title: Sensitivity and specificity of digital retinal imaging for screening diabetic retinopathy.
abstract: OBJECTIVE
  To assess the effectiveness of a non-mydriatic digital camera (45 degrees -30 degrees photographs) compared with the reference method for screening diabetic retinopathy.
  
  
  METHODS
  Type 1 and 2 diabetic patients (n = 773; 1546 eyes) underwent screening for diabetic retinopathy in a prospective observational study. Hospital-based non-mydriatic digital retinal imaging by a consultant specialist in retinal diseases was compared with slit-lamp biomicroscopy and indirect ophthalmoscopy through dilated pupils, as a gold standard, previously performed in a community health centre by another consultant specialist in retinal diseases. The main outcome measures were sensitivity and specificity of screening methods and prevalence of diabetic retinopathy.
  
  
  RESULTS
  The prevalence of any form of diabetic retinopathy was 42.4% (n = 328); the prevalence of sight-threatening including macular oedema and proliferative retinopathy was 9.6% (n = 74). Sensitivity of detection of any diabetic retinopathy by digital imaging was 92% (95% confidence interval 90, 94). Specificity of detection of any diabetic retinopathy was 96% (95, 98). The predictive value of the negative tests was 94% and of a positive test 95%. For sight-threatening retinopathy digital imaging had a sensitivity of 100%.
  
  
  CONCLUSIONS
  A high sensitivity and specificity are essential for an effective screening programme. These results confirm digital retinal imaging with a non-mydriatic camera as an effective option in community-based screening programmes for diabetic retinopathy.
authors.affiliation: Evaluation and Planning Unit, Canary Islands Health Service, Canary Islands, Spain. jlopbas@gobiernodecanarias.org
authors.forename: J
authors.initials: J
authors.lastname: Lopez-Bastida
authors.forename: F
authors.initials: F
authors.lastname: Cabrera-Lopez
authors.forename: P
authors.initials: P
authors.lastname: Serrano-Aguilar
mesh_terms: D003930:Diabetic Retinopathy / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008853:Microscopy / Q000592:standards*; D015878:Mydriasis / Q000175:diagnosis; D009887:Ophthalmoscopy / Q000592:standards*; D010781:Photography / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012015:Reference Standards; D012680:Sensitivity and Specificity