The Protein A ELISA kit (enzyme-linked immunosorbent assay) is a highly sensitive kit for detecting Protein A residues. It can accurately identify multiple imported and domestically produced Protein A variants. This kit enables sensitive, specific, and accurate detection of Protein A residues in intermediate, semi-finished, and finished products of various biological products. It also facilitates Protein A affinity resin manufacturers to monitor the shedding of Protein A under specific conditions.