Purpose: Previous research demonstrates that health state utility survey participants sometimes provide illogical responses, defined as rating a joint state utility as better than one of its component single states. Previous work, using the Time Trade-Off (TTO) method, found that education, anxiety, and response time have a statistically significant relationship with the rate of illogical responses participants gave. It remains an open question as to whether the elicitation method used, TTO vs. Standard Gamble (SG), has an impact on the rate of illogical responses. The current study is being conducted in part to answer this question.
Method: Survey and utility data are collected at two urban-based hospital prostate biopsy clinics from men following their biopsies. Face-to-face questionnaires and health state utility elicitations are administered on laptop computer by researchers trained in TTO and SG methodology. The elicitation includes health states pertaining to prostate cancer, stroke and Activities of Daily Living. Participants are randomly assigned by computer to either the TTO or SG elicitation procedure, and then answer questions about their demographics, the Hospital Anxiety and Depression Scale Anxiety Subscale. A targeted enrollment of N=150 is ongoing.
Result: To date, N=75 patients (median age; M=64, SD=8.0) have completed utility elicitations of either the TTO (n=37) or the SG (n=32) variety. The univariate analysis shows that SG group (M=3.2, SD=0.5) trends towards having more illogical responses than TTO group (M=4.4, SD=0.6). Additionally, a surprising finding was made -- the SG group shows significantly more anxiety on the HADS-Anxiety subscale, which was administered after the utility elicitations, than the TTO group, t (73) = -2.0, p<.05. This is a peculiar somewhat convincing finding because, although the HADS-anxiety Scale is designed to measure anxiety spanning the previous week, participants are randomized to the elicitation conditions.
Conclusion: Health state elicitation methods are known to influence utility values. These preliminary findings go further to suggest that SG elicitations might lead to more logical inconsistency in utilities, relative to TTO, and poses further questions about their psychological basis. As well, the elicitation procedure, particularly SG, might cause anxiety in respondents that could potentially influence response behavior in the reverse direction. However, more needs to be learned about the construct validity of health state utility ratings and the psychological basis for responses.
See more of: The 34th Annual Meeting of the Society for Medical Decision Making