Leiden University Scholarly Publications

Kaal, A.G. (2026)

Improving management of infectious diseases at the emergency department: from risk prediction to treatment strategies

Doctoral Thesis

Infections are one of the most common reasons people visit the emergency department (ED). Doctors must quickly decide which tests to order and which treatment is best. There is room for improvement: sometimes too many tests are performed, or unnecessarily intensive treatments are given. This thesis examined how infections in the ED can be treated more efficiently, without compromising safety.

First, we looked at blood cultures, used to detect bacteremia. These are costly and widely used, yet only a small proportion of patients test positive. Using the blood marker procalcitonin and a newly developed model, tested in the Netherlands, Spain, and the United States, about 30% of blood cultures could be avoided, while only 1 to 5% of true cases of blood poisoning were missed.
Next, we examined risk assessment: which patients face a higher risk of complications? Notably, 1 in 9 patients with a suspected infection turned out to have a different diagnosis,...Show moreInfections are one of the most common reasons people visit the emergency department (ED). Doctors must quickly decide which tests to order and which treatment is best. There is room for improvement: sometimes too many tests are performed, or unnecessarily intensive treatments are given. This thesis examined how infections in the ED can be treated more efficiently, without compromising safety.

First, we looked at blood cultures, used to detect bacteremia. These are costly and widely used, yet only a small proportion of patients test positive. Using the blood marker procalcitonin and a newly developed model, tested in the Netherlands, Spain, and the United States, about 30% of blood cultures could be avoided, while only 1 to 5% of true cases of blood poisoning were missed.
Next, we examined risk assessment: which patients face a higher risk of complications? Notably, 1 in 9 patients with a suspected infection turned out to have a different diagnosis, especially older patients and those with dementia. For pneumonia, hospitals using the CURB-65 risk score had fewer deaths than those using the PSI score. Finally, we looked at treatment itself: no difference was found between pneumonia patients treated with oral antibiotics versus intravenous antibiotics, while the oral group spent 2.5 fewer days in hospital.
This thesis shows there is room for more efficient infection care in the ED, through more targeted blood culture use, better risk assessment, and considering oral treatment over IV, contributing to less unnecessary diagnostics and treatment, without sacrificing safety.Show less

Diagnostic stewardship

Infectious diseases

Bacteremia

Antibiotic stewardship

Antibiotics

Emergency department

Predictive modelling

All authors

Kaal, A.G.

Supervisor

Steyerberg, E.W.

Co-supervisor

Nieuwkoop, C. van

Committee

Cessie, S. le; Nanayakkara, K.D.P.W.B.; Bonten, M.J.M.; Visser, L.G.

Qualification

Doctor (dr.)

Awarding Institution

Faculty of Medicine, Leiden University Medical Center (LUMC), Leiden University

Date

2026-09-16

ISBN (print)

9789465375946

Funding

Sponsorship

Stichting Fulbright Commission the Netherlands, Leids Universitair Fonds, Dr. Catharine van Tussenbroek Fonds, Hendrik Mullerfonds, het Cultuurfonds, afdeling Interne geneeskunde en Reumatologie HagaZiekenhuis.