Impact of Pre-Analytical Time on the Recovery of Pathogens from Blood Cultures: Results from a Large Retrospective Survey

Abstract

BackgroundPrompt identification of bloodstream pathogens is essential for optimal management of patients. Significant changes in analytical methods have improved the turnaround time for laboratory diagnosis. Less attention has been paid to the time elapsing from blood collection to incubation and to its potential effect on recovery of pathogens. We evaluated the performance of blood cultures collected under typical hospital conditions in relation to the length of their pre-analytical time.MethodsWe carried out a large retrospective study including 50,955 blood cultures collected, over a 30-month period, from 7,035 adult septic patients. Cultures were accepted by the laboratory only during opening time (Mon-Fri: 8am–4pm; Sat: 8am–2pm). Samples collected outside laboratory hours were stored at room temperature at clinical wards. All cultures were processed by automated culture systems. Day and time of blood collection and of culture incubation were known for all samples.ResultsA maximum pre-analytical interval of 2 hours is recommended by guidelines. When the laboratory was open, 57% of cultures were processed within 2 h. When the laboratory was closed, 4.9% of cultures were processed within 2 h (P<0.001). Samples collected when the laboratory was closed showed pre-analytical times significantly longer than those collected when laboratory was open (median time: 13 h and 1 h, respectively, P<0.001). The prevalence of positive cultures was significantly lower for samples collected when the laboratory was closed compared to open (11% vs 13%, P<0.001). The probability of a positive result decreased of 16% when the laboratory was closed (OR:0.84; 95%CI:0.80–0.89, P<0.001). Further, each hour elapsed from blood collection to incubation resulted associated with a decrease of 0.3% (OR:0.997; 95%CI:0.994–0.999, P<0.001) in the probability of a positive result.DiscussionDelayed insertions of cultures into automated systems was associated with lower detection rates, with potentially important consequences for patients. In each hospital setting the logistic factors able to shorten pre-analytical time should be carefully investigated and specifically targeted.

On-site blood culture incubation shortens the time to knowledge of positivity and microbiological results in septic patients

“…Current recommendations suggest blood culture incubation within 2 to 4 h [11,27]. Whereas only about one-third of all positive blood culture sets in the LAB group were incubated within 4 h, all sets in the ICU group were processed according to these recommendations within 1 h. In accordance with recently published data, we found an overall positivity rate of 18.6% [11,28]. Interestingly, there was a 6.5% higher positivity rate in the LAB group.…”

“…Similarly, the increased TTI on weekends has been described before. Other studies found shorter transportation periods of 3 to 4 h; however, these did not report corresponding turnaround times [9][10][11]. Kerremans et al reported a reduction of TTP defined as the time from collection to growth detection by 10 h if blood cultures were incubated immediately and continuously monitored [19].…”

“…The current Surviving Sepsis Campaign guidelines recommend "that blood cultures be obtained prior to initiating antimicrobial therapy if cultures can be obtained in a timely manner" and subsequent incubation within 4 h after diagnosis [10]. Every hour of delayed incubation results in a decreased probability of culture positivity [11]. Recent studies have demonstrated an association of delayed antimicrobial administration with increased progression of sepsis to septic shock and increased mortality [12,13].…”

The Impact of Transit Times on the Detection of Bacterial Pathogens in Blood Cultures: A College of American Pathologists Q-Probes Study of 36 Institutions

“…10 Several authors reported that delayed entry of blood culture bottles into the specimen incubator lengthens the overall time to pathogen detection or may result in microorganism loss. 7,8,11 This Q-Probes study aimed to assess whether this effect would be detected among participating laboratories, which portion of the preanalytic phase of blood culture collection might be problematic, whether transport and processing may be responsible for delayed pathogen detection, whether blood culture volume adequacy is associated with instrument time-to-detection, and to provide participants with important benchmarking data to compare their performance. This study found that most laboratories process blood cultures and place specimens on the instrument within 2 hours of collection (N ¼ 36; median ¼ 47 minutes; 75th percentile ¼ 108 minutes).…”

“…Delays in delivering blood culture specimens to the laboratory have the potential to prolong the time to detection of bacterial pathogens by blood culture instruments, and subsequently the identification of the pathogen to the caregiver. [6][7][8] Additionally, the insufficient acquisition of the proper volume of blood in blood culture bottles diminishes the sensitivity of the blood culture, and potentially could affect the time to pathogen detection by blood culture instruments. In turn, prolonged time to detection and subsequent identification of bacterial pathogens may delay appropriate antibiotic therapy, when the selection of empiric antimicrobial coverage was insufficient.…”