The sterile conditions used when inserting a central venous catheter (CVC) might be thought to decrease the contamination rate of blood cultures taken at CVC insertion; however, a previous retrospective study showed the opposite, that such blood cultures are contaminated more frequently than peripheral venipuncture blood cultures. The current study explored whether use of the CVC nonwire hub as a source of blood cultures decreased contamination while maintaining detection of true pathogens.
A prospective, observational study was performed from June 2010 to May 2011 in the general ICU of an academic, tertiary referral center. The proportions of blood cultures taken from wire and nonwire CVC hubs growing contaminants and true pathogens were compared. Risk factors for blood culture contamination were identified, and multivariate analysis was used to identify independent predictors of blood culture contamination.
Among 313 blood cultures taken from 227 CVCs in 139 patients, 27 of 141 wire hub (19%) vs nine of 172 nonwire hub (5%) cultures were contaminated (P < .001). Only hub of blood culture origin was associated with contamination on multivariate analysis (OR, 4.3; 95% CI, 1.9-9.5; P < .001). True pathogens grew in 19 of 141 wire hub (13%) vs 27 of 172 nonwire hub (16%) cultures (P = .581).
A higher proportion of blood cultures taken from the CVC lumen exposed to the guidewire were contaminated when compared with nonwire hub cultures; detection of true pathogens was equivalent. To limit detrimental sequelae of blood culture contamination, blood cultures obtained at CVC insertion should be taken from the nonwire hub.