Assessing the impact of health technology assessment.

Methodology for evaluation of impact of health technology assessments (HTAs) is outlined and its use illustrated by applying it to 21 HTAs produced by CETS. Impact on policies and technology diffusion was identified in documents, through interviews, questionnaires, and use of data banks. There was evidence that all but three reports influenced policy and that cost-minimization studies caused savings of between $16 million and $27 million annually. Precise estimates of impact will seldom be possible, but systematic documentation of effects is feasible.