What is an antinuclear antibody test used for?

Autoimmune disease. ANA (anti-nuclear antibody) is a blood test used by doctors that indicates the presence of an autoimmune condition in which the body's immune system is predisposed to recognize normal things in your body as foreign invaders that need to be attacked. The results are not specific for any particular disease if positive, but are a preliminary test, after which a range of possibilities are considered.