What Diseases Can Cause a Positive ANA?

An antinuclear antibody (ANA) test shows signs of autoimmune disease. Diseases that may cause a positive ANA include scleroderma, rheumatoid arthritis, thyroid disease, and other conditions.

If your doctor has ordered an antinuclear antibody (ANA) test, it's because they’re looking for signs of an autoimmune disease. These are diseases where your body’s immune system attacks some of your healthy cells. 

These tests are also called fluorescent antinuclear antibody (FANA) tests. 

One of the main diseases that this test is used to detect is lupus. More than 95% of people with lupus have a positive ANA result. 

There are, however, many other types of autoimmune diseases that this test could detect. Examples include: 

• Scleroderma
• Rheumatoid arthritis
• Mixed connective tissues disease
• Myositis — an inflammatory muscle condition
• Thyroid disease
• Autoimmune hepatitis
• Lymphomas
• Inflammatory bowel disease 

The white blood cells that are part of your immune system produce molecules called antibodies. Antibodies patrol your body looking for harmful, disease-causing agents — like viruses and bacteria. When they find something potentially dangerous, they summon other parts of your immune system and mount an attack. This creates an inflammatory response. 

Sometimes, though, your antibodies make mistakes and attack your own healthy proteins. This still triggers your immune system’s inflammatory response. Over time, this will damage your tissues and joints. It can cause a number of different symptoms depending on the underlying reason for the attack.   

Antibodies that attack your own body are called autoantibodies. Antinuclear antibodies are autoantibodies that specifically attack proteins in your cells’ nuclei.  

Almost all types of cells in your body have nuclei. Nuclei act as control centers in your cells. They also store your genetic information in the form of DNA. 

Many different proteins are involved with the nucleus. For example, some directly interact with the DNA, and others are found on the nuclear membrane. Any of these proteins could be the target of an autoantibody attack.

An ANA is a blood test. There are different ways to perform this test. 

One way is for your doctor or medical technician to dilute the liquid parts of your blood with a combination of salt and water called saline. This allows them to see how far they can dilute your sample and still get a positive reading. Different hospitals have different cutoff levels for the amount of dilution that can precede a positive result. 

In possible cases of FANA, your antibodies are labeled with a fluorescent tag. This makes them visibly glow under the right conditions. Both the intensity and pattern of fluorescence will give your medical team information about what your autoantibodies are doing.  

If your results are positive for the presence of antinuclear antibodies, then there are panels available — called antinuclear antibody panels — that can help your medical team pinpoint what proteins are involved in this autoimmune response.   

There is some flexibility affecting how your doctor interprets the results of your test. The ANA is often used as a jumping-off point for further tests as your medical team works toward an accurate diagnosis.  

The only risks associated with this test come from drawing your blood. This is easier in some people than it is in others. Potential risks associated with drawing your blood include: 

• Soreness where the needle was inserted
• Feeling lightheaded
• Fainting
• Excessive bleeding
• Blood accumulation beneath your skin — called a hematoma
• Infection — unlikely, but possible whenever there’s a break in your skin  

Each autoimmune disease has unique symptoms. Other symptoms are present in most autoimmune conditions. This could be because the presence of antinuclear antibodies contributes to some of these more common symptoms. 

Symptoms that could cause your doctor to order an ANA or FANA include: 

• Fever
• Joint pain
• Weight loss
• Skin rashes
• Tiredness 
• Chest pain

This test cannot definitively tell you that you have an autoimmune disease. The only thing that this test can tell you is whether or not you have detectable levels of antinuclear antibodies in your blood. 

On a positive note, if your results are negative, it’s very unlikely that you have lupus. 

Your doctor will need to evaluate the ANA results within the context of your current symptoms, health history, and family health history to continue with the diagnostic process. 

A positive result does not automatically mean that you have an autoimmune disease. You’ll likely need to undergo a slew of other tests if your ANA results come back positive. Autoimmune diseases can have very different effects on your body, so they require a wide range of tests. 

Your next steps will likely be based on the symptoms that you have and the conditions that may have caused those symptoms. Keep in mind, though, that some autoimmune diseases are easier to diagnose than others. Still, a positive ANA is a good first step to an accurate diagnosis. 

A positive result is not necessarily a cause for alarm. The results could be a false positive. 

Even if the test does pave the way to an autoimmune diagnosis, many of these conditions are treatable.  

Sometimes your ANA test results can come back positive even when you don’t have an autoimmune disease. This can happen to 3% to 15% of healthy people tested. These people simply have higher levels of antinuclear antibodies for a different reason. 

Certain factors make a false positive more likely to happen. These factors include: 

• Being older than 65 — your odds of having ANAs without an underlying health problem increase anywhere from 10% to 37% after this point
• Having cancer
• Having a current viral infection
• Having a chronic infection
• Being on certain medications 

In the case of a false positive, your doctor won’t be able to pinpoint any further signs of autoimmune disease because you don’t actually have one. Following careful analysis, they should be able to figure out that the test was a false positive. 

To cut down on the risk of getting a false positive, tell your doctor or healthcare provider if you know that you have a long-term infection. Some infections that can trigger a positive result on an ANA include: 

• Hepatitis C
• HIV
• Parvovirus

Also make sure that they’re up-to-date on all of the medications, recreational drugs, and supplements that you’re taking.