An anti-smooth muscle antibody (ASMA) test detects antibodies that attack smooth muscle. This test requires a blood sample.
Your immune system detects substances called antigens that may be harmful to your body. Viruses and bacteria are covered with antigens. When your immune system recognizes an antigen, it makes a protein called an antibody to attack it.
Every antibody is unique, and each one defends against only one type of antigen. Sometimes your body mistakenly makes autoantibodies, which are antibodies that attack your body’s own healthy cells. If your body starts attacking itself, you may develop an autoimmune disorder.
An ASMA test looks for the one type of autoantibody that attacks smooth muscle. Anti-smooth muscle antibodies are found in autoimmune liver diseases such as primary biliary cholangitis and autoimmune hepatitis (AIH).