PURPOSE: This study explores variation in health state descriptions and valuations derived from preference-based health-related quality of life instruments in the context of spinal cord injury (SCI).
METHODS: Individuals living with SCI were invited to complete a web-based, cross-sectional survey. The survey comprised questions regarding demographics, SCI classifications and characteristics, secondary health complications and conditions, quality of life and SCI-specific functioning in activities of daily living. Four preference-based health status classification systems were included; Assessment of Quality of Life 8-dimension questionnaire (AQoL-8D), EQ-5D-5L, Health Utilities Index (HUI) and SF-6D (derived from the SF-36v2). In addition to descriptive comparisons of index scores and item/dimension responses, analyses explored dimension-level correlation and absolute agreement (intraclass correlation coefficient (ICC)). Subgroup analyses examined the influence of individuals' self-reported ability to walk.
RESULTS: Of 609 invitations, 364 (60 %) individuals completed the survey. Across instruments, convergent validity was seen between pain and mental health dimensions, while sizeable variation pertaining to issues of mobility was observed. Mean index scores were 0.248 (HUI-3), 0.492 (EQ-5D-5L), 0.573 (AQoL-8D) and 0.605 (SF-6D). Agreement ranged from 'slight' (HUI-3 and SF-6D; ICC = 0.124) to 'moderate' (AQoL-8D and SF-6D; ICC = 0.634). Walking status had a markedly different impact on health state valuations across instruments.
CONCLUSIONS: Variation in the way that individuals are able to describe their health state across instruments is not unique to SCI. Further research is necessary to understand the significant differences in index scores and, in particular, the implications of framing mobility-related questions in the context of respondents' ability to walk.
Bibliographical noteAcknowledgments Financial support for this study was provided
entirely by a grant from the Rick Hansen Institute (Rick Hansen
Institute Translational Research Program, Grant #2012-29: Spinal
Cord Injury and Secondary Complications: A Mixed-Methods Evaluation of Preference-Based Instruments). The funding agreement ensured the authors’ independence in designing the study, interpreting the data, writing and publishing the report. We would also like to thank Health Utilities Inc. for the New Investigator Grant awarded to Dr. David Whitehurst, Dr. Davene Wright for her discussion of an early draft of this paper at the 2015 Vancouver Health Economics Methodology (VanHEM) meeting, Lidia Engel for her assistance with generating Fig. 1, and the two anonymous reviewers for their constructive and comprehensive comments.
- Health-related quality of life
- Quality-adjusted life years
- Spinal cord injury
- Disability U
- utility measurement
- Health state valuation