Antinuclear Antibody Test

This is a blood test to measure the presence of antinuclear antibody. This test is used do diagnose  autoimmune or rheumatic disease, particularly systemic lupus erythematosus (SLE).

What effects the Antinuclear Antibody Test

• The medications hydralazine (Apresoline), procainamide (Procan, Pronestyl, Promine), and certain anticonvulsants (such as Dilantin) can cause a form of systemic lupus erythematosus (SLE) called drug-induced lupus. Lupus resulting from these medications may cause a high antinuclear antibody (ANA) titer.
• Certain medications can cause an abnormally high ANA titer. These medications include some antibiotics (including isoniazid, penicillin, and tetracycline), birth control pills, and some diuretics.
• Aging can affect the levels of antinuclear antibodies, and some older adults (5% to 40%) may have mildly elevated levels.
• Rough handling, contamination, or inadequate refrigeration of the blood sample can cause inaccurate test results.

Purpose of Antinuclear Antibody Test

In autoimmune diseases, the body makes antibodies that work against its own cells or tissues. Rheumatic diseases (diseases that affect connective tissue, including the joints, bone, and muscle) are also associated with these antibodies. Autoantibodies are proteins built by the body, but instead of guarding against foreign material (including bacteria, viruses, and fungi) as normal antibodies do, they attack the body's own cells.

Autoimmune and rheumatic diseases can be difficult to diagnose. People with the same disease can have very different symptoms. A helpful strategy in the diagnosis of these diseases is to find and identify an autoantibody in the person's blood.

The antinuclear antibody test looks for a group of autoantibodies that attack substances found in the center (nucleus) of all cells. It is useful as a screen for many autoantibodies associated with diseases that affect the entire body (systemic diseases).

This test is particularly useful when diagnosing a person with symptoms of SLE, an illness that affects many body organs and tissues. If the test is negative, it is unlikely that the person has SLE; if the test is positive, more tests are done to confirm whether the person has SLE or another related disease. Other diseases, such as scleroderma, Sjögren's syndrome, Raynaud's disease, rheumatoid arthritis, and autoimmune hepatitis, often have a positive test for antinuclear antibodies.

Information about Antinuclear Antibody Test

Five to 10 mL of blood is needed for this test. The antinuclear antibody test is done by adding a person's serum to commercial cells mounted on a microscope slide. If antinuclear antibodies are in the serum, they bind to the nuclei of cells on the slide. Next, a second antibody is added to the mixture. This antibody is "tagged" with a fluorescent dye so that it can be seen. The second antibody attaches to any antibodies and cells bound together and, because of the fluorescent "tag," the areas with antinuclear antibodies seem to glow, or fluoresce, when the slide is viewed under an ultraviolet microscope.

If fluorescent cells are seen, the test is positive. When positive, the serum is diluted, or titered, and the test done again. These steps are repeated until the serum is so dilute it no longer gives a positive result. The last dilution that shows fluorescence is the titer reported.

The pattern of fluorescence within the cells gives the physician clues as to what the disease might be. The test result includes the titer and the pattern.

This test is also called the fluorescent antinuclear antibody test or FANA. Results are available within one to three days.