Cost of illness (COI) is a summary of the costs of a particular disease to society. This value includes direct costs of treating the disease such as healthcare system costs for diagnosis, treatment and management of disease progression and patients’ own costs (travel, over-the-counter medication), as well as indirect costs such as productivity loss resulting from time off employment. In a large proportion of the many reported cost of illness studies, estimates of resource utilisation are derived from different survey and registry sources, which are converted to costs using representative ‘unit costs’ and then aggregated across relevant population cohorts. In US cost of illness studies, charges may be used and converted to estimated costs using cost-to-charge ratios. Cost of illness studies are often used to highlight the large burden associated with particular conditions, as well as differentials by patient and other characteristics. Although such studies can provide useful baseline values for economic evaluations, they are not economic evaluations, as they do not estimate how the cost burden might change if new interventions are introduced. Costs ‘attributable’ to a condition may be estimated by comparing costs of matched samples with and without the condition. Calculation of ‘attributable costs’ for conditions that may be found in the same individuals (e.g. obesity and diabetes) may not be straightforward: cost of illness studies have been criticised for overestimating disease-specific costs.

How to cite: Cost of Illness [online]. (2016). York; York Health Economics Consortium; 2016.

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