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

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.