Prognostic value of serum angiotensin-converting enzyme activity for outcome of community-acquired pneumonia

Background: In a previous study, a relation between decreased serum angiotensin-converting enzyme (ACE) activity and physiological parameters was observed in patients with community-acquired pneumonia. The present study aims to further assess the prognostic value of serum ACE activity for outcome of community-acquired pneumonia. Methods: This was a prospective observational study including two cohorts of patients with community-acquired pneumonia (2004-2006; n=157 and 2007-2010; n=138). Serum ACE activity was measured at time of hospital admission. Based on reference values in healthy persons, patients were divided into subgroups of serum ACE activity: normal, low and extremely low. Physiological parameters, clinical outcomes and etiology were compared between the subgroups. Results: A total of 265 patients were enrolled in this study. Mean age was 60 +/- 19 years. In patients with low serum ACE activity (< 20 U/L, n=53), compared to patients with normal serum ACE activity (>= 20 U/L, n=212), C-reactive protein (CRP) was significantly increased, systolic blood pressure was significantly lower and there was a trend for higher heart rate and leukocyte counts. Furthermore, Streptococcus pneumoniae was significantly more identified in patients with low serum ACE activity. Serum ACE activity < 24 U/L was independently associated with bacteremia (adjusted OR 3.93 [95% CI 1.57-9.87]). Low serum ACE activity was not prognostic for length of hospital stay nor mortality. Conclusions: This study did not show prognostic value for serum ACE activity regarding clinical outcome in patients with community-acquired pneumonia. Serum ACE activity < 24 U/L at time of hospitalization appeared an independent indicator for the presence of bacteremia. Further research should elucidate the role of ACE in systemic infection and sepsis during pneumonia.