The principle of bead-based sandwich ELISA for C-P4H. C-P4H tetramer is captured by the monoclonal antibody against the α subunit (mab-α) coupled to magnetic beads. After a washing step rabbit polyclonal antibody against the β subunit (pab-β) binds to the protein. Goat anti-rabbit IgG labeled with alkaline phosphatase (GAR-AP) is used for the complex detection. The AP catalyzes reactions of substrate transformation with fluorescence signal generation.