Antinuclear antibodies (ANA) are a collective term for all autoantibodies that recognize conserved (i.e. occurring in all cells) nuclear antigens. In a narrower sense, ANA refers to those autoantibodies that cause nuclear staining in indirect immunofluorescence on tissue sections or tumor cell monolayers (e.g. HEp-2 cells). [Conrad K. et al., 2010, Lengerich: Pabst Science Publishers].
ANA are typical findings in inflammatory rheumatic diseases (systemic connective tissue diseases, also known as collagenoses), but can also be found with varying frequency in almost all other autoimmune diseases and tumors. Significant clinical representatives of autoimmune connective tissue diseases include systemic lupus erythematosus, Sjögren's syndrome, mixed connective tissue disease and scleroderma.
ANA indicate autoimmune hepatitis in chronic liver disease and an increased risk of chronic iridocyclitis (inflammation of the iris) in juvenile chronic arthritis. ANA are found relatively rarely in healthy people (and then usually with a low titer), but the frequency increases with the age of the test subjects. [Conrad K., et al., 2001, Lengerich: Pabst Science Publishers].
ANA diagnostics is performed in 2 stages. In the search stage, the cell nuclei of typical HEp-2 cells are stained using IIFT and usually characterized in more detail in the confirmation stage if the result is positive. The confirmation test usually works with extractable nuclear antigens (ENA), which are able to detect diagnostically relevant fractions of the ANA.