What Is a Smooth Muscle Antibody Test?
A smooth muscle antibody test is a type of blood test that is used to detect antibodies that attack smooth muscles. A smooth muscle antibody is a type of antibody that is known as an autoantibody. The role of autoantibody is to mistakenly attack the body's own cells and tissues. Smooth muscle antibodies target the smooth muscle tissues in the liver and other body parts. The primary role of smooth muscle is contraction. Blood is drawn from the patient for this test.
Every antibody is unique and is used to defend against only one type of antigen. However, sometimes the body mistakenly generates autoantibodies (antibodies that attack the body's healthy cells). If the body starts behaving this way, the affected individual may develop an autoimmune disorder.
Normally, the immune system detects infectious substances called antigens that may be harmful to the body. These antigens are covered with viruses and bacteria. The immune system after recognizing the foreign agent synthesizes a protein called an antibody to attack it.
Therefore, an anti-muscle antibody test detects the autoantibody that attacks smooth muscle. Anti-smooth muscle antibodies are primarily found in the blood in autoimmune liver diseases such as primary biliary cholangitis and autoimmune hepatitis.
What Is Autoimmune Hepatitis?
Autoimmune hepatitis is a disorder where the immune system produces smooth muscle autoantibodies attacking the liver tissues. There are two types of autoimmune hepatitis:
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Type 1 is the most common type of autoimmune hepatitis. Type 1 is predominantly found in women rather than men. It is also frequently present in people who are suffering from another autoimmune disorder.
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Type 2 is a less common type of disease. This form mostly affects girls that fall in the age group of two to fourteen years.
Suppose the person suffers from persistent chronic liver disease. In that case, the healthcare professional will advise a smooth muscle antibody test to help identify whether the person is suffering from active autoimmune hepatitis disease. Most hepatitis diseases worldwide are affected by viruses. Autoimmune hepatitis is an exceptional liver disease where the body's immune system attacks the host’s liver cells. Autoimmune hepatitis is a chronic liver condition that is characterized by liver cirrhosis or scarring and liver failure in advanced cases. The signs and symptoms include:
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Enlarged liver (hepatomegaly).
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Abdominal swelling.
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Liver tenderness.
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Dark-colored urine.
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Pale-colored stools.
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Jaundice (yellowish discoloration of skin and eyes).
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Burning or itching.
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Tiredness.
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Loss of appetite.
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Nausea and vomiting.
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Pain in the joints.
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Discomfort in the abdomen.
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Skin rash.
Autoimmune hepatitis is usually managed with medications that suppress the host’s immune system. When the disorder is diagnosed early, treatment is found to be more effective. Without treatment, autoimmune hepatitis poses serious health problems such as liver destruction, cirrhosis, and liver failure.
What Are the Other Names of Smooth Muscle Antibody?
Other names include:
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Anti-smooth muscle antibody.
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Actin antibody.
What Is Smooth Muscle Antibody Used For?
A smooth muscle antibody test is particularly used to diagnose autoimmune hepatitis. It is also used to identify if the disorder is type 1 or 2. Smooth muscle antibody tests are often used in conjunction with other diagnostic tests to rule out a diagnosis of autoimmune hepatitis. The other tests include:
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F-Actin Antibodies Test- F-actin is a protein present in the smooth muscles of the liver tissues and other body parts. F-actin antibodies attack the healthy liver tissues.
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Antinuclear Antibody Test- These antibodies attack certain healthy cells' nuclei.
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Alanine Transaminase and Aspartate Aminotransferase Tests- Both these enzymes are synthesized by the liver.
When Does One Need a Smooth Muscle Antibody Test?
One may require this test if either they or their child suffers from autoimmune hepatitis. The symptoms include:
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Extreme tiredness.
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Jaundice.
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Abdominal pain and discomfort.
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Joint and muscle pain.
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Nausea and vomiting.
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Unexplained weight loss.
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Loss of appetite.
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Urine is dark in color.
What Happens During a Smooth Muscle Antibody Test?
A health care professional will obtain a blood sample from a vein in the patient’s arm using a small needle. After the needle is pricked, a small amount of blood will be drawn into a test tube or vial. The patient may feel slightly stung when the needle moves in or out. This usually takes less than five minutes.
Does One Need to Do Anything to Prepare for a Smooth Muscle Antibody Test?
One do not require any special preparations for a smooth muscle antibody test.
What Are the Risks to a Smooth Muscle Antibody Test?
There is a very slight risk of having a blood test. The patient may have slight pain or bruising at the needle's location, but most symptoms disappear quickly.
What Do the Results Indicate?
If the results show high smooth muscle antibodies, it probably indicates that the affected individual has the type 1 form of autoimmune hepatitis. A lower amount of smooth muscle antibodies suggests that the patient has a type 2 form of the disease. If no smooth muscle antibodies were found, it indicates that the liver symptoms are being caused by some other disease than autoimmune hepatitis. Your doctor will order more tests to reach a diagnosis.
Is There Anything Else One Needs to Know About a Smooth Muscle Antibody Test?
If the test results show that a person or a child has smooth muscle antibodies, the healthcare provider may suggest a liver biopsy to confirm a diagnosis of autoimmune hepatitis. A liver biopsy is a procedure that removes a small sample of lesional liver tissue for histopathological testing.
Conclusion
Anti-smooth muscle antibody is a diagnostic blood test that is used to detect the presence of autoantibodies directed against smooth muscle. An autoantibody is a type of antibody that attacks the defence system of the body by mistake. Body’s own cells and tissues are attacked by the smooth muscle autoantibody. This smooth muscle antibody test is useful to confirm a diagnosis of autoimmune hepatitis. The blood sample is usually collected from the arm or the back of the hand. There are generally no risks attached to this test.
