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Antinuclear Antibodies (ANA)

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:

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.
  • A virus. Viral illness can cause an ANA to be positive, and later turn back to normal.

What To Think About

  • Autoimmune diseases can't 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, though, the more likely it is that the person has an autoimmune disease.
  • ANA levels can increase as a person ages.

Other Works Consulted

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

ByHealthwise Staff
Primary Medical ReviewerAnne C. Poinier, MD - Internal Medicine
Specialist Medical ReviewerKathleen Romito, MD - Family Medicine
Last RevisedJune 4, 2012
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WebMD Medical Reference from Healthwise

Last Updated: June 04, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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