Combination of biomarkers for the discrimination between bacterial and viral lower respiratory tract infections

Abstract

To investigate whether additional determinations of plasma lipopolysaccharide binding protein (LBP), procalcitonin (PCT), interleukin-6 (IL-6), IL-18, or soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) to C-reactive protein (CRP) improve the discrimination between bacterial and viral lower respiratory tract infections (LRTI). Out of 342 patients visiting the emergency department because of a suspected infection and ≥2 clinical signs of sepsis, 56 patients with proven bacterial (n = 39) or viral (n = 17) LRTI were included. The area under the ROC curves (AUC) of the five possible combinations of CRP with one other biomarker were compared with the AUC of CRP alone. Next, the same analysis was performed in the group of patients with a CRP concentration with <95% specificity for bacterial LRTI. While CRP, PCT, IL-6, sTREM-1, and LBP concentrations were significantly different between patients with bacterial or viral LRTI, the AUC of CRP (0.82, 95% CI 0.70-0.93) did not increase after combination analyses. After exclusion of patients with a CRP >150 mg/l, biomarker panel analyses did not improve diagnostic accuracy of CRP either. Combining CRP with LBP, PCT, IL-6, IL-18, or sTREM-1 does not improve differentiation between patients with a bacterial or viral LRTI compared with CRP alone.