Technology assessment for radiologists.

Health technology assessment is the systematic and quantitative evaluation of the safety, efficacy, and cost of health care interventions. This article outlines aspects of technology assessment of diagnostic imaging. First, it presents a conceptual framework of a hierarchy of levels of efficacy that should guide thinking about imaging test evaluation. In particular, the framework shows how the question answered by most evaluations of imaging tests, "How well does this test distinguish disease from the nondiseased state?" relates to the fundamental questions for all health technology assessment, "How much does this intervention improve the health of people?" and "What is the cost of that improvement?" Second, it describes decision analysis and cost-effectiveness analysis, which are quantitative modeling techniques usually used to answer the two core questions for imaging. Third, it outlines design and operational considerations that are vital if researchers who are conducting an experimental study are to make a quality contribution to technology assessment, either directly through their findings or as an input into decision analyses. Finally, it includes a separate discussion of screening--that is, the application of diagnostic tests to nonsymptomatic populations--because the requirements for good screening tests are different from those for diagnostic tests of symptomatic patients and because the appropriate evaluation methods also differ.