Anti nuclear antibody

Antinuclear antibody (ANA) tests identify antibodies present in serum that bind to autoantigens present in the nuclei of mammalian cells. Most of these antibodies are IgG, but IgM and IgA have also been detected. The enzyme-linked immunosorbent assay (ELISA) method involves the interaction of these antibodies present in the serum sample with a preprepared antigen and the addition of an antibody that adheres to this complex and induces a color change; the result is an optical density value (a photometric scale) that is read as positive, negative, or equivocal. [ The reference range for antinuclear antibody is negative by ELISA. If the ELISA method results in an abnormalor equivocal finding, the sample is titered using indirect immunofluorescence (IFA) assays on Hep-2 cells, and any value less than or equal to 1:40 dilution (or < 1.0 IU) is negative. [ The frequency of positivity on ANA screening test (on Hep-2 cells) is as follows: • Different connective tissue diseases are associated with a different frequency of ANA positivity (see the image below). An antibody pattern is reported with a positive titer and gives an indication of the likely diagnosis (see the image below). Pattern interpretation is subjective and thus frequently not specific for any individual disease state. A 7-mL blood serum sample is collected in a red-topped tube and may be stored at 48ºC for up to 72 hours or at -20ºC or colder (without freezing and thawing) indefinitely. For IFF, acetone-fixed substr...

Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by antinuclear antibodies (ANAs) that form immune complexes that mediate pathogenesis by tissue deposition or cytokine induction. Some ANAs bind DNA or associated nucleosome proteins, whereas other ANAs bind protein components of complexes of RNA and RNA-binding proteins (RBPs). Levels of anti-DNA antibodies can fluctuate widely, unlike those of anti-RBP antibodies, which tend to be stable. Because anti-DNA antibody levels can reflect disease activity, repeat testing is common; by contrast, a single anti-RBP antibody determination is thought to suffice for clinical purposes. Experience from clinical trials of novel therapies has provided a new perspective on ANA expression during disease, as many patients with SLE are ANA negative at screening despite previously testing positive. Because trial results suggest that patients who are ANA negative might not respond to certain agents, screening strategies now involve ANA and anti-DNA antibody testing to identify patients with so-called ‘active, autoantibody-positive SLE’. Evidence suggests that ANA responses can decrease over time because of the natural history of disease or the effects of therapy. Together, these findings suggest that, during established disease, more regular serological testing could illuminate changes relevant to pathogenesis and disease status. • Antinuclear antibodies (ANAs) bind DNA, RNA and complexes of nucleic acids and ...