We therefore designed this multicenter, retrospective observational study to assess serum levels of calprotectin, azurocidin, PCT, CRP, Interleukins and Tumor Necrosis Factor α (TNF-α), in healthy controls, patients with non-infectious Systemic Inflammatory Response Syndrome (SIRS), or sepsis/septic shock with blood cultures positive for Gram-negative bacteria. Here, CRP is linked to systemic inflammatory response syndrome.