Usefulness of infection biomarkers for diagnosing bacteremia in patients with a sepsis code in the emergency department.

The objective of this study was to assess the usefulness of the biomarkers lactate, C-reactive protein (CPR) and procalcitonin for the diagnosis of bacteremia in patients with suspected sepsis in the emergency department (ED) and according to the focus of infection. We conducted a retrospective study among patients included in the sepsis code of our ED between November 2013 and December 2017. We analyzed demographic variables, co-morbidity according to the Charlson Index and focus of infection, blood cultures and classification according to Gram staining. We determined the diagnostic performance of the biomarkers quantitatively and calculated the area under the curve (AUC) for global bacteremia and as a function of the focus of infection. We included 653 patients with a median age of 79 years (interquartile range: 66-86), of whom 287 (44.0% were women. The most frequent infectious focus was respiratory (36.1%]. Blood cultures were requested in 87.5% (569 cases). Of the tested samples, 31.3% were positive, of which 63.5% revealed Gram-negative (GN) bacteria. Procalcitonin obtained globally the best AUC 0.70 (95% CI: 0.65-0.75). The values with the best sensitivity and specificity were 2.54 ng/mL for procalcitonin, 4.1 mmol/L for lactate and 156 mg/L for CRP. We found an association between the median procalcitonin value and GN bacteria (6.02; IQR: 1.39-39.40) and Gram-positive bacteria (1.74; IQR: 0.22-15.61). Procalcitonin is the biomarker with the greatest capacity to diagnose bacteremia, particularly in GN infection. Stratification by focus is important since not all biomarkers discriminate in the same way.