Towards improving quality of the evidence base for medical decision-making

Jansen, M.S. (2026)

Doctoral Thesis

Research forms a cornerstone of modern medicine. However, concerns have been raised regarding the reliability, reproducibility, and overall value of the generated evidence for medical decision-making. This thesis aimed to address several challenges in the evidence base for medical decision-making, focusing on various stages within the research enterprise, from designing and executing studies to their translation in decision-making. Specifically, we examined potential optimism in sample size calculations of trial protocols and the role of research ethics committees (RECs) in evaluating them, identified predictors of premature trial termination, and assessed publication rates of small trials as well as potential predictors. Additionally, we identified factors that determine the need for real-world evidence (RWE) to inform market approval and reimbursement decisions. By tackling the abovementioned issues, this thesis aimed to contribute to improving the quality and efficiency of medical research.

• Meta-science
• Research waste
• Research ethics committees
• Sample size calculations
• Early trial termination
• Publication rates
• Clinical trials
• Real world evidence
• Regulatory decision-making
• Health technology assessment

• All authors: Jansen, M.S.
• Supervisor: Dekkers, O.M.; Groenwold, R.H.H.
• Committee: Bom, J.G. van der; Cessie, S. le; Mol. P.G.M.; Sturkenboom, M.C.J.M.
• Qualification: Doctor (dr.)
• Awarding Institution: Faculty of Medicine, Leiden University Medical Center (LUMC), Leiden University
• Date: 2026-01-21
• ISBN (print): 9789465229850
• Sponsorship: GetReal Institute