Assessing the prognostic value of age-adjusted EASIX for predicting mortality in surgical ICU patients: a retrospective cohort study

Surgical intensive care unit (SICU) patients face high mortality rates, necessitating early and accurate risk stratification. The Age-Adjusted Endothelial Activation and Stress Index (aEASIX), a simple biomarker for endothelial dysfunction, has shown promise in other cohorts but remains uninvestigated in a broad SICU population. This study aimed to evaluate the association between aEASIX and clinical outcomes in patients admitted to the SICU. This retrospective cohort study derived data from the MIMIC-IV database (Boston, MA, USA), enrolling 4,394 adult patients upon their initial admission to the SICU. The aEASIX index was calculated as: age (years) × [serum creatinine (mg/dL) × lactate dehydrogenase (U/L)/platelets (109/L)]. Because the aEASIX distribution was markedly skewed, we applied a natural-log transformation (LnaEASIX). The primary outcome was 28-day ICU mortality, and the secondary outcome was 28-day in-hospital mortality. Multivariable logistic regression, restricted cubic splines, and receiver operating characteristic (ROC) curve analyses were performed. The clinical utility of the model was quantified through decision curve analysis and calibration plots. The overall 28-day ICU and 28-day in-hospital mortality rates were 18.0% and 17.09%, respectively. After adjusting for confounders, a higher LnaEASIX was independently associated with an increased risk of both 28-day ICU mortality (OR 1.287, 95% CI 1.176–1.408, P < 0.001) and 28-day in-hospital mortality (OR 1.315, 95% CI 1.200–1.441, P < 0.001). A non-linear, dose–response relationship was observed for both outcomes. Predictive performance analysis indicated that LnaEASIX possesses fair discriminative capacity for both 28-day ICU mortality (AUC = 0.653) and 28-day in-hospital mortality (AUC = 0.649). Notably, LnaEASIX demonstrated favorable calibration and yielded the maximal net benefit in the context of 28-day ICU mortality. The aEASIX score demonstrates independent prognostic value for short-term mortality across a broad spectrum of SICU patients.