Objective: Apart from improved health outcomes, treatment convenience per se may have a value to individuals. This is sometimes referred to as process utility and can be estimated in terms of willingness-to-pay (WTP) or quality-adjusted life-years (QALYs). Previous research has produced multiple studies on QALY gains and WTP estimates of insulin-related attributes. There are, however, significant variations between studies, and it is not clear to what extent the value is a reflection of the true preferences or a consequence of the methodological approach. The aim of this study is to estimate the preferences for treatment attributes associated with basal insulin (administration frequency, administration flexibility, and treatment-induced weight gain) using both QALYs-elicited using time trade-off (TTO) and WTP-among a sample of the Swedish general population and among a sample of the Swedish diabetes population.
Methods: Data was collected using web-based surveys which were distributed to members of internet panels. The WTP survey presented five hypothetical scenarios with an offer to pay the incremental cost to receive basal insulin with improved attributes. The TTO survey presented six hypothetical scenarios where the respondent could choose between living for the rest of his/her life with diabetes and receiving treatment with a basal insulin with certain attributes or live for a shorter time with full health. The scenarios were combined with either a basal or a basal-bolus treatment regimen. Results from the TTO analysis were translated into monetary estimates using a threshold value of SEK500,000 per QALY.
Results: In total, 2012 responses were included. The ratings of the attributes were almost identical, irrespective of method for the general population, while it differed to some extent for the diabetes population. The methods produced the same value for flexibility, but the estimates generated with the TTO approach were higher for one less injection and avoided weight gain. The general population assigned a higher utility gain to convenience attributes, while the diabetes population assigned a higher utility gain to avoiding weight gain.
Limitations: About a quarter of the respondents did not accept the scenario in the WTP survey, i.e. protesters.
Conclusions: The ranking of the attributes was generally independent of evaluation method, but the TTO method resulted in similar or higher values compared to the WTP method.
Keywords: Diabetes; insulin; preferences; quality-adjusted life-years; time trade-off; willingness-to-pay.