[Economic evaluation of interventions in public health: potentials and limitations]

One of the main principles of economic evaluation refers to the scarcity of resources. So, choices must and will be made concerning the commitment of these resources to one use instead another. Economic evaluation can assume different methodological forms regarding the kind and complexity of programme to be assessed and the issue of outcome valuation, but each analytic technique compares the resources consumed by different relevant alternatives with the health improvements and other consequences arising from them. From a pragmatic point of view, four types of economic evaluation can be distinguished associated with different measurement and valuation of consequences: cost-minimization, cost-effectiveness, cost-utility and cost-benefit analysis. A first step of economic appraisal is definition and description of each competing alternative. Then, there are difficulties associated with measurement and valuation of both costs and effectiveness of alternatives. The assessment of public health interventions poses some special problems in terms of time profiles of cost and consequences. Most of the costs of a health programme incurred in the present while benefits will come later in the future. Therefore, cost and consequences must be discounted to reflect the existence of time preference. The last important point concerns the assessment of health consequences. Ideally, evaluation of efficacy takes the form of a well controlled randomized trial designed for this purpose. But, in many situations, this approach is not relevant, appropriate or feasible and efficacy appraisal must be developed on the basis of available data and "realistic" assumptions. So, every evaluation will contain some degree of uncertainty or imprecision and a sensibility analysis must be performed in order to test sensitivity of the results to alternative assumptions and uncertainty.