How many sources should be cultured for the diagnosis of a blood stream infection in children with cancer?

Blood stream infection (BSI) in a child with cancer is a life-threatening condition while blood cultures (BCs) play a crucial role for the diagnosis. The current practice of obtaining a BC from all sources-peripheral vein, central venous catheter (CVC), all lumens-is controversial and therefore in this study, our aim was to evaluate the utility of obtaining BCs from all these available sources. A retrospective study of BC sets obtained from all newly diagnosed patients with malignancy was conducted. A total number of 633 BC sets from 123 boys and 88 girls (median age: 5 5/12 years) were evaluated during infection episodes from January 1, 2005, to August 31, 2010. Among these cases, 134 were classified as true BSI (21%), 468 as non-BSI, and 31 as false-positive. In 64 cases, the results from peripheral and CVC sources were discordant: 57 catheter positive-peripheral negative and seven catheter negative-peripheral positive. Consequently, seven out of 134 true BSIs (5.2%) would not have been identified if only a BC from a CVC had been obtained. Moreover, if no BCs from all lumens had been obtained we would have missed up to 25% of true-positive BSIs. In the same way, if BCs from all sources had not been drawn we would not have detected up to 52% of true-positive BSIs. Conclusion: Obtaining BCs during an infection episode from all sources in a child with cancer is still mandatory.