The ANA or antinuclear antibody test is used to check a person for autoimmune disorders. Autoimmune disorders affect tissues and organs of the body. Systemic lupus erythematosus is the main disorder that ANA testing evaluates. ANA are antibodies produced by a person when the immune system can not differentiate between self and outside entities and they target the body itself. ANA testing can be used with specific testing for further confirmation to diagnose or rule out other autoimmune disorders like Sjögren syndrome, polymyositis and scleroderma.
There are two methods to test for ANA: Indirect fluorescent antibody (IFA): In this method, a person's blood sample is mixed with cells that are affixed to a slide. Autoantibodies that may be present in the blood react with the cells. The slide is treated with a fluorescent antibody reagent and examined under a microscope. The presence (or absence) and pattern of fluorescence is noted. Immunoassays--these methods are usually performed on automated instrumentation but may be less sensitive than IFA in detecting ANA. ANA testing is not used for monitoring SLE in its course hence it is not commonly ordered.