Performance of differential time to positivity as a CLABSI diagnostic test

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To assess the performance of differential time to positivity (DTP) for the diagnosis of catheter-related bloodstream infections (CRBSI)” Orihuela-Martín et al (2019).

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 (AUROC) and performance characteristics of a DTP≥2h were computed.

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

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

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Reference:

Orihuela-Martín, J., Rodríguez-Núñez, O., Morata, L., Cardozo, C., Puerta-Alcalde, P., Hernández-Meneses, M., Ambrosioni, J., Linares, L., Bodro, M., Guerrero-León, M.L.A., Río, A.D., Garcia-Vidal, C., Almela, M., Pitart, C., Marco, F., Soriano, A. and Martínez, J.A. (2019) Performance of differential time to positivity as a routine diagnostic test for catheter-related bloodstream infections: a single centre experience. Clinical Microbiology and Infection. July 6th. doi: 10.1016/j.cmi.2019.07.001. .

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