Background: Plasma levels of neutrophil elastase (NE) are elevated in several inflammatory diseases and thus this enzyme might be a critical inflammatory marker. However, the role of NE in the pathogenesis of pneumonia has not been determined. The association between the severity of pneumonia and blood levels of inflammatory markers could be relevant to developing a useful indicator of severity and new therapeutic strategies for pneumonia.
Methods: We searched for a useful predictive marker and a new therapeutic strategy against pneumonia, using a prospective, multicenter, population-based investigation. Several inflammatory markers in the circulation including NE, cytokines, defensins, C-reactive protein (CRP) and white blood cell (WBC) counts as well as clinical features were prospectively monitored in 28 adult patients with moderate (n=11) and severe pneumonia (n=17) over a period of 14 days.
Results: The value of plasma NE was the highest at entry and significantly declined 2 days later. Trends of cytokines, defensins, CRP and WBC counts were similar but blunter. Microorganisms and the outcome of initial treatment did not significantly affect plasma NE levels. Baseline values of plasma NE were significantly higher in severe, than in moderate pneumonia and this difference between the two types of pneumonia persisted longer than those of any other markers.
Conclusions: Neutrophil elastase appears to play a critical role in severe pneumonia and determination of its concentration in blood could be a useful indicator of severity. Furthermore, clinical trials of anti-NE drugs in patients with severe pneumonia should be promising.