Clinical Features and 1-Year Prognosis of Patients with Suspected Sepsis and Positive Blood Cultures in the Emergency Department: A Single-Center Retrospective Study

Background and Objectives: Sepsis is a life-threatening condition characterized by organ dysfunction due to a dysregulated host response to infection. Blood cultures (BCs) remain the gold standard for diagnosing bloodstream infections, yet their positivity rate is limited and culture-negative sepsis remains poorly characterized. This study aimed to identify clinical and laboratory predictors of BC positivity in patients with suspected sepsis and to evaluate the prognostic implications of BC results on 28-, 90-, and 365-day survival. Materials and Methods: We retrospectively analyzed adult patients admitted to the Emergency Department of Policlinico di Bari (March 2023–December 2025) with sepsis or septic shock (Sepsis-3 criteria). After excluding contaminated cultures, 912 patients were included (602 culture-positive; 310 culture-negative) with a 1-year follow up. Predictors of BC positivity were assessed using logistic regression and ROC analysis; survival was evaluated with Kaplan–Meier curves and Cox models adjusted for age and Sequential Organ Failure Assessment (SOFA) score. We also evaluated time-to-positivity (TTP) for all blood culture isolates. Results: Culture-positive patients presented with greater initial severity, including higher rates of septic shock, elevated procalcitonin, CRP, lactate, and SOFA scores, and more frequent thrombocytopenia. Procalcitonin showed good discriminatory ability (AUC (area under the ROC curve) 0.785; cutoff 0.85 ng/mL; sensitivity 59.8%; specificity 83.8%). Key laboratory thresholds included a procalcitonin cutoff of 0.85 ng/mL, while CRP and platelet count did not show meaningful discriminatory cutoffs beyond their significant differences between culture-positive and culture-negative patients. Survival was consistently lower in culture-positive patients at 28 days (72.9% vs. 85.9%), 90 days (57.5% vs. 71.8%), and 365 days (44.3% vs. 61.2%). However, in adjusted Cox regression, BC positivity was not independently associated with 1-year mortality (HR 1.46; p = 0.092), whereas age and SOFA score remained significant predictors. Conclusions: Blood culture positivity identifies patients with greater initial severity, explaining their poorer unadjusted survival. However, culture positivity itself is not an independent predictor of long-term mortality, as age and organ dysfunction remain the main determinants of outcome. Procalcitonin showed solid discriminatory ability for true bacteremia.