Guide to Design and Development of Health-State Utility Instrumentation

Growing interest in methods of quantifying health-related quality of life has resulted in demand for a manual describing general techniques that may be customized by health researchers and used to measure preferences in applications having a wide variety of objectives. This report is intended to provide practice guidelines to researchers who require information about the design, construction and administration of instruments used to obtain estimates of health utility. The focus is on the steps required to conduct a study in which preferences are measured; the theory that underlies utility measurement is not presented. Utility scores may be used to assess the health-related quality of life for specific health states. Utility scores are also useful in evaluations, such as cost-utility analyses, in which the costs of health care interventions are compared to their consequences both in terms of quantity and quality of life. In order to obtain reliable, valid, and responsive utility scores, however, the instruments must be carefully designed, tested and executed. Experience to date indicates that careful instrument development requires time, effort and care. Three major instruments are described: rating scale, standard gamble and time trade-off. Methodologically correct techniques are recommended where possible and suggestions, based on experience, are presented for situation in which theoretical or empirical evidence is lacking. The guide discusses the criteria for selection of techniques, materials, interviewers and respondents. Examples of an interviewer training manual, interview scripts and data recording forms are also included. Detailed diagrams provide specifications for assembling visual aids (i.e., interviewing props) and an extensive bibliography will direct readers interested in specific issues to appropriate references.