This kit is an Enzyme-Linked Immunosorbent Assay (ELISA). The plate has been pre-coated with Human Hcy antibody. Hcy present in the sample is added and binds to antibodies coated on the wells. And then biotinylated Human Hcy Antibody is added and binds to Hcy in the sample. Then Streptavidin-HRP is added and binds to the Biotinylated Hcy antibody. After incubation unbound Streptavidin-HRP is washed away during a washing step. Substrate solution is then added and color develops in proportion to the amount of Human Hcy. The reaction is terminated by addition of acidic stop solution and absorbance is measured at 450 nm.