Lupus is an autoimmune disease. This means the immune system attacks the body's own cells. The ANA blood test detects autoantibodies that signal a number of autoimmune diseases.
The test has a range of uses. It is best as a diagnostic guide for doctors, who should use it while weighing up other factors such as symptoms.
Contents of this article:
What is the ANA blood test?
The ANA blood test measures antinuclear autoantibodies in the blood.
The ANA blood test may signal autoimmune diseases such as lupus, type 1 diabetes, and rheumatoid arthritis.
The test helps with the diagnosis of autoimmune diseases.
What are antinuclear autoantibodies?
Antinuclear autoantibodies (ANA) are antibodies that cause the immune system to attack the nucleus of the body's own cells.
The immune system's cells usually respond to antibodies. Antibodies are special proteins that enable immune cells to target and attack foreign cells and particles.
In this way, the immune cells can normally tell apart cells and particles that belong to the body and those that don't.
When immune cells attack the body's tissue, the antibodies triggering this are known as autoantibodies. These are what lie behind autoimmune diseases.
Antinuclear autoantibodies cause the immune system to attack the nucleus of a cell. This is the part of a cell that contains its genetic material.
The cell nucleus can be thought of as the cell headquarters, providing all the instructions for the cell.
What are autoimmune disorders?
Autoimmunity and autoimmune disorders are conditions in which the immune system is overactive. It attacks the body's own cells.
Normally, the immune system targets foreign material. In autoimmunity, autoantibodies react to antigens produced by the body itself.
A number of autoimmune conditions are linked to high levels of antinuclear antibodies. They may be grouped as ANA-associated rheumatic diseases, or AARD, including:
- Systemic lupus erythematosus (SLE) - often referred to simply as lupus
- Sjögren's syndrome - dry mouth and dry eyes caused by the immune system attacking the salivary and tear glands
- Systemic sclerosis - also called scleroderma, a thickening of the skin and other potential problems
- Mixed connective tissue disease - when there are a number of problems together, such as SLE and systemic sclerosis
- Raynaud's phenomenon - when extremities such as the fingers change color in the cold because of autoimmunity affecting blood flow
Lupus and the ANA blood test
Lupus is an autoimmune disorder that is much more common in women than men.
It is very rare for someone who has lupus to be negative for the antinuclear antibody blood test. A negative ANA blood test can give reassurance that a condition is not lupus.
The American College of Rheumatology say more than 95 percent of people who have lupus test positive for ANA. The means the test is very sensitive.
Not everyone who is ANA-positive has lupus. This means the test is not very specific. Some people who have antinuclear autoantibodies are actually healthy.
A diagnosis of lupus will need to be made based on symptoms and a physical examination, not just the autoantibody test.
Symptoms of lupus
Fatigue is a common symptom of lupus.
Symptoms of lupus are varied and can come and go. People's symptoms vary widely in how severe they are. Some have mild symptoms while others have severe ones.
While there are many possible lupus symptoms, the most common ones are:
- Fatigue - an extreme tiredness or loss of energy and there can be muscle pain and fever
- Pain in the feet or hands caused by joint inflammation - this is often worse in the morning
- Skin rash - this usually affects the face, hands, and feet
The rash on the face often has a typical appearance known as butterfly rash. This is the rash bridging across the nose and cheeks.
Lupus rash is often sensitive to the sun, so applying sunscreen is recommended.
What to expect from the ANA blood test
A blood test for ANA is done in the same way as any regular blood test.
Blood for the test is taken from a vein via a needle and syringe, or vial. The vein may be reached through the skin on the inside of the elbow or the back of the hand.
The needle prick is quick and usually only mildly painful. A successful blood sample should not result in anything more than a tiny wound.
It should be possible to return to normal activities after giving the blood sample.
Getting ready for the ANA blood test
The ANA blood test does not need any special preparation.
There is no need to avoid food and drink before giving the sample. People should still ask their doctor about whether to fast or not, however. This is because other tests may be done on the blood at the same time that do require fasting.
Several drug treatments can affect the level of antinuclear antibodies. Doctors need to be aware of any medications being taken before the sample is given.
ANA blood test for lupus screening
The antinuclear antibody test is very sensitive to lupus. Many experts believe the test is used too much, however.
The ANA test is not recommended for routine screening of lupus.
While this blood test is that it is good at confirming or ruling out a case of lupus when other factors are considered, it is not very specific. Without other factors such as symptoms being taken into account, a positive test could suggest another problem instead of lupus. Healthy people can also have a positive ANA test result without having an autoimmune disease.
Drugs may be administered to treat lupus, but there is no cure.
Lab analysis of ANA blood tests
Scientists analyze the blood sample for antinuclear autoantibodies. They do this by:
- Incubating the sample in cells that have large nucleuses
- Making the autoantibodies glow
- Using a special microscope to see the fluorescence
- Analyzing both the intensity and pattern of the glowing stain
- Different patterns can suggest alternate autoimmune disorders
What happens after a positive ANA test?
Getting a positive result for antinuclear autoantibodies may result in the diagnosis of an autoimmune disorder. If there is a positive result with no other signs or symptoms, it might be ignored.
Any medical process following a positive result depends on the overall picture. This determines what disorder, if any, there may be that explains the raised level of ANA.
If the result accompanies a set of symptoms and a history that gives a diagnosis of lupus, the doctors will manage the condition. It cannot be cured, though.
Drug treatments might include painkillers called nonsteroidal anti-inflammatories, or NSAIDs. Examples of these include ibuprofen and naproxen.
Other medications used against lupus include:
- Hydroxychloroquine or chloroquine - these reduce inflammation
- Corticosteroids - these also reduce inflammation
- Rituximab or Belimumab - if other treatments do not work, these inhibit immune cells