Clinical and laboratory variables identifying bacterial infection and bacteraemia in the emergency department.

Background: While early antimicrobial treatment is of critical importance to patients with severe infections, excessive use of antibiotics has caused escalating bacterial resistance. Better diagnostic tools are needed to secure antibiotic stewardship.

Methods: The diagnostic value of clinical and laboratory variables in predicting infections that require antibiotic treatment was evaluated in a prospective observational study of 404 adult patients admitted from the emergency department (ED) with suspected severe infections. We also investigated the association of these variables with bacteraemia and severe sepsis.

Results: In a univariate analysis, increased levels of C-reactive protein (CRP), procalcitonin (PCT), interleukin 6 (IL-6), lipopolysaccharide binding protein (LBP), white blood cell count (WBC), neutrophils, respiratory rate (RR) (p ≤ 0.001), and a decreased haemoglobin (Hb) level (p = 0.005) were associated with an indicated demand for antibiotics (n = 286). In a multivariate analysis, only WBC, Hb, RR, and CRP remained independent predictors. When compared to the clinician's ability to make accurate antibiotic decisions, all variables tested had inferior diagnostic accuracy except CRP. Increased levels of PCT, IL-6, LBP, CRP, bilirubin, and RR were significantly associated with bacteraemia (n = 68) (p ≤ 0.001). Of these, PCT and IL-6 were also associated with severe sepsis (n = 156) (p < 0.001). In a multivariate analysis, CRP, RR, PCT, and bilirubin remained associated with bacteraemia.

Conclusions: Special attention should be directed to CRP, WBC, RR, and Hb when selecting patients for antibiotic treatment in the emergency department. PCT, IL-6, and LBP did not provide additional guidance on antibiotic decisions and better tests are required in order to improve antibiotic stewardship.