Distribution and clinical determinants of time‐to‐positivity of blood cultures in patients with neutropenia

Abstract

The expected TTP offers guidance in the management of patients with neutropenia and suspected bacteraemia. The knowledge of negative BC can support a change in working diagnosis, and impact clinical decisions as soon as 24 hours after BC collection.

Current time-to-positivity of blood cultures in febrile neutropenia: a tool to be used in stewardship de-escalation strategies

“…Our study showed a median TTP of 12 h with 92.1% episodes being positive within the first 24 h. These results are similar to the published work by Lambregts et al [15] reporting 190 episodes of BSI throughout a 4-year period for febrile neutropenic individuals with onco-haematological diseases in a tertiary care hospital with a stem cell transplant programme. Even though these authors measured TTP since collection of blood cultures, and our paper reports TTP from start of incubation, the main results are similar, with a median TTP of 15.6 h and 91.6% of episodes having a TTP <24 h. However, that paper reveals significant weaknesses.…”

“…However, progressive advances and continued monitoring in microbiological laboratories have shortened the time-to-positivity (TTP) of blood cultures significantly. Current information exploring the TTP of blood cultures from individuals with onco-haematological diseases with febrile neutropenia is scarce [15]. Determining the probability of bacteraemia when blood cultures have remained negative within the first 24 h would have a great impact on assisting the promptness of antibiotic stewardship de-escalation strategies.…”

Blood culture time-to-positivity: making use of the hidden information

“…Even with important differences between the two institutions, Cobos-Trigueros et al could define a two-step algorithm to predict C. glabrata bloodstream infection, reaching performance measures of 79% (sensitivity), 90% (specificity), 59% (positive predictive value) and 96% (negative predictive value) [6]. In Puerta-Alcade et al's work, the frequency of positive bottles within 24 h (92.1%, [2]) and TTP variation according to pathogen groups were confirmed elsewhere [3], including paediatric patients with sepsis [6]. Several studies focused on specific patient groups (e.g.…”

“…Concerning the potential usefulness of TTP to guide antimicrobial therapy, most works have addressed onco-haematological patients with febrile neutropenia [2,3], probably because these patients combine a high risk of antimicrobial selective pressure with a high risk of bloodstream infection. In this issue, Puerta-Alcade et al advocate, based on a retrospective study, early deescalation at 24 h [2] instead of 48e96 h as commonly advised because (i) the great majority of episodes with positive blood culture are positive within the first 24 h, (ii) positive episodes with TTP 24 h are commonly optimally treated infections, catheter-related infections, or infections caused by slowly growing microorganisms such as Candida or anaerobic Gram-negative bacteria, and (iii) growth of multidrug-resistant Gram-negative bacilli is exceptional beyond 24 h. With similar logistics, other studies show short TTP in agreement with Puerta-Alcade et al's results: median TTP, although it varied between bacterial groups, was 24 h except for yeasts (see ref.…”

“…Delay of bottle loading is one of the most important confounding factors because it both increases TTP (due to delay) and reduces TTP because the bacteria start to grow at room temperature. Lambregts et al tried to take into account this point by defining TTP from the collection time ('TTP sensu latu'), which reflects real life better than 'TTP sensu strictu' [3]. However, external validity is still hampered, because time to bottle load also widely varies between institutions.…”