Which type of test is primarily used to detect anti-nuclear antibodies?

The indirect fluorescent antibody test is the primary method used to detect anti-nuclear antibodies (ANAs). This test involves exposing patient serum to a substrate containing fixed tissue sections that display various cellular antigens. If ANAs are present, they will bind to these antigens and can be visualized using fluorescently labeled secondary antibodies. The resulting fluorescence indicates the presence of autoantibodies, and the pattern of fluorescence can provide additional insights into the specific autoimmune conditions present, helping in the diagnosis of diseases such as systemic lupus erythematosus or scleroderma.

Other methods, while useful in certain contexts, are not as specifically tailored for ANA detection. For example, the enzyme-linked immunosorbent assay, while capable of detecting antibodies, is more commonly used for antigen-specific assays rather than the broad spectrum of nuclear antigens associated with ANAs. Western blotting, although it is excellent for confirming the presence of specific antibodies, is typically used after initial screening tests like the indirect fluorescent antibody test or ELISA. Radioimmunoassay, primarily used for hormone and drug level measurements, does not have the specificity required for detecting ANAs. Thus, the indirect fluorescent antibody test remains the gold standard for this purpose.