Testing the "Nonstopping" Time Trade-Off: Is It Better Than the Composite Time Trade-Off?

Objectives: There are several issues of concern for the composite time trade-off (c-TTO) used to estimate EQ-5D-5L value sets. The "nonstopping" TTO (n-TTO) differs from the c-TTO mainly in 2 aspects: (1) n-TTO uses a standardized top-down or bottom-up routing; and (2) n-TTO continues when indifference is indicated by respondents. In this study, we aimed to test the feasibility of n-TTO and compared it with c-TTO.

Methods: The study was conducted in parallel in Norway and Singapore. In both countries, members of the general population were invited to complete 10 n-TTO or c-TTO tasks. Acceptability and feasibility of n-TTO were assessed using respondents' feedback, administration time, and valuation success rate. Characteristics of the TTO data derived from c-TTO and n-TTO tasks were examined at task, individual, as well as group levels.

Results: In both Norway and Singapore, the success rate of n-TTO tasks was high (> 95%) and the n-TTO tasks took less time to complete than the c-TTO tasks, and there were fewer or smaller "spikes" in the distributions of n-TTO data compared to c-TTO data. In Norway, the individual-level n-TTO and c-TTO data had similar distribution and logical consistency profiles. In Singapore, n-TTO was inferior to c-TTO in logical consistency; however, a similar degree of nonmonotonicity was observed in modeling of n-TTO and c-TTO data.

Conclusions: The noniterative n-TTO appeared to be feasible and may generate data with better distribution in shorter time than c-TTO. Further research is needed to assess this new health-state valuation method.