(IP) assays are analogous to IFA in that antibody presence is identified on antigenic substrates visually. However, in the indirect IP instead of fluorescent dye-antibody conjugates, enzyme-antibody conjugates (principally peroxidase enzymes) are reacted with their corresponding substrates to produce a product which can be seen with a light microscope, eliminating the requirement for costly fluorescent microscopic equipment.

Immunoperoxidase stains are used in the immunohistochemical examination of tissues. These stains are based on antibodies which will bind to specific antigens, usually of protein or glycoprotein origin. This allows the presence or distribution of particular molecules in the sample to be studied.