Looking at a long list of laboratory tests can feel like trying to decode a different language. Antinuclear antibody (ANA) testing is commonly used to narrow down potential diagnoses — especially for autoimmune diseases like lupus and Hashimoto’s disease.

While ANA tests are part of the diagnostic journey, they can’t confirm any specific health condition. Keep reading to learn more about how ANA testing differs between lupus and Hashimoto’s disease and how doctors use symptoms and other tests to diagnose these conditions.

What Is an ANA Test?

An ANA test measures specific immune proteins (antinuclear antibodies) in your blood. Your immune system makes antibodies to protect you against infections and foreign substances.

🗳️ Have you had an ANA test while being evaluated for lupus or Hashimoto’s disease?

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Autoantibodies mistakenly target your body’s own cells and tissues. Antinuclear antibodies specifically attack the nucleus inside your cells. The nucleus holds DNA and proteins.

Many people without any autoimmune disease can have some antinuclear antibodies in their bloodstream. This is because other factors can also trigger your immune system to make ANA, such as:

According to a study in the journal Reumatologia, ANAs can also be present in the blood of some healthy people, especially women and older people. However, high ANA levels can point to health problems, like autoimmune diseases. A positive ANA test is only the first step, though. By itself, it can’t diagnose a specific health condition. You need other tests to find out what’s happening.

Autoimmune diseases that cause ANA positivity include:

ANA Test for Lupus

An ANA test may be the first step in diagnosing SLE. Over 95 percent of people with lupus have a positive ANA test. However, only 11 percent to 13 percent of those who do test positive actually have lupus. This means doctors need other tests to make an official lupus diagnosis.

Since most people with lupus have a positive ANA test, a negative test can help rule out the diagnosis. However, you can still have lupus without antinuclear antibodies.

ANA Test for Hashimoto’s Disease

In Hashimoto’s disease, your immune system creates proteins known as autoantibodies that target your thyroid tissue, causing it to attack your thyroid. This causes inflammation and damages your thyroid.

People with Hashimoto’s disease can also have a positive ANA test. A study of 154 people with autoimmune thyroid disease showed that 17.5 percent of people were positive for ANAs, while in another study 35 percent had positive ANAs. One small study of 32 people with Hashimoto’s thyroiditis showed that 47 percent had positive ANAs.

Higher levels of other autoantibodies against thyroid tissue mean that you’re more likely to have antinuclear antibodies too. Examples of these autoantibodies include:

Hashimoto’s disease doesn’t always cause high ANA. Instead, people are usually positive for anti-Tg and anti-TPO antibodies.

Tests That Help Identify Hashimoto’s

Antinuclear antibodies may not be seen in people with Hashimoto’s disease. Remember, you can have an autoimmune disease without a positive ANA test. Instead, your symptoms and other blood tests will help make a diagnosis.

Signs and Symptoms of Hashimoto’s Disease

Most people with Hashimoto’s disease have hypothyroidism, or low levels of thyroid hormones. Without enough hormones, your body can’t function normally. In rare cases, Hashimoto’s thyroiditis may cause hyperthyroidism, or high levels of thyroid hormones.

It can be hard to diagnose Hashimoto’s at first because many people don’t have any symptoms. As your thyroid hormone levels keep falling, you may notice:

Other Tests for Hashimoto’s Disease

If you have symptoms of Hashimoto’s disease, your doctor will likely order blood tests. These tests usually confirm whether you have the disease.

Some blood tests look for autoantibodies seen in Hashimoto’s disease, such as anti-TPO, anti-Tg, and anti-TSH receptor autoantibodies.

Because Hashimoto’s damages the thyroid gland, your hormone levels change. High TSH and low thyroxine (T4) levels often point to hypothyroidism. This is because the brain signals to the thyroid to make more TSH. However, the damaged thyroid can’t use TSH to make more T4, the main thyroid hormone.

An enlarged thyroid can be a sign of Hashimoto’s disease — but other conditions can affect its size. An ultrasound takes pictures of the thyroid gland to find out why it may be abnormally large. Thyroid nodules, or small bumps in the tissue, can also cause a goiter.

When a Positive ANA Test Needs Further Evaluation

Getting a positive ANA test can be alarming, and it can leave you wondering what’s next for your health. Remember, some people have antinuclear antibodies in their blood, even if they don’t have an autoimmune disease.

It’s a good idea to follow up with your doctor if you have high ANA levels and signs of an autoimmune disease. They can run more tests for lupus or other autoimmune conditions to rule out potential causes.

The sooner you get the right diagnosis, the better you can treat inflammation and prevent lasting damage. Lupus and Hashimoto’s disease have different treatment plans to control your symptoms and protect your body.

Talk to Your Doctor About Your ANA Test Results

If you recently had an ANA test and want to learn more about your results, talk to your doctor. It’s best not to try to interpret the results yourself — they can be confusing, and you may come to the wrong conclusion.

There’s plenty of information available on the internet, but your doctor knows your health history best. They can help you better understand your ANA test results in the context of your own health.