Self- and proxy-rating of the ICECAP-O for people with dementia: A cross-sectional linguistic validation study in Germany and Portugal

BACKGROUND: The capability concept became a recognized approach to the measurement of quality of life. The ICECAP-O for older people aims to measure capabilities and has recently been used in people with dementia (self-rating) and informal carers (substituted judgement). However, linguistic validation studies have so far been lacking.

METHODS: A cross-sectional cognitive interview study with 15 people with dementia (PwD) and 23 informal carers (ICs) was conducted in Germany and Portugal. Respondents were asked to reveal their understanding of the ICECAP-O and the capability approach as well as the response process. A summarising content analysis was performed.

RESULTS: Despite the small sample, our linguistic validation of the German and Portuguese translations detected considerable difficulties or deviations in item comprehension when compared with the intended meaning. In some cases, the item interpretations did not reflect the entire scope of the associated capability dimension, though they were basically correct. Moreover, participants were not able to differentiate some items appropriately from one another, and some misinterpretations occurred. ICs relied mainly on observable behaviour, emotions, or verbal expressions of the PwD. Therefore, ICs found items that ask about the achievement of individual expectations or thoughts about the future difficult to assess. Only very few PwD clearly indicated that they understood the capability approach. ICs in Germany had more difficulties understanding the capability concept than in ICs Portugal.

DISCUSSION: This linguistic validation study in Germany and Portugal indicates a need for some rephrasing and refinements of the ICECAP-O translated items in both countries to fully encompass some dimensions and avoid misinterpretations. Further studies with larger samples are necessary. Based on our findings, the current German version for ICs' substituted judgement cannot be recommended for this kind of respondents without further advancements.