Modified Sequential Organ Failure Assessment score for prehospital critical care: defining thresholds and clinical implications.

BACKGROUND: The modified Sequential Organ Failure Assessment (mSOFA) score demonstrates excellent discrimination for short-term mortality in prehospital settings; however, actionable risk stratification thresholds remain undefined. We aimed to determine and validate clinically relevant mSOFA cutoff points and evaluate their association with mortality and care intensity. METHODS: In this prospective, multicentre cohort study across three Spanish and one Austrian emergency medical services (Jan 1, 2021, to April 30, 2026) divided in derivation and validation cohorts, we included adults with acute disease evaluated by advanced life support units. The mSOFA score (0-17 points) was calculated using point-of-care biomarkers obtained within 15 min of patient contact. The primary outcome was 2-day in-hospital mortality. Optimal thresholds were determined using LOESS curves, Youden index, and monotonic trend analysis. RESULTS: Among 14,726 (plus 2100 for validation) patients (median age 67 years [IQR 51-80]; 5906 [40%] female), 2-day mortality was 5.6%. Five mSOFA categories demonstrated progressively increasing mortality: physiologic stability (0-2 points; n = 9436; mortality 0.1%), compensated at risk (3-4 points; n = 2623; mortality 2.5%), significant imbalance (5-7 points; n = 1781; mortality 16.1%), multiorgan failure (8-10 points; n = 673; mortality 45.3%), and critical multiorgan failure (≥11 points; n = 216; mortality 76.4%). Negative predictive values exceeded 98% in low-risk categories. These results were confirmed in validation datasets. CONCLUSIONS: This study establishes the first empirically derived thresholds for prehospital mSOFA scoring. The five-category framework demonstrated a robust mortality gradient and consistent associations with care intensity markers, providing a foundation for standardised triage protocols. Prospective validation is required before implementation.