title: Use of HbA1c for diagnoses of diabetes and prediabetes: comparison with diagnoses based on fasting and 2-hr glucose values and effects of gender, race, and age.
abstract: BACKGROUND
  Glycated hemoglobin (HbA1c) has been advocated for the diagnosis of diabetes and prediabetes. Its performance has been commonly assessed in corroboration with elevated fasting plasma glucose (FPG), but not the combination of FPG and 2-hr glucose values. This study assesses receiver operating characteristics (ROC) curves of HbA1c pertaining to the diagnoses of prediabetes and diabetes by FPG and/or 2-hr glucose, and the effects of age, gender, and race.
  
  
  METHODS
  We assessed the utility of HbA1c for diagnosing diabetes and prediabetes among 5395 adults without known diabetes from the National Health and Nutrition Examination Survey (NHANES) 2005-2010.
  
  
  RESULTS
  Current cutoffs of HbA1c for diabetes (6.5%) or prediabetes (5.7%) exhibited low sensitivity (0.249 and 0.354, respectively) and high specificity in identifying patients diagnosed using both FPG and 2-hr glucose, resulting in large false-negative rates (75.1% and 64.9%). Misdiagnosis rates increased with age and in non-Hispanic whites and Mexican Americans. When HbA1c was combined with FPG for diagnoses, the false-negative rate remained high for diabetes (45.7%), but was reduced for prediabetes (9.2%).
  
  
  CONCLUSIONS
  When assessed against diagnoses using both FPG and 2-hr glucose, HbA1c had low sensitivity and high specificity for identifying diabetes and prediabetes, which varied as a function of age and race. Regarding recently released American Diabetes Association (ADA) and joint European guidelines, it is important to consider that HbA1c values below 6.5% and 5.7% do not reliably exclude the presence of diabetes and prediabetes, respectively. Overall, the data argue for greater use of oral glucose tolerance tests (OGTTs) and both FPG and 2-hr glucose values for diagnosis of diabetes and prediabetes.
authors: 1 Department of Nutrition Sciences, University of Alabama at Birmingham , Birmingham, Alabama.
authors: Fangjian
authors: F
authors: Guo
authors: Douglas R
authors: DR
authors: Moellering
authors: W Timothy
authors: WT
authors: Garvey
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D019540:Area Under Curve; D001786:Blood Glucose / Q000032:analysis*; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000097:blood / Q000175:diagnosis*; D004797:Enzyme-Linked Immunosorbent Assay; D005188:False Negative Reactions; D005215:Fasting; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D011236:Prediabetic State / Q000097:blood / Q000175:diagnosis*; D012372:ROC Curve; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014481:United States; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human