Anti-Smooth Muscle Antibody
Last updated: October 8, 2014
Synonyms: anti-Actin antibody, F Actin antibody
CPT Code: 86255
Description: Anti-smooth muscle antibody (AMSA) is an autoantibody to cytoskeletal components of smooth muscle – principally actin. Hence it is often referred to as anti-actin antibody. The etiology and function of these antibodies are unknown. These are commonly assessed when considering autoimmune hepatitis.
Method: ASMA is detected by indirect immunofluorescence using smooth muscle tissue as substrate.
Normal Values: A negative result has a titer <1:20.
— Autoimmune hepatitis: Typical of Type 1 AIH. Titers are >1:160 in >95% of cases.
—Primary biliary cirrhosis: ASMA may be seen in as many as 30% of PBC patients.
—Other conditions: Acute viral infections (e.g., mononucleosis), chronic viral hepatitis (especially hepatitis C), cirrhosis and other autoimmune diseases.
Indications: ASMA assay may be useful in diagnosing autoimmune chronic active hepatitis and distinguishing it from PBC. The lack of specificity hinders its clinical usefulness.
Comment: Identification of specific cytoskeletal antigens and their antibodies may improve the usefulness of ASMA tests.
Soares A1, Cunha R, Rodrigues F, Ribeiro H. Smooth muscle autoantibodies with F-actin specificity. Autoimmun Rev 2009;8:713-6. PMID: 19232552
Zamanou A, Tsirogianni A, Terzoglou C, Balafas A, et al. Anti-smooth muscle antibodies (ASMAs) and anti-cytoskeleton antibodies (ACTAs) in liver diseases: a comparison of classical indirect immunofluorescence with ELISA. J Clin Lab Anal 2002; 16:194-201. PMID: 12112392