The Anti-Scl-70 antibody test is a blood test used to detect the presence of antibodies against the Scl-70 protein (topoisomerase I), which is often associated with systemic sclerosis (scleroderma). It helps in diagnosing and monitoring the progression of this autoimmune disease, particularly the form known as diffuse systemic sclerosis. The test is typically used when a doctor suspects an autoimmune disorder affecting the skin and internal organs.