Introduction: Early diagnosis of infective endocarditis is important for the clinical outcome since mortality increases with a longer diagnostic delay. The diagnosis of infective endocarditis is mainly based on clinical features, echocardiography and blood culture findings. Unfortunately negative blood cultures have been reported in up to 30% of proved cases. The aim of the study was to investigate usefulness of serum cytokines concentrations in diagnosis and monitoring of infective endocarditis.
Material and Method: The study group consisted of 30 patients with acquired rheumatic valvular heart diseases and ongoing infective endocarditis. The diagnosis of infective endocarditis was established on clinical examination, echocardiography, laboratory investigations (inflammatory parameters) and positive blood cultures (in 26 patients). Control group consisted of 10 patients with acquired rheumatic valvular heart diseases without infective endocarditis. Serum interleukin-1a (IL-1a), interleukin-6 (IL-6) and a tumor necrosis factor-a (TNF-a) concentrations were measured three times during antimicrobial treatment (mean interval 16±8 days).
Results: Serum IL-1a and TNF-a concentrations were not elevated in any patient or control (IL-1a<3.9 pg/ml, TNF-a<10 pg/ml - below calibration range). Serum IL-6 concentrations were elevated in all measuring points in patients with infective endocarditis (first: 36.7±48.1, second: 19.2±17.5 third: 8.7±5.7 pg/ml) with a significant tendency to decrease during treatment (ANOVA, p<0.01). In all controls serum IL-6 concentrations were below calibration range (<3.2 pg/ml).
Conclusions: 1. Elevated serum IL-6 concentrations may suggest ongoing infective endocarditis and could be an additional parameter in diagnosis and monitoring treatment of the disease. 2. Serum IL-1a and TNF-a concentrations were not affected. Further understanding the role of serum cytokines concentrations in diagnosing, prognosis and monitoring of infective endocarditis could be useful in clinically uncertain diagnosis especially  while blood cultures are negative.

Keywords: Cytokines, infective endocarditis, Diagnosis