Comparison of utility of blood cultures from intravascular catheters and peripheral veins: a systematic review and decision analysis

Blood cultures are sometimes obtained from intravascular catheters for convenience. However, there is controversy regarding this practice. The authors compared the diagnostic test characteristics of blood cultures obtained from intravascular catheters and peripheral veins. Relevant studies for inclusion in this review were identified through PubMed (January 1970-October 2005) and the Cochrane Central Register of Controlled Trials. Studies that reported clear definitions of true bacteraemia were included in the analysis. Two reviewers independently extracted the data. Six studies were included in the analysis, providing data for 2677 pairs of blood cultures obtained from an intravascular catheter and a peripheral venipuncture. A culture obtained from an intravascular catheter was found to be a diagnostic test for bacteraemia with better sensitivity (OR 1.85, 95% CI 1.14-2.99, fixed effects model) and better negative predictive value (almost with statistical significance) (OR 1.55, 95% CI 0.999-2.39, fixed effects model) but with less specificity (OR 0.33, 95% CI 0.18-0.59, random effects model) and lower positive predictive value (OR 0.41, 95% CI 0.23-0.76, random effects model) compared to a culture taken by peripheral venipuncture. In a group of 1000 patients, eight additional patients with true bacteraemia would be identified and 59 falsely diagnosed as having bacteraernia by a blood culture obtained from an intravascular catheter compared to results of the peripheral blood culture. Given the consequences of undertreating patients with bacteraernia, the authors believe that, based on the available evidence, at least one blood culture should be obtained from the intravascular catheter.