An investigation of the overlap between the ICECAP-A and five preference-based health-related quality of life instruments.

BACKGROUND: The ICEpop CAPability measure for Adults (ICECAP-A) is a measure of capability wellbeing developed for use in economic evaluations. It was designed to overcome perceived limitations associated with existing preference-based instruments, where the explicit focus on health-related aspects of quality of life may result in the failure to capture fully the broader benefits of interventions and treatments that go beyond health. The aim of this study was to investigate the extent to which preference-based health-related quality of life (HRQoL) instruments are able to capture aspects of capability wellbeing, as measured by the ICECAP-A. METHODS: Using data from the Multi Instrument Comparison project, pairwise exploratory factor analyses were conducted to compare the ICECAP-A with five preference-based HRQoL instruments [15D, Assessment of Quality of Life 8-dimension (AQoL-8D), EQ-5D-5L, Health Utilities Index Mark 3 (HUI-3), and SF-6D]. RESULTS: Data from 6756 individuals were used in the analyses. The ICECAP-A provides information above that garnered from most commonly used preference-based HRQoL instruments. The exception was the AQoL-8D; more common factors were identified between the ICECAP-A and AQoL-8D compared with the other pairwise analyses. CONCLUSION: Further investigations are needed to explore the extent and potential implications of 'double counting' when applying the ICECAP-A alongside health-related preference-based instruments.