Simon Harding, Ayesh Alshukri, Duncan Appelbe, Deborah Broadbent, Philip Burgess, Paula Byrne, Christopher Cheyne, Antonio Eleuteri, Anthony Fisher, Marta García-Fiñana, Mark Gabbay, Marilyn James, James Lathe, Tracy Moitt, Mehrdad Mobayen Rahni, John Roberts, Christopher Sampson, Daniel Seddon, Irene Stratton, Clare Thetford, Pilar Vazquez-Arango, Jiten Vora, Amu Wang, and Paula Williamson
Background Systematic annual screening for sight-threatening diabetic retinopathy is established in several countries but is resource intensive. Personalised (individualised) medicine offers the opportunity to extend screening intervals for people at low risk of progression and to target high-risk groups. However, significant concern exists among all stakeholders around the safety of changing programmes. Evidence to guide decisions is limited, with, to the best of our knowledge, no randomised controlled trials to date. Objectives To develop an individualised approach to screening for sight-threatening diabetic retinopathy and test its acceptability, safety, efficacy and cost-effectiveness. To estimate the changing incidence of patient-centred outcomes. Design A risk calculation engine; a randomised controlled trial, including a within-trial cost-effectiveness study; a qualitative acceptability study; and an observational epidemiological cohort study were developed. A patient and public group was involved in design and interpretation. Setting A screening programme in an English health district of around 450,000 people. Participants People with diabetes aged ≥ 12 years registered with primary care practices in Liverpool. Interventions The risk calculation engine estimated each participant’s risk at each visit of progression to screen-positive diabetic retinopathy (individualised intervention group) and allocated their next appointment at 6, 12 or 24 months (high, medium or low risk, respectively). Main outcome measures The randomised controlled trial primary outcome was attendance at first follow-up assessing the safety of individualised compared with usual screening. Secondary outcomes were overall attendance, rates of screen-positive and sight-threatening diabetic retinopathy, and measures of visual impairment. Cost-effectiveness outcomes were cost/quality-adjusted life year and incremental cost savings. Cohort study outcomes were rates of screen-positive diabetic retinopathy and sight-threatening diabetic retinopathy. Data sources Local screening programme (retinopathy), primary care (demographic, clinical) and hospital outcomes. Methods A seven-person patient and public involvement group was recruited. Data were linked into a purpose-built dynamic data warehouse. In the risk assessment, the risk calculation engine used patient-embedded covariate data, a continuous Markov model, 5-year historical local population data, and most recent individual demographic, retina and clinical data to predict risk of future progression to screen-positive. The randomised controlled trial was a masked, two-arm, parallel assignment, equivalence randomised controlled trial, with an independent trials unit and 1 : 1 allocation to individualised screening (6, 12 or 24 months, determined by risk calculation engine at each visit) or annual screening (control). Cost-effectiveness was assessed using a within-trial analysis over a 2-year time horizon, including NHS and societal perspectives and costs directly observed within the randomised controlled trial. Acceptability was assessed by purposive sampling of 60 people with diabetes and 21 healthcare professionals with semistructured interviews analysed thematically; this was a constant comparative method until saturation. The cohort was an 11-year retrospective/prospective screening population data set. Results In the randomised controlled trial, 4534 participants were randomised: 2097 out of 2265 in the individualised arm (92.6%) and 2224 out of 2269 in the control arm (98.0%) remained after withdrawals. Attendance rates at first follow-up were equivalent (individualised 83.6%, control 84.7%) (difference –1.0%, 95% confidence interval –3.2% to 1.2%). Sight-threatening diabetic retinopathy detection rates were non-inferior: individualised 1.4%, control 1.7% (difference –0.3%, 95% confidence interval –1.1% to 0.5%). In the cost-effectiveness analysis, the mean differences in complete-case quality-adjusted life years (EuroQol-5 Dimensions, five-level version, and Health Utilities Index Mark 3) did not significantly differ from zero. Incremental cost savings per person not including treatment costs were from the NHS perspective £17.34 (confidence interval £17.02 to £17.67) and the societal perspective £23.11 (confidence interval £22.73 to £23.53). In the individualised arm, 43.2% fewer screening appointments were required. In terms of acceptability, changing to variable intervals was acceptable for the majority of people with diabetes and health-care professionals. Annual screening was perceived as unsustainable and an inefficient use of resources. Many people with diabetes and healthcare professionals expressed concerns that 2-year screening intervals may detect referable eye disease too late and might have a negative effect on perceptions about the importance of attendance and diabetes care. The 6-month interval was perceived positively. Among people with dementia, there was considerable misunderstanding about eye-related appointments and care. In the cohort study, the numbers of participants (total 28,384) rose over the 11 years (2006/7, n = 6637; 2016/17, n = 14,864). Annual incidences ranged as follows: screen-positive 4.4–10.6%, due to diabetic retinopathy 2.3–4.6% and sight-threatening diabetic retinopathy 1.3–2.2%. The proportions of screen-positive fell steadily but sight-threatening diabetic retinopathy rates remained stable. Limitations Our findings apply to a single city-wide established English screening programme of mostly white people with diabetes. The cost-effectiveness analysis was over a short timeline for a long-standing disease; the study, however, was designed to test the safety and effectiveness of the screening regimen, not the cost-effectiveness of screening compared with no screening. Cohort data collection was partly retrospective: data were unavailable on people who had developed sight-threatening diabetic retinopathy or died prior to 2013. Conclusions Our randomised controlled trial can reassure stakeholders involved in diabetes care that extended intervals and personalised screening is feasible, where data linkage is possible, and can be safely introduced in established screening programmes with potential cost savings compared with annual screening. Rates of screen-positive diabetic retinopathy and sight-threatening diabetic retinopathy are low and show consistent falls over time. Involvement of patients in research is crucial to success. Future work Future work could include external validation with other programmes followed by scale-up of individualised screening outside a research setting and economic modelling beyond the 2-year time horizon. Trial registration This trial is registered as ISRCTN87561257. Funding This project was funded by the National Institute for Health and Care Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 11, No. 6. See the NIHR Journals Library website for further project information. Plain language summary Diabetic retinopathy remains a leading cause of vision loss for people with diabetes. Annual photographic screening allows early detection and prompt treatment in many countries. A new approach is to vary how often this is undertaken at each visit, after calculating each person’s risk of progression; we have called this ‘individualised’ screening. We tested this variable-interval risk-based approach against annual screening in a randomised controlled trial of 4534 people in Liverpool. Six-, 12- or 24-month intervals represented high, medium and low risks, respectively, of becoming screen-positive by the next appointment. With our patient and public involvement group, we designed a computer-based risk-calculation system using personal information from screening, general practitioners and hospitals. Attendance rates at the next screening appointment were similar in the individualised (84%) and annual (control) (85%) groups. Similar amounts of sight-threatening diabetic retinopathy were detected in the two arms (1.4% individualised, 1.7% control), with 43% fewer visits. In this study in a single geographical region, savings estimated to accrue to the NHS per person over 2 years were £17.34 and £23.11 for wider society, but estimates did not include treatment costs. During interviews, 60 people with diabetes and 21 healthcare professionals said that individualised screening would be acceptable because of increasing rates of diabetes and the chance to target high-risk people. Patients had anxieties about the reliability of the risk-calculation and restricting access, requesting opportunities for earlier screening if risks changed. Varying screening intervals based on a person’s own risk of progression appears feasible and safe. Low-risk people would be spared unnecessary appointments. Introducing an individualised approach could now move to wider testing and validation in other UK and international settings. The trial only ran for 2 years and was in a long-established programme with low rates of disease, so monitoring of attendance and retinopathy rates should be included as part of wider testing. Scientific summary Background Diabetic retinopathy remains the most common cause of visual impairment in working populations worldwide. Systematic annual screening to detect and treat sight-threatening diabetic retinopathy (STDR) is established in several countries including the United Kingdom (UK) and has greatly improved the detection of treatable disease. With the rapid increase in the prevalence of diabetes, new approaches to screening are required. Risk stratification, personalised (individualised) medicine, and clinical bioinformatics offer opportunities to extend the screening interval for people at low risk of progression and to target those at high risk. However there is significant concern among people with diabetes, healthcare professionals and health commissioners in the UK around the safety and acceptability of changing an established and successful programme. To ensure that health care is available for all it is imperative that it is not only efficacious but cost-efficient, that is, it delivers care at an affordable cost for commissioners. Evidence to guide these decisions is very limited and there are no randomised controlled trials (RCTs). Much of the data on prevalence and incidence of diabetic retinopathy and progression to more severe stages of disease come from the 1980s to 1990s and before the introduction of systematic screening and improvements in diabetes and blood pressure control. Data on the current progression rates in screening populations are limited and are reported variably. We conducted a programme of quantitative and qualitative research to develop and test the acceptability, safety, efficacy and cost-effectiveness of an individualised approach to screening for STDR. To provide data for future planning of early detection programmes and the design of future research studies we designed a longitudinal observational cohort study of the population of people with diabetes in Liverpool. We aimed to investigate the prevalence and incidence of the stages in the natural history of diabetic retinopathy, namely screen-positive, sight-threatening and treatable disease, and visual impairment, all key patient-centred outcomes in the disease. Changes to the programme and their implications A number of changes to the programme occurred in the early years. A systematic review was published at around the time of the programme start. We used these data to design aspects of the study and conducted a literature review instead. Data for the cohort study proved not to be available on people who had died prior to programme start. We adopted a mixed retrospective and prospective analysis but this added some difficulty in interpreting the findings. In 2016 resources were repurposed from the cohort study to support recruitment of the RCT, which was behind schedule. The scope of the cohort study was narrowed to focus only on the data available from the screening programme, meaning that we were unable to complete data collection on the patient-centred outcomes after sight-threatening retinopathy had been confirmed, namely treatment and visual impairment. Recruitment of non-attenders proved beyond the resources available and was abandoned. Further research is needed to address these unanswered questions. Methods The programme included the development of a bespoke data warehouse, the development of a risk-calculation engine, a RCT, a within-trial cost-effectiveness study, a qualitative study of acceptability, and an observational cohort study. We recruited and fully embedded a seven-person patient and public involvement group which was maintained throughout the programme. The setting was the screening programme of a single English health district (clinical commissioning group). All people with diabetes aged 12 years and over registered with general practices in the Liverpool city area were invited by letter to participate in the research programme. Consent was through an opt-out process. A purpose-built dynamic data warehouse was developed to support all aspects of the programme including bespoke processes addressing inconsistency in routinely collected data, multiple data platforms and lack of technical manuals. Data on eligible participants were sourced from primary care (demographic, clinical), Liverpool Diabetes Eye Screening Programme (retinopathy) and hospital outcomes (true screen-positive, STDR). Data were cross referenced against opt-out records before further use within the programme. A risk-calculation engine was developed for the assessment of individual risk of progressing to screen-positive using patient-focused covariate selection, a continuous-time Markov model, 5-year historical local population data, and the most recent individual demographic, retina and clinical data. The risk-calculation engine was linked to the data warehouse. The Patient and Public Involvement group determined the risk criterion of