KE30006 is a quantitative measurement of total antibody (IgG and IgM) to SARS-COV-2 S-RBD protein in serum or plasma. The principle of the kit is capture ELISA. anti-human antibody has been pre-coated onto microplate well. The samples or standard are added to the well, after incubation the wells are washed and a horseradish peroxidase conjugated S-RBD protein is added to each well. Producing an complex " anti-human antibody and sample and SARS-CoV-2 S-RBD protein-HRP conjugated" . after incubation the wells are washed, followed by Tetramethyl-benzidine (TMB) reagent. Solution containing sulfuric acid is used to stop color development and the color intensity which is proportional to the quantity of bound protein is measurable at 450nm with the correction wavelength set at 630 nm.