Clinical usefulness of blood cultures in hospitalized patients with community-acquired pneumonia

Background: The clinical role of blood cultures (BC) in the management of hospitalized patients with community-acquired pneumonia (CAP) is controversial. Aim: To evaluate the clinical usefulness of blood cultures in CAP. Material and methods: We prospectively studied 244 immunocompetent adults with two or more BC obtained at admission. The diagnostic yield of BC and its impact on antibiotic therapy were assessed. Results: Mean age ((x) over bar +/- sd) of patients was 67 +/- 20 years, 80% bad underlying diseases and 29% received antibiotics prior to admission. Hospital length of stay was 10.4 +/- 10 days and global mortality was 7%. The diagnostic yield of BC was only 8.2% (20 patients). Mortality was significantly higher in patients with positive BC (20%) than in those with negative BC (5.8%). In only one of the 20 patients with, positive BC (0.4% of total study population), attending physicians changed empiric antimicrobial therapy based on these results. Conclusions: This study confirms that the diagnostic yield of BC in CAP hospitalized patients is low, that mortality in bacteremic patients is high and suggests that clinical usefulness of BC to guide changes on empiric antimicrobial therapy is limited, in part because attending physicians seldom use such information.