LabCorp Test

Actin (Smooth Muscle) Antibody (ASMA) Blood Test

Quick Overview

Detection of antibodies aids in the diagnosis of autoimmune liver diseases such as autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC).

Test #006643


Availability: In stock

Also Known As Antiactin, ASMA, Smooth Muscle Antibodies
Preparation No special preparation required.
Test Results 2-4 days. May take longer based on weather, holiday or lab delays.


There are no requirements to abide to before taking the actin antibody blood test.  Individuals preparing for the test may eat, drink, and take their medicines as usual before going in to give blood for the test.  Test results tend to vary by age, so the critical level for an adult and for a child will be different.

Why It Is Used

The actin antibody blood test, also known as the actin smooth muscle antibody (ASMA) blood test, is used to test for the presence of autoimmune hepatitis.  The test is able to differentiate between the two types of autoimmune hepatitis: Type 1 and Type 2.  Type 2 hepatitis is much more prevalent in the United States than it is in other countries, although Type 1 is still the more prevalent disease even in the United States.  A doctor may suspect hepatitis and order this test if a patient is presenting with symptoms of jaundice and extreme fatigue.  The test can also be ordered to test for primary biliary cirrhosis (PBC) - another autoimmune disease.

How It Works

In a healthy body there are no antibodies present on the smooth muscles.  However, if an individual has an autoimmune disease these antibodies may start to form.  The number of antibodies does not always correlate to the severity of the disease, but the longer an individual has an autoimmune disease such as hepatitis or cirrhosis the more antibodies there will be on the smooth muscles in the body. 

Autoimmune hepatitis attacks one’s liver and causes inflammation and reduced functioning.  If the autoimmune hepatitis is left untreated, it can lead to scaring and permanent damage to the liver.  This can eventually result in liver failure, which can lead to death.  If one shows symptoms of an autoimmune disease such as jaundice, fatigue, joint pain, abdominal discomfort, or nausea or vomiting, it is very important to take the ASMA blood test.  With early detection and treatment the condition can be stabilized with medication.  If not caught early enough, or if one does not respond to drug treatment, a liver transplant is the only other option. 

Type 1, also known as classic, autoimmune hepatitis can occur at any age, whereas Type 2 autoimmune hepatitis normally develops in children.  Doctors and researchers are not exactly clear what causes the disease, but have identified several risk factors.  Some of these risk factors include being female (especially for Type 2), a history of getting infections, history of the use of certain antibiotics, a family history of the disease, and having another autoimmune disease. 


Again, antibodies are not naturally present on the smooth muscles, so the presence of these antibodies indicated some sort of abnormality or problem.  When there are large numbers of antibodies on the smooth muscles it normally indicates either Type 1 or Type 2 autoimmune hepatitis, whereas only a small number of antibodies on the smooth muscles is more likely to be the result of cirrhosis.  There are several other less common infections and cancers that can cause antibodies to form on smooth muscles.

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