you have PBC.
Some people have positive AMA tests without having PBC. Certain other types of liver or autoimmune diseases may also cause elevated AMA levels.
If you have a positive test, you will probably need additional testing to confirm your diagnosis. In particular, your doctor may order a liver biopsy to remove tissue from the liver. Your doctor may also order a CT or MRI of your liver.