Patient education: Antinuclear antibodies (The Basics)

What are antinuclear antibodies? — 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 they 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 their 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.

What is an ANA test? — An ANA test is a blood test that measures the amount of ANA in your blood.

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.

Why might a doctor or nurse order an ANA test? — 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:

●Lupus

●Scleroderma

●Mixed connective tissue disease

●Polymyositis

●Dermatomyositis

●Rheumatoid arthritis

Other autoimmune diseases affect only 1 part of the body, such as the thyroid (a gland in the neck), liver, or lungs.

What does a negative ANA test result mean? — If you have a negative result, you probably do not have an autoimmune disease.

What does a positive ANA test result mean? — 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. They 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.

More on this topic

Patient education: Lupus (The Basics)
Patient education: Rheumatoid arthritis (The Basics)
Patient education: Dermatomyositis (The Basics)
Patient education: Polymyositis (The Basics)
Patient education: Systemic sclerosis (scleroderma) (The Basics)
Patient education: Polyarteritis nodosa (The Basics)
Patient education: Vasculitis (The Basics)
Patient education: Sjögren's syndrome (The Basics)
Patient education: Antinuclear antibodies (ANA) (Beyond the Basics)

Patient education: Antinuclear antibodies (ANA) (Beyond the Basics)
Patient education: Polymyositis, dermatomyositis, and other forms of idiopathic inflammatory myopathy (Beyond the Basics)
Patient education: Systemic lupus erythematosus (Beyond the Basics)
Patient education: Rheumatoid arthritis symptoms and diagnosis (Beyond the Basics)
Patient education: Vasculitis (Beyond the Basics)
Patient education: Sjögren's syndrome (Beyond the Basics)