MHB4 Comparison of Standard Gamble, Time Trade-Off, and Visual Analog Scale Scores for Hypothetical Stroke Health States Using a Computer-Based Program

The most frequently used techniques for conducting utility assessments are the Standard Gamble (SG), the Time Trade-Off (TTO), and the Visual Analog Scale (VAS).
OBJECTIVES: The objectives of this study were to compare scores obtained on the SG, TTO, and VAS for hypothetical stroke health states; to determine the effect of age and gender on utility scores; to identify any ceiling or floor effects, and to determine the presence of interviewer effects.
METHODS: Forty-nine PharmD students from the College of Pharmacy at the University of Iowa were selected as the sample, and utility assessments were conducted by two interviewers, for hypothetical stroke scenarios adapted from the Glasgow Outcomes Sale. The health states evaluated were Good Recovery, Moderate Disability, Severe Disability, and a Vegetative State. Two rounds of interviews were separated by a period of 4 months. Regresion analysis was used to identify the factors influencing utility scores.
RESULTS: Mean SG scores for the four health states were 82.2, 62.7, 26.3, and 3.3, respectively. TTO scores for the four health states were 79.9, 57.3, 24.6, and 2.9, respectively. However, VAS scores were found to be higher than both TTO and SG scores. Neither age nor gender were found to be statistically significant determinants of reported utility scores. Interviewer effects were found for one out of 12 assessments in round 1, while none were observed in round 2. Floor effects were observed for all three techniques for the vegetative state.
CONCLUSION: Further research using larger, more representative samples from the general population is required to establish the validity of computer-based programs for utility assessments.