Prehospital National Early Warning Score Outperforms Shock Index in Predicting Mortality and Resource Utilisation in Adult Trauma: A Systematic Review

Abstract

INTRODUCTION: Early recognition of severely injured trauma patients is essential in the prehospital setting. Emergency Medical Services (EMS) frequently rely on simple physiological measures to guide triage, yet validated prognostic tools for prehospital trauma remain limited. The Shock Index (SI) and National Early Warning Score (NEWS) are physiological scoring systems that may support early risk stratification. This systematic review evaluates the prognostic accuracy of prehospital SI and NEWS for mortality and resource utilisation in adult trauma. METHODS: A systematic search of CINAHL, Medline and Cochrane databases (2015-2025) identified studies reporting associations between prehospital SI or NEWS and overall mortality in adult trauma patients. Paediatric studies, Emergency Department only cohorts, isolated body-region trauma, and modified scoring systems were excluded. Due to substantial heterogeneity in study design, populations and outcome measures, a narrative synthesis was undertaken. RESULTS: Twenty-two studies met inclusion criteria, with numbers ranging from 184 patients to 1439,221 patients across diverse EMS systems. Across individual studies, prehospital SI showed variable discrimination for mortality, with AUROC values ranging from poor to moderate (0.48-0.79), although elevated SI (>0.9) consistently correlated with increased mortality, transfusion, and critical care needs. Prehospital NEWS demonstrated excellent discrimination for short-term mortality (AUROC 0.87-0.96) and reliably predicted transfusion and resource utilisation. Comparative studies showed NEWS outperforming SI across all mortality endpoints. SI accuracy was reduced in geriatric and isolated TBI populations, with low SI (<0.4) showing potential prognostic value in severe TBI. CONCLUSION: Prehospital NEWS provides superior prognostic accuracy compared with SI for predicting mortality and resource utilisation in adult trauma. SI may still assist in identifying patients requiring urgent intervention, but its overall predictive performance is limited. Incorporating NEWS into prehospital trauma assessment may enhance early risk stratification and support EMS decision-making.