The ICEpop CAPability measure for Older people (ICECAP-O) and the Adult Social Care Outcomes Toolkit (ASCOT) are preference-based measures for assessing quality of life (QOL) from a broader perspective than do traditional health-related QOL measures such as the EuroQol five-dimensional questionnaire (EQ-5D). Measurement properties of these instruments have not yet been directly compared.
The purpose of this study was to compare the test-retest reliability, construct validity, and responsiveness of the three-level EQ-5D (EQ-5D-3L), ICECAP-O, and ASCOT in frail older adults living at home.
Cross-sectional data and longitudinal data were used. Parameters for reliability (the intraclass correlation coefficient) and agreement (standard error of measurement) were used to assess test-retest reliability after 1 week. We formulated hypotheses about correlations with other measures and tested these to assess construct validity and responsiveness (longitudinal validity).
The reliability parameters for all three scales were considered good (intraclass correlation coefficient values above 0.70). Standard error of measurement values were less than 10% of the scale. Hypotheses regarding construct validity were in general accepted; the EQ-5D-3L was more strongly associated with physical limitations than were ICECAP-O and ASCOT and less strongly with instruments measuring aspects beyond health. Longitudinally, as hypothesized, mental health was most strongly associated with ICECAP-O, and self-perceived QOL, mastery, and client-centeredness of home care most strongly with ASCOT.
Our findings support the adoption of ICECAP-O and ASCOT as outcome measures in economic evaluations of care interventions for older adults that have a broader aim than health-related QOL because they are at least as reliable as the EQ-5D-3L and are associated with aspects of QOL broader than health.