Serum level of YKL-40 is elevated in patients with Streptococcus pneumoniae bacteremia and is associated with the outcome of the disease.

YKL-40 is secreted by activated macrophages and neutrophils. Elevated serum concentrations of YKL-40 are found in patients with diseases characterized by inflammation or ongoing fibrosis. The aim of this study was to evaluate serum YKL-40 levels in patients with Streptococcus pneumoniae bacteremia and to correlate these levels with clinical findings and outcomes. YKL-40 was determined by ELISA and 89 patients were included in the study. Serum YKL-40 levels were significantly higher in patients with S. pneumoniae bacteremia (median 342 mug/l; range 20-20, 400 mug/l) than in age-matched healthy subjects (44 mug/l; 20-184; p<0.001). Serum YKL-40 levels were related to the severity of the infection, with significantly higher serum YKL-40 levels being observed in patients who needed hemodialysis (p<0.001), pharmacological treatment of hypotension (p<0.001) and mechanical ventilation (p =0.003) compared to those in patients who did not need this supportive treatment. Nineteen patients died and these patients had significantly higher serum YKL-40 levels (980 mu g/l; 88-20,400 mu g/l) than those of survivors (256 mu g/l; 20-9,100 mu g/l; p<0.001). Serum YKL-40 level was an independent prognostic factor of survival in logistic multivariate regression analysis (p = 0.002). In conclusion, high serum levels of YKL-40 indicated a poorer prognosis for patients with S. pneumoniae bacteremia.