Performance of a modified Sequential Organ Failure Assessment score in pre-hospital critical care to predict short-term mortality: a prospective, multicentre, validation cohort study.

Background: Scoring systems have demonstrated their usefulness in predicting short-term mortality when applied by emergency medical services (EMS). However, their implementation should be supported by validation studies using real-world data. This work aims to validate a previously developed modified Sequential Organ Failure Assessment (mSOFA) score and conduct external revalidation for its use in prehospital critical care to predict short-term mortality. Methods: This prospective, observational, multicentre, EMS-based validation and external validation study, was conducted across three EMS systems in Spain (one for validation and two for revalidation). Adults with undifferentiated acute conditions who were transported with high priority to the emergency department (ED), excluding pregnancy, cardiac arrest, and palliative patients. The primary outcome was 2-day all-cause in-hospital mortality. Prehospital and in-hospital demographic data, vital signs, and point-of-care testing variables were collected to calculate mSOFA and SOFA scores. Score performance was evaluated through validation/revalidation and a random quasi-stratified K-fold cross-validation scheme. Findings: Between January 1, 2021, and March 30, 2025, a total of 12,212 patients were enrolled (validation cohort#1 (n = 9063), revalidation cohort#2 (n = 1816), and revalidation cohort#3 (n = 1333)). The median age was 67 years (IQR: 51-80), and 41.1% (5040 patients) were female. The overall 2-day mortality rate was 5% (609 cases). The mSOFA score showed an AUC of 0.949 (95% CI: 0.939-0.958) in the validation cohort, and 0.939 (95% CI: 0.925-0.954) and 0.944 (95% CI: 0.921-0.967) in the two revalidation cohorts. Comparison between mSOFA and SOFA scores for 2-day mortality revealed statistically significant differences (p < 0.0001), with AUCs of 0.947 (95% CI: 0.939-0.954) for mSOFA and 0.927 (95% CI: 0.917-0.937) for SOFA. Interpretation: Our findings suggest that the mSOFA score shows good discriminatory power for predicting short-term mortality, consistent across different cohorts. Study limitations included not blinded extractors, time limit of primary outcome, and patients' heterogeneity. This validates score performance in other health systems and demonstrates a better mSOFA performance over the SOFA score. Future work will pursue clinical validation of the score via a randomized clinical trial. Funding: This work was supported by the Institute of Health Carlos III, co-financed by the European Union, by the Basque Government, and by the University of the Basque Country.