The Antinuclear Antibody (ANA) test is a blood test that detects antinuclear antibodies (ANAs) in your blood. ANAs are antibodies that mistakenly attack the body's own cells, specifically targeting the cell nuclei. A positive ANA test can be a sign of an autoimmune disorder, where the immune system attacks healthy tissues.   Why is the ANA test done? To help diagnose autoimmune diseases: Such as systemic lupus erythematosus (SLE or lupus), rheumatoid arthritis, scleroderma, Sjogren's syndrome, and mixed connective tissue disease. To investigate certain symptoms: Such as unexplained joint pain, muscle aches, fatigue, rashes, and fever.