Principle of the Assay The AssayMax Human Tissue Factor Pathway Inhibitor (TFPI) ELISA kit is designed for detection of human TFPI in plasma, serum, milk, and cell culture samples. This assay employs a quantitative sandwich enzyme immunoassay technique that measures TFPI in less than 4 hours. A polyclonal antibody specific for TFPI has been pre-coated onto a 96-well microplate with removable strips. TFPI in standards and samples is sandwiched by the immobilized polyclonal antibody and biotinylated polyclonal antibody specific for TFPI, which is recognized by a streptavidin-peroxidase conjugate. All unbound material is then washed away and a peroxidase enzyme substrate is added. The color development is stopped and the intensity of the color is measured.