Chapter 9. Exploring Longitudinal Data

Summary

The majority of studies involving QoL assessment include repeat assessments over time. Thus, in a randomised trial and other studies there may be a baseline assessment, followed by a series of further assessments during the active treatment period, followed by (often less frequent) further assessments. QoL data are therefore longitudinal in form, the analysis and presentation of which is relatively straightforward if the number of observations per patient is equal. However, for QoL assessment this will seldom if ever be the case. The final dataset will usually be very ragged with the numbers of assessments available for analysis differing from patient to patient. In this chapter we introduce a summary of such data by means of the area under QoL curve. However, the main focus is on how such longitudinal data can be represented in a graphical format.