title: The potential impact and optimal cut-points of using glycated haemoglobin, HbA1c, to detect people with impaired glucose regulation in a UK multi-ethnic cohort.
abstract: BACKGROUND
  Recommended diagnostic cut-points to detect impaired glucose regulation (IGR, also termed prediabetes: impaired fasting glucose and/or impaired glucose tolerance based on WHO 1999 criteria) are HbA1c 6.0-6.4% and 5.7-6.4% from an International Expert Committee and American Diabetes Association, respectively. We investigated the impact on prevalence/phenotype from using these criteria compared to IGR detected on oral glucose tolerance testing (OGTT) and determined optimal HbA1c cut-points for IGR in a multi-ethnic cohort.
  
  
  METHODS
  Analysis of 8696 participants in the LEADER study of primary care individuals aged 40-75 years without diabetes, in Leicestershire (UK) who underwent OGTT and had HbA1c measured.
  
  
  RESULTS
  Use of OGTT detected less people with IGR (n=1407, 16.2%) compared to HbA1c 6.0-6.4% (n=1610, 18.5%) and HbA1c 5.7-6.4%(n=3904, 44.9%), a 1.1- and 2.8-fold increase in prevalence, respectively. There were 930 (10.7%) and 534 (6.1%) people with IGR on OGTT not detected using HbA1c 6.0-6.4% and 5.7-6.4%, respectively. From ROC curve analysis, the optimal cut-point for detecting IGR in white Europeans was HbA1c>or=5.8%, sensitivity/specificity 61.5%/67.9%, but in south Asians HbA1c>or=6.0%, sensitivity/specificity 63.8%/69.4%.
  
  
  CONCLUSIONS
  Recommended HbA1c cut-points to detect IGR significantly increase numbers detected, however introduce a change in people identified. Using HbA1c 6.0-6.4% lacks sensitivity in white Europeans, but is a reasonable option in south Asians.
authors.affiliation: Division of Diabetes and Endocrinology, Department of Cardiovascular Sciences, Leicester Royal Infirmary, Leicester, UK. samiul.mostafa@uhl-tr.nhs.uk
authors.forename: Samiul A
authors.initials: SA
authors.lastname: Mostafa
authors.forename: Kamlesh
authors.initials: K
authors.lastname: Khunti
authors.forename: Balasubramanian Thiagarajan
authors.initials: BT
authors.lastname: Srinivasan
authors.forename: David
authors.initials: D
authors.lastname: Webb
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Gray
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Davies
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D001786:Blood Glucose / Q000032:analysis; D015331:Cohort Studies; D005260:Female; D018149:Glucose Intolerance / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology / Q000208:ethnology; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D010641:Phenotype; D017410:Practice Guidelines as Topic; D011236:Prediabetic State / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology / Q000208:ethnology; D012680:Sensitivity and Specificity; D006113:United Kingdom / Q000453:epidemiology; D044465:White People
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human