Evaluation of serum cytokine concentrations in patients with infective endocarditis

Background and aim of the study: Early diagnosis of infective endocarditis is important for clinical outcome, as mortality increases if diagnosis is d elayed. Diagnosis is based on clinical features, echocardiography and blood culture findings, but negative blood cultures have been reported in 5-15% of proven cases. The study aim was to investigate serum cytokine levels in patients with infective endocarditis, and the possible use of these data in diagnosis and monitoring of the disease. Methods: The study group comprised 40 patients with acquired rheumatic valv ular heart disease and ongoing infective endocarditis. A diagnosis of infec tive endocarditis was established by clinical examination, echocardiography , laboratory investigations (inflammatory parameters) and positive blood cu ltures (n = 34). Two control groups included patients with acquired rheumat ic valvular heart disease: 15 without infective endocarditis, and 15 with a ctive urinary tract infection with significant bacteriuria. Serum interleuk in-1 alpha (IL-1 alpha), interleukin-6 (IL-6) and tumor necrosis factor-alp ha (TNF-alpha) levels were measured on three occasions during antimicrobial treatment (mean period 14 +/- 7 days). Results: Serum IL-1 alpha and TNF-alpha levels were not elevated in the stu dy group, or in controls (IL-1 alpha <3.9 pg/ml; TNF-alpha <10 pg/ml). Seru m IL-6 levels were elevated on all occasions in patients with infective end ocarditis (first measurement: 37.0 +/- 44.3 pg/ml; second 18.7 +/- 16.4; th ird 8.5 +/- 5.2) with a significant tendency to decrease during treatment ( p <0.01, ANOVA). In all controls without infection the serum IL-6 concentra tions were below calibration range (<3.2 pg/ml). In the control group with active urinary tract infection, IL-6 concentrations were slightly (but not significantly) elevated (4.49 +/- 1.82 pg/ml, p = NS). Conclusion: Elevated serum IL-6 levels may suggest ongoing infective endoca rditis and might be used to aid in diagnosis and monitoring of treatment of the disease. Serum IL-1 alpha and TNF-alpha levels were not affected. A fu rther understanding of the role of serum cytokine concentrations in the dia gnosis, prognosis and monitoring of infective endocarditis might be valuabl e in clinically uncertain diagnoses, especially when blood cultures are neg ative.