Differential time to positivity: vascular catheter drawn cultures for the determination of catheter-related bloodstream infection

Abstract

Background: Vascular access catheter-related infections are common. The purpose of this study was to evaluate the accuracy of differential time to positivity (DTP) comparing 2 blood cultures drawn through different lumens of a multi-lumen central venous catheter (CVC DTP) for the diagnosis of catheter-related bloodstream infection (CRBSI).

Methods: This study was performed at a single institution (Health Sciences Centre, Winnipeg, Manitoba, Canada). Microbiology laboratory blood culture records for the period January to November 2009 were retrospectively reviewed. All adult patients with a positive peripheral blood culture and a minimum of 2 positive central line cultures (same organism) drawn from separate lumens of a multi-lumen CVC, all obtained at the same time on the same day, were included in the study. DTP supporting CRBSI diagnosis was defined as a difference in time to positivity of ≥ 2 h between a peripheral blood culture and a CVC blood culture (peripheral DTP), or between 2 CVC blood cultures from different lumens of a multi-lumen catheter (CVC DTP). Peripheral DTP was used as the reference standard for CRBSI diagnosis.

Results: Thirty-five episodes of bacteremia from 33 patients were included in this study. CVC DTP had a sensitivity of 76.5% and a specificity of 88.9% for CRBSI diagnosis, using peripheral DTP as the reference standard.

Conclusions: These data suggest that CVC DTP may be of benefit in the diagnosis of CRBSI. Further study is required to better define the patient population/catheter type for which CVC DTP would be of greatest benefit.