title: Individualised risk assessment for diabetic retinopathy and optimisation of screening intervals: a scientific approach to reducing healthcare costs.
abstract: OBJECTIVE
  To validate a mathematical algorithm that calculates risk of diabetic retinopathy progression in a diabetic population with UK staging (R0-3; M1) of diabetic retinopathy. To establish the utility of the algorithm to reduce screening frequency in this cohort, while maintaining safety standards.
  
  
  METHODS
  The cohort of 9690 diabetic individuals in England, followed for 2 years. The algorithms calculated individual risk for development of preproliferative retinopathy (R2), active proliferative retinopathy (R3A) and diabetic maculopathy (M1) based on clinical data. Screening intervals were determined such that the increase in risk of developing certain stages of retinopathy between screenings was the same for all patients and identical to mean risk in fixed annual screening. Receiver operating characteristic curves were drawn and area under the curve calculated to estimate the prediction capability.
  
  
  RESULTS
  The algorithm predicts the occurrence of the given diabetic retinopathy stages with area under the curve =80% for patients with type II diabetes (CI 0.78 to 0.81). Of the cohort 64% is at less than 5% risk of progression to R2, R3A or M1 within 2 years. By applying a 2 year ceiling to the screening interval, patients with type II diabetes are screened on average every 20 months, which is a 40% reduction in frequency compared with annual screening.
  
  
  CONCLUSIONS
  The algorithm reliably identifies patients at high risk of developing advanced stages of diabetic retinopathy, including preproliferative R2, active proliferative R3A and maculopathy M1. Majority of patients have less than 5% risk of progression between stages within a year and a small high-risk group is identified. Screening visit frequency and presumably costs in a diabetic retinopathy screening system can be reduced by 40% by using a 2 year ceiling. Individualised risk assessment with 2 year ceiling on screening intervals may be a pragmatic next step in diabetic retinopathy screening in UK, in that safety is maximised and cost reduced by about 40%.
authors.affiliation: Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
authors.forename: S H
authors.initials: SH
authors.lastname: Lund
authors.affiliation: Faculty of Medicine, University of Iceland, Reykjavik, Iceland Risk ehf, Reykjavik, Iceland.
authors.forename: T
authors.initials: T
authors.lastname: Aspelund
authors.affiliation: Health Intelligence plc, Cambridge, UK.
authors.forename: P
authors.initials: P
authors.lastname: Kirby
authors.affiliation: Health Intelligence plc, Cambridge, UK.
authors.forename: G
authors.initials: G
authors.lastname: Russell
authors.affiliation: Risk ehf, Reykjavik, Iceland.
authors.forename: S
authors.initials: S
authors.lastname: Einarsson
authors.affiliation: Risk ehf, Reykjavik, Iceland.
authors.forename: O
authors.initials: O
authors.lastname: Palsson
authors.affiliation: Faculty of Medicine, University of Iceland, Reykjavik, Iceland Risk ehf, Reykjavik, Iceland.
authors.forename: E
authors.initials: E
authors.lastname: Stefánsson
mesh_terms: D000465:Algorithms; D019540:Area Under Curve; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D003930:Diabetic Retinopathy / Q000175:diagnosis* / Q000191:economics; D018450:Disease Progression; D004739:England / Q000453:epidemiology; D005189:False Positive Reactions; D005260:Female; D017048:Health Care Costs; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000191:economics*; D008433:Mathematics; D011237:Predictive Value of Tests; D012372:ROC Curve; D018570:Risk Assessment; D013997:Time Factors
keywords: Clinical Trial; Diagnostic tests/Investigation; Epidemiology; Public health; Retina