Test Overview

An antinuclear antibody (ANA) test measures the amount and pattern of antibodies in your blood that work against your own body (autoimmune reaction).

The body's immune system normally attacks and destroys foreign substances such as bacteria and viruses. But in disorders known as autoimmune diseases, the immune system attacks and destroys the body's normal tissues. When a person has an autoimmune disease, the immune system produces antibodies that attach to the body's own cells as though they were foreign substances, often causing them to be damaged or destroyed. Rheumatoid arthritis and systemic lupus erythematosus are examples of autoimmune diseases.

An ANA test is used along with your symptoms, physical examination, and other tests to find an autoimmune disease.

Why It Is Done

An ANA test is done to help identify problems with the immune system, such as:

• Rheumatoid arthritis.
• Lupus.
• Polymyositis.
• Scleroderma.
• Sjögren's syndrome.

How To Prepare

In general, there's nothing you have to do before this test, unless your doctor tells you to.

How It Is Done

A health professional uses a needle to take a blood sample, usually from the arm.

How long the test takes

The test will take several minutes.

How It Feels

When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.

Risks

There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.

Results

If there are more antibodies in the blood than normal, the test is positive. When the test is positive, most labs do other tests right away to look for the cause. These tests can find out which antibodies are in the blood in higher amounts than normal.

Sometimes ANA test results can be positive when a person is healthy. Though the test is positive, the level of antibodies is usually low.

Some healthy people can have an increased amount of ANA in their blood. For instance, this can happen in some people with a family history of autoimmune disease. ANA levels can also increase as a person ages.

Autoimmune diseases can't be diagnosed by the results of the ANA test alone. Other tests are needed to help identify diseases such as lupus or rheumatoid arthritis.

Positive test

A positive ANA test may be caused by:

• Autoimmune connective tissue diseases. Examples include:
  • Rheumatoid arthritis. More than one-third of people with rheumatoid arthritis have a positive ANA test.
  • Systemic lupus erythematosus (SLE). Almost all people with SLE have a positive ANA test. But most people with a positive ANA test don't have SLE.
  • Scleroderma.
  • Sjögren's syndrome.
  • Juvenile idiopathic arthritis.
  • Polymyositis.
  • Raynaud's syndrome.
• Autoimmune diseases of other organs. Examples include:
  • Addison's disease.
  • Diseases of the blood cells, such as vitamin B12 deficiency, immune thrombocytopenia (ITP), and hemolytic anemia.
  • Liver disease, such as hepatitis.
  • Thyroid disease, such as Hashimoto's thyroiditis.
• Medicines, such as those used to treat high blood pressure, heart disease, and tuberculosis (TB).
• Viral infections.