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Development of EQ-5D-5L bolt-ons for cognition and vision



OBJECTIVES Evidence suggests that, in specific circumstances, the EQ-5D is insensitive to changes or differences in health status. One possible solution is to add 'bolt-on' dimensions to the core EQ-5D dimensions, to provide additional information about the impact of certain conditions or symptoms on health. In this study, we developed EQ-5D-5L bolt-ons for cognition (5L-Cog) and vision (5L-Vis). METHODS The development process involved three stages. First, systematic literature reviews were conducted for outcome measures used in cognitive impairment and visual impairment. Items were extracted from existing measures and mapped to a set of dimensions. Common terminology was also recorded. Second, we conducted focus groups in the UK with people who have experience of either impairment. Participants were encouraged to describe the impact of their own experience of cognitive impairment or visual impairment, with reference to dimensions and terminologies identified in the literature reviews. The findings were used to develop candidate 5L-Cog and 5L-Vis descriptors. Third, we conducted interviews in the UK and Australia with people who have experience of either impairment. Interviewees were asked to complete the EQ-5D-5L with candidate 5L-Cog or 5L-Vis descriptors, followed by cognitive debriefing. RESULTS Candidate descriptors related to dimensions such as memory (for 5L-Cog), visual acuity (for 5L-Vis), mood (for both), and social functioning (for both). Various terminologies were identified in the review, with 'problems', 'limitations', 'difficulties', and 'feelings' being used in both contexts. Focus group participants expressed preferences for different terms and identified problematic words. CONCLUSIONS Qualitative research methods can be used to develop bolt-on descriptors for the EQ-5D that are meaningful to people with lived experience. However, it is challenging to identify a suitable range of participants where people with relevant lived experience constitute a heterogeneous population. In a subsequent phase of the study, 5L-Cog and 5L-Vis descriptors will be tested quantitatively.
In certain circumstances, the EQ-5D is insensitive to changes or differences in health status.
‘Bolt-on’ dimensions could provide additional information about certain conditions or symptoms.
Previous research has highlighted cognition and vision as good candidates for bolt-ons.
Cognition and vision bolt-ons have been used in the past, but with limited development.
No study has developed bolt-on descriptors in a programme of qualitative and quantitative research.
Chris Sampson
Rebecca Addo
Phil Haywood
Mike Herdman
Bas Janssen
Brendan Mulhern
Katie Page
Oona Reardon
Marina Rodes Sanchez
Justine Schneider
Koonal Shah
Clare Thetford
To identify the dimensions of health-
related quality of life that are important to
people with lived experience of cognitive
impairment and visual impairment.
To develop EQ-5D-5L bolt-on descriptors
for cognition and vision, using suitable
Recruitment of people with a range of
experiences, including carers.
Focus groups: two for each bolt-on, 4-9
Semi-structured interviews: three for
each bolt-on.
Thematic analysis of transcriptions.
Participants identified a variety of distinct cognition-specific dimensions.
These were described using various terms, which we grouped together for coding.
The vision group mostly described their experiences with reference to their level of vision in general.
Specific characteristics of visual function were not framed as capturing the impact on quality of life.
Similar generic dimensions arose in both groups, in varying degrees.
Certain terminology used in the study, including ‘impairment’, was identified as problematic.
The term ‘cognitionwas not recognised as useful.
The vision group tended to use the term ‘sight’ or ‘seeing’ rather than ‘vision’.
Some participants preferred the term ‘difficultiesto ‘problems’.
In general, the existing ‘severity’ terminology of the EQ-5D-5L was acceptable (e.g.
This is the first study to report on the development of bolt-ons using focus groups.
To develop a generic descriptor, it is necessary to recruit people with a range of different
experiences. It was very difficult to coordinate focus groups with such a group, which meant that
we needed to conduct interviews in lieu of more focus groups.
People do not conceptualise the impact of impairment on their health-related quality of life in terms
of their functioning. Rather, people consider broader impacts on quality of life. This made the
identification of specific terminology relating to functioning a challenge.
Without prompting, the participants identified dimensions (both specific and broad) that are not
currently captured by the EQ-5D, implying the legitimacy of the bolt-ons research.
Cognitive impairment is made of up distinct functional impacts, implying the need for a multi-item
The functional impact of visual impairment was described in general terms. Some people spoke
about characteristics of visual function, but these were too diverse to be useful as bolt-ons.
Some participants disliked negative framing (e.g. “problems”) or ‘clinical’ terms (e.g. “impairment”).
The development of bolt-on descriptors using focus groups is challenging
because of the need to recruit a heterogeneous population.
A cognition bolt-on will probably require multiple items.
‘Vision in general’ may be a suitable single-item bolt-on.
The current structure of the EQ-5D-5L is amenable to bolt-ons for cognition
and vision.
Terminology is very important certain words are not meaningful to people
with lived experience.
It will be necessary to test a range of wordings in qualitative interviews.
Quantitative research is needed to determine the additional information
provided by the candidate bolt-ons.
This study was commissioned by
the EuroQol Research Foundation.
Views expressed are those of the authors and do not necessarily reflect the views of the EuroQol Group
Mental stamina
Understanding things
Understanding words
Remembering things
Figuring things out
Vision in general
Sight, seeing, blindness, light perception
Vision-related activities
Driving, reading
Characteristics of visual function
Colours, depth perception, distance, visual field
Personal characteristics
Sense of self
Social identity
... The criteria have been developed as part of an ongoing project to develop bolt-on dimensions for vision and cognition using a structured qualitative and quantitative approach [20]. The draft criteria were also considered during the literature review and focus group stages of that larger project. ...
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Purpose ‘Bolt-on’ dimensions are additional items added to multi-attribute utility instruments (MAUIs) such as EQ-5D that measure constructs not included in the core descriptive system. The use of bolt-ons has been proposed to improve the content validity and responsiveness of the descriptive system in certain settings and health conditions. EQ-5D bolt-ons serve a particular purpose and thus satisfy a certain set of criteria. The aim of this paper is to propose a set of criteria to guide the development, assessment and selection of candidate bolt-on descriptors. Methods Criteria were developed using an iterative approach. First, existing criteria were identified from the literature including those used to guide the development of MAUIs, the COSMIN checklist and reviews of existing bolt-ons. Second, processes used to develop bolt-ons based on qualitative and quantitative approaches were considered. The information from these two stages was formalised into draft development and selection criteria. These were reviewed by the project team and iteratively refined. Results Overall, 23 criteria for the development, assessment and selection of candidate bolt-ons were formulated. Development criteria focused on issues relating to i) structure, ii) language, and iii) consistency with the existing EQ-5D dimension structure. Assessment and selection criteria focused on face and content validity and classical psychometric indicators. Conclusion The criteria generated can be used to guide the development of bolt-ons across different health areas. They can also be used to assess existing bolt-ons, and inform their inclusion in studies and patient groups where the EQ-5D may lack content validity.
... [8,11,13,14]. However, qualitative assessment of selected bolt-on dimensions is limited [15,16]. ...
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Objectives A number of bolt-ons have been proposed for the EQ-5D, including two psoriasis-specific bolt-ons, skin irritation and self-confidence. The study investigates and compares the relevance and comprehensiveness of these psoriasis-specific bolt-ons and the EQ-5D-5L and explores the potential conceptual overlaps between the existing five dimensions and the two bolt-ons. Methods Psoriasis patients were purposively sampled according to age and gender. Semi-structured interviews, where participants were asked to complete the EQ-5D-5L and the bolt-ons while thinking aloud, were conducted. Probes were used to investigate the thought processes of patients regarding the dimensions, wording, recall period and relevant concepts not captured by the EQ-5D-5L and bolt-ons. Data were analysed thematically. A focus group was used to confirm the findings. Results Overall, 16 patients completed the interviews. Sixteen and fifteen patients considered skin irritation and self-confidence relevant areas to describe psoriasis problems. Three patients considered itching a form of discomfort, and thus, pointed out a potential overlap between pain/discomfort and skin irritation. Twelve patients reported overall 10 general health- or psoriasis-related concepts that are not captured by the EQ-5D-5L, including itching, social relationships and sex life. Eleven patients reported that the recall period of the EQ-5D-5L might be subject to bias because of the daily or within-day fluctuations of their symptoms. Conclusions The skin irritation and self-confidence bolt-ons contribute to improve content validity of the EQ-5D-5L in patients with psoriasis. The qualitative approach taken in this study expands the existing methodological framework for the development and testing validity of bolt-ons for the EQ-5D.
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