Japanese preference weights of the Adult Social Care Outcomes Toolkit for Carers (ASCOT-Carer)

Purpose: We developed preference weights of the Adult Social Care Outcomes Toolkit for Carers (ASCOT-Carer) in Japan.

Methods: We used best-worst scaling (BWS) and composite time trade-off (cTTO) to determine the preference weights for ASCOT-Carer states in the general population. TTO values were applied to convert the BWS scores to utilities. The sample number was approximately 1000 for the BWS survey and 200 for the TTO survey. Whereas face-to-face surveys by computer-assisted interviewing were adopted for the TTO tasks, a web-based survey was used for the BWS tasks. In the BWS tasks, the ASCOT-Carer states were presented, and the "best," "worst," "second best," and "second worst" domains in a profile were selected. A mixed logit model was applied to the BWS data.

Results: The respondents' background was similar to that of the general population, although the number of people in the age and sex categories was equal. The preference weights for calculating the utilities of the ASCOT-Carer states were estimated. The estimated utilities of the ASCOT-Carer states were distributed between 1 and 0.02. All preference weights were consistent. The item with the highest preference weight was level 1 in the "space and time to be yourself." The least preferred item was level 4 in the "space and time to be yourself" and "control over daily life" domains.

Conclusion: We established Japanese preference weights for ASCOT-Carer states, the first weights of an Asian country. The estimated utilities can contribute to the measurement of caregivers' social care-related QoL and perform of cost-effectiveness analyses.

Keywords: ASCOT; Best–worst scaling (BWS); Caregiver; Preference; Quality of life; Time trade-off (TTO).