Definition of Anti-nuclear antibody

Anti-nuclear antibodies (ANAs, also known as anti-nuclear factor or ANF) are antibodies present in higher than normal numbers in autoimmune disease. The ANA test measures the pattern and amount of autoantibody which can attack the body's tissues as if they were foreign material. Everyone has a small amount of autoantibody, but in about 5% of the population this is raised, and about half of this 5% have an autoimmune disease.