According to the American College of Rheumatology, antinuclear antibodies (ANA) are proteins created within the body that fight the body’s cells at a nuclear level. Although white blood cells typically create antibodies to fight infections, ANA occurs when these antibodies turn against the body’s own healthy cells and tissues.
The Mayo Clinic indicates that ANA levels are measured via a blood test ordered by a physician. If the blood test is positive for ANA, it may indicate autoimmune dysfunction. ANA test results may be used in conjunction with other laboratory tests and history of symptoms to determine whether or not an autoimmune disease is present within the body.