Health risk appraisal: some methodologic considerations.

This is an outline of the structure and limitations of existing health risk appraisal tools (HRA). A general model is discussed, where average populations risk data are modified in a risk computation algorithm. This process requires information on risk relevant characteristics of the individual and rules or assumptions where sufficient data do not exist. The basis for risk estimation algorithms, the derivation of risk factors, and their combination into composites are described. HRA feedback to the individual user is discussed, including summarization of risk results in terms of risk age and life expectancy.