Figures 4A, B illustrate the sequential changes in IL-6 concentrations after ED arrival. The reduction in IL-6 concentrations in the non-respiratory failure group (p = 0.0676) was more prominent after admission than that in the respiratory failure group (p = 0.8711). Figure 4C illustrates the ROC curve referring to the relationship between changes in serum IL-6 concentrations after admission and the development of respiratory failure later in the hospitalization course (ROC area, 0.696; confidence interval 0.515–0.877, p = 0.072). Here, IL6 is linked to respiratory failure.