Circulating cytokines as markers of systemic inflammatory response in severe community-acquired pneumonia

To assess the influence of empirical antibacterial therapy on systemic inflammatory response in patients with severe community-acquired pneumonia (CAP).

Thirty consecutive patients with CAP meeting systemic inflammatory response syndrome (SIRS) criteria were recruited into this study. Blood samples for measurement of interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10) and C-reactive protein (CRP) concentrations were drawn on days 1, 3, 5, 7 and 10. For analysis, these patients were divided into two subgroups according to British Thoracic Society (BTS) severity score and to clinical response to the initial antibacterial therapy.

In the group with severe CAP (n= 15), serum concentrations of IL-6 (P = 0.0001), IL-8, (P = 0.001), IL-10 (P = 0.0001) and CRP (P = 0.0001) were significantly higher compared to patients from the non-severe group (n= 15). IL-6 presented with a sharp decrease between days 1 and 3 in non-responders with severe CAP (P = 0.004). IL-6 concentrations on day 1 were significantly associated with a response to empirical antibacterial treatment by day 3.

Despite the absence of a clinical response to empirical antibacterial treatment as assessed by conventional clinical parameters on day 3 in patients with severe CAP meeting SIRS criteria, there was a marked reduction in the degree of the systemic inflammatory response as reflected by IL-6 levels.