Cost-of-illness methodologies for water-related diseases in developing countries

The COI approach described focuses on potential health benefits from project interventions and takes into account potential cost savings, both direct (avoided medical care expenses) and indirect (productivity gains in a population no longer affected by the disease or illness). Implementation of COI health benefit studies involves important precursor and follow up steps. These include (1) defining the context and scope of the study, (2) determining the health effects of the intervention, (3) assessing data characteristics and availability, and (4) presentation of results to policymakers. COI studies conducted without proper "ground work" and adequate follow-up will likely prove irrelevant or ineffectual. The use of a multidisciplinary approach in all aspects of the study, including the design, implementation, and presentation/follow-up, is important. Disciplinary areas that should be involved if at all possible include epidemiology, biostatistics, survey research, economics, and policy analysis. In addition, the "investment" of decisionmakers in the analysis and its results should be encouraged from the beginning through close collaboration. The report provides a step-by-step guide to the "best case" data needs and calculations for a COI-based study in developing countries. The methodology addresses such issues as disease seasonality and its impact on production, access to medical care, substitutability of labor, and impact of other diseases, among other factors. Detailed tables specifying data needs and flow charts describing the analytic steps are included. Spreadsheet table shells are provided in an appendix as a guide to how data might be collected and arrayed. COI studies can be implemented at various levels -- local, regional, and national. Data limitations (and resource limitations on the collection of new data) are likely to be highly constraining factors in the implementation of fully developed COI studies in developing countries. Thus, the report discusses data considerations and suggests ways to overcome data gaps or, at a minimum, to make the gap and resulting assumptions explicit. Appended to the report is a detailed review of recent theoretical studies and applied work in developing systematic approaches to conducting economic impact studies of developing country health programs. Weaknesses and caveats identified in the studies, as well as lessons learned in them, were incorporated to the extent possible into the proposed methodology. Important next steps for this research include the trial application of the proposed COI methodology to an actual country situation. A field test would provide critical information not available from the literature- review-and-consultation approach of this task regarding the feasibility of the methodology. An important area for further research is the empirical measurement of the economic effects of programs having different effects on the distribution of disease severity. A program that has little effect on disease incidence but which changes the distribution from numerous severe cases (with severe economic impact) to an equal number of mild-to-moderate cases (with little or no economic impact) may be more desirable than a program that reduces incidence overall but leaves the same distribution of disease severity. (Author abstract, modified)