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Anti-smooth muscle antibody

  • Definition
    • 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.

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

  • Normal Results
    • 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.

  • What Abnormal Results Mean
  • Risks
    • 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)
  • References
    • 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.