Usefulness of cytokines interleukin-6 and interleukin-2R concentrations in diagnosing active infective endocarditis involving native valves.

The most important diagnostic value in infective endocarditis (IE) is isolation of the causative microorganism. Because premature antibiotic treatment is commonly administered before the assessment of blood cultures, the percentages of isolated microorganisms has decreased significantly within the last decades. Therefore, additional criteria for the diagnosis of IE may be helpful. It was hypothesized that assessment of interleukin-6 (IL-6) and interleukin-2R (IL-2R) may provide new diagnostic criteria for inflammation in IE. IL-6 and IL-2R serum concentrations, white blood cell count (WBC), and C-reactive protein (CRP) were measured in the blood of 47 patients with IE at the time of diagnosis and during treatment. WBC and CRP were elevated in patients with IE at the time of diagnosis. Both parameters were higher (p <0.05) in patients with positive blood cultures when compared with negative cultures. The differences persisted during the first week of treatment (p <0.01). In contrast, IL-6 and IL-2R concentrations were elevated (p <0.001) independently of the status of blood cultures. Serum concentrations of IL-6 and IL-2R decreased continuously during antibiotic treatment. Assessment of IL-6 and IL-2R could thus provide new diagnostic criteria for inflammation in IE, and these interleukins could also be suitable for monitoring the course of inflammation during treatment.