The immunofluorescent antinuclear antibody (ANA or FANA) test is more specific for lupus tests. The ANA test is positive in virtually all people with systemic lupus. If the ANA test comes back negative it is considered a normal result, and it is very good evidence against lupus as an explanation for the symptoms. If the ANA test result comes back above the normal range the test is said to be positive. A positive ANA test by itself is not proof of lupus. The ANA is only a test and like a high cholesterol value, a positive ANA doesn't necessarily equate having a disease. The ANA test may also be positive in individuals
with other connective tissue diseases;
being treated with certain drugs, including procainamide, hydralazine, isoniazid, and chlorpromazine;
with conditions other than lupus, such as scleroderma, rheumatoid arthritis, infectious mononucleosis and other chronic infectious diseases such as lepromatous leprosy, subacute bacterial endocarditis, malaria, etc., and liver disease.
ANA test reports include a titer (or strength) of the antibody. The titer indicates how many times an individual's blood must be diluted to get a sample free of anti-nuclear antibodies. Thus, a titer of 1:640 shows a greater concentration of anti-nuclear antibodies than a titer of 1:320 or 1:160. A high titer of this antibody (greater than 1:1280) is usually associated with rheumatic disease but has nothing to do with how active a person's lupus is. Therefore, it is not necessary to repeat the ANA in someone who has lupus. Other blood tests (complement factors C3 and C4, anti-DNA, the complete blood count, and urinalysis) are the best laboratory index of lupus activity.
Approved by the Lupus Foundation of America's
Patient Education Committee.