The use of qualitative methods in developing the descriptive systems of preference-based measures of health-related quality of life for use in economic evaluation.

OBJECTIVES To describe how qualitative methods can be used in the development of descriptive systems of preference-based measures (PBMs) of health-related quality of life. METHODS The requirements of the National Institute for Health and Clinical Excellence and other agencies together with the increasing use of patient-reported outcome measures has led to an increase in the demand for PBMs. Recently, interest has grown in developing new PBMs and while previous research on PBMs has mainly focused on the methods of valuation, research into the methods of developing descriptive systems is an emerging field. RESULTS Traditionally, descriptive systems of PBMs were developed by using top-down methods, where content was derived from existing measures, the literature, or health surveys. A contrasting approach is a bottom-up methodology, which takes the views of patients or laypeople on how their life is affected by their health. This approach generally requires the use of qualitative methods. Qualitative methods lend themselves well to the development of PBMs. They also ensure that the measure has appropriate language, content validity, and responsiveness to change. While the use of qualitative methods in the development of non-PBMs is fairly standard, their use in developing PBMs was until recently nonexistent. CONCLUSIONS In this article, we illustrate the use of qualitative methods by presenting two case studies of recently developed PBMs, one generic and one condition specific. We outline the stages involved, discuss the strengths and weaknesses of the approach, and compare with the top-down approach used in the majority of PBMs to date.