Blood Cultures (BCs) are an essential diagnostic tool for the detection of bacteremia and fungemia and are required to guide specific antimicrobial therapy in septic patients. BCs are commonly performed in the Emergency Department (ED); however, contaminated BCs (i.e., false-positive BCs) are a common problem and represent up to half of all positive BCs [1, 2]. Indeed, false-positive BCs due to specimen contamination with skin bacteria range from 0.6% to over 6% and associated with unnecessary exposure to antimicrobials and their associated toxicity, additional cultures and other diagnostic tests, and prolonged hospital stays [1, 5-7]. Contaminated BCs increase laboratory costs by approximately 20%, are associated with a nearly 40% increase in antibiotic charges, and as much as 5 additional days in the hospital [1, 8-10]. Several techniques have been used to reduce BC contamination including the use of specific disinfection materials [2, 11], educational interventions [2, 6, 12, 13], collection from separate venipuncture sites [5, 7], use of the outmoded double-needle technique [7], commercial BC kits [3, 14, 15], and reliance on specially trained staff or dedicated phlebotomy teams [2, 7, 8, 16]. The aims of the present study were to assess BC contamination in the ED and the impact of monthly monitoring of BC contamination and feedback on contamination rate.

The contamination rate of BCs in January 2017 before the intervention started was 7.8%. In response, 12 workshops were conducted in February and March, with an average attendance of 5 to 10 staff nurses and students. These workshops were initially offered to nurses on duty in the morning and afternoon and, in March, very early morning sessions were also offered to those working in the night shift. After covering 90% of staff involved in BC collection, workshops were offered as needed to new staff nurses or those who collected more than two contaminated BCs. The intervention led to a decrease in contamination from 9.4% in February to 2.4% in December Fig. (1). The overall trend of contamination showed a decrease during the project period, apart from a slight increase in the summer (likely due to shortage of staff during vacations season), to a sustainable level below 3%. Results of all BCs collected during the study period are presented in Table 1 and Fig. (2). Half of the positive BCs in January and 62.3% in February were contaminated; in contrast, 24.0%, 25.3%, 21.3% and 28.2% in September, October, November and December, respectively were contaminated. This represents a consistent improvement in the predictive value that a positive culture is significant.

The most common microorganisms and contaminants recovered from BCs during the study are shown in Table 2 and 3, respectively. CoNS, Escherichia coli, and Staphylococcus aureus represented 52.1% of all BC isolates. When the total positive BCs were analyzed for contaminants, 60.9% were CoNS. More than one bacterial species was present in 10 of 324 positive BCs (3.1%) and at least one bacterial contaminant was recovered from the majority (82%) of the mixed cultures.

Fig. (2). Monthly contamination versus true positive blood cultures, 2017.

Bloodstream infections are a serious medical condition, associated with significant morbidity and mortality. The latter varies between 14% and 34%, depending on whether the infection originates in the community or the hospital [17, 18]. Early administration of appropriate antimicrobial agents directly influences the patient outcomes [19] and BCs are needed for organism identification and susceptibility testing to guide the selection of specific, appropriate antimicrobials. However, the value of BC is related directly to the incidence of false-positive results. In many EDs, BC collection frequently occurs without attention to a standardized process for specimen collection [20]. Although it is recommended that target rates for BC contamination should not exceed 3% [4], the contamination rate in many institutions actually exceeds 7% [1, 8, 14] with the highest rates found in ED settings [6, 20-22]. In our institution, 7.8% of the total BCs collected from ED in January 2017 were contaminated. This triggered an ad hoc quality improvement team to develop and implement a corrective action plan to improve the standard of BC collection technique. The cause of high ED contamination rates was likely multifactorial, including frequent staff turn-over, fast-paced working environments, and the time pressure of collecting specimens before administering an initial dose of antibiotics or the need to intervene in the management of other patients while collecting BCs [6, 20-22]. While adherence to evidence-based best practice when collecting BCs is supposed to be the standard of care, compliance can be unsatisfactory and the high BC contamination rate might be a result of the lack of training and education, lack of surveillance and monitoring, inadequate staffing, shortage of materials, or the use of poor quality materials [7]. From previously published work, hospital-wide educational intervention had led to reductions in contamination rates at our institution, but rates for the ED remained high due to lack of attendance [13]. Because our hospital did not invest in the establishment of a dedicated phlebotomy team for BC collection, the present study investigated the effect of detailed monitoring and monthly feedback on contamination rate. During educational sessions, it was found that some of the nurses were not aware of the existence of the BC collection protocol. Although nurses in the ED are busy with their clinical work by nature, it must be emphasized that appropriately collected BC will lead to less contamination and therefore less work, due to unnecessary admissions, antibiotic use, and repeat of laboratory investigations. Gibb et al. found that monitoring and feedback of the incidence of contamination were successful in achieving a 50% reduction, although the rate of contamination in BCs collected by nonphlebotomists did not change [23]. The present study showed a 75.6% reduction in contamination rate, comparing data from January and February (av. 8.6%) before the start of intervention to data from November and December (av. 2.1%). While it is not new to show that monitoring of BC results and feedback reduces the contamination rate, the present study led to the assessment of staff competency in drawing blood for cultures, availability of a clear protocol or policy, currently used practices, contamination rates, and the effect of educating staff nurses regarding the contamination rate. This is the first study showing successful reduction of BC contamination in the ED where all BCs were collected by nurses and not by a phlebotomy team.

Clinicians often respond to these false-positive tests by initiating diagnostic studies and treatments that would otherwise not have been pursued. Two studies estimated that BC contaminants were associated with increased length of hospital stay, by 1 day and 3 days, and additional hospital charges, by $8,720 and $8,750 per patient, respectively [8, 24]. A similar case-control study showed statistically significant differences between false positive and true negative results in the mean length of hospital stay (5.4 days) and total costs ($7,502) [10]. If we take the average contamination rate in January and February as a representative rate before the start of the project, we can compare the cost of contamination with and without the intervention. By using the estimated cost of $8000 per false positive BC, the difference in hospital costs in our institution during a 12-month period assuming no intervention (8.6% contamination rate [January-February]) and the same period with the effect of the current project (2.1% contamination rate [November-December]) is approximately $1,384,000 ($1,824,000 vs. $440,000). While educational interventions lead to reduction in BC contamination, maintaining acceptable contamination rates can be quite challenging. A recent review suggests that venipuncture and the use of phlebotomy teams are effective for reducing BC contamination rates and are recommended as evidence-based “best practice” [25]. In addition, several studies support that phlebotomy teams are not only cost-effective but also cost-saving solely based on reduced BC contamination, driven by reduced hospital length of stay, pharmacy and laboratory services [2, 8, 16, 21]. The estimated savings per year achieved by the current project would counterbalance the cost of adoption of a phlebotomy team.

Limitations in this quality improvement project included the lack of a control group. No attempts were made to determine neither the number of admissions, patient’s call back, diagnostic investigations nor antibiotic use among patients with contaminated BCs. Although it was possible to reduce the contamination rates to acceptable levels, it is harder to maintain the competency of a large number of healthcare workers, which requires continuous follow-up interventions. Because nurses are understaffed and extremely busy with their clinical responsibilities, they are unlikely to be able to comply consistently with the recommended best practice BC collection protocol.

In conclusion, the increase in patient morbidity and excess costs caused by false-positive BC supports the use of substantial efforts to decrease the rate of contamination. While the current project aimed at examining education of the ED nurses on proper performance of BC collection procedures, there are difficulties in achieving long-term sustainable low contamination rate, and the utilization of a dedicated phlebotomy team may likely be more effective and easy to follow.

This study was presented on the American Society for Microbiology (ASM Microbe), 2017 at New Orleans/USA, abstract no. 2017-A-4494-MICROBE.