Assessing blood culture appropriateness in solid organ transplant recipients: a diagnostic stewardship approach.

Objective: Diagnostic stewardship of blood culture utilization is important to mitigate the risks associated with unnecessary culturing. Although blood culture algorithms have been studied previously, there is a lack of data on their application among solid organ transplant (SOT) recipients. This study aims to retrospectively apply a blood culture algorithm (initially developed for a non-immunocompromised population) to adult SOT recipients and assess its performance.

Methods: We conducted a manual retrospective review of adult SOT recipients with a blood culture event (BCE) between February 2022 and January 2024 at a single academic medical center. BCEs were categorized as appropriate, inappropriate, or lacking documentation, according to a previously established institutional blood culture algorithm.

Results: Of 737 BCEs among adult SOT recipients, 185 (25%) were inappropriate. Within the subset of inappropriate BCEs, 178 (96%) yielded negative cultures, while 7 (4%) were deemed contaminants. No true positives were identified. Inappropriate BCEs were most commonly triggered by isolated fever and/or leukocytosis (136, 74%), and lower urinary tract infection (17, 9%). 17 of 18 BCEs due to donor blood culture positivity at the time of organ transplantation resulted in a negative blood culture in the recipient.

Discussion: Once applied retrospectively, our institutional blood culture algorithm did not miss any true positive bloodstream infections among adult SOT recipients. This study provides initial evidence supporting the cautious application of blood culture diagnostic algorithms in adult SOT populations. Further prospective investigations are warranted to validate these findings.