Anti-extractable nuclear antigen (ENA) antibody screen
The detection of specific antinuclear antibodies (ANA) is an important tool in the evaluation of systemic rheumatic diseases. It is apparent that specific systemic rheumatic diseases have distinct ANA staining patterns which reflect the different nuclear antigens recognised by the autoantibodies. The so-called extractable nuclear antigens are a family of proteins characterised in detail which are recognised by autoantibodies in patients with specific autoimmune diseases. Autoantibodies to extractable nuclear antigens (ENAs) are present in patients with SLE, Lupus overlap syndromes, DLE, SCLE, neonatal lupus syndromes, Mixed Connective Tissue Disease (MCTD), Sjogren’s syndrome, inflammatory (Dermato-) polymyositis, anti-synthetase syndrome and various forms of systemic sclerosis. The type of ENA detected is often an indication of the type or subtype of disease.Patients often have more than one ENA. Samples positive for ANA will be screened using an antigen mixture which contains Ro52, Ro60 (SSA), La (SSB), RNP, Sm, Centromere (CENP-B) Scl-70, and Jo1 antigens. Samples positive for the initial screen are investigated further. The sensitivity and specificity of individual antibodies for these diseases is variable e.g Sm and Scl-70 antibodies are specific for SLE and DcSSc respectively, whilst Ro60 and La antibodies occur in Lupus and Sjogren’s syndrome. The isolated presence of high titre anti-RNP antibodies is suggestive of MCTD. The presence of a speckled ANA (> 1/80) is often a clue to the presence of anti-ENAs present in patients with SLE, DLE, SCLE Lupus overlap syndromes (Mixed Connective Tissue Disease), Sjogren’s syndrome and SSc. The ENAs associated with scleroderma or myositis are much rarer than the others. For additional information on ENAs and centromere antigens see specific pages.
Connective tissue diseases including SLE, Scleroderma, Sjorgen’s, MCTD, myositis.
This ENA screen will detect antibodies recognising Ro52, Ro60, La, Sm, RNP, Scl-70, Jo1 or the centromere antigen (See specific pages for details). All positive samples will be investigated further.
Serum Separator Tube (SST)
Fluorescence enzyme linked immunoassay (Phadia Immunocap 250): Human recombinant Ro, La, RNP, Jo1, Scl70, Centromere protein; bovine Sm protein IgG antibodies.
Heparinised plasma may cause interference.
5 – 7 days
Immunology The James Cook University Hospital