Clinical Performance of BIO-S and BIO-SC Composite Bioscores for 28-Day Mortality Stratification in Adults with Sepsis and Septic Shock

Background: Short-term mortality stratification in sepsis remains clinically challenging, particularly because outcome is influenced by acute inflammation, coagulation abnormalities, organ dysfunction, and baseline comorbidity burden. This study evaluated the clinical performance of the BIO-S and BIO-SC composite bioscores for 28-day mortality stratification in adults with sepsis and septic shock. Methods: We conducted a prospective observational monocentric cohort study including 572 adult patients admitted between January 2022 and December 2024. BIO-S integrated procalcitonin (PCT), neutrophil-to-lymphocyte ratio (NLR), International Normalized Ratio (INR), and Sequential Organ Failure Assessment (SOFA) score, while BIO-SC extended this model by adding the Charlson Comorbidity Index (CCI). Prognostic performance was assessed using receiver operating characteristic (ROC) curve analysis, DeLong comparisons, bootstrap validation, calibration analysis, Kaplan–Meier survival curves, and Cox proportional hazards models. Results: The cohort included 418 patients with sepsis and 154 patients with septic shock. Overall 28-day mortality was 31.5% and was significantly higher in septic shock than in sepsis, 77.9% versus 14.4%, p < 0.001. BIO-S and BIO-SC showed strong discriminatory ability for 28-day mortality, with areas under the curve (AUCs) of 0.889 and 0.897, respectively. BIO-SC had the highest AUC, although the difference between BIO-SC and BIO-S was not statistically significant by the DeLong test, p = 0.328. At the optimal thresholds, BIO-S showed 97.8% sensitivity and 69.4% specificity, while BIO-SC showed 89.4% sensitivity and 77.8% specificity. Both bioscores stratified observed mortality across predefined risk categories and remained significantly associated with 28-day mortality in adjusted Cox models. Conclusions: BIO-S and BIO-SC showed clinically relevant performance for 28-day mortality stratification in adults with sepsis and septic shock. BIO-SC provided a numerically higher AUC and slightly better calibration, suggesting that comorbidity burden may improve prognostic characterization, although further independent multicenter validation is needed before broader clinical implementation.