Comparative prognostic performance of SOFA-1 and SOFA-2 in patients with sepsis at ICU admission

SOFA-1 underpins Sepsis-3 definitions but may no longer optimally reflect contemporary ICU practice; SOFA-2 was recently developed from large multinational datasets, yet its prognostic performance in septic populations remains unknown. We aimed to compare the prognostic performance of SOFA-1 and SOFA-2 in ICU patients with sepsis.

Retrospective cohort study.

This study was conducted using the MIMIC-IV database. A total of 30,667 adult patients (≥18 years) with first ICU admissions meeting Sepsis-3 criteria were included.

ICU mortality and in-hospital mortality. We compared discrimination (AUC), calibration, net reclassification improvement (NRI), integrated discrimination improvement (IDI), decision curve analysis and time-dependent survival.

Among 30,667 patients, 87.0% met both SOFA-1 and SOFA-2 criteria, 12.0% met only SOFA-2 criteria, and 1.0% met only SOFA-1 criteria. SOFA-2 total scores were systematically higher than SOFA-1, driven primarily by updated renal, cardiovascular and brain scoring criteria. SOFA-2 demonstrated modestly but consistently better discrimination for ICU mortality (AUC 0.779 vs. 0.755; P < 0.001) and hospital mortality (AUC 0.745 vs. 0.725; P < 0.001), with significant reclassification improvement for ICU mortality (NRI 0.143; IDI 0.020). In multivariable Cox models, SOFA-2 achieved higher AUCs for 7-day (0.790 vs. 0.771), 28-day (0.709 vs. 0.697) and 90-day mortality (0.682 vs. 0.671; all P < 0.001), with consistent advantages across all prespecified subgroups.

SOFA-2 provides modestly but consistently better prognostic performance than SOFA-1 in septic ICU patients. Whether this incremental gain justifies the added scoring complexity warrants prospective evaluation.