CRP and systemic inflammatory response syndrome: Although the statistical power of this subgroup analysis is limited by the modest sample size, ESR recorded the highest AUC (0.846 [95% CI: 0.747–0.946]) among single inflammatory biomarkers—outperforming CRP and NLR—and demonstrated the strongest prognostic association excluding the composite APPLEfast score, thereby supporting its potential utility even in acute high-risk settings like SIRS.