Share this page
Print this article
Was this page helpful?

ENA Panel

Also known as: Antibodies to Saline-extracted Antigens; anti-RNP; anti-ribonucleoprotein; anti-SSA; SSA (Ro); anti-Sjögren Syndrome A; anti-SSB; SSB (La); anti-Sjögren Syndrome B; anti-Sm; Smith antibody; Scl-70; anti-topoisomerase; Scleroderma antibodies; anti-Jo-1
Formal name: Extractable Nuclear Antigen Antibodies
Related tests: ANA; Autoantibodies; Anti-dsDNA

At a Glance

Why Get Tested?

To help diagnose and distinguish between autoimmune disorders

When to Get Tested?

When your ANA (Antinuclear Antibody) test is positive; when you have symptoms that suggest an autoimmune disorder

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

The Test Sample

What is being tested?

An ENA (Extractable Nuclear Antigen Antibodies) panel detects the presence of one or more specific autoantibodies in the blood. Autoantibodies are produced when a person's immune system mistakenly targets and attacks the body's own tissues. This attack can cause inflammation, tissue damage, and other signs and symptoms that are associated with an autoimmune disorder.

ENA are a subset of antinuclear antibodies (ANA), antibodies directed against proteins found in the nucleus of cells. Certain autoimmune disorders are characteristically associated with the presence of one or more extractable nuclear antigen antibodies. This association can be used to help diagnose an autoimmune disorder and to distinguish between disorders.

The ENA panel is typically a group of 4 or 6 autoantibody tests. The number of tests offered will depend on the laboratory and the needs of the doctors and patients it serves. ENA panel tests, and other less common ENA tests, can also be ordered separately.

A 4-test ENA panel will include:

Autoantibody Also Known As
Anti-RNP Anti-U(1)RNP, Anti-Ribonucleoprotein
Anti-Sm Smith Antibody
Anti-SS-A (Ro) Anti-Sjögren Syndrome A
Anti-SS-B (La) Anti-Sjögren Syndrome B

A 6-test ENA panel will add:

Autoantibody Also Known As
Scl-70 Scleroderma Antibodies; anti-topoisomerase
Anti-Jo-1 Antihistidyl Transfer RNA Synthase Antibodies

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

How is it used?

The ENA panel is usually ordered following a positive ANA test in people who have clinical signs of an autoimmune disorder. The 4-test ENA panel is used to help diagnose mixed connective tissue disease (MCTD), systemic lupus erythematosus (SLE), and Sjögren syndrome. The 6-test ENA can also help identify scleroderma and polymyositis.

For more on these diseases, visit the American Autoimmune Related Diseases Association web site.

An ENA panel may also be ordered if a doctor suspects that a person with a known autoimmune disorder has developed an additional disorder.

^ Back to top

When is it ordered?

An ENA panel is ordered when a person has symptoms that could be due to an autoimmune disorder AND has a positive ANA test, especially when the ANA presents as a "speckled" fluorescent pattern. Signs and symptoms of autoimmune disorders are highly variable and can involve several different areas of the body. They may include:

In most cases, an ENA panel will not be ordered when a person has a negative ANA test.

The ENA panel, or one or more of its component tests, may be repeated when initial test results are negative but clinical signs persist. Testing may also be ordered when a person has been diagnosed with an autoimmune disorder and at some point develops symptoms that may be due to an additional autoimmune disorder.

^ Back to top

What does the test result mean?

Diagnoses of autoimmune diseases are typically based on the characteristic signs and symptoms and on results of autoantibody tests. ENA panel results help support the diagnosis of autoimmune disorders. Studies have shown that each of these autoantibodies is frequently detected in people who have a specific autoimmune disorder and is less frequently detected or not detected in those without the disease.

The pattern of positive and negative results obtained with an ENA panel is evaluated in conjunction with a person's clinical findings. If someone has symptoms that suggest a specific autoimmune disorder and the corresponding ENA autoantibody is positive, then it is likely that the person has that condition.

If a person has symptoms but the autoantibody is not present, it could mean that they have not yet developed the autoantibody, or it may mean that the person's symptoms are due to another condition.

The interpretation of ENA panel testing is provided in the table below:

Autoantibody Findings That Help Support the Diagnosis of an Autoimmune Disorder
Anti-RNP Positive in 95-100% of MCTD; may also be positive with SLE and Scleroderma
Anti-Sm Positive in up to 30% of those with SLE; very specific for this disease
Anti-SS-A (Ro) Positive in up to 75% of those with Sjögren's syndrome; may also be positive with SLE and scleroderma
Anti-SS-B (La) Positive in up to 60% of those with Sjögren's syndrome; may also be positive with SLE and scleroderma; rarely present without anti-SS-A
Scl-70 Positive in up to 60% of those with Scleroderma
Anti-Jo-1 May be positive with Polymyositis and Pulmonary Fibrosis

MCTD = Mixed Connective Tissue Disease
SLE = Systemic Lupus Erythematosus

^ Back to top

Is there anything else I should know?

ENA are referred to as "extractable" or "saline-extracted" because of the laboratory method originally used to discover and work with these antigens. More than 100 ENA antigens have been identified, but only a few are routinely tested.

^ Back to top

Common Questions

1.  Will my ENA autoantibodies ever go away?

Levels may fluctuate, but once a person has developed an autoantibody, they will continue to have it.

^ Back to top

2.  Can the ENA panel be performed at my doctor's office?

No. The ENA tests require specialized equipment and skilled laboratory technologists. Your sample will need to be sent to a laboratory that performs these tests.

^ Back to top

3.  My doctor ordered only a 4-test ENA panel, not a 6-test ENA panel. Will something be missed?

The panel performed will generally be the one offered by the laboratory that tests your sample. If a 4-test panel is ordered and your doctor is interested in additional tests, she can order the others separately as needed to ensure that the tests she is interested in are performed and so that nothing will be missed.

^ Back to top

4.  Should everyone have an ENA panel done?

Autoantibody testing is only necessary when a person has symptoms that suggest an autoimmune disorder. Most people will never need to have an ENA panel performed.

^ Back to top

Ask a Laboratory Scientist

This form enables you to ask specific questions about your tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. If your questions are not related to your lab tests, please submit them via our Contact Us form. Thank you.

* indicates a required field




  Patient, Family member or Friend
  Laboratorian or Other Medical Professional
  Other



You must provide a valid email address in order to receive a response.



| Read The Disclaimer


Spam Prevention

| |

Article Sources

« Return to Related Pages

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

(© 1995-2010). Unit Code 89035: Antibody to Extractable Nuclear Antigen Evaluation, Serum. Mayo Clinic, Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/89035 through http://www.mayomedicallaboratories.com. Accessed March 2010.

(© 2006-2010). Extractable Nuclear Antigen Antibodies (RNP, Smith, SSA, & SSB): 0050652. ARUP's Laboratory Test Directory [On-line information]. Available online at http://www.aruplab.com/guides/ug/tests/0050652.jsp through http://www.aruplab.com. Accessed March 2010.

Hill, H. and Tebo. (Updated 2009 November). Mixed Connective Tissue Disease – MCTD. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/MCTD.html?client_ID=LTD# through http://www.arupconsult.com. Accessed March 2010.

Hill, H. and Tebo. (Updated 2009 August). Connective Tissue Diseases. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/ConnectiveTissueDz.html?client_ID=LTD through http://www.arupconsult.com. Accessed March 2010.

(© 1995-2010). Unit Code 83631: Connective Tissue Diseases Cascade, Serum. Mayo Clinic, Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/print.php?unit_code=83631 through http://www.mayomedicallaboratories.com. Accessed March 2010.

Klein-Gitelman, M. (Updated 2009 September 29). Mixed Connective Tissue Disease. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/1006966-overview through http://emedicine.medscape.com. Accessed March 2010.

Hildebrand Jr., G. and Battafarano, D. (Updated 2009 July 24). Undifferentiated Connective Tissue Disease. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/334482-overview through http://emedicine.medscape.com. Accessed March 2010.

Hajj-ali, R. (Revised 2008 February) Mixed Connective Tissue Disease (MCTD). Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec04/ch032/ch032c.html through http://www.merck.com. Accessed March 2010.

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 81-82.

Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 128-129, 136-139.