Sepsis is a life-threatening organ dysfunction caused by a dysregulated response to infection, with mortality from 10–15%, up to 40% in septic shock. Timely antibiotics reduce mortality but rely on early identification, which is challenged by the heterogeneous early presentation. Effective risk stratification improves timely detection of patients at risk of rapid deterioration and death. The aims of this thesis were to examine early detection and treatment in acute care,identify risk factors, and explore the association between blood culture positivity, site of infection, sepsis, and mortality.

The importance of early treatment was underscored in Study I,where inappropriate initial antibiotic therapy increased mortality risk among the most severely ill (OR 10.42). Study II, showed that a prehospital delay more >24 hours (OR 6.17) and incorrect empirical antibiotic treatment (OR 5.50) were strong risk factors for mortality.

In both studies, the highest triage priority level (RETTS red) failed to detect >50% of patients who died within 30 days. In Study III prehospital lactate >3mmol/L was a predictor of mortality in patients with suspected sepsis (OR 2.20), even stronger among patients with lower triage priority (RETTS non-red) (OR3.02), and. Adding prehospital lactate >3mmol/L to increase priority among RETTS nonred improved early detection with a number needed to treat of (NNT) 9.1. In Study IV, BC positives presented more disease severity and inflammation but no difference in mortality compared to BC negatives (10.8%). Abdominal infections were associated with BC positivity (OR 2.35) and respiratory infections with BC negativity (OR 0.30). UTI was associated with lower mortality risk (OR 0.23).

In summary, improved knowledge and risk stratification are needed to enhance outcomes, and prehospital lactate >3 mmol/L may support earlier detection.