Timing of Blood Cultures in the Setting of Febrile Neutropenia: An Australian Institutional Experience

Objective: Febrile neutropenia (FN) is a hematological emergency requiring urgent investigations to exclude infection and treatment with broad-spectrum antibiotics. Despite frequent blood cultures (BCs) being taking during episodes of FN, in the current literature BC positivity rates remain low in FN. This study aims to determine the BC positivity rate in FN hematology patients and determine the utility of collecting BCs beyond 24 h of commencing broad-spectrum antibiotics. Materials and
Methods: BC results between 2014 and 2016 from all FN hematology patients were analyzed. Patient episodes of FN (PEFNs) were defined as a continuous period of FN where the interval between BC samples was a maximum of two days. In total from 2014 to 2016, 379 patients experienced 914 PEFNs and had 4267 BCs collected.
Results: Overall BC positivity rates and BC-positive PEFN rates were 8.16% and 13.35%, respectively. Within the first 24 h, the positivity rate of the first BCs was 3.49%, while subsequent BC positivity within the first 24 h was 11.96%. BC positivity rates declined after 24 h to 2.18%.
Conclusion: It is likely that BCs beyond 24 h of commencing broad-spectrum antibiotics will rarely identify relevant microorganisms. Not collecting BCs after 24 h would likely reduce laboratory test costs, patient discomfort, and iatrogenic anemia.