When the dissociation concentration of urea was 4 mol/liter and with the AI calculation method set to 0.371, the results of SARS-CoV-2 IgM analyses in 19 serum samples with positive RF-IgM turned negative, whereas those of SARS-CoV-2 IgM in 14 serum samples from COVID-19 patients remained positive (Fig. 2). Here, CD40LG is linked to COVID-19.