The present invention provides methods and compositions useful in the diagnosis and management of autoimmune diseases. In particular, the present invention provides improved methods and compositions for the diagnosis and management of Graves' disease. The methods of the present invention not only avoids the need for radioactivity and are much simpler, economical, and rapid than methods traditionally used for the diagnosis of Graves' disease, but also improve upon the sensitivity and detection abilities of previous luciferase-based autoantibody detection assays.