SOFA-2 Versus SOFA-1 for Mortality Prediction in Infection-Triggered ICU Patients

Abstract

Background

Accurate assessment of organ dysfunction is essential for risk stratification in critically ill patients. The traditional Sequential Organ Failure Assessment score (SOFA-1) is widely used but reflects clinical practices from the 1990s. The updated SOFA-2 incorporates revised thresholds aligned with current organ-support strategies; however, its prognostic performance in infection-focused intensive care unit (ICU) populations remains uncertain. We compared SOFA-1 and SOFA-2 for predicting 28-day mortality in ICU patients undergoing blood culture acquisition ≥48 h after admission.

Methods

We conducted a retrospective cohort study of adult ICU patients who underwent blood culture sampling ≥48 h after ICU admission between June 2022 and August 2024. SOFA-1 and SOFA-2 scores were calculated at the time of index blood culture. Mortality prediction was assessed using receiver operating characteristic analysis with paired DeLong comparisons. Associations with 28-day mortality were examined using logistic regression and Cox proportional hazards models adjusted for age and comorbidity burden. Clinical utility was evaluated using decision curve analysis.

Results

Among 403 patients, 28-day mortality was 54%. SOFA-2 scores were lower than SOFA-1 in 70% of patients, resulting in frequent downward reclassification across severity strata. Discriminative performance for 28-day mortality was similar for SOFA-1 and SOFA-2 (AUC 0.707 vs 0.700; ΔAUC = 0.007; p = .031). Calibration and net clinical benefit were comparable between scores. In adjusted time-to-event analyses, only the very severe category (>10) was independently associated with mortality in both scoring systems, with a numerically higher hazard ratio for SOFA-2.

Conclusions

In this infection-triggered ICU cohort, SOFA-2 did not demonstrate consistent prognostic superiority over SOFA-1 for 28-day mortality prediction. Despite systematic score redistribution, overall discrimination and clinical utility were similar, with any apparent advantage of SOFA-2 confined to the highest-risk subgroup. Further validation in infection-enriched ICU populations is warranted.