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Test Code AABG Actin (Smooth Muscle) Antibody (IgG)

Specimen Required

0.5 mL serum

Specimen Minimum Volume

0.25 mL

Specimen Stability

Room temperature: 14 days:Refrigerated: 14 days: Frozen: 30 days

Rejection Due To

Gross hemolysis • Lipemia • Microbially contaminated serum • Specimens containing heavy, visible particulate

Day(s) and Time(s) Performed

Set up: Tues-Sat a.m.; Report available: Next day

Method Name

Enzyme Linked Immunosorbent Immunoassay (ELISA)

Collection Container / Tube

Preferred: Gold SST Tube
Other Acceptable Container: None

Transport Container

Plastic screw-cap vial

Transport / Storage Conditions

Room temperature

Reference Values

<20 U Negative

≥20 U


Antibodies recognizing actin are the main component of smooth muscle antibodies associated with autoimmune liver disease. Actin antibodies are found in approximately 75% of patients with autoimmune hepatitis (AIH) type 1, approximately 65% of patients with autoimmune cholangitis, approximately 30% of patients with primary biliary cirrhosis, and approximately 2% of healthy people. High values are closely correlated with AIH type 1.

CPT Codes


Clinical Reference

Actin is the major antigen to which smooth muscle antibodies react in autoimmune hepatitis. F-Actin IGG antibodies are found in 52-85% of patients with Autoimmune Hepatitis (AIH) or chronic active hepatitis and in 22% of patients with Primary Biliary Cirrhosis (PBC). Anti-Actin antibodies have been reported in 3-18% of sera from normal healthy controls.