Anti-nuclear antibodies (ANA) are possible signs of autoimmune diseases, such as lupus, scleroderma, Sjögren’s syndrome, juvenile arthritis, or polymyositis and dermatomyositis. White blood cells in the body’s immune system make antibodies to spot and attack foreign agents that cause infections or disease.
Sometimes, antibodies target normal proteins in our body by mistake. This can trigger inflammation that leads to joint or tissue damage. These antibodies are called autoantibodies. Everyone has small amounts of autoantibodies.
ANAs are one type of autoantibody. A positive ANA blood test means autoantibodies are present, but it’s not a sure sign of an autoimmune disease.
The Fluorescent Antinuclear Antibody Test (FANA) is one way to test blood for positive ANA. A doctor will view fluorescent-labeled antibodies under a microscope and look for certain patterns and intensity.
FANA titer reading is determined by adding saline (salt water) to the liquid portion of the blood. Some labs will report any titer above 1:160 as positive. Your physician will interpret ANA results based on your clinical history.
ANA is a popular initial test to evaluate lupus. More than 95% of people with lupus will test positive for ANA, so a negative ANA test may help exclude that diagnosis. However, only about 11-13% of people with a positive ANA test have lupus. Up to 15% of completely healthy people have a positive ANA test, so ANA tests don’t confirm diagnosis of lupus, or any autoimmune or connective tissue disease.
A negative ANA test result means no autoantibodies are present. However, a positive ANA reading alone doesn’t indicate an autoimmune disease. ANA production is strongly age-dependent, and increases in healthy people over age 65. Even healthy people with viral infections can have a positive ANA for a short time.
A positive ANA reading simply tells your doctor to keep looking for disease. For a definite diagnosis, you will need more blood tests and a physical exam, and to give your doctor a full history of your symptoms.
• Some medications cause a positive ANA. Tell your doctor about all the medications you take, including prescription, over-the-counter and street drugs.
• Other conditions, such as cancer, can cause a positive ANA.
One positive ANA test result is not a sure sign of autoimmune disease, so you may not need any immediate treatment. Lab levels vary. Some autoantibodies are normal, so your positive result may not indicate any problem.
Your rheumatologist will determine what to do next, such as run additional blood tests to look for signs of an autoimmune disease, or your doctor may decide to watch and wait.
Work with your doctor and ask any questions you have about ANA. Remember, if your ANA reading does lead to an autoimmune diagnosis, there are treatments available for these diseases.