What is the impact of disease prevalence upon health technology assessment?

As national budgets for health care will remain under stress for the foreseeable future, health technology assessment (HTA) aimed at offering guidance to policy-making will have an increasing role to play in optimizing resources. The emergence of new treatment paradigms and health technologies, and the prevalence studies which determine when a disease is a current or future burden for patients and the community are in the roots of the HTA process. Analysing studies on screening test strategies and health care policy, this paper revisits two key concepts in epidemiology, prevalence and incidence, in order to show their major impact upon HTA. Utilization of the predictive values of screening tests that include prevalence in their calculations, and analysing all options for screening strategies are necessary in HTA. Cost-effectiveness analyses and statistical models should include potential externalities, especially the impact of prevention and treatment on infectious disease prevalence. Beyond estimates of cost-effectiveness ratios, decision makers also need to know by how much their annual health care budget is likely to increase or decrease in the years following the emergence of new technologies: hence the importance of incidence- or prevalence-based economic evaluations. As new paradigms are occurring, especially in the field of oncology, with treatments targeted to 'small' groups of patients identified through genetic testing, prevalence data are strongly needed. Precise estimates of disease prevalence, in general populations as well as in risk or targeted groups, will therefore be necessary to improve HTA process.