What Is an Antinuclear Antibody Test?

An antinuclear antibody test looks for autoimmune diseases such as lupus or rheumatoid arthritis.

The ANA blood test is just one part of a doctor’s autoimmune disease diagnosis, along with a listing of your symptoms, a physical exam, and other tests.

What Are Antibodies?

They are proteins your immune system makes to fight off bacteria, viruses, and other germs.

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.

Antinuclear antibodies (ANAs) are a type of autoantibody that attacks proteins inside your cells. People with some autoimmune diseases will test positive for ANAs.

Why Would My Doctor Order This Test?

Your doctor might order an ANA test if you have symptoms of an autoimmune disease, such as:

How Should You Prepare?

You usually don't need to prepare for an ANA test. 

Let your doctor know what medicines, vitamins, and supplements you take. Some medications can affect the ANA test results.

What Happens During the Test?

A lab tech will take a sample of your blood -- usually from a vein in your arm. He will first tie a band around the upper part of your arm to make your vein fill with blood and swell up. Then he'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. A piece of gauze and a bandage will go over the area to stop the bleeding.

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.

Are There Any Risks?

The blood test has very few risks. You might feel a slight sting as your blood is drawn. Afterward, you may have a small bruise.

You may also have a slight chance of:

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What Do My Results Mean?

Your test is positive if it finds antinuclear antibodies in your blood. A negative result means it found no ANAs.

A positive test is not very specific. It could mean anything from nothing at all to the presence of an autoimmune disease like lupus, a disease that damages joints, skin, and other organs. About 95% of people with lupus will test positive for antinuclear antibodies.

A positive test result can also mean that you have one of these other autoimmune diseases:

Even if your ANA test result is negative, it's possible that you have an autoimmune disease. You might need other tests if your symptoms don't go away.

The ANA test result can sometimes also be positive if you have one of these conditions:

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 confirm which exact one you have.

If your ANA test is positive, your doctor might then test you for ANAs that are specific to certain diseases:

  • Anti-centromere -- diagnoses scleroderma
  • Anti-double-stranded DNA (anti-dsDNA) -- diagnoses lupus
  • Anti-histone -- diagnoses lupus that was caused by medicine you took
  • 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 to confirm your diagnosis. Also find out how your test results will affect your treatment.

WebMD Medical Reference Reviewed by Sabrina Felson, MD on February 16, 2019

Sources

SOURCES:

American Association for Clinical Chemistry: "ANA."

American College of Rheumatology: "Antinuclear Antibodies (ANA)."

Cleveland Clinic: "Antinuclear Antibody Test in Children."

Lupus Research Alliance: "A Positive ANA Test: Should You Worry?"

Mayo Clinic: "ANA test: How you prepare." "Results," "Why It's Done."

National Heart, Lung, and Blood Institute: "What to Expect With Blood Tests."

UpToDate: "Antinuclear antibodies (ANA) (Beyond the Basics)."

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