Arthritis Health Center

Results

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

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 do not 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, idiopathic 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.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking medicine. Many medicines can change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.
• Aging. Some older adults may have mildly elevated levels. These people do not have lupus.
• A virus. Viral illness can cause an ANA to be positive, and later turn back to normal.

What To Think About

• Autoimmune diseases cannot be diagnosed by the results of the ANA test alone. A complete medical history, physical examination, and the results of other tests are used with the ANA test to help identify autoimmune diseases, such as systemic lupus erythematosus (SLE) or rheumatoid arthritis.
• 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. The higher the ANA level is, however, the more likely it is that the person has an autoimmune disease.
• ANA levels can increase as a person ages.