KE30001 is a qualitative measurement of Anti-SARS-CoV-2 N protein Human IgG in plasma. The principle of the kit is indirect ELISA. N protein 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-NP 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.