Availability of this IVD will enable patient selection for appropriate disposition, such as the intensive care unit (ICU), and use of medical therapies, such as early goal-directed therapy (EGDT), thereby reducing mortality and increasing effectiveness of resource allocation. A considerable literature exists of host plasma protein changes during sepsis. Furthermore, in preliminary studies measuring more than 100 host proteins in blood of over 300 patients with SS, we have identified a number of candidate biomarkers of SS. We propose to inventory, replicate and validate the utility of these biomarkers of SS, and to identify novel plasma biomarkers of SS, through literature review and a prospective clinical study employing 2 proteomic technologies (mass spectrometry and multiplexed immunoassays), mass spectrometry-based plasma metabolomics and sequencing of mRNA derived from peripheral blood lymphocytes. We intend to enroll 1200 patients with sepsis (evidence of infection and 2 or more criteria of the systemic inflammatory response syndrome, SIRS) at 3 US tertiary care hospitals and emergency departments (ED), and to monitor their course both by established clinical severity indices (Acute Physiology and Chronic Health Evaluation [APACHE II] and Pneumonia Patient Outcomes Research Team [PORT]scores, and metabolic endpoints such as lactate, base deficit and pH) and ascertainment of complicating events (such as SS, septic shock, acute renal failure (ARF), acute respiratory distress syndrome (ARDS),disseminated intravascular coagulopathy (DIC) and death). It is anticipated that approximately 60% of the patients will develop SS.