Also Known As
Mitochondrial Antibody
PDC (pyruvate kinase dehydrogenase) antibody
Formal Name
Antimitochondrial Antibody and Antimitochondrial M2 Antibody
This article was last reviewed on
This article waslast modified on
21 June 2018.
At a Glance
Why Get Tested?

To help diagnose primary biliary cirrhosis (PBC)

When To Get Tested?

When a doctor suspects that a person may have primary biliary cirrhosis

Sample Required?

A blood sample taken from a vein in your arm

Test Preparation Needed?

None

On average it takes 7 working days for the blood test results to come back from the hospital, depending on the exact tests requested. Some specialist test results may take longer, if samples have to be sent to a reference (specialist) laboratory. The X-ray & scan results may take longer. If you are registered to use the online services of your local practice, you will be able to access your results online.

If the doctor wants to see you about the result(s), you will be offered an appointment. If you are concerned about your test results, you will need to arrange an appointment with your doctor so that all relevant information including age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), can be considered.

Lab Tests Online-UK is an educational website designed to provide patients and carers with information on laboratory tests used in medical care. We are not a laboratory and are unable to comment on an individual's health and treatment.

Reference ranges are dependent on many factors, including patient age, gender, sample population, and test method, and numeric test results can have different meanings in different laboratories.

For these reasons, you will not find reference ranges for the majority of tests described on this web site. The lab report containing your test results should include the relevant reference range for your test(s). Please consult your doctor or the laboratory that performed the test(s) to obtain the reference range if you do not have the lab report.

For more information on reference ranges, please read Reference Ranges and What They Mean.

What is being tested?

This test measures whether antimitochondrial antibodies (AMA) are present in the blood. Moderate or high levels of AMA are strongly associated with primary biliary cirrhosis (PBC). PBC is an autoimmune disorder that causes inflammation and scarring of the bile ducts inside the liver, causing continual liver damage and blockage of the bile flow. It is found most frequently in women between the ages of 35 and 60. More than 90% of those affected by PBC will have high levels of antimitochondrial antibodies.

Increased AMA levels are seen much less often in autoimmune hepatitis, sclerosing cholangitis, liver disease due to chronic inflammatory bowel disease, and bile duct obstruction.

There are nine types of AMA (M1 – M9) of which M2 and M9 are the most clinically valuable. Antibodes to M2 target the pyruvate dehydrogenase (PDC) complex. The presence of the M2 type has been particularly evident in primary biliary cirrhosis, while the other AMA types may be found in other conditions and are not indicative of PBC.

In some laboratories, if testing for AMA is positive, then further tests for the M2 subtype is performed. Some laboratories have started to offer the AMA-M2 test instead of the AMA, which reduces the number of false positives from non-M2 antibodies.

How is the sample collected for testing?

A blood sample is taken by inserting a needle into a vein in the arm.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

Accordion Title
Common Questions
  • How is it used?

    The AMA test is requested to help diagnose primary biliary cirrhosis (PBC). PBC is a serious condition in which the bile system in the liver are gradually destroyed. (For more about this disease, see the links listed under Elsewhere on the Web).

    Other tests that may be requested include:

    These tests can help in the diagnosis of PBC, and may distinguish it from other autoimmune conditions which case liver damage, and they may provide information about the degree of liver damage. The best test for diagnosis of PBC is a liver biopsy.

  • When is it requested?

    The AMA or AMA-M2 test is requested when your doctor suspects that you have an autoimmune disorder such as PBC. You may have symptoms such as tiredness, jaundice and itchiness, but many patients affected with early PBC have no symptoms. The condition is often initially identified because a patient has elevated levels of enzymes which come from the liver and indicated that it is diseased. The enzyme alkaline phosphatase (ALP), is often elevated and this is found during routine blood tests.

    An AMA or AMA-M2 test may be requested 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?

    High levels of AMA or AMA-M2 in the blood are the most likely due to PBC. Low levels of AMA may also be present in patients with autoimmune hepatitis, liver or bile obstruction, and with infections such as syphilis or acute infectious hepatitis. AMA may also be present in patients with other autoimmune disorders related to PBC such as systemic lupus erythematosus, rheumatoid arthritis, Sjogren syndrome, scleroderma, and thyroiditis

    Levels of AMA may be lower in children and in those with compromised immune systems. The level of AMA is not related to the severity of PBC symptoms or to a patient’s prognosis.

  • Is there anything else I should know?

    By themselves, AMA and AMA-M2 can not be used to diagnose PBC, but in conjunction with other laboratory tests and clinical symptoms, a diagnosis of PBC can be made. When high levels of AMA or AMA-M2 are present and the doctor suspects PBC, a liver biopsy may be performed to look for the signs of primary biliary cirrhosis in the liver tissue. Imaging scans of the liver may also be used to look for bile duct obstruction.

    About 50% of the cases of PBC will be discovered before the patient has noticeable symptoms.

  • What causes primary biliary cirrhosis (PBC)?

    The cause of PBC is currently not known. It appears to be an autoimmune condition. It is not infectious and not inherited. 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 patients will have no or few symptoms for many years. For more information, consult with your doctor and see the related links.

  • I am M2 antibody positive, but have no symptoms and normal liver tests, what does that mean?

    Up to 0.5% of the population are M2 AMA positive, only 10% of these will ever go on to develop PBC.  PBC can only be diagnosed with the combination of abnormal liver function tests (alkaline phosphatase) and M2 AMA (with or without a liver biopsy).
    If liver function is normal at baseline it could be repeated annually if the M2 antibody is confirmed on a second (repeat) test, with the reassurance that 90% of people will never develop problems.