Inflammatory parameters and prediction of prognosis in infective endocarditis

Procalcitonin (PCT) is widely used in critically ill patients to diagnose clinically significant infection and sepsis. Aim of this study was to evaluate the prognostic value of PCT in comparison to white blood cell count (WBC) and C-reactive protein (CRP) for clinical outcome and its correlation with microbiological etiology in patients with infective endocarditis (IE).

A retrospective single-center analysis was performed from 2007 till 2009. All patients were diagnosed having IE according to Duke standard criteria. Before starting antibiotic therapy, WBC, CRP and PCT were measured and blood cultures were taken for microbiological diagnosis of the etiological pathogen. Patients were followed up during in-hospital stay for poor outcome, defined as death or serious complications due to IE.

During the study period 50 patients (57 ± 17 years, 72% male) fulfilling Duke criteria for IE were identified. In all patients PCT measurements before start of antibiotic therapy were available. In ROC analysis, a cut-off for PCT > 0.5 ng/mL was most accurate for the prediction of poor outcome with a sensitivity of 73% and specificity of 79%, a positive predictive value of 79% and a negative predictive value of 73%. Patients with a PCT > 0.5 ng/mL had an odds ratio of 12.8 (95% CI 2.5-66.2) for finding Staphylococcus aureus in blood cultures.

For the first time, this study shows that in IE, an initial value of PCT > 0.5 ng/mL is a useful predictor of poor outcome, i.e. death or serious infectious complications. PCT > 0.5 ng/mL should raise the suspicion of Staphylococcus aureus as the etiological pathogen, whereas PCT levels < 0.5 ng/mL make staphylococcal infection unlikely.