Anti-Smooth Muscle Antibody Test: An Important Test for Autoimmune Hepatitis

Medically Reviewed by Jennifer Robinson, MD on February 20, 2024
3 min read

An anti-smooth muscle antibody (ASMA) test is a blood test that detects autoantibodies that attack the smooth muscle cells in the body, often in the liver. Autoantibodies are antibodies made by your body that attack your own body cells. 

ASMAs were first discovered in 1965 in people with chronic active hepatitis. 

Usually, your immune system will attack foreign bodies like a parasite or a virus with the antibodies made for defending your body. Autoantibodies like ASMAs think that your own cells and tissues are foreign bodies and tell your immune system to kill them.

ASMAs — also known as smooth muscle antibodies — attack smooth muscle tissues throughout certain parts of the body. The ASMA test searches for these antibodies in the blood.

‌Smooth muscle antibodies can be found with medical conditions like:‌ 

  • Hepatitis‌
  • Infectious diseases‌
  • Rheumatic disorders‌
  • Cancer

The most common target of ASMAs is smooth muscle tissues in the liver, leading to diseases like autoimmune hepatitis and primary biliary cholangitis.

When diagnosed early, autoimmune hepatitis can be treated by using immunosuppressive drugs. Without treatment, it may lead to liver failure.

Though autoimmune hepatitis can occur in any population, it is more common in women.

You should talk to your doctor or health practitioner about getting an ASMA test — or a smooth muscle antibody test if you are having symptoms that are becoming more frequent. They include:

  • Nausea ‌
  • Changes in appetite
  • Yellowing of eyes and skin ‌
  • Stomach pain
  • Joint pain
  • Rashes on the skin or pain in the joints 

You don’t need to do any special preparations for an ASMA test. Blood may be drawn in your doctor’s office, a clinic, or a laboratory‌.

Normally, very little to no ASMAs are found in your blood.

If your blood test shows a high amount of ASMAs, you may have autoimmune hepatitis. It means that your immune system is attacking healthy cells in your liver using autoantibodies.

Your doctor will order a biopsy to confirm the diagnosis of autoimmune hepatitis.

If you’re not showing strong symptoms of autoimmune hepatitis, your doctor may choose not to treat you. They’ll ask you to get periodic blood tests — including the ASMA test — along with some other tests to make sure your liver is healthy.

If you start having autoimmune hepatitis symptoms more often and they get worse, your doctor may want to start treatment. First-line treatment for this disease often includes steroids, which weakens your immune system and can have side effects like weight gain, decreased number of white blood cells, and weakened bones.  

Some people need years of treatment until their symptoms actually disappear. But if symptoms return, treatment needs to be restarted.

The long-term effects of ASMAs — specifically autoimmune hepatitis — are difficult to predict. The disease state may be acute or chronic.

If you have a positive ASMA test, it’s important to choose a doctor who specializes in treating not only liver disorders but autoimmune conditions, as well.