Overview
The extractable nuclear antigen test, known as an ENA test, is a blood test that checks for proteins in your blood, also known as antibodies. The ENA test is used to help diagnose certain autoimmune diseases. ENA stands for extractable nuclear antigen because these proteins can be taken out (extracted) from the cells in the body.
These antibodies are types of autoantibodies. Autoantibodies are made by the immune system which helps your body fight off bacteria and viruses. Autoantibodies mistakenly target and attack the body's own healthy tissues.
The ENA test is sometimes called an ENA panel. This is because the ENA test is a panel of 4 to 6 blood tests taken from a blood sample. Each ENA panel checks for different autoantibodies.
The ENA test can be a step that your health care team uses to diagnose diseases where the body's immune system attacks healthy tissues, called autoimmune diseases.
Why it's done
Your health care professional may refer you to a doctor trained in autoimmune and arthritis conditions, called a rheumatologist. If the rheumatologist thinks you may have an autoimmune disease, they may order some additional tests.
ANA test
An antinuclear antibodies test, known as an ANA test, finds antinuclear antibodies in the blood. The immune system usually makes antibodies to help the body fight infection. In contrast, antinuclear antibodies often attack the body's own tissues. If your rheumatologist suspects you have an autoimmune disease, you may need an ANA test to get more information. A positive ANA test result means you have antinuclear antibodies, while a negative test means that you don't have them.
ENA test
The ENA test is often used as a follow-up test after a positive ANA test. The ENA test can be the next step in finding out if you have an autoimmune disease and which one you have.
If you have a positive ANA test, an ENA test can check the blood for the presence of antinuclear antibodies that are known to be markers of certain diseases.
The ENA test can help your health care team and your rheumatologist diagnose autoimmune diseases such as:
- Lupus. This also is known as systemic lupus erythematosus. The most common symptoms are fatigue, fever and weight loss. Lupus can affect the joints, skin, kidneys, blood cells, brain, heart and lungs. Lupus often causes a facial rash that resembles the wings of a butterfly.
- Mixed connective tissue disease. Early symptoms of this disease often involve the hands. But symptoms can be the same as those for other autoimmune disorders, making it difficult to diagnose this disease. Many people with this disease also have Sjogren's syndrome.
- Sjogren's syndrome. This condition often happens in people who have other immune system disorders. Its two most common symptoms are dry eyes and a dry mouth.
- Scleroderma. This also is known as systemic sclerosis. It is a group of rare diseases that cause hardening and tightening of the skin. It also may cause problems in the blood vessels, organs and digestive system.
- Polymyositis and dermatomyositis. People who have other autoimmune diseases are at higher risk of developing these diseases. Symptoms of polymyositis and dermatomyositis include muscle weakness and skin rash.
If you're diagnosed with an autoimmune disease, your health care team may use the ENA test in the future to check how the disease changes over time.
How you prepare
An ENA test uses a blood sample. If your health care team is only using the blood sample for an ENA test, you can eat and drink as usual before the test. If the blood sample may be used for more tests, you might need to not eat, called fast, for a time before the test. Your health care team will give you directions before the test.
Some medicines can affect the test and can cause the test results to show you have autoantibodies when you don't. So bring your health care team a list of the medicines and supplements you take.
What you can expect
For an ENA test, a member of your health care team takes a blood sample by inserting a needle into a blood vessel, called a vein, in your arm. The blood sample goes to a lab for testing. You can return to your usual activities right away.
Results
Your ENA test is positive if test results show the blood sample has autoantibodies. Your rheumatologist can use a positive ENA test result, along with a physical exam and other tests, to see if you have certain autoimmune diseases.
ENA test results can be hard to understand. Generally, an expert should review the results. It's important to talk about the results with your rheumatologist and ask any questions you may have.