An analysis of the ROC curves for the group of patients with severe COVID-19 and convalescents (Table 3, Figure 2B) showed that the AUC value for the relative reactivity of AGP glycans with SNA was 0.960 (95% confidence interval: 0.926–0.993, p = 0.0000, proposed cut-off point: 0.187 AU, with a sensitivity of 100% and a specificity of 86.2%), which indicates the high clinical usefulness of this parameter, allowing for the differentiation of the above-mentioned study groups. Here, ATP5MK is linked to COVID-19.