Summary

• Antinuclear antibodies (ANA) are autoantibodies made by the immune system that mistakenly attacks healthy cells, especially the cell nucleus.
• An ANA test is mostly used as a screening tool for systemic autoimmune diseases and is not used to monitor disease activity.
• ANA results alone cannot diagnose an autoimmune disease.
• ANA can also be positive in healthy people, infections, drugs, and cancers, and some people with autoimmune disease can have a negative ANA.
• A positive ANA test may indicate a need for more specific antibody tests and further clinical evaluation to make a diagnosis.

What are antinuclear antibodies?

Your immune system protects you by making antibodies that fight harmful things such as bacteria and viruses. Sometimes, the immune system mistakenly produces antibodies that attack your own body. These are called autoantibodies.

ANA are autoantibodies that attack the nucleus of healthy cells. Having them in your blood can indicate an underlying autoimmune process.

There are many types of autoimmune disorders, each affecting the body differently, and symptoms can take months or even years to appear. ANA can be present without symptoms or inflammation. Many healthy people have low levels of ANA. They generally increase with age (especially over 65) and are more common in females. Infections, and cancers as well as some medications can cause higher levels of ANA. High levels are more likely to be associated with autoimmune disease. Although ANA is useful for diagnosis, its levels do not necessarily reflect disease severity over time.

Why get tested?

ANA testing is mainly used as a screening test in the diagnosis of systemic autoimmune rheumatic diseases. These include systemic lupus erythematosus (SLE), scleroderma, Sjögren's disease (SjD, formerly Sjögren’s syndrome), rheumatoid arthritis (RA), juvenile idiopathic arthritis (JIA), autoimmune hepatitis (AIH), idiopathic inflammatory myopathies (IIM) and mixed connective tissue disease (MCTD).

Most people with SLE or scleroderma have a positive ANA result, so a negative ANA test may help rule out these conditions. Certain ANA patterns (see Results) may also help distinguish subtypes of scleroderma. More than 80 per cent of people with SjD have a positive ANA.

ANA can also be used to check drug-caused autoimmune reactions. Some medications may trigger symptoms similar to SLE, known as drug-induced lupus (DIL). Symptoms usually go away once the medication is stopped.

It is important to note that only about 10 to 15 per cent of people with a positive ANA are eventually diagnosed with an autoimmune disease. ANA should only be ordered when a person has symptoms suggestive of a systemic rheumatic disease, such as unexplained joint/muscle pain, fatigue, rashes or inflammation. It is not recommended as a routine screening test in people without symptoms.

A positive ANA result may indicate a need for more specific antibody tests, such as anti-double-stranded DNA, anti-histone, anti-extractable nuclear antigen, rheumatoid factors, myositis specific antibodies or liver autoantibodies.

Diagnosis of autoimmune diseases is based on:

• Clinical symptoms
• Multiple laboratory tests
• Inflammatory markers
• Imaging (if needed)

Having the test

Sample

Blood.

Any preparation?

None.

Your results

ANA results are usually reported as a titre and a staining pattern if immunofluorescence technique is used.

Titre (dilution of blood)
A titre tells you how concentrated the antibody is. Instead of giving a direct concentration, the lab measures how far the blood can be diluted and still show a positive reaction. The result represents the amount of antibodies seen in the test sample, with higher titres indicating more antibodies.

A titre of 1:160 or higher is often considered positive, while lower titres (1:40 or 1:80) can be seen in healthy people.

Pattern (staining pattern)
This indicates how antibodies appear under a microscope when stained. The pattern suggests which specific antibodies may be present and helps guide further testing. Some patterns are associated with specific autoimmune diseases:

An example of what a positive result might look like:

Test: ANA by IIF (Indirect Immunofluorescence)
Result: Positive
Titre: 1:320
Pattern: Homogeneous
Reference Intervals: Titre – less than1:80

Notes on results

A negative ANA result means that ANA were not detected at the laboratory’s screening titre. This makes s systemic autoimmune rheumatic disease less likely.

However, a negative result does not completely rule out autoimmune disease. Repeat testing if there is a strong clinical suspicion, as autoantibodies can take years to appear. In most cases, a negative result usually does not require additional antibody testing unless clinically indicated. Some rare autoantibodies may not be detected by ANA test. More specific autoantibody tests may still be appropriate if symptoms strongly suggest autoimmune disease.

A positive ANA result only indicates the presence of autoantibodies that can target the body’s own cells. It does not confirm an autoimmune disease. An ANA test may be positive before symptoms develop. Some autoimmune diseases, such as SLE, can take months or years to diagnose because symptoms may come and go.

• Positive ANA result can also be found in healthy people, infections, thyroid disorders, drugs and cancers.
• A higher titre (e.g., 1:320 or 1:640) is more likely to be clinically relevant than a lower titre (e.g., 1:80 or 1:160).
• Follow-up antibody testing is needed if symptoms suggest autoimmune disease.
• Repeating the ANA test is generally not useful for monitoring disease activity.
• ANA levels can vary widely among individuals with the same autoimmune disease, like SLE.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.

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