Development of Preference Weights for the 10-item Singapore Caregiver Quality Of Life Scale: A Discrete Choice Experiment

Background Evaluating informal caregivers’ quality of life (QoL) is essential for health economic evaluations. However, commonly used preference-based, caregiver-specific instruments lack anchoring to death, hindering the calculation of quality-adjusted life years. Furthermore, these instruments were developed in Western countries, leaving a gap for culturally appropriate instruments originally established in the East. This study aims to develop preference weights for the validated 10-item Singapore Caregiver Quality Of Life Scale (SCQOLS) to establish a culturally appropriate, death-anchored utility framework. Methods An online survey was administered to caregivers residing in Singapore and caring for adults. The questionnaire comprised discrete choice experiment (DCE) and visual analogue scale (VAS) tasks. DCE data were fitted to a conditional logit model. The DCE latent utility was anchored to death by mapping the VAS data onto the dead-full health scale, generating the SCQOLS preference weights for utility computation. Respondents’ SCQOLS utility was compared with the EQ-5D-5L utility for discriminative ability. Concurrent validity and test-retest reliability were evaluated using external data. Results Among 1,036 respondents, 925 who passed data quality checks were analyzed. They had a mean age of 38.6 years, 51.8% were female, 24.5% were sole informal caregivers, and 68.6% cared for their parents. The items “ Poor appetite ” and “ Uncertain financial situation ” were the most important (relative importance 15.3% and 14.5%, respectively), whereas “ Aches and pains ” was the least (6.2%). The SCQOLS utility ranges between 0.247 and 1. The sample mean was 0.730 (standard deviation: 0.131), with no floor effect and a mild ceiling effect of 1.51%. It demonstrated non-inferior discriminative ability to the EQ-5D-5L utility, and exhibited strong concurrent validity against the Brief Assessment Scale for Caregivers (correlation coefficient ≥ 0.714) and satisfactory test-retest reliability (intraclass correlation ≥ 0.821). Conclusions The SCQOLS preference weights will facilitate health economic evaluations, supporting healthcare decision-making and resource allocation in Singapore, with potential extension to other Asian countries.