All you need to know about the ANA blood test

The Antinuclear Antibody (ANA) Blood Test is an important tool for investigating autoimmune disorders. But it’s not suitable for everyone. There are lots of reasons antinuclear antibodies may be raised, which are unrelated to autoimmune disease. So, a positive result can sometimes lead to unnecessary worry and further investigations. 

So, when is it useful to take an ANA blood test and what do the results mean?

In this article, we cover:

• What is an ANA blood test?
• Do I need an ANA blood test?
• How can I check my ANA levels?
• How accurate is an ANA blood test?
• Is an ANA blood test useful for monitoring lupus?
• What causes a positive ANA result?
• What do my results mean?
• What should I do if my results are positive?
   

What is an ANA blood test?

An antinuclear antibody test measures the presence of antinuclear antibodies in your blood. ANAs are made by the body when your immune system mistakenly attacks the nuclei of your cells – hence, the name antinuclear.

ANAs can indicate an immune response and may point to various conditions, such as lupus or rheumatoid arthritis. These conditions are sometimes called autoimmune conditions or connective tissue diseases. But ANA results are sometimes positive in healthy people.

ANA results are usually reported as a titre, which tells you the concentration of antibodies in your blood.
 

Do I need an ANA blood test?

Whether an ANA blood test is right for you will depend on your pre-test probability. This is the likelihood of having a disease, based on your symptoms, examination, and risk factors.

Symptoms of autoimmune conditions are often non-specific and could be due to many other causes. For example, fatigue is a very common symptom, but it may be due to lack of sleep, an unhealthy lifestyle, or stress. Or there are other medical causes of tiredness. 

The ANA blood test is most valuable for people who have more specific symptoms or multiple symptoms of autoimmune disease.

More specific signs and symptoms of an autoimmune condition include [1]:

• A photosensitive skin rash
• Joint pain and inflammation
• Alopecia (hair loss)
• Raynaud’s phenomenon
• Dry mouth and eyes
• Recurrent miscarriages
• Frequent mouth ulcers
• Fluid around the heart and lungs which may cause shortness of breath
• Enlarged lymph nodes
• Anaemia or low platelets

Having risk factors for connective tissue disease can also increase your pre-test probability. 

Risk factors for connective tissue disease include:

• Your sex – women are much more likely to develop an autoimmune condition than men.
• Family history – autoimmune conditions are more likely if a close relative is also affected.
   

How can I check my ANA levels?

You can take a test from home with our Antinuclear Antibodies ANA Blood Test.
 

How accurate is an ANA blood test?

ANA blood tests are non-specific. This means that around three in ten healthy people will receive a positive result, even though they do not have an autoimmune condition. This is called a false-positive result and is one of the main drawbacks of the test.

False-negative results are also possible, but less likely. This is when a person with an autoimmune condition receives a negative result. This occurs in about one in 20 cases.
 

Is an ANA blood test useful for monitoring lupus?

No. An ANA blood test may be useful in diagnosing lupus, but it’s not useful for monitoring disease activity or flares. The best tests to monitor lupus are erythrocyte sedimentation rate (ESR), anti-dsDNA antibodies, and complement levels [1].
 

What causes a positive ANA result?

If ANAs are detected beyond a certain threshold, you’ll receive a positive result. But having a positive result doesn’t mean you have a disease. Around three in ten people without disease will receive a positive result [1]. This is most common in women over 65.

However, the presence of ANAs is associated with several conditions, from autoimmune conditions and infections to cancer [2].

Autoimmune conditions that may cause a positive ANA result include:

• Systemic lupus erythematosus (SLE or lupus)
• Sjögren’s disease
• Rheumatoid arthritis
• Scleroderma
• Mixed connective tissue disease
• Polymyositis or dermatomyositis

Organ-specific autoimmune disease that may cause a positive ANA result include:

• Thyroid disease (such as Hashimoto’s thyroiditis or Graves’ disease)
• Liver or bowel disease (such as autoimmune hepatitis, primary biliary cholangitis, or inflammatory bowel disease)
• Lung disease (idiopathic pulmonary fibrosis)

Drugs that may cause a positive ANA result include [3]:

• Blood pressure and heart medications (such as hydralazine and methyldopa)
• Anti-fungal treatments (terbinafine)
• Tuberculosis treatment (isoniazid)
• Anti-seizure medications (phenytoin)
• Schizophrenia medications (chlorpromazine)

Other causes of a positive ANA result include:

• Cancer (though this is rare)
• Chronic infections (such as hepatitis C, glandular fever, tuberculosis, and schistosomiasis)

A positive ANA result may mean you’re more likely to develop an autoimmune condition in the future or that you have a relative with an autoimmune disease. 
 

What do my results mean?

ANA results are often given as a titre (the amount of ANA detected) and the staining pattern.

Titres

If ANAs are detected, the lab will continue diluting the sample until it is no longer detectable. The higher the titre, the more likely it is to represent a true positive result. For example, a result of 1:1280 shows a strongly positive result, whereas 1:160 shows a weaker positive result.

Likelihood of a true positive result [3]:

• A result of 1:40 occurs in 20–30% of healthy individuals
• A result of 1:80 occur in 10–15% of healthy individuals
• A result of 1:160 occur in 5% of healthy individuals
• A result of 1:320 occur in 3% of healthy individuals

Another method of testing is to measure the intensity of fluorescence, which is usually measured in IU/ml.

Staining patterns

Different staining patterns give clues to the significance of ANA and the type of disease.

Common staining pattens and their associations [4]:

• Homogenous – SLE, mixed connective tissue disease, drug-induced lupus
• Speckled – SLE, Sjögren’s disease, polymyositis/dermatomyositis, scleroderma
• Nucleolar – scleroderma, polymyositis
• Centromere – scleroderma
• Peripheral – SLE, scleroderma

It’s important to remember that your ANA results are not enough to make a diagnosis. But they can give you helpful clues.
 

What to do if your result is positive

If you think you have an autoimmune disease or if you have a positive ANA result, it’s best to discuss this with your doctor. They may need to arrange further tests.

If you have taken a test with Medichecks, our doctors will advise you on what to do next.
 

References

1. Binder A, Ellis S. When to order an antinuclear antibody test. BMJ. 2013;347: f5060. doi:10.1136/bmj.f5060
2. Patient education: Antinuclear antibodies (ANA) (Beyond the Basics) - UpToDate. [cited 4 Aug 2023].
3. Chee M. When to check antinuclear antibodies. NHS; 2020.
4. Practitioners TRAC of general. Antinuclear antibody test. In: Australian Family Physician [Internet]. The Royal Australian College of general Practitioners; [cited 4 Aug 2023].