This kit uses the Sandwich-ELISA principle. The microtiter plate strips has been pre-coated with an affinity purified antibody to Rat F1+2. Standards or samples containing Rat F1+2 are added to the plate and reacted with capture antibody. A second anti-Rat F1+2 antibody labeled biotin is then added and binds to Rat F1+2 captured on the plate. After that, Streptavidin-Horseradish Peroxidase (SA-HRP) is added to form a sandwich complex of solid phase antibody-Rat F1+2-biotin labelled antibody-SA-HRP. And then, TMB substrate solution is added to all wells and incubated. An enzyme-catalyzed reaction generates a blue color in the solution, thereafter, stop solution is added to stop the substrate reaction and the color turns yellow. The yellow solution is read at a wavelength of 450nm. The concentration of Rat F1+2 in the samples is then calculated from the OD value by establishing a standard curve.