When S100A9 was combined with APACHE II and IL-6 to predict 28-day mortality in sepsis, the AUC of the combined model increased from 0.78 (95% CI 0.73–0.83, p < 0.001) to 0.84 (95% CI 0.80–0.89, p < 0.001), demonstrating improved predictive performance(Fig 3B, Table 5). Here, S100A9 is linked to Sepsis.