ANA ELISA Kit

Autoantibodies are hallmarks of autoimmunity, and in particular, antinuclear antibodies (ANAs), anti-DNA antibodies, and extractable nuclear antigens (ENAs) are the most relevant autoantibodies in systemic autoimmune rheumatic diseases (SARDs), and all are relevant to the classification, diagnosis, and monitoring of patients with connective tissue diseases (CTDs). In the last century, systemic lupus erythematosus (SLE) was the only autoimmune disease in which the importance of ANAs was known, and then researchers gradually discovered that autoimmune phenomena and ANAs also play a very important role in other diseases, such as mixed connective tissue disease, rheumatoid arthritis, antiphospholipid syndrome, systemic sclerosis, inflammatory myelopathies, nephritis, and autoimmune hepatitis. This growing understanding of the different autoimmune diseases is due to the enormous development of technologies, from LE cells to IIF, ELISA, chemiluminescence or immunoblotting analyses, to multi-analytical techniques.

Figure 1. Evolution of ANA request from the 1950s to 2022 according to the involvement of autoimmune phenomena in different diseases and technological development
(Source: Irure-Ventura J, et al. 2022)

Indirect immunofluorescence (IIF) assay using HEp-2 cells is the gold standard method for screening ANAs in SARDs. If the ANA results for HEp-2 cells are positive, further studies are necessary to determine the specific autoantibodies responsible for the IIF pattern, such as anti-dsDNA or anti-ENA antibodies. Positive ANA results in HEp-2 cells should be communicated to the clinician in a standardized manner, including end-point titer and immunofluorescence patterns, as well as anticellular terminology with reference to reflex testing and possible autoantibody associations, to add value to the laboratory results and aid in clinical decision making.

In recent years, clinical laboratories have increasingly used different solid-phase assays (SPA), including ELISA, fluorescent enzyme-linked immunoassay (FEIA), and chemiluminescent immunoassay (CIA), to screen for ANA-associated SARDs and to confirm autoantibody specificity in the event of a positive screening result. SPA is less sensitive but more specific in screening for ANA-related SARDs than the IIF assay. However, consideration must be given to how the cut-off points for the different assays are chosen in order to be considered as positive results, as the differences in performance observed between assays are largely related to these cut-off points.

antinuclear antibodies ELISA Kit