Anti-smooth muscle antibody
Anti-smooth muscle antibody is a blood test that detects the presence of antibodies against smooth muscle.
Why is the Test Performed?
Your doctor may order this test if you have signs of certain diseases (such as hepatitis and cirrhosis) that can trigger the body to form antibodies against smooth muscle.
How is the Test Performed?
Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
Preparation for the Test
No special preparation is needed.
How will the Test 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.
Anti-smooth muscle antibody Risks
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Normal Results for Anti-smooth muscle antibody
Normally, there are no antibodies present.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
A positive test may be due to:
- Chronic active hepatitis
- Cirrhosis
- Infectious mononucleosis
The test also helps distinguish autoimmune hepatitis from systemic lupus erythematosus.
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Reviewed By: Michael E. Makover, MD, professor and attending in Rheumatology at the New York University Medical Center, New York, NY. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
Copyright 2011 A.D.A.M., Inc.
