Outcomes research is a subset of clinical evaluation that is increasingly being defined as a separate scientific discipline. It produces information that appears to be particularly attractive for use in pharmaceutical product promotion. As a result, FDA frequently must determine when this information is adequate to support labeling and advertising claims. Discussion of outcomes evidence is complicated by a lack of consistency in the terminology used, but perhaps more importantly, by a lack of understanding, and perhaps agreement on, the evidentiary standards that should apply to these data. FDA interacts with ISPOR and others to clarify issues and facilitate policy development in this area.

This lack of clarity is at least partly the result of the very different but overlapping categories of what appears to fall under the umbrella of outcomes research, according to the focus of ISPOR and others (Figure 1). Each category has its own special set of scientific and regulatory issues. For example, health-related quality of life (HRQL) is assessed in ways similar to other clinical endpoints but poses major problems because it usually assesses multiple endpoints so that attaining consistent results is difficult, and because the meaning of its results is often not straightforward. On the other hand, economic endpoints, although they can be measured as clinical endpoints in trials, are often assessed using observational methods and models, and raise special problems of generalizability.