The AUC of AEC on admission in predicting ICU transfer among elderly COVID-19 patients was 0.828 (95% CI, 0.732–0.923), whereas the AUCs of CRP and ferritin were 0.867 (95% CI, 0.784–0.951) and 0.838 (95% CI, 0.730–0.947), respectively, with no significant difference in the pairwise comparison of ROC curves (P > 0.05; Figure 3 and Table 7). Here, CRP is linked to COVID-19.