Actin (Smooth Muscle) Antibody (ASMA) Blood Test

What is the purpose of this test?

Order this Actin Smooth Muscle Antibody (ASMA) Blood Test, which detects antibodies that attack healthy tissues to help screen for autoimmune hepatitis. The body's immune system can produce autoantibodies known as smooth muscle antibodies (SMA), which attack its own actin, a protein found in smooth muscle and other tissues, with a higher affinity for the liver. This test measures the quantity of SMA (or antibody against actin) present in the blood. The production of smooth muscle or actin antibodies is frequently associated with autoimmune hepatitis. Still, it may occasionally be observed in other liver diseases, such as primary biliary cholangitis (PBC), albeit typically at lower antibody levels.

Autoimmune hepatitis is a liver disease caused by the immune system attacking liver cells, leading to acute or chronic inflammation. Viruses, drugs or toxins, hereditary disorders, or alcohol abuse do not cause this condition. It can result in liver cirrhosis and failure. Although it can affect anyone, 80% of patients are women. In the United States, over 70% of those diagnosed with this disease have either SMA or actin antibodies, often with ANA. Most of these antibodies target a protein called actin or F-actin, with F-Actin IgG antibodies found in 52-85% of patients with autoimmune hepatitis or chronic active hepatitis and 22% of those with primary biliary cirrhosis.

When should I order an ASMA Blood Test?

Individuals may order this test if they have experienced symptoms related to autoimmune hepatitis. Common signs or symptoms of autoimmune hepatitis include:

• Fatigue
• Jaundice
• Abdominal pain
• Joint pain
• Nausea
• Skin rashes
• Loss of appetite
• Dark-colored urine