Anti-nuclear antiboies (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. Autoantibodies are present in low titres in the general population, but in about 5% of the population, their concentration is increased, and about half of this 5% have an autoimmune disease.