A qualitative exploration of the content and face validity of preference-based measures within the context of dementia

Abstract

Background Assessing the cost-effectiveness of interventions for people with dementia, based on cost per quality-adjusted life years (QALYs) gained, requires that the measures used to derive QALYs are preference-based whilst also being valid, feasible to use, comprehensible and acceptable for people with dementia. The aim of this study was to assess the content and face validity of six preference-based measures (PBMs) within the context of dementia. Methods Qualitative focus groups and interviews were conducted with community-dwelling individuals with mild dementia and carers of people with dementia. After exploring participants’ understanding of ‘quality of life’ (QoL), six PBMs were assessed for content and face validity: two measures assessing health-related QoL (EQ-5D-5L and AQoL-8D); two covering broader aspects of capability wellbeing and social care-related QoL (ICECAP-O and ASCOT); and two dementia-specific QoL measures (DEMQOL-U and AD-5D). A random mix of one health-related QoL measure, one wellbeing measure, and one dementia-specific measure was explored in each session. All sessions were audiotaped and transcribed verbatim. Data were analysed thematically. Results Nine individuals with mild dementia and 17 carers of people with dementia participated across 4 focus groups and 10 interviews. Participants perceived 9 broad QoL domains as relevant to them: Activity, Autonomy, Cognition, Communication, Coping, Emotions, End-of-Life, Physical Functioning, and Relationships. These domains had limited overlap with the content of the six PBMs. Assessment of face validity was summarized into eight themes: (1) ambiguous questions, (2) double –barrelled questions, (3) difficult/abstract questions, (4) judgemental/confronting questions, (5) lack of relevance and comprehensiveness, (6) response options, (7) layout/format and (8) proxy-response. There was no clear preference for one of the six measures explored; participants identified advantages and disadvantages across all measures. Although particularly designed for individuals with dementia, dementia-specific QoL measures were not always favoured over non-specific measures. Conclusion Given the shortcomings of PBMs identified in this study, further empirical comparative analyses are necessary to guide the selection of PBMs for future dementia research.

A Qualitative Investigation of Older Adults’ Conceptualization of Quality of Life and a Think-Aloud Content Validation of the EQ-5D-5L, SF-12v2, Warwick Edinburgh Mental Well-Being Scale, and Office of National Statistics-4.

“…These issues have been noted in previous content validation studies of the EQ-5D-3L in older populations. 13,39 The ONS-4 worthwhile item was interpreted in different ways, to mean worthwhile either to themselves or to society, consistent with findings from a previous content validation. 44 Response option selection issues were also seen for the SF-12v2 moderate activities item.…”

“…These themes closely reflect the World Health Organization definition of healthy aging, which centers on maintaining functional ability to enable the well-being of older adults 12 and key themes identified in the literature. 2,3,[37][38][39] This provides support that these themes are generalizable to older adults more broadly. Developers of PROMs for use in older adults should consider these core domains.…”

“…Response shift has been widely observed in older adults' responses to PROMs. 39,[41][42][43] Response shift affects the validity of responses and comparisons across participants given that, if different individuals use different strategies or reference points to assess their health, scores are not comparable.…”

“…The ease of answering the EQ-5D, combined with a lack of comprehensiveness are also reflective of previous findings. 13,39 Therefore, it may require adaptation, either through permanent adaptation or the additional of bolt-on dimensions for use in older respondents. [45][46][47] Additional dimensions suggested to improve the comprehensiveness of each measure for older adults included: social contact, coping/support, future security, the way people were treated, and control/independence.…”

A multidomain decision support tool to prevent falls in older people: the FinCH cluster RCT

“…59 At the same time, several economic evaluations in care home populations have been published that show the EQ-5D can be used in this population 20,60 and may be more responsive than the DEMQOL-P-U. 59 Recently, however, a qualitative study comparing six preference-based measures (in terms of face and content validity) in the context of dementia found that no single instrument was favoured, 61 such that choice of a preference-based measure remains on the research agenda.…”