What is an antimitochondrial antibody test?
The mitochondria create energy for the cells in your body to use. They’re critical to the normal functioning of all cells.
Antimitochondrial antibodies (AMAs) are an example of an 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.
The AMA test identifies elevated levels of these antibodies in your blood. The test is most often used to detect an autoimmune condition known as primary biliary cholangitis (PBC), previously known as primary biliary cirrhosis.
PBC is caused by an immune system attack on the small bile ducts within the liver. Damaged bile ducts cause scarring, which can lead to liver failure. This condition also brings an increased risk of liver cancer.
Symptoms of PBC include:
- itchy skin
- yellowing of the skin, or jaundice
- pain in the upper right abdomen
- swelling, or edema of the hands and feet
- a buildup of fluid in the abdomen
- dry mouth and eyes
- weight loss
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 the disorder. If this should occur, your doctor may order further tests, including the following:
Anti-nuclear antibodies (ANA): Some patients with PBC also test positive for these antibodies.
Albumin: This is a protein made in the liver. Low levels can be indicative of liver damage or disease.
C-reactive protein: This test is often ordered to diagnose lupus or heart disease, but it can also be an indication of other autoimmune conditions.
Anti-smooth muscle antibodies (ASMA): This test is often administered alongside ANA tests and is useful in diagnosing autoimmune hepatitis.
AMA testing can also be used to check you for PBC if a routine blood test shows that you have higher levels of alkaline phosphatase (ALP) than normal. An elevated ALP level can be a sign of bile duct or gallbladder disease.
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 and sent to a lab for analysis.
Your doctor will contact you to explain your results when they become available.
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.
Normal test results are negative for AMA. A positive AMA means that there are detectable levels of antibodies in the bloodstream. Although a positive AMA test is most often associated with PBC, it can also be positive in autoimmune hepatitis, lupus, rheumatoid arthritis, and graft-versus-host disease. These antibodies are just one part of an autoimmune state that the body is generating.
If you have positive results, you will probably need additional testing to confirm your diagnosis. In particular, your doctor may order a liver biopsy to take a sample from the liver. Your doctor may also order a CT or MRI of your liver.