ROC analysis of all results from the COVID-19 group and the control group gave areas under the ROC curve (AUC) of 0.693 (0.651–0.733) for Vircell-IgM/A, 0.880 (0.849–0.907) for Euroimmun-IgA, 0.937 (0.913 to 0.957) for Vircell-IgG, and 0.935 (0.910 to 0.955) for Euroimmun-IgG (Fig. 6). The gene discussed is CD40LG; the disease is COVID-19.