Reducing blood culture contamination in the emergency department: an interrupted time series quality improvement study

Abstract

Objectives: Blood culture contamination is a common problem in the emergency department (ED) that leads to unnecessary patient morbidity and health care costs. The study objective was to develop and evaluate the effectiveness of a quality improvement (QI) intervention for reducing blood culture contamination in an ED.

Methods: The authors developed a QI intervention to reduce blood culture contamination in the ED and then evaluated its effectiveness in a prospective interrupted times series study. The QI intervention involved changing the technique of blood culture specimen collection from the traditional clean procedure to a new sterile procedure, with standardized use of sterile gloves and a new materials kit containing a 2% chlorhexidine skin antisepsis device, a sterile fenestrated drape, a sterile needle, and a procedural checklist. The intervention was implemented in a university-affiliated ED and its effect on blood culture contamination evaluated by comparing the biweekly percentages of blood cultures contaminated during a 48-week baseline period (clean technique) and 48-week intervention period (sterile technique), using segmented regression analysis with adjustment for secular trends and first-order autocorrelation. The goal was to achieve and maintain a contamination rate below 3%.

Results: During the baseline period, 321 of 7,389 (4.3%) cultures were contaminated, compared to 111 of 6,590 (1.7%) during the intervention period (p < 0.001). In the segmented regression model, the intervention was associated with an immediate 2.9% (95% confidence interval [CI] = 2.2% to 3.2%) absolute reduction in contamination. The contamination rate was maintained below 3% during each biweekly interval throughout the intervention period.

Conclusions: A QI assessment of ED blood culture contamination led to development of a targeted intervention to convert the process of blood culture collection from a clean to a fully sterile procedure. Implementation of this intervention led to an immediate and sustained reduction of contamination in an ED with a high baseline contamination rate.

Figure 1

Fishbone diagram outlining factors the task force identified as contributors to a high emergency department blood culture contamination rate. CVC: central venous catheter; PIV: peripheral intravenous catheter.

Figure 2

Process maps of blood culture collection methods during (A) the baseline period prior to implementation of the sterile blood culture intervention, and (B) the intervention period after implementing the sterile blood culture intervention. Blood culture collection technique was not standardized during the baseline period; the method mapped represents the most common technique used. CVC: central venous catheter; PIV: peripheral intravenous catheter; g: gauge; ml: milliliter

Figure 3

Checklist outlining optimal technique for using the sterile blood culture kit to collect a blood culture specimen. Each kit contained a checklist.

Figure 4

Segmented regression analysis displaying the percentage of blood cultures contaminated during two-week intervals, March 1, 2009 – January 29, 2011. The sterile blood culture intervention was implemented on January 31, 2010, followed by a four week implementation phase that was not included in trend line calculations. Baseline period and intervention period trend lines were generated with an autoregressive integrated moving average (ARIMA) model (solid lines). The baseline period trend line was projected into the intervention period to display expected estimates of contamination assuming the intervention had not been implemented (dashed line).