Cost-of-Illness in Rare Diseases.

Cost-of-illness (COI) studies quantify the economic burden of a disease, including direct healthcare and non-healthcare costs and productivity losses. Different approaches can be adopted to evaluate the resources associated to a disease and to calculate the total costs. Prevalence-based studies estimate the total costs of a disease during a given period, while incidence-based studies measure lifetime costs from onset until death. Data can be collected from individuals, using a bottom-up approach, or from population statistics, using a top-down approach. Different perspectives are possible, but the broadest and also mostly used is the societal one. Appropriate discounting should be applied for future costs and a sensitivity analyses of main parameters should be performed. The main limitation of COI studies is that they don't account the outcomes or benefits of possible treatments.There is a lack of COI studies in the field of rare diseases. A multinational COI study (BURQOL-RD) evaluated recently the burden of 10 rare diseases in Europe, using a prevalence-based method with a bottom-up approach to quantify resources from a societal perspective, which is the mostly used methodology for COI studies in rare diseases; however, several other studies illustrate different approaches to conduct COI analysis in this field, such as incidence-based methods or narrower perspectives.COI studies are useful to inform policy-makers about the magnitude of a disease. To support correctly the decision-making process, it is necessary to identify the cost-drivers through COI studies with robust design and standardized methodology.