What Is an Antinuclear Antibody Test?
An antinuclear antibody test is a blood test that looks for certain kinds of antibodies in your body. It’s also called an ANA or FANA (fluorescent antinuclear antibody) test.
Antibodies are proteins that your immune system makes to fight off bacteria, viruses, and other germs. But sometimes, your immune system can mistake parts of your own body for foreign invaders. It releases special antibodies, called “autoantibodies,” that attack your cells and tissues. Autoantibodies can damage your joints, skin, muscles, and other parts of your body. And they can be a sign of autoimmune diseases, including:
- Systemic lupus erythematosus, the most common type of lupus
- Rheumatoid arthritis
- Sjogren’s syndrome
Sometimes people with cancer or people taking certain medications test positive on an ANA test. Some people with no health conditions test positive on ANA tests.
Why Would I Need This Test?
Your doctor might order an ANA test if you have symptoms of an autoimmune disease, such as:
Preparing for an ANA Test
You usually don't need to prepare for an ANA test. But let your doctor know ahead of time what medicines, vitamins, and supplements you take. They can affect the ANA test results.
Antinuclear Body Test Procedure
A lab tech will take a sample of your blood -- usually from a vein in your arm. They'll tie a band around the upper part of your arm to make your vein fill with blood and swell up. Then they'll clean the area with an antiseptic and insert a needle into your vein. Your blood will collect into a vial or tube.
The blood test should only take a couple of minutes. After your blood is drawn, the needle and band will be removed, and you'll get a piece of gauze and a bandage placed over the area.
The blood sample will go to a lab to be tested. The lab will check to see if there are antinuclear antibodies in your blood.
Antinuclear Body Test Risks
The blood test has very few risks. You might feel a slight sting as your blood is drawn. You may notice a small bruise later.
You may also have a slight chance of:
- Dizziness or fainting
Antinuclear Antibody Test Results
Your test is positive if it finds antinuclear antibodies in your blood. A negative result means it found none. A positive test doesn’t mean that you have an autoimmune condition. Between 3% and 15% of people with no conditions have antinuclear antibodies. Some medicines or other diseases also can cause them.
Not everyone who has an autoimmune disease will test positive. That’s why the ANA blood test is just one part of a doctor’s autoimmune disease diagnosis. They’ll also consider your symptoms, do a physical exam, and most likely do other tests.
Conditions that usually cause a positive ANA test include:
- Systemic lupus erythematosus
- Sjögren's syndrome -- a disease that causes dry eyes and mouth
- Scleroderma -- a connective tissue disease
- Rheumatoid arthritis -- this causes joint damage, pain, and swelling
- Polymyositis -- a disease that causes muscle weakness
- Mixed connective tissue disease -- a condition that has symptoms of lupus, scleroderma, and polymyositis
- Juvenile chronic arthritis -- a type of autoimmune arthritis that affects children
- Dermatomyositis -- a rare disease that causes weak muscles and a rash
- Polyarteritis nodosa -- a rare disease that causes the blood vessels to swell up and damage organs
- Autoimmune hepatitis
The ANA test result can sometimes also be positive if you have one of these conditions:
- Raynaud's syndrome -- a disease that makes your fingers and toes turn blue and feel cold
- Thyroid diseases -- Hashimoto's thyroiditis, Grave's disease
- Liver diseases -- autoimmune hepatitis, primary biliary cirrhosis
- Inflammatory bowel disease
- Lung diseases -- idiopathic pulmonary fibrosis
- Viral infections
About 20% of healthy people will test positive for antinuclear antibodies, even though they don't have an autoimmune disease. You're more likely to have a false positive result if you:
Would I Need Any Other Tests?
The ANA test only shows that you may have an autoimmune disease; it can't detect the exact one.
If your ANA test is positive, your doctor might test you for ANAs that are specific to certain diseases:
- An anti-centromere test diagnoses scleroderma.
- An anti-double-stranded DNA (anti-dsDNA) test diagnoses lupus.
- An anti-histone test diagnoses lupus that was caused by medicine you took.
- An ENA panel helps your doctor see which autoimmune disease you have.
Make sure you understand the results of your ANA test. Ask what other tests you need for your diagnosis to be confirmed. Also find out how your test results will affect your treatment.