Antimitochondrial antibody

Definition

Antimitochondrial antibodies (AMA) are substances (antibodies) that form against mitochondria. The mitochondria are an important part of cells. They are the energy source inside the cells. These help the cells work properly.

This article discusses the blood test used to measure the amount of AMA in the blood.

How the Test is Performed

A blood sample is needed. It is most often taken from a vein. The procedure is called a venipuncture.

How to Prepare for the Test

Your health care provider may tell you not to eat or drink anything for up to 6 hours before the test (most often overnight).

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others may feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the Test is Performed

You may need this test if you have signs of liver damage. This test is most often used to diagnose primary biliary cholangitis, formerly called primary biliary cirrhosis (PBC).

The test may also be used to tell the difference between bile system-related cirrhosis and liver problems due to other causes such as a blockage, viral hepatitis, or alcoholic cirrhosis.

Normal Results

Normally, there are no antibodies present.

What Abnormal Results Mean

This test is important for diagnosing PBC. Almost all people with the condition will test positive. It is rare that a person without the condition will have a positive result. However, some people with a positive test for AMA and no other sign of liver disease may progress to PBC over time.

Rarely, abnormal results may also be found that are due to other kinds of liver disease and some autoimmune diseases.

Risks

Risks for having blood drawn are slight, but can include:

• Excessive bleeding
• Fainting or feeling lightheaded
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

References

Daniels L, Khalili M, Goldstein E, Bluth MH, Bowne W, Pincus MR. Evaluation of liver function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 22.

Eaton JE, Lindor KD. Primary biliary cholangitis. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 91.

Kakar S. Primary biliary cholangitis. In: Saxena R, ed. Practical Hepatic Pathology: A Diagnostic Approach. 2nd ed. Philadelphia, PA: Elsevier; 2018:chap 26.