Diabetic retinopathy (DR) is the commonest cause of visual loss in adults. Screening for DR aims to detect sight-threatening disease (STDR) and refer people with diabetes (PWD) into the hospital eye service (HES) for appropriate treatment. STDR is a definition with limited relevance to PWD. In England the screening interval has been set at 12 months for all PWD; follow up intervals in the HES are variable. Evidence to support the delivery of the pathway is limited to screening research cohorts and with minimal input from users. There are large potential cost savings to the NHS by varying the screen interval but no cost-effectiveness research data other than from limited modelling. The safety and acceptability of extending the screen interval in low risk groups has not been investigated.
We will conduct a mixed qualitative and quantitative programme of research aiming to strengthen the evidence base for screening for DR in the UK and beyond. Our approach integrates PWD and professionals at key review points within the programme and introduces care focussed on the individual. Our research team has extensive experience in research in the field and the support of key stakeholders in the UK; it includes academics, service leads and users from all relevant disciplines. We will conduct work streams which will inform each other and develop during the programme. In a development year we overcame important obstacles to improve our chances of success.
A whole population cohort (n=18,000) including those within the HES will be recruited and followed to measure risk of progression to patient centred endpoints of treatment and visual impairment. A data warehouse will receive all relevant data from PWD streamed from primary and secondary care. A personalised method of calculating screen interval using a risk calculation engine fed from the warehouse will be developed and evaluated in a randomised controlled trial (RCT) of over 5000 patients. Comparison will be between our risk-based variable interval screening and usual care. Risk factors tested will be demographic (eg. age, deprivation, ethnicity), ocular (eg. previous and current retinopathy severity, previous treatment, vision) and systemic (eg. diabetes control and duration, blood pressure, lipids). Qualitative research methods will be used to assess patient and professional experience and acceptability of risk to underpin interval selection. Direct data collection on costs will allow new health economics insights to be developed and a cost-effectiveness analysis of the RCT.
We will deliver new knowledge on patient-centred risks associated with DR and a validated individualised risk-based screening model ready for implementation in the NHS within 3 years of the end of the programme. Our findings will include data on cost-effectiveness, patient safety and acceptability, including of risk of missed disease, to underpin interval setting