Performance of differential time to positivity as a routine diagnostic test for catheter-related bloodstream infections: a single-centre experience

Clin Microbiol Infect. 2020 Mar;26(3):383.e1-383.e7. doi: 10.1016/j.cmi.2019.07.001. Epub 2019 Jul 6.

Abstract

Objective: To assess the performance of differential time to positivity (DTP) for the diagnosis of catheter-related bloodstream infections (CRBSI).

Methods: From all episodes of bloodstream infections (BSI) diagnosed during a 15-year period (2003-17) those in which a paired set of blood cultures drawn from a catheter and a peripheral vein were positive for the same microorganism and had a clinically and/or microbiologically defined source were selected. To assess diagnostic discrimination ability and accuracy of DTP for CRBSI, area under the receiver operating characteristic curves (AUC) and performance characteristics of a DTP ≥2 h were computed.

Results: A total of 512 BSI were included, of which 302 (59%) were CRBSI. Discrimination ability of DTP was low for Staphylococcus aureus (AUC 0.656 ± 0.06), coagulase-negative staphylococci (AUC 0.618 ± 0.081), enterococci (AUC 0.554 ± 0.117) and non-AmpC-producing Enterobacteriaceae (AUC 0.653 ± 0.053); moderate for Pseudomonas aeruginosa (AUC 0.841 ± 0.073), and high for AmpC-producing Enterobacteriaceae (AUC 0.944 ± 0.039). For the entire sample, DTP had a low-to-moderate discrimination ability (AUC 0.698 ± 0.024). A DTP ≥2 h has a low sensitivity for coagulase-negative staphylococci (60%) and very low for S. aureus (34%), enterococci (40%) and non-AmpC-producing Enterobacteriaceae (42%). A DTP cut-off of 1 h improved sensitivity (90%) for AmpC-producing Enterobacteriaceae.

Conclusions: Differential time to positivity performs well for diagnosing CRBSI only when AmpC-producing Enterobacteriaceae and P. aeruginosa are involved. Performance is low for common Gram-positive organisms and non-AmpC-producing enteric bacilli; a negative test should not be used to rule out CRBSI due to these microorganisms. A DTP ≥1 h may improve accuracy for AmpC-producing Enterobacteriaceae, particularly Enterobacter spp.

Keywords: Bacteraemia; Catheter-related bloodstream infections; Central venous catheters; Diagnostic tests; Differential time to positivity.

Publication types

  • Historical Article

MeSH terms

  • Aged
  • Aged, 80 and over
  • Biomarkers
  • Catheter-Related Infections / diagnosis*
  • Catheter-Related Infections / epidemiology
  • Catheter-Related Infections / etiology
  • Catheter-Related Infections / history
  • Catheterization, Central Venous / adverse effects
  • Diagnostic Tests, Routine* / methods
  • Diagnostic Tests, Routine* / standards
  • Disease Management
  • Female
  • History, 21st Century
  • Humans
  • Male
  • Middle Aged
  • ROC Curve
  • Reproducibility of Results
  • Sepsis / diagnosis*
  • Sepsis / epidemiology
  • Sepsis / etiology
  • Sepsis / history
  • Spain / epidemiology
  • Symptom Assessment
  • Time Factors

Substances

  • Biomarkers