ENA screening: ANAS from serum.
Extractable Nuclear Antigen Antibodies, fluorescent antinuclear antibody test, FAN, antibodies to extractable nuclear antigen, (EIA) serum
- CENP-B (centromeres)
- ribosomal P-protein
- SS-A (Ro)
- SS-B (La)
The test measures antibodies to nuclear antigens. These are antibodies directed against nuclei (nucleus) of the body's own cells. The ENA test can be used to determine whether the body makes antibodies against itself.
The immune system produces these so-called autoantibodies (auto means self) when it fails to distinguish between its own cells and foreign cells. Production of autoantibodies can lead to autoimmune diseases. These diseases are usually accompanied by inflammation and all that goes with it, fever, pain and fatigue.
Examples of these nuclear antibodies are anti-nRNP, anti-Sm, anti-SSA/Ro, anti SSB/La, Scl-70 Jo-1 and anti-CEN-P.
The different antibodies can be found in autoimmune diseases such as SLE (systemic lupus erythematosus), Sjögrens syndrome, MCTD (mixed connective-tissue disease), CREST syndrome, polymyositis or dermatomyositis. The occurrence of the different types of antibodies varies from disorder to disorder.
A positive result means that autoantibodies have been detected. This may indicate an autoimmune disease, but not necessarily. Especially in older people, autoantibodies may be demonstrated without an autoimmune disease. In healthy elderly people (>65 years), the false positive rate can be as high as almost 40%.
Also the use of some medications can lead to the production of autoantibodies while there is no autoimmune disease.
A negative result (no antibodies detected) makes a number of autoimmune diseases unlikely. But it does happen (about 5% of the time) that someone does have an autoimmune disease, but does not produce autoantibodies. Given the variable nature of SLE, for example, there is no harm in repeating the test later if it is suspected.
In case of a positive result, further testing is done to see why the result is positive
If the result is positive, you will have to reckon with extra costs.