Lay summary
Over 14,000 patients are admitted to intensive care each year in Aotearoa. About half will develop infections. Identifying bacterial infections that require antibiotics from viral or other causes is a longstanding problem in many care settings and can lead to unneeded antibiotic use. Procalcitonin is an easily measurable biomarker that can help diagnose bacterial infections but its utility in intensive care is unclear. We will study 100 intensive care patients with Māori equally represented in our cohort. Daily procalcitonin will be measured from leftover, routine bloodwork. A pharmacometrics, population-based approach will be used for analysis. A physico-kinetic model will describe procalcitonin production and elimination. Factors that describe patients, their health and treatments will be included into the model. The model will support clinical decisions on starting and stopping antibiotics, improve interpretation of procalcitonin in intensive care, and can be extended to other care settings where similar needs exist.