Antinuclear antibodies in systemic autoimmune disease

Diagnosis of systemic autoimmune diseases, including systemic lupus erythematosus (SLE), can be supported by detection of antinuclear antibodies (ANA). Additional support may be provided by detecting antibodies against double-stranded (ds) DNA, standard extractable nuclear antigens (ENA) or certain disease-specific antigen combinations, including a myositis panel for idiopathic inflammatory myopathy (IIM). The detection of ANA has classically been effected by indirect immunofluorescence (IIF) analysis of patient serum using HEp-2 cells. Although this method of ANA testing can be highly sensitive for systemic autoimmune disease, its specificity is restricted as ANA occurs in subjects with a variety of other conditions as well as in healthy subjects. Consequently, ANA testing by HEp-2 IIF should only be performed when sufficient relevant clinical suspicion is present, to avoid false-positive results. For some systemic autoimmune diseases, including Sjogren's syndrome and IIM, classical ANA testing is less sensitive and direct testing of antibodies against a standard ENA or a myositis panel, respectively, can be more successful to find autoantibodies.