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Extractable Nuclear Antigen (ENA) panel

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Extractable Nuclear Antigen (ENA) Panel Test

The Extractable Nuclear Antigen (ENA) panel detects a heterogeneous group of autoantibodies that react with various ribonucleoprotein-associated proteins. These antibodies were first identified in patients with rheumatoid arthritis, systemic lupus erythematosus (SLE), and mixed connective tissue diseases (MCTD), giving rise to the term ENA antibodies.

Clinical Significance

  • ENA screening is used to detect autoantibodies against nuclear and cytoplasmic antigens in serum.
  • These antibodies are diagnostic and prognostic markers for various systemic connective tissue diseases.
  • ENA screening is not specific to any single autoimmune disease, but it helps identify autoimmune rheumatic conditions such as:
    • Rheumatoid arthritis (RA)
    • Systemic lupus erythematosus (SLE)
    • Systemic sclerosis (scleroderma)
    • Sjögren’s syndrome
    • Mixed connective tissue disease (MCTD)
  • Take the test at least 2 hours after the last meal.
  • Avoid smoking for 3 hours before the test.
  • Avoid physical and emotional stress for 1 hour before the test.

This test is recommended for patients with symptoms of systemic autoimmune diseases, including:

  • Joint swelling
  • Tissue swelling (edema)
  • Brain fog or difficulty concentrating
  • Persistent low-grade fever
  • Chronic fatigue
  • Muscle pain (myalgia)
  • Hair loss (alopecia)
  • Skin changes (rashes, discoloration)
  • Numbness, especially in the hands and feet

Negative ENA Test Result:

  • If negative, the test is repeated if clinical suspicion of autoimmune disease remains.
  • Persistent negative results suggest non-autoimmune causes of symptoms.

Positive ENA Test Result:

A positive result provides preliminary evidence of an immune system disorder but does not specify the disease. Additional autoantibody tests are required for confirmation.

Associated Autoimmune Diseases

A positive ENA panel may indicate:

  • Rheumatoid arthritis (RA, chronic polyarthritis)
  • Autoimmune hepatitis
  • Idiopathic inflammatory myopathies (IIM)
    • Dermatomyositis
    • Polymyositis
  • Mixed connective tissue disease (MCTD)
  • Primary biliary cirrhosis (PBC)
  • Progressive systemic sclerosis (PSS, systemic scleroderma)
  • Sjögren’s syndrome
  • Systemic lupus erythematosus (SLE)
  • Drug-induced lupus (DIL)