Antinuclear antibodies, called "ANA" for short, are
proteins in the blood. They are made by the body's infection-fighting system, which is also
called the immune system.
Normally, a person's immune system makes antibodies when he or she gets an infection. The antibodies attack the germs causing the infection.
If a person's immune system isn't working normally, it sometimes makes antibodies that attack his or her own body. This is called an autoimmune disease. Antibodies that attack a person's own body are also called autoantibodies. ANA are specific autoantibodies that attack substances inside of cells.
Autoantibodies can damage different parts of the body, including the blood, skin, joints, kidneys, lungs, and nervous system.
An ANA test is a blood test that measures the amount of ANA in your
A "negative" result means that you have no (or very little) ANA in your blood.
A "positive" result means that you have ANA in your blood.
A doctor or nurse will order an ANA test to help figure out if you have an autoimmune disease. Many types of autoimmune diseases can cause a positive ANA test result. Some autoimmune diseases affect the whole body. These include:
• Mixed connective tissue disease
• Rheumatoid arthritis
Other autoimmune diseases affect only one part of the body, such as the thyroid (a gland in the neck), liver, or lungs.
If you have a negative result, you probably donot have an autoimmune disease.
If you have a positive result, you might have
an autoimmune disease.
It's important to know that a positive result does not always mean a person has an autoimmune disease. Some people with a positive ANA result do not have an autoimmune disease and never get one. The higher the number (called the "titer") of your ANA test, the greater the chance that you have an autoimmune disease.
Also, some people with a positive ANA result do not have an autoimmune disease, but have an infection instead.
To figure out whether you have an autoimmune disease, your doctor will also learn about your symptoms, do an exam, and order other lab tests. He or she might order blood tests that look for more specific autoantibodies. These can help your doctor figure out which type of autoimmune disease you might have.