KE30003 is a quantitative measurement of the human IgG for 2019-nCoV S-RBD in serum and plasma. The principle of the kit is indirect ELISA. S-RBD Recombinant Protein 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 anti-Human IgG is added to each well. Producing an complex " Recombinant Protein-human anti-S-RBD IgG antibody-HRP conjugated antibody" . 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.