ROC curve showed also that the elevation of serum TLR-4 could be a potential diagnostic marker of high CSS among COVID-19 patients with (AUC = 0.78 ± 0.06; P value = 0.0001*) (Fig. 4c), but the association with hypoxia was non-significant with (AUC = 0.63 ± 0.08 p = 0.1). Here, TLR4 is linked to COVID-19.