Anti-nuclear antibodies are relatively non-specific markers of autoimmune disease, particularly connective tissue diseases. They can be induced by some chronic infections. The test is used as an initial screen to assess the need for more specific tests (ENA and anti-DNA antibodies) which are automatically carried out on ANA positive samples The presence of ANA in significant titre (>1/80) is not specific for SLE, occurring in 15-50% of patients with other auto-immune diseases e.g. Rheumatoid Arthritis, Scleroderma, Sjogren’s Dermato-myositis and in autoimmune liver disease. ANAs bind to many different nuclear antigens. The different antigens lead to different patterns of staining of the nuclei e.g. Homogeneous, speckled, nucleolar, centromere, each of which may be associated with different connective tissue or liver diseases. Anti-nucleolar antibodies can be associated with scleroderma though they are poorly specific. Anti-centromere antibodies are strongly associated with limited scleroderma (CREST syndrome).
There are a large number of less common staining patterns mostly having poor correlation with specific autoimmune diseases. Anti-nuclear antibodies are detected on the liver-kidney-stomach tissue used in our autoimmune screen. However the assay is far more meaningful when carried out using slides coated with fixed Hep2 cells. These are a rapidly dividing cell line with large nucleii which are now used almost universally for ANA detection.
Note that the improved cell line, Hep2000 that we use for this assay is transfected with the Ro60 antigen which could be missed in earlier versions of the test. As a result, a negative ANA will almost always rule out a positive ENA or anti- DNA (However see Anti-Ro.)
Preliminary investigation of connective tissue diseases; autoimmune liver disease.
The presence of ANA occurs in a number of autoimmune conditions e.g. SLE, Scleroderma, Sjorgen’s and other connective tissue disorders including rheumatoid arthritis. In many cases the subsequent testing for ENA and anti-DNA antibodies will provide additional information. In rheumatological patients, positive ANA in the absence of ENA or anti-DNA is usually of no specific diagnostic value, though it can suggest evolving connective tissue disease which will later be characterised by more specific autoantibodies. ANA (particularly giving a homogeneous staining pattern) are also found in chronic infections, liver disease and in some cancers. Note that treatment of patients with modern “biological” drugs such as anti-TNF (for RA or Crohns) or interferon commonly induces ANA sometimes in high levels.
Indirect immunfluorescence mouse tissue (liver kidney stomach) or Hep 2000 cell line.
Assay range notes
Positive: titre on Hep2000 cells 1:40-1:640