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Clinical science
Validation of a novel diabetic retinopathy utility index using discrete choice experiments
  1. Eva K Fenwick1,2,3,
  2. Nick Bansback4,
  3. Alfred Tau Liang Gan1,
  4. Julie Ratcliffe5,
  5. Leonie Burgess6,
  6. Tien Yin Wong1,3,7,
  7. Ecosse Luc Lamoureux1,2,3
  1. 1 Health Services Research Unit, Singapore Eye Research Institute, Singapore, Singapore
  2. 2 Ophthalmology, University of Melbourne, Melbourne, Victoria, Australia
  3. 3 Health Services and Systems Research, Duke-NUS Medical School, Singapore, Singapore
  4. 4 School of Population and Public Health, University of British Columbia, Vancouver, British Columbia, Canada
  5. 5 Institute for Choice, Business School, University of South Australia, Adelaide, South Australia, Australia
  6. 6 Sax Institute, Haymarket, Ultimo, Australia
  7. 7 Singapore National Eye Centre, Singapore, Singapore
  1. Correspondence to Dr Ecosse Luc Lamoureux, Ophthalmology, University of Melbourne, Victoria, VIC 3010, Australia; ecosse{at}unimelb.edu.au

Abstract

Background/aims To validate a preference-based Diabetic Retinopathy Utility Index (DRU-I) using discrete choice experiment (DCE) methods and assess disutilities associated with vision-threatening DR (VTDR: severe non-proliferative DR, proliferative DR and clinically significant macular oedema) and associated vision impairment.

Methods The DRU-I comprises five quality-of-life dimensions, including Visual symptoms, Activity limitation/mobility, Lighting and glare, Socio-emotional well-being and Inconvenience, each rated as no, some, or a lot of difficulty. The DRU-I was developed using a DCE comprising six blocks of nine choice sets which, alongside the EuroQoL-5D (EQ-5D-3L) and Vision and Quality of Life (VisQoL) utility instruments, were interviewer-administered to participants. To ensure the DRU-I was sensitive to severe disease, we oversampled patients with VTDR. Data were analysed using conditional logit regression.

Results Of the 220 participants (mean±SD age 60.1±11.3 years; 70.9% men), 57 (29.1%) and 139 (70.9%) had non-VTDR and VTDR, respectively, while 157 (71.4%), 20 (9.4%) and 37 (17.3%) had no, mild or moderate/severe vision impairment, respectively. Regression coefficients for all dimensions were ordered as expected, with worsening levels in each dimension being less preferred (theoretical validity). DRU-I utilities decreased as DR severity (non-VTDR=0.87; VTDR=0.80; p=0.021) and better eye vision impairment (none=0.84; mild=0.78; moderate/severe=0.72; p=0.012) increased. DRU-I utilities had low (r=0.39) and moderate (r=0.58) correlation with EQ-5D and VisQoL utilities, respectively (convergent validity).

Discussion The DRU-I can estimate utilities associated with vision-threatening DR and associated vision impairment. It has the potential to assess the cost-effectiveness of DR interventions from a patient perspective and inform policies on resource allocation relating to DR.

  • diabetic retinopathy
  • quality of life
  • utility
  • discrete choice experiment
  • vision impairment
  • health economics

https://doi.org/10.1136/bjophthalmol-2019-313899

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    Footnotes

    • Contributors EKF contributed to the conception of the work, interpretation of the data and drafting of the manuscript; EKF and NB conducted the data analysis, assisted with interpretation of results and drafted sections of the paper; LB contributed to the methodology and study design and revised the manuscript critically for important intellectual content; JR and TYW revised the manuscript critically for important intellectual content; ELL contributed to the conception of the work, interpretation of the data and revised the manuscript critically for important intellectual content.

    • Funding This project was funded by Pfizer Australia (WS904143); Royal Victorian Eye and Ear Hospital; EKF was funded by the Australian National Health and Medical Research Council (NHMRC) Early Career Fellowship (1072987). ELL was funded by the NHMRC Senior Research Fellowship (1045280). The Centre for Eye Research Australia receives Operational Infrastructure Support from the Victorian Government.

    • Disclaimer The sponsor or funding organisation had no role in the design or conduct of this research.

    • Competing interests None declared.

    • Patient consent for publication Not required.

    • Ethics approval This study was granted ethical approval by the Royal Victorian Eye and Ear Hospital Human Research Ethics Committee (11/1035H) and was conducted in accordance with the Declaration of Helsinki.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement Data are available on request.

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