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BACKGROUND: Affordability concerns have become increasingly relevant in health systems globally when deciding on the adoption and coverage of new interventions. However, a standardised approach for defining budget impact remains elusive. This study aimed to contribute to filling this gap by systematically identifying budget impact thresholds (BITs) currently in use, proposing BIT categories, and illustrating how these estimates could be applied across 182 countries to support local deliberations. METHODS: We conducted a systematic review following Cochrane methods and PRISMA reporting guidelines (PROSPERO protocol CRD42020221652). Articles describing budget impact or affordability thresholds proposed or used by national or regional health systems were retrieved from MEDLINE and Embase (search performed from Jan 1, 2016, to March 1, 2025, with no language restrictions). Two reviewers independently selected studies and extracted data. The database search was complemented by a consultation with health technology assessment agencies belonging to the main national and regional networks in Asia, Latin America, and globally. To facilitate cross-country comparisons, we standardised the BITs as a proportion of each country's current health expenditure. Based on the standardised threshold values, we proposed BIT categories aligned with current practices in health systems. These categories were subsequently extrapolated to 182 countries based on World Bank health expenditure data. FINDINGS: A total of 5086 records were screened, of which 22 met inclusion criteria, resulting in the identification of 22 BITs in 13 countries. Higher BITs were associated with more stringent policy actions. Based on our findings, we defined four levels of budget impact based on threshold values expressed as proportion of current health expenditures: low (<0·005%), moderate (0·005% to <0·01%), high (0·01% to <0·02%), and very high (≥0·02%). INTERPRETATION: Our study offers a comprehensive overview of current affordability frameworks and proposes a robust method for interpreting budget impact globally, addressing a crucial gap in research and policy making. While the proposed framework facilitates cross-country comparison and may support more informed and consistent budget allocation decisions, it is not intended as a definitive tool, and its application should be adapted to each country's context. FUNDING: Institute for Clinical Effectiveness and Health Policy, Inter-American Development Bank, and Argentina's Ministry of Health.
Pichón-Rivière et al. (Thu,) studied this question.