Anti Smooth Muscle Antibodies (ASM)

Smooth muscle antibodies are directed toward actin, myosin, and occasionally against other contractile proteins in muscle cells. Smooth muscle antibodies can present in a variety of liver disease states. Smooth muscle antibodies can be useful in differentiating liver disease when used in conjunction with other laboratory results and the patients clinical symptoms.

Normal range:

IFA: negative; if positive, results are tittered, ELISA: <1:40 titer.

ASM titers >1:40 are significant.

Use

Aids in the diagnosis of chronic active hepatitis

Differential diagnosis of liver disease

Rule out SLE (test usually negative in SLE)

Interpretation

Increased In

Chronic active hepatitis

Autoimmune hepatitis type 1

Hepatitis B

Hepatitis C

Primary biliary cirrhosis

Primary sclerosing cholangitis

Overlap syndromes

Decreased In

NA

Limitations

A positive test is not diagnostic for any one disease state.

Low titers are seen in acute viral hepatitis, PBC, infection mononucleosis, malignant myeloma, and ovarian carcinoma.