Anti-Mitochondrial Antibodies (AMA) are antibodies that target the mitochondria, which are the powerhouses of the cells. They are commonly used as a diagnostic marker for primary biliary cholangitis (PBC), an autoimmune disease that affects the liver. The test is performed by taking a blood sample from the patient and measuring the presence of AMA using an immunoassay. Elevated levels of AMA indicate a high likelihood of PBC.