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.
To help diagnose autoimmune hepatitis and distinguish it from other causes of liver injury
Normal results
Normal results mean that no significant ASMAs are detected in your blood. The result may be reported as a ratio or in units (U). A negative titer, or normal range, is considered to be a ratio less than 1:20 or less than 20 U.
Abnormal results
Detected levels of ASMAs are reported as a ratio or in units (U).
Weakly positive ASMA results are from 1:20 to 1:30, or 20 to 30 U.
Positive AMSA results are greater than 1:30, or greater than 30 U.
