Early follow-up blood cultures-frequency and outcomes of repeat blood culture collection within 48 hours of emergency department workup: an observational study.

Objective: To determine the frequency and outcomes of early follow-up blood cultures (BCs) collected within 48 hours of patients being investigated for bacteremia in the emergency department (ED), as well as the number of new pathogens isolated.

Design: Retrospective observational study of patients who had BCs collected in the ED between October 2019 and July 2020.

Methods: This study was conducted in a large, metropolitan ED with annual census of over 82,000 adult presentations. ED patients who had BCs collected during the study period were identified, and those who had BCs recollected within 48 hours were identified as having early follow-up BCs. The characteristics of these patients were compared to those without early follow-up BC collection. Logistic regression analyses were conducted to determine relationships between specific pathogens in EDBCs and early follow-up BC collection.

Results: During the study period, 68,330 patients were treated in the ED, and BCs were collected from 1821 (2.7%). Of these, 449 (24.7%) had BCs recollected within 48 hours of their initial ED workup (early follow-up BCs) and were re-cultured 789 times across their collective stays. Five patients (1.1%) grew pathogens not isolated in EDBCs, all of which were susceptible to concurrent antimicrobials. No new pathogens were isolated in BCs taken >48 hours post ED workup.

Conclusions: Collection of early follow-up BCs was common. However, the rate of new pathogen growth was low and contributed minimally to patient management. Given associated costs and patient discomfort, the practice should be discouraged unless to clarify potential false positive results in ED BC.