Anti-smooth muscle antibody is a blood test that detects the presence of antibodies against smooth muscle. The antibody is useful in making a diagnosis of autoimmune hepatitis.
How the Test is Performed
A blood sample is needed. This may be taken through a vein. The procedure is called a venipuncture.
How to Prepare for the Test
No special steps are needed to prepare for this test.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
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.
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 & Fordtran's Gastrointestinal and Liver Disease. 9th ed. Philadelphia, PA: Elsevier Saunders; 2010:chap 88.
Update Date 1/20/2015
Updated by: Gordon A. Starkebaum, MD, Professor of Medicine, Division of Rheumatology, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.