The present disclosure relates to methods for detecting functional autoantibodies and to diagnostic and prognostic applications of the methods. In certain embodiments, the present disclosure provides a method of detecting a functional autoantibody against an antigenic target, the method comprising exposing a cell expressing the antigenic target to the autoantibody, wherein the antigenic target has an activity to alter the level of reactive oxygen or nitrogen species in the cell and binding of the autoantibody to the antigenic target alters the activity of the antigenic target, and detecting the functional antibody on the basis of a change in the level of the reactive oxygen or nitrogen species in the cell.