Antimitochondrial Antibodies

Antimitochondrial antibodies (or AMA) are types of antibody that react with the lining of the mitochondria. These antibodies are found within the blood of the large majority of patients with primary biliary cirrhosis, or PBC. Mitochondria themselves use oxygen to create energy, so normal functioning is necessary for our bodies.

There are tests for determining whether AMA exist in the blood. The most common test will involve a patient’s serum diluted onto tissue from a rat’s stomach or kidney. Since mitochondria are present in all cells, the test involves seeing whether the antibodies bind to the mitochondrial linings (this is observed with a microscope). The test determines the most dilute version of the serum sample that will still bind to the mitochondria, and this level is termed ‘titer’. If the titer number is greater, then there is a higher level of AMA in the serum from the patient in question.

The test for AMA is extremely useful. AMA is present in around 95-98% of cases of PBC, which means that this test is extremely useful in diagnosing the condition. When this condition is present the AMA titer is usually 1 to 40 or greater. This provides a very specific diagnosis for an adult, suggesting the presence of PBC. The titer itself shows that the same can be diluted to 40 times its original volume and still contain enough AMA to bind with the mitochondria.