Appropriateness of obtaining blood cultures in patients with community acquired pneumonia.

Community acquired pneumonia (CAP) is a common disease and blood cultures are frequently performed to identify a causative agent, but doing this results in an economic burden. We evaluated the appropriateness of performing blood cultures in clinical practice and determined predictors for positive blood cultures in CAP patients. We reviewed patients diagnosed with CAP at Khon Kaen Hospital, Thailand between January 1 and December 31, 2009. Clinical features, and results of blood and sputum cultures were studied. Clinical factors predictive for positive blood cultures were evaluated by multiple logistic analysis. During the study period 1,160 patients were diagnosed with pneumonia; of those, 261 patients (22.5%) met the criteria for CAP. All patients were performed blood and sputum cultures. Blood cultures were positive in 24 patients (9.2%); 15 patients had severe pneumonia. On multivariate analysis, neutrophils comprising more than 80% of the white blood cell count in peripheral blood was the only significant predictor for a positive blood culture. The adjusted odds ratio was 3.713 (95% confidence interval was 1.333-10.340). In our study population blood cultures are only appropriate among CAP patients with a neutrophil count greater than 80%.