Blood culture contamination is a common problem faced by medical centers and leads to significant cost. A possible method to reduce contamination is to discard the initial aliquot of blood, which contains skin and bacteria.
To determine whether the rate of contaminant blood cultures could be reduced by changing the order of draw to divert the first 7 mL to a gold- or green-top tube.
A preintervention and postintervention study was conducted. During the 18-month intervention phase (September 2015-February 2017), all nurses in the emergency department and inpatient floor phlebotomists collected blood cultures by drawing the first 7 mL of blood into a gold- or green-top tube followed by drawing blood for blood culture bottles. The 18 months immediately preceding the study period (February 2014-July 2015) were used for comparison.
There was an overall statistically significant decrease in contamination rate from 2.46% in the prediversion protocol group to 1.70% in the postdiversion protocol group ( < .001). Emergency department drawn cultures and inpatient cultures showed significant decrease in contamination rates between the preprotocol and postprotocol groups, 2.92% versus 1.95% ( < .001) for emergency department, and 1.82% versus 1.31% ( = .03) for inpatient. We noted less month-to-month variation during the study period compared with the preintervention period.
By using this simple diversion method, we were able to improve blood culture contamination rates for our emergency department and inpatients while incurring no added cost to the procedure.