Timing of Specimen Collection for Blood Cultures from Febrile Patients with Bacteremia

Abstract

Bloodstream infections are an important cause of morbidity and mortality. Physician orders for blood cultures often specify that blood specimens be collected at or around the time of a temperature elevation, presumably as a means of enhancing the likelihood of detecting significant bacteremia. In a multicenter study, which utilized retrospective patient chart reviews as a means of collecting data, we evaluated the timing of blood culture collection in relation to temperature elevations in 1,436 patients with bacteremia and fungemia. The likelihood of documenting bloodstream infections was not significantly enhanced by collecting blood specimens for culture at the time that patients experienced temperature spikes. A subset analysis based on patient age, gender, white blood cell count and specific cause of bacteremia generally also failed to reveal any associations.Bloodstream infections (BSIs) occur more than 200,000 times annually in the United States, with associated mortality rates of 35 to 60% (20,33,34). Prompt administration of appropriate antimicrobial therapy plays an important role in reducing the mortality associated with this condition (9,12,14, 15,16,18,22,26,31). In patients with bacteremia, the optimization of therapy is ultimately predicated on rapid documentation of positive blood cultures, expeditious performance of in vitro antimicrobial susceptibility tests, and timely reporting of results (2,23,33). Numerous factors influence the likelihood of detecting bacteremia. These factors include the volume of blood specimens cultured and the number of blood cultures performed (1,8,10,11,17,21,25,27,29). The conventional practice has been to obtain blood specimens at or around the time of a temperature elevation as a means of enhancing the likelihood of documenting bacteremia (5, 32). This practice is based on the principle that the presence of organisms in the intravascular space leads to the elaboration of cytokines, which in turn causes body temperatures to rise.The value of attempting to time the collection of blood for culture around temperature elevations is complicated by the fact that many patients with bacteremia, especially those that are elderly, may be hypothermic at the time that they are bacteremic or may be unable to mount a febrile response to infection (7). Furthermore, there are numerous causes of fever other than bacteremia, e.g., ischemia, drug reactions, immunological conditions, and malignancy (4). This issue is further complicated by the observation made more than 50 years ago by Bennett and Beeson: bacteremia actually precedes temperature elevations by 1 or 2 h (3). These researchers noted that blood cultures were frequently negative at the time of the temperature spike and concluded that, ideally, blood cultures should be drawn some time prior to elevations in temperature. More recently, Jaimes et al. found that fever was not a useful independent predictor of bacteremia and needed to be considered in light of other factors, such as hypotension, white blood cell (WBC) counts, an...

Multidisciplinary team review of best practices for collection and handling of blood cultures to determine effective interventions for increasing the yield of true-positive bacteremias, reducing contamination, and eliminating false-positive central line–associated bloodstream infections

“…The authors concluded that emphasis should be placed on obtaining adequate volume, collection of appropriate numbers of sets, and use of aseptic technique. 127 …”

Diagnosis of Bloodstream Infections in Children

“…A retrospective, multicenter study of 1,436 adult patients found no significant association between enhanced recovery of bacteria and collection of blood cultures at the time of fever spike. The authors concluded that, at least in the adult population, the timing of blood culture collection is not important and should be based on convenience (24). This coincides with IDSA/ASM guidelines that collection should be dictated based on the patient's acuity (22).…”

Blood culture series benefit may be limited to selected clinical conditions: time to reassess

“…Current guidelines advocate 2-3 sets obtained simultaneously from different venipunctures or serially within 0-24 hours for optimal detection of bacteremia and interpretation of blood culture results [1][2][3][4][5]. The potential benefits of multiple sets include better detection of bacteremia, distinguishing contaminants and the recognition of persistent bacteremia [4].…”