Cost-of-illness studies in the United States: A systematic review of methodologies used for direct cost

Objectives: We undertake a systematic review to examine the methods used by researchers in developing cost-of-illness (COI) studies. This review aims to categorize the approaches that the published literature uses in terms of perspective, scope, components of care analyzed in the literature, data sets, and valuation approaches used for direct cost. It draws conclusions regarding the adequacy of current COI research methods and makes recommendations on improving them. Methods: The online bibliographic information service HealthSTAR (which incorporates MEDLINE) was used to search for COI studies in the research literature published during the period from 2000 to 2004. The search strategy used the term "cost of illness" as a MeSH (medical subject heading) term. Results: The HealthSTAR literature search identified references to 650 articles. Review of abstracts resulted in the identification of 170 of these for a more detailed review. This process identified 52 articles that met all criteria of COI studies. We identified 218 components of care analyzed across the 52 articles. Private-insurance or employer-claims data sets comprised the largest source of utilization and cost information among the studies. Conclusion: Analyzing cost of illness presents useful opportunities for communicating with the public and policymakers on the relative importance of specific diseases and injuries. Our research, however, indicates that COI studies employ varied approaches and many articles have methodological limitations. Without well-accepted standards to guide researchers in their execution of these studies, policymakers and the general public must be wary of the methods used in their calculation and subsequent results.