Safety, Efficacy and Cost Effectiveness of Individualised Screening for Diabetic Retinopathy: The ISDR Randomised Controlled Trial

Background: Varying diabetic retinopathy (DR) screening intervals, informed by personal risk-levels, empowers people with diabetes (PWD), and offers reallocation of resources to high risk groups, while addressing the increasing prevalence of diabetes. Safety data on extending intervals is minimal. We evaluated the safety, efficacy and cost effectiveness of individualised risk-based variable-interval population screening compared to usual care, with design input from PWD. Methods: Two-arm, parallel assignment, equivalence randomised controlled trial (minimum 2 year follow-up) in PWD aged ≥12 years registered with one English screening programme. Randomisation was 1:1 to individualised screening (6, 12 or 24 months for high, medium and low risk) determined by a risk calculation engine, using local demographic, screening and clinical data, or to annual screening (control). Primary outcome was attendance (safety). A secondary safety outcome was the development of sight threatening DR (STDR). Cost effectiveness was evaluated within a 2 year time horizon from NHS and societal perspectives. Findings: 4534 participants were randomised, 2265 to the individualised and 2269 to the control arm. Attendance rates at first follow-up were equivalent between individualised (1754/2097, 83·6%) and control (1883/2224, 84·7%) arms (difference -1·0, 95% CI -3·2 to 1·2). STDR detection rates were non-inferior: individualised 1·4%, control 1·7% (- 0·3, -1·1 to 0·5). Sensitivity analyses confirmed findings. Incremental QALYs/person were non-significant: EQ-5D-5L 0·035 (CI -0·04, 0·13), HUI3 0·009 (CI -0·09, 0·10). Incremental cost savings were £21·31 (CI 15·24, 26·79)/person for the NHS and £28·87 (CI 21·08, 35·78) including societal costs. 43·2% fewer screening appointments were required in the individualised arm. Interpretation: Stakeholders involved in diabetes care can be reassured by this largest ophthalmic RCT in DR screening to date that extended and individualised risk-based intervals can be safely and cost effectively introduced in established screening programmes. Trial Registration Number: ISRCTN 87561257. Funding Statement: This study was funded by the UK National Institute for Health Research (NIHR) (Programme Grants for Applied Research, RP-PG-1210-12016). Declaration of Interests: We declare no competing interests. Professor Mark Gabbay is part-funded by the NIHR Collaboration for Leadership in Applied Health Research and Care North West Coast. Ethics Approval Statement: A UK NHS Research Ethics Committee approved the trial (14/NW/0034).