PRM124 - Examination of preferences elicited from the general public: Subgroup comparisons of results from the time trade-off and standard gamble instruments

Abstract

The time trade-off (TTO) and the standard gamble (SG) are two methods used for the direct measurement of health-related quality of life, expressed as health utilities (HU), among the general public. Significant overall correlation was observed in a previous systematic review comparing TTO and SG values reported by the general public (19 pertinent publications, 77 study arms and 24 diseases). In the present analysis, correlation was further explored among specific demographic, clinical and analytic subgroups. When a sufficient sample of study arms was available, Spearman’s rank correlation test was applied to test the correlation between mean or median TTO and SG by sorting the TTO values in increasing increments of 0.1, based on the following subgroups: incremental HU, disease, gender, age, income, education level and employment status. Significance was defined as p-value<0.05. Significant positive correlation was observed between mean TTO and SG values for all increments of TTO except when TTO<0.5 (r = 0.429), for ocular disease (r = 0.976), skin disease (r = 0.964) and arthritis (r = 0.956). A post-hoc analysis quadrupling the sample of studies with TTO<0.5 resulted in significant positive correlation, indicating that the lack of significant correlation was possibly due to the scarcity of studies. The series of subgroup analyses focusing on median incremental HU values or median HU values associated with skin disease resulted in similar findings to the analysis of means. No analysis of demographic subgroups could be undertaken due to the limited study sample. A correlation between TTO and SG outcomes reported by members of the general public was observed for numerous subgroups. It is possible that correlation would have been observed in additional subgroups, but was not, due to the limited study sample.