BACKGROUND: Early assessment and intervention are crucial for improving survival in septic shock. This study aimed to address the shortcomings of existing scoring systems in predicting the risk of early death, particularly in identifying patient populations that require more precise prognostic assessments. METHODS: This retrospective study included 143 patients with septic shock admitted to the intensive care unit of a tertiary hospital between January 1, 2019, and June 30, 2024. Patients were stratified by 28-day survival status. Binary logistic regression analysis identified independent predictors of early mortality and developed a prognostic model, which was validated using receiver operating characteristic curves. RESULTS: Among the patients, 106 survived, whereas 37 died. Multi-factor binary logistic regression analysis identified the sequential organ failure assessment (SOFA) score and the C-reactive protein-albumin-lymphocyte (CALLY) index as significant independent predictors of 28-day mortality (p <
0.05), culminating in the formulation of the "SOFAplusCALLY" model. This model showed superior predictive accuracy compared to other Scoring systems (area under the curve: 0.90, p <
0.01) and was validated for robustness in both training and validation cohorts. CONCLUSIONS: The CALLY index and SOFA score independently forecast 28-day mortality in adults with septic shock, offering substantial clinical utility for forecasting patient prognosis. The SOFAplusCALLY model, synthesized from both indices, comprehensively assesses the clinical status of patients with septic shock and enhances prognostic accuracy, which is crucial for clinical decision-making and resource allocation.