The Wondfo RCI functions by detecting IgM/IgG antibodies for SARS-CoV-2. 10 μL of plasma or serum are inserted into the testing device, and antibodies that fight against SARS-CoV-2 contained in the sample attach to recombinant antigens that cover colloidal gold particles, ultimately creating a complex of antigen-antibody/colloidal gold particles. 80 μL of buffer solution must also be inserted into the testing device under the sample cavity. The results of the RCI can be read within 15 minutes. A major limitation of RCI is that it is not capable of differentiating between acute disease and infection from the past.