Autoimmune diseases cause the body to attack itself, which leads to inflammation and results in damage to muscles, tissues, and organs. The body produces antibodies specific to each autoimmune disease; the antibody levels measured in your blood are then used by your doctor to diagnose the disease that is causing your symptoms. Scl-70 antibody is a blood test that is mainly used to diagnose scleroderma, and to monitor your response to treatment. High blood levels of Scl-70 antibodies are also seen in people with rheumatoid arthritis, Sjogren's syndrome, SLE (systemic lupus erythematosus), and other autoimmune diseases affecting connective tissue (CREST syndrome). There can be false negative results with this test.