Antibodies that attack healthy proteins within the cell nucleus are called antinuclear antibodies (ANAs). Doctors may order an ANA test if you have signs or symptoms of an autoimmune disorder.

Antibodies are proteins made by your immune system. They help your body recognize and fight infections. Antibodies normally target harmful substances, such as bacteria and viruses, by activating the immune system to get rid of them.

Sometimes antibodies mistakenly target your healthy cells and tissues. This is known as an autoimmune response. Antibodies that attack healthy proteins within the nucleus — the control center of your cells — are called antinuclear antibodies (ANAs).

When the body receives signals to attack itself, it can give rise to autoimmune diseases such as lupus, scleroderma, mixed connective tissue disease, autoimmune hepatitis, and others. Symptoms vary by disease, but they may include rashes, swelling, arthritis, or fatigue.

It’s normal to have some ANAs, but having too many of these proteins is a sign of an active autoimmune disease. An ANA panel helps determine the level of ANAs in your blood.

You may have an autoimmune disorder if the level is high. Conditions such as infections, cancer, and other medical problems can also result in a positive ANA test.

A doctor will likely order an ANA panel if you have signs or symptoms of an autoimmune disorder. An ANA test may indicate that you have some type of autoimmune condition, but it can’t be used to diagnose a specific disorder.

If your test comes back with a positive result, your doctor will need to do more specific and detailed testing to determine if an autoimmune disease is causing your symptoms.

No preparation is needed for the ANA panel. However, it’s important to tell your doctor about any medications or supplements that you’re taking, even over-the-counter ones. Some drugs, such as certain seizure and heart medications, can affect the accuracy of the test.

The ANA panel is similar to other blood tests. A phlebotomist (a technician who performs blood tests) will tie an elastic band around your upper arm so your veins swell with blood. This makes it easier for them to find a vein.

After cleaning the site with an antiseptic, they’ll insert a needle into a vein. You might feel some moderate pain when the needle goes in, but the test itself isn’t painful.

Blood is then collected in a tube attached to the needle. Once the blood is collected, the phlebotomist will remove the needle from your vein and cover the puncture site.

For infants or children, a lancet (small scalpel) may be used to puncture the skin, and blood may be collected in a small tube called a pipette. It may also be collected on a test strip.

The blood is then sent to a lab for examination.

The risks of doing an ANA panel are minimal. People with veins that are harder to access may experience more discomfort than others during the blood test. Other risks can include:

  • excessive bleeding
  • infection at the puncture site
  • fainting
  • hematoma (blood building up under the skin)

A negative test means that certain autoimmune diseases are less likely to be present. Other tests may still be needed based on your symptoms. Some people with autoimmune diseases may get a negative test result for ANA but positive result for other antibodies.

A positive ANA test means that you have high levels of ANA in your blood. A positive ANA test is usually reported as both a ratio (called a titer) and a pattern, such as smooth or speckled. Certain diseases are more likely to have certain patterns.

The higher the titer, the more likely the result is a “true positive” result, meaning you have significant ANAs and an autoimmune disease.

For example, for a ratio of 1:40 or 1:80, the possibility of an autoimmune disorder is considered low. A ratio of 1:640 or greater indicates a high possibility of autoimmune disorder, but results will need to be analyzed by a doctor and additional tests performed to draw a conclusion.

However, a positive result doesn’t always mean that you have an autoimmune disease. Up to 15 percent of completely healthy people have a positive ANA test. This is called a false-positive test result.

ANA titers can also increase with age among healthy people, so it’s important to talk with a doctor about your symptoms and what your result means to you.

If your primary doctor ordered the test, they may recommend a referral to a rheumatologist — an autoimmune disease specialist — to review any abnormal ANA results. They can often help determine if your test results are related to a specific condition.

A positive ANA test alone can’t diagnose a specific disease. However, some conditions that are associated with a positive ANA test include:

  • systemic lupus erythematosus (lupus): an autoimmune disorder that can affect different parts of your body, including your heart, kidneys, joints, and skin
  • autoimmune hepatitis: an autoimmune disorder that causes inflammation of your liver, along with rashes, joint pain, fatigue, poor appetite, and nausea
  • rheumatoid arthritis: an autoimmune disorder that causes joint destruction, pain, swelling, and stiffness in your joints and affects your lungs, heart, eyes, and other organs
  • Sjögren’s disease: an autoimmune disorder that affects your salivary and lacrimal glands, which produce saliva and tears
  • scleroderma: an autoimmune disorder that primarily affects your skin and other connective tissues but can affect organs as well
  • autoimmune thyroid disease: a range of conditions that affect your thyroid, including hypothyroidism and hyperthyroidism
  • polymyositis or dermatomyositis: autoimmune conditions that cause pain, weakness, and inflammation of your muscles, and can include a rash

Labs can differ in their standards for a positive test. Talk with a doctor about what your levels mean and how your symptoms may be explained by the presence of ANAs. If your ANA test comes back positive, your doctor will need to run more tests in order to help determine if the results are related to a specific condition.

The ANA test is especially helpful in diagnosing lupus. More than 95 percent of people with lupus will get a positive ANA test result. However, not everyone who gets a positive test result has lupus, and not everyone with lupus will have a positive test result. So the ANA test can’t be used as the only method of diagnosis.

Speak with a doctor about additional tests that can be done to determine if there’s an underlying cause for the increased ANAs in your blood.