Synonyms: ASMA
Related tests: AMA, ANA, LKM
Clinical significance
Anti-smooth muscle antibodies are directed against the filaments of smooth muscle (actin, myosin, tubulin). These antibodies, especially anti-actin antibodies, when present at high titre, are specific for type 1 autoimmune hepatitis (70%). Other conditions in which they may be present are primary biliary cirrhosis, alcoholic cirrhosis, viral hepatitis and other autoimmune diseases.
Clinical indications
Type 1 autoimmune hepatitis.
Sample type
The patient must have a blood sample taken.
Preparation
You must fast for at least 8 hours; a small amount of water is allowed. You must have been standing or sitting upright for at least 30 minutes.
Notes
Taking nitrofurantoin can give false positive values.
High titres are significant for autoimmune hepatitis. Low titres are found in infectious diseases (mononucleosis), cancer and occasionally in normal people.