Test Catalog

Test ID: SMA    
Smooth Muscle Antibodies, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Evaluating patients with chronic liver disease in whom the diagnosis of chronic active autoimmune hepatitis is suspected

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Sera from patients with autoimmune chronic active hepatitis contain antibodies to smooth muscle antigens that are detectable by indirect immunofluorescence on substrates that contain smooth muscle. The antibodies are predominantly of the IgG isotype.


Other diseases in this differential diagnosis group include primary biliary cirrhosis, chronic viral hepatitis, and alcoholic chronic hepatitis.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


If positive, results are titered.

Reference values apply to all ages.

Interpretation Provides information to assist in interpretation of the test results

Antibody titers in the range of 80 to 320 occur commonly in patients with active chronic hepatitis; lower titers (usually <80) may occur in the other conditions mentioned earlier.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Serologic tests for autoantibodies, including smooth muscle antibodies, should not be relied upon exclusively to determine the etiology or prognosis of patients with liver disease.


A positive result for antismooth muscle antibodies may occur in patient who do not have autoimmune hepatitis. A negative result does not exclude a diagnosis of autoimmune hepatitis.

Clinical Reference Recommendations for in-depth reading of a clinical nature

Czaja AJ, Homburger HA: Autoantibodies in liver disease. Gastroenterology 2001;120:239-249