title: Relation between fasting glucose and retinopathy for diagnosis of diabetes: three population-based cross-sectional studies.
abstract: BACKGROUND
  The WHO and American Diabetes Association criteria for diagnosing diabetes mellitus assume the presence of a glycaemic threshold with high sensitivity for identifying retinopathy. However, this assumption is based on data from three previous studies that had important limitations in detecting retinopathy. We aimed to provide updated data for the relation between fasting plasma glucose (FPG) and retinopathy, and to assess the diagnostic accuracy of current FPG thresholds in identifying both prevalent and incident retinopathy.
  
  
  METHODS
  We examined the data from three cross-sectional adult populations: those in the Blue Mountains Eye Study (BMES, Australia, n=3162), the Australian Diabetes, Obesity and Lifestyle Study (AusDiab, Australia, n=2182), and the Multi-Ethnic Study of Atherosclerosis (MESA, USA, n=6079). Retinopathy was diagnosed from multiple retinal photographs of each eye, and graded according to the modified Airlie House Classification system. Plasma glucose concentrations were measured from fasting venous blood samples.
  
  
  RESULTS
  The overall prevalence of retinopathy was 11.5% in BMES (95% CI 10.4-12.6%), 9.6% in AusDiab (8.4-10.9), and 15.8% in MESA (14.9-16.7). However, we found inconsistent evidence of a uniform glycaemic threshold for prevalent and incident retinopathy, with analyses suggesting a continuous relation. The widely used diabetes FPG cutoff of 7.0 mmol/L or higher had sensitivity less than 40% (range 14.8-39.1) for detecting retinopathy, with specificity between 80.8% and 95.8%. The area under receiver operating characteristic curves for FPG and retinopathy was low and ranged from 0.56 to 0.61.
  
  
  CONCLUSIONS
  We saw no evidence of a clear and consistent glycaemic threshold for the presence or incidence of retinopathy across different populations. The current FPG cutoff of 7.0 mmol/L used to diagnose diabetes did not accurately identify people with and without retinopathy. These findings suggest that the criteria for diagnosing diabetes could need reassessment.
authors.affiliation: Centre for Eye Research Australia, University of Melbourne, VIC, Australia. twong@unimelb.edu.au
authors.forename: Tien Y
authors.initials: TY
authors.lastname: Wong
authors.forename: Gerald
authors.initials: G
authors.lastname: Liew
authors.forename: Robyn J
authors.initials: RJ
authors.lastname: Tapp
authors.forename: Maria Inês
authors.initials: MI
authors.lastname: Schmidt
authors.forename: Jie Jin
authors.initials: JJ
authors.lastname: Wang
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
authors.forename: Ronald
authors.initials: R
authors.lastname: Klein
authors.forename: Barbara E K
authors.initials: BE
authors.lastname: Klein
authors.forename: Paul
authors.initials: P
authors.lastname: Zimmet
authors.forename: Jonathan
authors.initials: J
authors.lastname: Shaw
mesh_terms: D000328:Adult; D000368:Aged; D001315:Australia / Q000453:epidemiology; D001786:Blood Glucose; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D003930:Diabetic Retinopathy / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D005215:Fasting / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy; D015995:Prevalence; D014481:United States / Q000453:epidemiology
chemical_list: D001786:Blood Glucose