Laboratory markers of systemic inflammation as predictors of bloodstream infection in acutely ill patients admitted to hospital in medical emergency

The aim of the present study was to determine whether the presence of an infectious focus or of fever alone can predict bloodstream infection and whether levels of C-reactive protein, procalcitonin, interleukin (IL)-6, IL-8, and soluble IL-2 receptor (sIL-2R) improve the diagnosis of community-acquired bloodstream infection. Markers of systemic inflammation were studied in 92 patients with community-acquired infection. On admission to hospital, 54 patients had an infectious focus, 25 had fever without an infectious focus, and 13 had neither. The presence of focus or fever predicted bloodstream infection (n=13 patients) with a sensitivity of 100% (95% confidence interval, 75-100), a specificity of 16% (95% CI, 9-26), a negative predictive value of 100% (95% CI, 75-100), and a positive predictive value of 16% (95% CI, 9-26). Positive predictive values of C-reactive protein, procalcitonin, IL-6, IL-8, and sIL-2R, all measured on admission, were also low (33-44%). Eight febrile patients in whom an infectious focus was found during a 3-day follow-up period had higher on-admission IL-6 (P=0.005) and sIL-2R (P=0.046) levels than did 17 febrile patients without an infectious focus. In conclusion, markers of systemic inflammation do not improve the diagnosis of community-acquired bloodstream infection; however, they may aid in identifying patients with fever due to occult infection.