Also known as:Mitochondrial Antibody
Formal name:Antimitochondrial Antibody and Antimitochondrial M2 Antibody
Related tests:ANCA/MPO/PR3 Antibodies, Liver/Kidney Microsomal Antibody, ALP, ALT, Liver Panel, Smooth Muscle Antibody, ANA
Why Get Tested?
To help diagnose primary biliary cirrhosis (PBC)
When to Get Tested?
When you have abnormal results on a liver panel and/or symptoms that your health care practitioner suspects may be due to PBC
A blood sample drawn from a vein in your arm
Test Preparation Needed?
How is it used?
The AMA test or the AMA-M2 test may be ordered to help diagnose primary biliary cirrhosis (PBC). PBC is a serious condition in which the biliary system in the liver is gradually destroyed. (For more about this disease, see the links listed on the Related Pages tab under Elsewhere on the Web).
Other tests that may be ordered include:
- Smooth muscle antibodies (SMA)
- Antinuclear antibodies (ANA)
- Alkaline phosphatase (ALP)
- IgM level
- Prothrombin time (PT)
- C-reactive protein (CRP)
These tests often help detect PBC, distinguishing it from other autoimmune conditions causing liver damage, and may be useful predictors of the need for a liver transplant.
When is it ordered?
The AMA or AMA-M2 test is ordered when a health care practitioner suspects that someone has an autoimmune disorder such as PBC that is affecting the liver. A person may have symptoms that include:
- Itching (pruritus)
- Abdominal pain
- Enlarged liver
Many of those affected with early PBC do not have any symptoms. The condition is often initially identified because a person has abnormal results on a liver panel (elevated liver enzymes), especially alkaline phosphatase (ALP).
An AMA or AMA-M2 test may be ordered along with or following a variety of tests that are used to help diagnose and/or rule out other causes of liver disease or injury. These causes can include infections, such as viral hepatitis, drugs, alcohol abuse, toxins, genetic conditions, metabolic conditions, and autoimmune hepatitis.
What does the test result mean?
A high AMA or AMA-M2 level (titer) in the blood indicates that the most likely cause of symptoms and/or liver damage is PBC. The level of AMA is not related to the severity of PBC symptoms or to a person's prognosis.
A negative AMA or AMA-M2 means that it is likely that a person's symptoms are due to something other than PBC, but the result does not rule out the condition. About 5-10% of those with PBC will not have significant amounts of AMA or AMA-M2.
Is there anything else I should know?
By themselves, AMA and AMA-M2 are not diagnostic of PBC, but in conjunction with other laboratory tests and clinical symptoms, the diagnosis of PBC can be made. A liver biopsy may be performed to look for characteristic signs of primary biliary cirrhosis in the liver tissue and to confirm the diagnosis but is not always necessary. Imaging scans of the liver may also be ordered to look for bile duct obstructions.
About 50% of the cases of PBC will be discovered before a person has noticeable symptoms.
What is being tested?
Antimitochondrial antibodies (AMA) are autoantibodies that are strongly associated with primary biliary cirrhosis (PBC). This test detects and measures the amount (titer) of AMA in the blood.
Primary biliary cirrhosis is a chronic autoimmune disorder that causes inflammation and scarring of the bile ducts inside the liver. It is a slow-progressing disease that causes worsening liver destruction and blockage of the bile flow. Blocked bile ducts can lead to a build-up of harmful substances within the liver and may eventually lead to permanent scarring (cirrhosis). PBC is found most frequently in women between the ages of 35 and 60. About 90-95% of those affected by PBC will have significant titers of antimitochondrial antibodies.
AMA are autoantibodies that develop against antigens within the body. There are nine types of AMA antigens (M1 - M9) of which M2 and M9 are the most clinically significant. The presence of the M2 type of AMA has been particularly evident in PBC, while the other types may be found in other conditions. Some laboratories offer the AMA-M2 as a more specific test for PBC.
For more information on PBC, click on the Related Pages tab and see links listed under Elsewhere on the Web.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
- What causes primary biliary cirrhosis (PBC)?
The cause is currently not known. It is not infectious and not inherited, although an increased susceptibility to develop autoimmune disorders may occur in some families. It can occur in anyone at any age, but it is primarily seen in middle-aged women.
- How fast does PBC progress?
The course and severity of PBC is difficult to predict. Many people will have no or few symptoms for many years. For more information, consult with your health care provider and see the related links.
- Can I have an AMA or AMA-M2 test done in my doctor's office?
No, the test requires specialized equipment and will not be offered by all laboratories. Your blood will likely be sent to a reference laboratory.
- If I have AMA, will the antibodies ever go away?
The titer may vary over time but, in most cases, once a person has detectable AMA, they will continue to do so.
© 2017 American Association for Clinical Chemistry, republished from Lab Tests Online.*
Descriptions of clinical laboratory tests were originally prepared for use on Lab Tests Online, an award-winning patient education website on clinical laboratory testing. Lab Tests Online is produced by the American Association for Clinical Chemistry (AACC), a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare. The Lab Tests Online website is developed in collaboration with other laboratory professional societies and is funded in part through corporate sponsorships.