Integrating patient-reported outcomes.

This paper discusses the relations between different types of patient-reported outcomes that may be collected in clinical studies. Two models are presented that argue that there is a linear relation between the different outcomes. When needs-based quality of life (QoL) is incorporated into the model it is proposed that a two-dimensional relation is more appropriate. The new model is illustrated by data collected using different types of outcome measures. Finally, the different outcomes are related to their purpose in clinical studies.