title: HbA(1c) measurement for the diagnosis of diabetes: is it enough?
abstract: OBJECTIVE
  To analyse the performance of HbA(1c) in diagnosing Type 2 diabetes based on fasting plasma glucose and/or 2-h plasma glucose measurements after a 75-g oral glucose tolerance test.
  
  
  METHODS
  This is a study of diagnostic test accuracy in individuals referred to the Clinical Pathology Department for oral glucose tolerance testing. After fasting overnight, HbA(1c), fasting plasma glucose and 2-h plasma glucose were measured. The receiver operating characteristic curve was used to evaluate the diagnostic performance of HbA(1c).
  
  
  RESULTS
  Four hundred and ninety-eight subjects (195 male, mean age 56 years) were enrolled and 115 (23.1%) were diagnosed with diabetes according to glucose-based methods and only 56 (11.2%) individuals were identified by HbA(1c) ≥ 6.5% (48 mmol/mol) (sensitivity 20.9%, specificity 95.3%). There is poor agreement between the newly recommended criterion and the current glucose-based diagnostic criteria (κ = 0.217; P < 0.001), probably because the diagnostic methods identify different populations of patients. Adding a glucose-based method into an algorithm, as proposed by the UK Department of Health, improved HbA(1c) performance.
  
  
  CONCLUSIONS
  HbA(1c) ≥ 6.5% (48 mmol/mol) showed limited sensitivity to diabetes diagnosis, although with high specificity. The results suggest that this cut-off point would not be enough to diagnose diabetes. Its use as the sole diabetes diagnostic test should be interpreted with caution to assure the correct classification of diabetic individuals.
authors.affiliation: Postgraduate Program in Endocrinology, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: G
authors.initials: G
authors.lastname: Cavagnolli
authors.forename: J
authors.initials: J
authors.lastname: Comerlato
authors.forename: C
authors.initials: C
authors.lastname: Comerlato
authors.forename: P B
authors.initials: PB
authors.lastname: Renz
authors.forename: J L
authors.initials: JL
authors.lastname: Gross
authors.forename: J L
authors.initials: JL
authors.lastname: Camargo
mesh_terms: D001786:Blood Glucose / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test / Q000379:methods*; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D012680:Sensitivity and Specificity; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin