Dr Leigh Martens

General Practitioner

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Release Version: Beta

Blood-tests Explained


Disclaimer:

This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion

ENA Panel


At a Glance

Why Get Tested?

To help diagnose and distinguish between autoimmune disorders as well as to monitor autoimmune disease progression

When to Get Tested?

When your antinuclear antibody (ANA) test is positive; when you have symptoms that suggest an autoimmune disorder; when monitoring the activity of 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 extractable nuclear antigen (ENA) panel detects the presence of one or more autoantibodies in the blood that react with proteins in the cell nucleus. These proteins are known as "extractable" because they can be removed from cell nuclei using saline.

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.

Certain autoimmune disorders are characteristically associated with the presence of one or more anti-ENA antibodies. This association can be used to help diagnose an autoimmune disorder and to distinguish between disorders.

The ENA panel typically consists of a group of 4 or 6 autoantibody tests. The number of tests performed will depend on the laboratory and the needs of the health practitioners and patients it serves. Individual ENA panel tests can also be ordered separately.

A 4-test ENA panel will include:

Autoantibody Test Formally 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 include the four tests listed above as well as:

Autoantibody Test Formally 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.

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 for people who have signs and symptoms 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 panel can also help identify scleroderma and polymyositis/dermatomyositis. 

For more on these diseases, visit the National Institute of Arthritis and Musculoskeletal and Skin Diseases web site.

An ENA panel may also be used to monitor the activity of a particular autoimmune disorder.

When is it ordered?

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

  • Fever and persistent fatigue
  • Muscle pain
  • Joint swelling and/or pain
  • Skin rash
  • Sensitivity to ultraviolet light
  • Raynaud phenomenon
  • Proteinuria
  • Neurologic symptoms such as seizures, depression, psychoses
  • Hemolytic anemia (low red blood cell count) or leukopenia (low white blood cell count)

In most cases, an ENA panel will not be ordered when a person has a negative ANA test. If no antinuclear antibodies are present, then the person is extremely unlikely to test positive for a specific antinuclear antibody (which is what the ENA panel tests).

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. A health practitioner also may order testing to monitor the activity and/or progression of a known autoimmune disorder.

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 to detect and distinguish between different 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 the individual has not yet developed the autoantibody, or it may mean that the person's symptoms are due to another condition.

Interpretation of results for the tests included in an ENA panel are provided in the table below. A positive test result means that the person has more of that autoantibody in their blood than the designated reference value.

Autoantibody Test Results That Support an Autoimmune Disorder Diagnosis
Anti-RNP Positive result seen in 95-100% of mixed connective tissue disease (MCTD) cases; may also be positive with SLE and scleroderma
Anti-Sm Positive result seen in 30% of those with SLE; very specific antibody marker for this disease
Anti-SS-A (Ro) Positive result seen in 75% of those with Sjögren's syndrome; may also be positive with SLE and scleroderma
Anti-SS-B (La) Positive result seen in 60% of those with Sjögren's syndrome; may also be positive with SLE and scleroderma; rarely present without anti-SS-A
Scl-70 Positive result seen in 60% of those with scleroderma; highly specific antibody marker for this disease
Anti-Jo-1 Positive result seen in 30% of those with polymyositis; may be positive with pulmonary fibrosis

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 antigens have been identified in this way, but only a few are routinely tested.