How is it used?When is it ordered?What does the test result mean?Is there anything else I should know?
The ASMA test is primarily ordered along with
antinuclear antibodies (ANA) to help diagnose
autoimmune hepatitis. Other autoantibodies, such as liver-kidney microsomal type 1 (LKM1) antibodies and
antimitochondrial antibodies (AMA), may also be ordered to help diagnose autoimmune hepatitis and distinguish it from other causes of
liver disease or injury.
The anti-actin test may be ordered as an initial screening test for autoimmune hepatitis instead of the ASMA test. If it is positive, it may be followed by the ASMA to confirm the finding.
This test and the
ANA test are ordered when a doctor suspects that the patient has
autoimmune hepatitis. They are usually ordered when a patient presents with symptoms such as fatigue and
jaundice (yellowing of the skin and eyes) along with abnormal findings on liver tests (such as
aspartate aminotransferase (AST) and/or
bilirubin), results that may be found during routine blood tests.
ASMA and ANA are usually ordered following or sometimes with a variety of tests that are used to help diagnose and/or rule out other causes of liver injury. These causes can include infections (such as viral hepatitis), drugs, alcohol abuse, toxins, genetic conditions, metabolic conditions, and primary biliary cirrhosis.
An anti-actin test may be ordered instead of the ASMA when the doctor wants to screen for autoimmune hepatitis. This test is relatively new. In some cases, it is taking the place of the ASMA test; in others it may be followed by an ASMA for confirmation. The ultimate clinical utility of the anti-actin test has yet to be established.
What does the test result mean?NOTE: A standard reference range is not available for this test. Because
reference values are
dependent on many factors, including patient age, gender, sample population, and test
method, numeric test results have different meanings in different labs. Your lab report
should include the specific reference range for your test. Lab Tests Online strongly
recommends that you discuss your test results with your doctor. For more information on
reference ranges, please read Reference Ranges
and What They Mean.
When significant amounts of ASMA and
ANA are present in the blood, the most likely cause is
autoimmune hepatitis. When both are present, then
systemic lupus erythematosus can be essentially ruled out (ANA will be positive with lupus, but ASMA will not).
When anti-actin antibodies are present in significant quantities in a patient with clinical signs of autoimmune hepatitis, then it is likely that the patient has the condition. In most cases, if the anti-actin is positive, the ASMA will also be positive. Since actin is only one of several cytoskeleton proteins, it is possible for a person to have anti-smooth muscle antibodies even when the anti-actin test is negative.
Is there anything else I should know?
Concentrations of ASMA may be lower in children and in those with compromised immune systems, and levels may vary over the course of the disease. Up to 20% of patients with
autoimmune hepatitis will not be positive for ASMA,
ANA, or LKM1 antibodies.
Small amounts of ASMA may be present, along with AMA, in up to 50% of patients with primary biliary cirrhosis and may be found in other conditions such as infectious mononucleosis and some cancers. Anti-actin antibodies may be present in about 22% of patients with primary biliary cirrhosis
The presence of ASMA, anti-actin antibodies, and ANA are highly suggestive of autoimmune hepatitis but not diagnostic. When significant concentrations of both are present and the doctor suspects autoimmune hepatitis, then a liver biopsy may be performed to look for characteristic signs of damage and scarring in the liver tissue.
