The AntiProthrombin Screen is an indirect solid phase enzyme immunometric assay (ELISA). It is designed for the quantitative measurement of IgG/IgM/IgA autoantibodies directed against Prothrombin. The microplate is coated with highly purified prothrombin. The microplate can be divided into 12 modules of 8 wells each or can be used completely for 96 determinations. Each well can be separated from the module ("breakaway"). The binding of present autoantibodies, formation of the sandwich complexes and enzymatic colour reaction take place during three different reaction phases. To read the optical density a microplate reader with a 450 nm filter is required. Bichromatic measurement with a 600690 nm reference is recommended.