ANA, fluorescent antinuclear antibody test, FANA
This blood test is done to help your doctor diagnose a type of illness called an autoimmune disease. Your immune system is your body's defense system against foreign invaders like viruses and bacteria. In some cases, your immune system can become confused and mistake normal cells in your body for foreign invaders. When that happens, your body can make proteins called antibodies that attack your own cells.
When antibodies attack cells in your body, they cause swelling and redness known as inflammation. Antinuclear antibodies attack normal proteins in the center structure – or nucleus – of your body's cells. Antinuclear antibodies are found in many autoimmune diseases, including lupus, scleroderma, and rheumatoid arthritis.
Your doctor may order this test if you have symptoms of an autoimmune disease. Common symptoms of autoimmune diseases that may stem from antinuclear antibodies include:
Finding antinuclear antibodies in your blood tells your doctor only that you may have one of many autoimmune diseases. Your doctor may order other tests depending on your symptoms and your physical exam.
Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
A positive test for ANA does not mean you have an autoimmune disease. The test detects small amounts of these antibodies in up to 15 percent of healthy people. Antinuclear antibodies are measured in titers. A titer above 1:160 is considered a positive test result. A positive result may mean:
You have systemic lupus erythematosis, or SLE. About 95 percent of people with this autoimmune disease test positive for antinuclear antibodies.
You have another type of autoimmune disease.
You have a temporary condition, like an infection, that's causing your antinuclear antibodies to go up.
You are one of the 15 percent of normal people who have positive antinuclear antibodies without any disease.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries small risks that include bleeding, infection, bruising, and a sense of lightheadedness. When the needle pricks your arm, you may feel a slight sting or pain. Afterward, the site may be sore.
Many conditions can trigger a positive antinuclear antibody test in the absence of an autoimmune disease. Conditions that may cause a "false positive" test include:
Being older than 65
Taking certain medications
Having a viral infection
Having a long-term infection
You don't need any special preparation for this test. Tell your doctor whether you have had any recent or long-term infections. Also, let your doctor know about any medications you are taking, including over-the-counter medications, herbs, and supplements.