García-Pérez, LidiaLinertová, RenataValcárcel-Nazco, CristinaPosada De la Paz, ManuelGorostiza, InigoSerrano-Aguilar, Pedro2021-04-192021-04-192021Orphanet J Rare Dis . 2021 Apr 13;16(1):178.http://hdl.handle.net/20.500.12105/12683Objective: The aim of this scoping review was to overview the cost-of-illness studies conducted in rare diseases. Methods: We searched papers published in English in PubMed from January 2007 to December 2018. We selected cost-of-illness studies on rare diseases defined as those with prevalence lower than 5 per 10,000 cases. Studies were selected by one researcher and verified by a second researcher. Methodological characteristics were extracted to develop a narrative synthesis. Results: We included 63 cost-of-illness studies on 42 rare diseases conducted in 25 countries, and 9 systematic reviews. Most studies (94%) adopted a prevalence-based estimation, where the predominant design was cross-sectional with a bottom-up approach. Only four studies adopted an incidence-based estimation. Most studies used questionnaires to patients or caregivers to collect resource utilisation data (67%) although an important number of studies used databases or registries as a source of data (48%). Costs of lost productivity, non-medical costs and informal care costs were included in 68%, 60% and 43% of studies, respectively. Conclusion: This review found a paucity of cost-of-illness studies in rare diseases. However, the analysis shows that the cost-of-illness studies of rare diseases are feasible, although the main issue is the lack of primary and/or aggregated data that often prevents a reliable estimation of the economic burden.engVoRhttp://creativecommons.org/licenses/by/4.0/Cost-of-illnessEconomic burdenRare diseasesScoping review.Atribución 4.0 Internacional3384961316110.1186/s13023-021-01815-31750-1172Orphanet Journal of Rare Diseasesopen access