Antibody Coating Method: Antibodies are immobilized on the surface of solid-phase carriers such as microplate wells to capture antigens. Washing steps separate bound complexes from free components. It is the core solid-phase technique for immunoassays like ELISA.

Free Method: Antibodies and antigens react freely in liquid phase without solid-phase immobilization. Unbound free molecules in the solution are directly detected. This method is widely applied in the detection of serum free antibodies and drug competitive binding analysis.