Using Proportional and Absolute Shortfall in Reimbursement Decision-Making in the Netherlands: Implications for Oncology Drugs for Older Patients.

In the Netherlands, proportional shortfall is the primary metric for threshold-setting in cost-effectiveness analyses, while absolute shortfall is also reported and considered during appraisal. Although conceptually and mathematically related, the two metrics can yield discordant results. Their theoretical differences are well recognised; nevertheless, debate continues regarding which metric should be used for operationalising disease severity in health technology assessment (HTA). This study describes the rationale behind the combined use of proportional and absolute shortfall by the National Health Care Institute (ZIN) and provides empirical evidence on how the two severity metrics relate in real-world reimbursement practice. We analysed proportional and absolute shortfall levels reported in 56 of all 57 appraised reimbursement dossiers published by ZIN between May 2018 and April 2026. While the two metrics are systematically related, we observed a distinct cluster of 28 dossiers showed high proportional shortfall (mean 0.88) but relatively low absolute shortfall (mean 14.28 QALYs). Of these, 27 concerned oncology drugs for older patients, which were significantly more likely to fall into this cluster than non-oncology drugs. These findings demonstrate that differences between proportional and absolute shortfall, previously discussed largely at a theoretical level, translate into observable patterns in reimbursement practice. By making explicit how the two metrics profile technologies differently, this study contributes empirical evidence to ongoing policy discussions about the operationalisation of disease severity in HTA. More specifically, the analysis clarifies how ZIN's current practice of reporting both metrics may support more transparent, better-informed and consistent use of disease severity in reimbursement decision-making.