Comparison of the lactate-to-albumin ratio, Shock index, and injury severity score for predicting in-hospital mortality among trauma patients presenting to the emergency department: a retrospective study

Aims: Rapid and accurate risk stratification is vital in trauma care. This study compared the prognostic performance of the lactate-to-albumin ratio (LAR), the Shock Index (SI), and the Injury Severity Score (ISS) in predicting in-hospital mortality among adult trauma patients presenting to the emergency department (ED). Methods: Single-center retrospective cohort of consecutive adult (≥18 years) trauma presentations to a tertiary ED (January 2022–January 2025). Cases with missing core variables were excluded. Discrimination for ICU admission, invasive mechanical ventilation, and in-hospital mortality was quantified by area under the ROC curve (AUC) with 95% CIs and compared pairwise using DeLong tests. Youden-optimized thresholds were summarized with positive/negative likelihood ratios, predictive values, and Youden’s J. In-hospital mortality associations were examined using univariable and prespecified multivariable logistic regression. Results: A total of 4.942 patients were included, and the in-hospital mortality rate was 3.1%. The ISS consistently performed better than the SI and the LAR. For intensive care unit (ICU) admission, the AUCs were 0.943 for ISS, 0.829 for SI, and 0.801 for LAR. For the need for mechanical ventilation, the AUCs were 0.938 for ISS, 0.813 for SI, and 0.788 for LAR. For in-hospital mortality, the AUCs were 0.851 for ISS, 0.763 for LAR, and 0.757 for SI. DeLong tests showed that ISS was significantly superior to both SI and LAR in predicting in-hospital mortality (p