Background: Clinical findings are unreliable for establishing the diagnosis of central venous catheter-related bloodstream infection (CRBSI) because of their poor sensitivity and specificity. Therefore, in order to establish a diagnosis of CRBSI, when this is clinically suspected and the central venous catheter (CVC) is to be preserved, ESPEN recommend that paired quantitative blood cultures (pour plates) or paired qualitative blood cultures from a peripheral vein and from the catheter are recommended, with continuous monitoring of the differential time to positivity (DTP). However, it is unclear whether quantitative or qualitative cultures provide the optimal method for diagnosing CRBSI in patients with intestinal failure (IF). A retrospective evaluation was undertaken in intestinal failure patients with long term CVCs to evaluate DTP against pour plates for the diagnosis of CRBSI.

Methods: A list of patients with a diagnosis of CRBSI was obtained from the intestinal failure (IF) unit database for a five year period, 2013 to 2017. Microbiology records were reviewed to obtain further information about blood culture and pour plate examinations. Organisms and times of collection, loading and positivity were recorded. Patients with a contemporaneous set of central and peripheral pour plates and blood cultures were included in an analysis of the sensitivity of DTP compared to pour plates.

Results: There were 61 (45.5%) episodes in 56 patients where complete sets of central and peripheral blood cultures and pour plates were received. All 61 episodes had positive central blood cultures, 59 (96.7%) had positive central line pour plates and 17 (27.9%) had positive peripheral pour plates. Using pour plates as the gold standard, DTP sensitivity was 96.0% for 50 episodes where pour plates were consistent with CRBSI. The sensitivity increased to 100% for 17 episodes where there were no delays in either collection or loading of blood cultures.

Conclusions: This is the first evaluation to support the use of DTP as a sensitive test in diagnosing CRBSI in IF patients and provides confidence to IF centres where pour plate cultures are not available. DTP can be used as a primary diagnostic test for CRBSI in patients with IF; however, in order for this to be of maximum value to clinicians, time to positivity needs to be routinely reported with blood culture results.