18 antigen ENA panel

What is ENA?

             ENA or Extractable nuclear antigens are a group of antigens inside the cell nucleus against which the anti-nuclear antibodies (ANAs) react. When we see a positive ANA, it would not always mean lupus. An ANA which reacts with dsDNA, histones, nucleosomes could mean lupus. However there are ANAs which react against many other antigens.

            An individual patient’s disease profile might be different depending upon the presence of various anti-nuclear antibodies in them. For example, presence of ANA against SCL70 would mean presence of scleroderma rather than lupus.

When do you test for ENA?

Whenever you get a positive ANA, with a pattern other than homogenous pattern.  This is because a homogenous pattern is usually due to lupus and a specific testing for dsDNA would be enough. However, a mixed pattern, speckled pattern or nucleolar pattern might be due to other antigens and hence can be positive in various other diseases. It is thus ordered in any patient with positive ANA and symptoms of autoimmune disease. 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)

Which antigens can be tested and which diseases can be diagnosed by ENA testing?

There are more than 100 antigens identified but all are not of clinical use. Usually 4 to 6 antigen ENA panels are commonly tested.

 NCRD currently is testing 18 antigen ENA panel.

Autoantibody Test

Results That Support an Autoimmune Disorder Diagnosis

Anti-U1RNP

Positive result seen in 95-100% of mixed connective tissue disease (MCTD) cases; may also be positive with SLE and scleroderma

Anti-Sm1

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

 

What about the cost?

It used to be NPR 10,000 but now is being run at NPR 5000 by National Center for Rheumatic Disease (NCRD)