Anti-smooth muscle antibody

A blood sample is needed. This may be taken through a vein. The procedure is called a venipuncture.

No special steps are needed to prepare for this test.

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.

You may need this test if you have signs of certain liver diseases, such as hepatitis and cirrhosis. These conditions can trigger the body to form antibodies against smooth muscle.

Anti-smooth muscle antibodies are not often seen in diseases other than autoimmune hepatitis. Therefore, it is helpful to make the diagnosis. Autoimmune hepatitis is treated with immunosuppressive medicines. People with autoimmune hepatitis often have other autoantibodies. These include:

• Antinuclear antibodies.
• Anti-actin antibodies.
• Anti-soluble liver antigen/liver pancreas (anti-SLA/LP) antibodies.
• Other antibodies may be present, even when the anti-smooth muscle antibodies are absent.

The diagnosis and management of autoimmune hepatitis may require a liver biopsy.

Normally, there are no antibodies present.

Note: Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.

A positive test may be due to:

• Chronic active autoimmune hepatitis
• Cirrhosis
• Infectious mononucleosis

The test also helps distinguish autoimmune hepatitis from systemic lupus erythematosus.

Risks associated with having blood drawn are slight, but may include:

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

Czaja AJ. Autoimmune hepatitis. In: Feldman M, Friedman LS, Brandt LJ, eds. Sleisenger and Fordtran's Gastrointestinal and Liver Disease. 11th ed. Philadelphia, PA: Elsevier; 2021:chap 90.

Ferri FF. Laboratory values and interpretation of results. In: Ferri FF, ed. Ferri's Best Test: A Practical Guide to Clinical Laboratory Medicine and Diagnostic Imaging. 5th ed. Philadelphia, PA: Elsevier; 2023:139-252.

Tanaka A. Autoimmune Hepatitis: 2019 Update. Gut Liver. 2020;14(4):430-438. doi: 10.5009/gnl19261. PMID: 32301319; PMCID: PMC7366136. www.ncbi.nlm.nih.gov/pmc/articles/PMC7366136/. 

Williams MJ, Gordon-Walker TT. Hepatology. In: Penman ID, Ralston SH, Strachan MWJ, Hobson RP, eds. Davidson's Principles and Practice of Medicine. 24th ed. Philadelphia, PA: Elsevier; 2023:chap 24.

Updated by: Neil J. Gonter, MD, Assistant Professor of Medicine, Columbia University, NY and private practice specializing in Rheumatology at Rheumatology Associates of North Jersey, Teaneck, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.