Antigen detection by ELISAs (sandwich ELISA)
The reagent wells of the microplate coated with monospecific antibodies are incubated with diluted patient samples. If the sample contains the respective antigens, these bind to the antibody-coated reagent well. In a further step, a peroxidase-labelled antibody (conjugate) is added, which binds to another epitope of the antigen. When the peroxidase substrate tetramethylbenzidine (TMB) has been added, the peroxidase catalyses a colour reaction. The intensity of the results colour solution is proportional to the antigen concentration in the patient sample within the measurement range and can be converted into a concentration by means of a calibration curve in the quantitative tests.