The Queensland Bloodstream Infections (QBSI) study: rationale, protocol development and future directions

Background: Although the availability of high-quality surveillance data is critical to inform efforts to reduce the major burden of bloodstream infections (BSIs), there remains a paucity of comprehensive population-based investigations worldwide. Objective: To describe the rationale and protocol development of the Queensland BSI (QBSI) study. Methods: Population-based laboratory surveillance was performed for all BSIs occurring in the publicly funded healthcare system in Queensland, Australia during 2000–2023. Linkages to statewide hospital admissions and vital statistics databases have been performed to determine clinical determinants and mortality outcomes for a minimum of 1 year post-BSI. Results: Standardised definitions were developed to identify incident episodes of BSI and classify them according to type of onset. More than 3.7 million blood cultures were processed during the study period of which a total of 444,279 positive blood cultures were initially identified. Hospital registrations statewide within two years before index culture and one year after were included (n = 2,425,688 with 10,341,136 associated International Statistical Classification of Diseases (ICD) codes during 2000–2023). Comorbidities were classified using previously developed ICD-based algorithms for adults and children and all-cause case-fatality at 30, 90 and 365 days was chosen as the primary outcome measure. Conclusions: The QBSI study is an evolving program designed to comprehensively examine the epidemiology and outcome of BSIs occurring among residents of this large Australian state. Our aim is to share our experiences to support the development of collaborating centres elsewhere to accelerate epidemiology knowledge and ultimately reduce the major burden due to BSI in populations worldwide.