OHE and the University of Technology Sydney are leading a study funded by the EuroQol Research Foundation to develop ‘bolt-on’ descriptors for the EQ-5D. The goal is to develop and test new questions that can be used with people who have cognitive impairment or visual impairment. We’re currently seeking research participants.
The EQ-5D descriptive system forms the basis of a questionnaire that is widely used in health research. In particular, the EQ-5D is used to estimate quality-adjusted life years (QALYs), which are the cornerstone of value in health technology assessment in the UK and elsewhere. However, in certain circumstances, the EQ-5D has been shown to perform less well than other measures of health outcome. In particular, the EQ-5D sometimes does not detect meaningful changes in cognitive function and visual function. This has led some researchers to call for the development of ‘bolt-on’ items, which would be additional aspects of health added to the core set of five EQ-5D domains (mobility, self-care, usual activities, pain/discomfort, anxiety/depression). The EuroQol Group is keen to explore the development of bolt-ons, though it is not committed to expanding the EQ-5D at this stage.
In collaboration with the University of Technology Sydney, the University of Central Lancashire, and the University of Nottingham, we have been funded by the EuroQol Research Foundation to develop bolt-on descriptors for cognition and vision. Researchers are increasingly recognising the need for health outcome measurement to be patient-centred, which means that the development of new measures should be informed by the views of people who will ultimately be asked to complete the questionnaires. To this end, our work will employ both qualitative and quantitative research methods to develop candidate bolt-ons. The project is organised into three phases.
Phase 1: Development of descriptors
In the first part of the study, we will generate a set of possible descriptors that might make for suitable bolt-on items. To do this, we’re conducting literature reviews and focus groups. By reviewing health status measures that are currently used in the context of cognitive impairment and visual impairment, we can understand how the impact of cognition and vision problems is currently captured. We can also identify the various terminologies that are used in questionnaires. The groundwork of the literature review will guide a set of focus groups, which we will be conducting in the UK. Participants will have varying degrees of impairment and will be asked to discuss the ways in which cognitive or visual impairment affects their quality of life, and how they would describe that.
Phase 2: Qualitative testing
Based on the findings from Phase 1, we’ll carry out a series of interviews with people who have experience of cognitive impairment or visual impairment. We’ll ask participants to complete EQ-5D-5L questionnaires with candidate bolt-on descriptors, followed by cognitive debriefing. This will help us to understand potential difficulties with comprehensibility or accessibility.
Phase 3: Quantitative testing
Once we have a set of possible bolt-on descriptors, they will be subject to psychometric testing. This will involve a cross-sectional survey conducted online and by telephone, which will ask participants to complete the EQ-5D-5L questionnaire with candidate bolt-on items, as well as other condition-specific instruments. The testing will include classical psychometrics and regression, factor analysis, and Rasch analysis.
We are currently conducting Phase 1 of the study and we are looking for participants to take part in focus groups and interviews. If you have experienced cognitive impairment or visual impairment, or you are a caregiver for somebody who has, please consider volunteering your time to our research.
If you are a researcher, you can follow the progress of our project on ResearchGate.
For more information about the study, or to express an interest in taking part, please contact Chris Sampson.
Cubí-Mollá, P., de Vries, J. and Devlin, N., 2014. A Study of the Relationship between Health and Subjective Well-Being in Parkinson’s Disease Patients. Value in Health, 17(4), pp.372–379. DOI. RePEc.
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