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.
Medicines, such as those used to treat high
blood pressure, heart disease, and tuberculosis (TB).
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.
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
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
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.