The immune system produces antibodies that fight unwanted invaders to keep the body healthy.
Sometimes, however, the system goes wrong, and it incorrectly identifies an individual's own tissue as a threat and attacks it.
Lupus is an autoimmune disease, which means that it involves the immune system attacking the body's cells.
A doctor can test for antinuclear autoantibodies (ANAs) in the blood, and if they are present, a person may have an autoimmune disease.
When making a diagnosis, a doctor will consider the test result and a range of other factors, including the person's medical history and symptoms.
In this article, we describe what a person receiving the ANA blood test can expect and when the test is necessary.
What is the ANA blood test?
This test measures levels of ANAs in the blood, and a positive result can point to an autoimmune disease.
What are ANAs?
A doctor carries out the ANA blood test as they would any other blood test.
These antibodies cause the immune system to attack the nuclei, or processing centers, of the body's own cells and tissues.
Antibodies are proteins that instruct immune cells to target and attack foreign cells and particles.
The cells of the immune system usually respond to antibodies, and this allows the immune cells to distinguish between particles that belong to the body and others that may cause harm.
Antibodies that trigger the immune system to attack the body's own tissue are called autoantibodies. These are the basis of autoimmune diseases.
ANAs cause the immune system to attack the nucleus of a cell, which contains its genetic material.
A person with a high level of ANAs may have an autoimmune condition. Doctors sometimes call these conditions ANA-associated rheumatic diseases.
- systemic lupus erythematosus, or lupus
- Sjogren's syndrome, in which the immune system attacks the salivary and tear glands, leading to dryness in the mouth and eyes
- systemic sclerosis, or scleroderma, which causes thickening of the skin and potentially other issues
- mixed connective tissue disease, in which a number of autoimmune problems occur together, such as lupus and systemic sclerosis
- Raynaud's phenomenon, in which the autoimmune process affects the blood flow and extremities, such as fingers, change color in cold temperatures
Lupus and the ANA blood test
Lupus is much more common among women than men.
An ANA test will often give a positive result in a person with this autoimmune disease. A negative ANA test is often confirmation that an individual does not have lupus.
The American College of Rheumatology report that more than 95 percent of people with lupus test positive for ANA. As a result, doctors consider the test to be highly sensitive for this condition.
Not everyone with a positive ANA result has lupus, however. A person can have ANAs in the bloodstream without having an autoimmune disorder.
To make a diagnosis, a doctor will also need to consider a person's symptoms and perform a physical examination.
Symptoms of lupus
Symptoms vary in type and severity, and they can be intermittent.
The most common include:
- Fatigue: Lupus often causes extreme tiredness and a loss of energy.
- Pain in the feet or hands: This results from joint inflammation, and it is often worse in the morning. Lupus can also cause muscle pain and a fever.
- Skin rash: The rash that characterizes lupus usually affects the face, hands, and feet.
On the face, the rash often appears across the nose and cheeks. Medical professionals refer to this as butterfly rash.
A lupus rash is often sensitive to the sun, so applying sunscreen is important.
What to expect
An ANA test is like any regular blood test.
The healthcare professional will take a blood sample using a needle and syringe or vial, often via a vein on the inside of the elbow or the back of the hand.
Usually, the needle prick is quick and only mildly painful, but it may leave a tiny wound.
A person will likely be able to return to regular activities after giving the blood sample.
Getting ready for the ANA blood test
Confirm any necessary preparations for the ANA blood test with a doctor ahead of time.
A person does not need to make any special preparation, such as avoiding food or drink, before giving the blood sample.
However, it is important to confirm this ahead of time. The doctor may also be performing other blood tests that do require fasting.
Several medicines can affect ANA levels. The healthcare provider should be aware of any current medications before taking the sample.
The ANA test is very sensitive to lupus, but a positive result does not necessarily mean that the person has the condition.
The test can guide a diagnosis when considered with other factors, such as a person's symptoms, but medical professionals do not recommend the test for routine screenings.
The ANA test can also give a false-negative result. A person may have a negative result but still have lupus, especially the disease is in the early stages.
Lab analysis of ANA blood tests
To check the blood sample for ANAs, a scientist will:
- incubate the sample in cells with large nuclei
- make the autoantibodies glow
- use a specialized microscope to see the fluorescence
- analyze both the intensity and pattern of the glowing stain
Different patterns can suggest different autoimmune disorders.
A positive result on an ANA test may help a doctor to diagnose an autoimmune disorder.
However, if after a positive result neither the person nor the doctor recognizes any signs or symptoms, the medical team may disregard the result.
The steps that follow a positive result depend on the person's overall health. Their symptoms will help determine the cause of the ANA levels.
If the result accompanies a set of symptoms and a medical history that confirm a lupus diagnosis, the doctor will advise the individual about how to manage the condition. There is currently no cure for lupus.
Drug treatments may include painkillers called nonsteroidal anti-inflammatory drugs. Examples of these include ibuprofen and naproxen.
Other medications that can help manage lupus symptoms include:
- hydroxychloroquine or chloroquine, for reducing inflammation
- corticosteroids, which can also soothe inflammation
- rituximab or belimumab, more powerful treatments that inhibit immune cells if anti-inflammatory medications do not have the desired effect
People with lupus can have full, active lives with the appropriate medical management.
The ANA test is a highly sensitive but nonspecific test that can help rule out autoimmune conditions such as lupus.
A doctor administers the test in a very similar way to other blood tests, and the person does not need to make special preparations.
While doctors often use the test to confirm a diagnosis of lupus, it can provide false-negative and -positive results.
Confirming any diagnosis requires a doctor to gain a thorough understanding of a person's symptoms and medical history.
Does a negative ANA mean that I definitely do not have lupus?
Unfortunately, a negative ANA test does not guarantee that you do not have lupus. The ANA test is reported to have a false negative rate of about 5 percent.
However, most people who do have lupus and initially test negative will go on to test positive at a later date. It is important to know that a diagnosis of lupus should never be based solely on an ANA test, but an ANA test should be used to support a diagnosis made based on clinical signs.Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.