ENA Panel
An extractable nuclear antigen (ENA) panel is a blood test that identifies antibodies against proteins in your body’s cells. These antibodies mistakenly identify your own body’s cells as harmful, causing your immune system to destroy them. Healthcare providers use an ENA panel to diagnose autoimmune diseases, like lupus and Sjögren’s syndrome.
What is an ENA panel?
An ENA (extractable nuclear antigen) panel is a blood test that looks for antibodies that cause your immune system to attack healthy parts of your body. It can help your healthcare provider diagnose or rule out autoimmune diseases.
Antibodies are a part of your immune system that identify and help your body fight off harmful pathogens (germs), like viruses and bacteria. Autoimmune diseases cause your body to make antibodies that mistakenly attack proteins that are part of your body’s natural functions. These proteins have identifiable markers on them called antigens that the antibodies attack.
When do you have to get an ENA?
Your provider might order an ENA panel if you test positive on an antinuclear antibody test (ANA) and you have symptoms of an autoimmune disorder.
If you’re pregnant and have a lupus diagnosis, your provider may recommend you get one or more tests from an ENA panel. This can help monitor for neonatal lupus, a condition where your antibodies pass through the placenta to the fetus. Neonatal lupus can lead to complications with the fetus, including heart block.
What diseases does an ENA panel test for?
The antibodies that an ENA panel tests for are most commonly associated with:
- Lupus (systemic lupus erythematosus/SLE).
- Sjögren’s syndrome.
- Mixed connective tissue disease (MCTD).
- Scleroderma/systemic sclerosis.
- Polymyositis.
- Dermatomyositis.
How does an ENA panel work?
A lab technician will use a sample of your blood to run an ENA panel. They’ll use special markers that attach to the antibodies they’re looking for. The markers “light up” or change color so the lab can see them.
What antibodies does an ENA panel test for?
An ENA panel usually looks for four to six antibodies that react to antigens in your cells. Each antibody is associated with autoimmune diseases and other conditions (shown in the table here).
| Antibody | Also called | Most commonly seen in |
|---|---|---|
| Anti-SSA | Anti-Ro | Sjögren’s syndrome, systemic lupus. Anti-Ro antibodies are also sometimes seen in neonatal lupus, cutaneous lupus, scleroderma, idiopathic inflammatory myopathies and primary biliary cholangitis (PBC). |
| Anti-SSB | Anti-La | Sjögren’s syndrome, lupus. Anti-La antibodies are also sometimes seen in neonatal lupus, scleroderma, dermatomyositis, polymyositis, PBC and autoimmune hepatitis. |
| Anti-Smith | Anti-Sm | Lupus, MCTD. |
| Anti-RNP | – | MCTD, lupus (SLE), discoid lupus erythematosus, scleroderma. |
| Anti-Scl-70 | – | Scleroderma, lupus. |
| Anti-Jo-1 | – | Polymyositis, dermatomyositis, ILD. |
How do I prepare for an ENA panel?
You don’t need to do anything to prepare for an ENA test. You can eat and take medications as you usually would.
What should I expect during an ENA panel?
A provider will use a small needle to take a sample of your blood from your arm. You might feel pain or discomfort briefly when the provider inserts and removes the needle. If you’re afraid of needles, it helps to look away. The provider will send the sample to a lab to perform the test.
What are the risks of an ENA panel?
There are minimal risks of an ENA panel. Sometimes, a provider might need to stick your skin with the needle multiple times to find a vein, which can feel unpleasant. Blood draws also carry slight risks of:
- Feeling lightheaded or fainting.
- A large bruise or blood collecting under your skin (hematoma).
- Infection.
- Excessive bleeding.
What type of results do you get with an ENA panel and what do the results mean?
Results might be negative, positive or borderline (also called equivocal). Normal ranges might vary according to the lab that performs the test. Your lab report should include a reference range along with your result.
A positive result means the test detected the antibody in your blood. A negative result means no antibodies or very few antibodies to specific antigens were detected in your blood.
Does a positive ENA mean I have lupus?
No one result on an ENA test means you have a specific disease, like lupus. For instance, people with Sjögren’s syndrome are often positive for anti-SSA and anti-SSB antibodies, but they can also be positive in someone with lupus or other conditions. Your provider will look at your ENA panel, your symptoms and other test results to make a diagnosis.
When should I call my doctor?
Contact your provider if you have any questions about the results of your test. Go to the ER if you have signs of infection, including pain, swelling, pus or fever.
References
- Buvry C, Cassagnes L, Tekath M, et al. Anti-Ro52 antibodies are a risk factor for interstitial lung disease in primary Sjögren syndrome. (https://pubmed.ncbi.nlm.nih.gov/32056839/) Respir Med. 2020 Mar;163:105895. Accessed 4/3/2023.
- Laboratory Diagnosis: Chemistry, Immunology, Serology. In: Gomella LG, Haist SA, eds. Gomella and Haist’s Clinician’s Pocket Reference. 12th ed. McGraw Hill; 2022.
- Yoshimi R, Ueda A, Ozato K, Ishigatsubo Y. Clinical and pathological roles of Ro/SSA autoantibody system. (https://pubmed.ncbi.nlm.nih.gov/23304190/) Clin Dev Immunol. 2012;2012:606195. Accessed 4/3/2023.
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