What is an Antimitochondrial Antibody (AMA)?
An Antimitochondrial Antibody (AMA) is an autoantibody that is found in the serum of patients with primary biliary cirrhosis (PBC). It is a type of antibody specifically directed against mitochondrial antigens, which are proteins located inside mitochondria.
Antimitochondrial antibodies are a specific type of autoantibody. Autoantibodies are antibodies that are produced by one's own immune system and target one's own cellular structures, instead of targeting external pathogens. They are associated with autoimmune diseases, where the body mistakenly attacks itself. Antimitochondrial antibodies are a specific type of autoantibody that target mitochondria.
Preparation for Testing an AMA
In order to test for Antimitochondrial Antibodies, a blood sample is taken from the patient and sent to a pathology laboratory. The sample is treated with chemicals and DNA elements to see if the antibody is present. The antibodies are detected through a process called immunoassay and are measured in units per milliliter (U/mL) of serum.
Types of Antimitochondrial Antibodies
There are three main types of Antimitochondrial Antibodies:
- AMA-M2 - Is the most common type. It is found in 97% of patients with PBC, as well as in patients with other autoimmune diseases.
- AMA-M1 - This type of antibody is detected in about 50% of patients with PBC.
- AMA-M9 – This type is detected in about 10% of patients with PBC.
Risks Associated with Antimitochondrial Antibodies
The presence of Antimitochondrial Antibodies indicates an autoimmune disorder such as PBC. These antibodies can damage the liver, leading to fibrosis, cirrhosis, and eventually liver failure. There is also an increased risk of developing bile duct cancer as well.
When to Test for Antimitochondrial Antibodies
It is recommended to test for Antimitochondrial Antibodies if the patient is experiencing any of the following symptoms: fatigue, loss of appetite, weight loss, dark urine, jaundice, itching, or joint pain. Additionally, Antimitochondrial Antibodies are tested if the patient has a history of autoimmune diseases such as rheumatoid arthritis, Sjögren's syndrome, or SLE.
In some cases, such as in the diagnosis of PBC, doctors may request for Antimitochondrial Antibody testing as part of the initial work-up of a suspected patient. Patients with positive AMA may also be referred for liver biopsy in order to determine the extent of the disease.
Antimitochondrial Antibodies are autoantibodies directed against mitochondrial antigens. They are most commonly found in patients with PBC, but they can also indicate other autoimmune disorders. Testing for Antimitochondrial Antibodies is recommended for patients with symptoms of autoimmune diseases, or for those with a history of such diseases. A positive AMA test can indicate the presence of PBC, and patients may be referred for further testing such as liver biopsy in this case.