Each one of these states was assigned an index value on a 0 to 1 scale using a best-worst scaling (choice) task3 conducted with 255 older people in the UK.4 On this scale, 0 is assigned to the ‘no’ capability state and 1 to the ‘full’ capability state. The ICECAP-O measure is currently being used in a number of health and social care trials in Europe and elsewhere. Exploration of the feasibility and validity of the measure is ongoing.5

As the ICECAP-O measure was developed with, and valued by, older people (65+), it is most appropriate for this population, but a capability measure may also be valuable in the general adult population. Work has been funded by the UK Medical Research Council to develop such a measure of capability for the adult population (18+). As with the ICECAP-O, qualitative methods are being used to develop the ICECAP-A descriptive system and quantitative methods to value (score) the wellbeing states. There are four phases of the research: (i) developing conceptual attributes of wellbeing; (ii) developing the ICECAP-A profile measure; (iii) valuing the ICECAP-A states; and (iv) testing the validity and reliability of ICECAP-A.  In the first phase in-depth interviews with 36 informants are being used to define conceptual attributes of wellbeing for the adult population. The second phase will use semi-structured interviews with up to 25 of these informants to develop meaningful terminology for the adult population. The third phase will use interviewer administered best-worst scaling experiments with 400 respondents from a general adult population sample to obtain index values for the ICECAP-A attributes. The final phase will explore the validity and reliability of the measure; much of this work will be alongside trials and other studies, although a ‘think aloud’ study of the ICECAP-A and EQ-5D with up to 50 participants will also be conducted.

The work on developing conceptual attributes of wellbeing began in early 2009. Informants have been purposively sampled from four geographical areas, selected for socio-economic diversity. Informants have been chosen to ensure that the resulting sample offers diversity in terms of informants’ sex, age, ethnicity and health. Face-to-face, in-depth, interviews, lasting around one hour are being used to explore wellbeing. Interviews begin with straightforward questions about family, employment, health, housing and so on, to provide contextual material for the interview. ‘Content mining’ questions are then used to explore what informants value in their lives and why; for example if an informant had recently moved house, their motive for moving may be probed and they may be asked to contrast what they (dis)liked about their old house and their new house. This in turn may, for example, reveal the value they place on factors such as ‘convenience’ or ‘open spaces’.

Ultimately the aim in this phase is to go beyond the set of well-documented influences on quality of life (such as family, employment and housing) to a set of attributes of wellbeing, such as those developed for ICECAP-O.