title: The changing relationship between HbA1c and FPG according to different FPG ranges.
abstract: OBJECTIVE
  Since the American Diabetes Association included hemoglobin A1c (HbA1c) in the diagnostic criteria for diabetes in 2010, the clinical use of HbA1c has remained controversial. We explored the use of HbA1c for diagnosing diabetes and intermediate hyperglycemia in comparison with fasting plasma glucose (FPG).
  
  
  METHODS
  We screened 3710 adult subjects (mean age = 55.24 years) comprising 1704 males and 2006 females. We drew an receiver operating characteristic (ROC) curve to evaluate the ability of HbA1c to diagnose diabetes and intermediate hyperglycemia according to FPG. We used Kappa coefficient and Pearson's correlation coefficient to evaluate the relationship between HbA1c and FPG in different FPG ranges.
  
  
  RESULTS
  The areas under ROC curve to diagnose diabetes and intermediate hyperglycemia were 0.859 (95 % CI 0.827-0.892) and 0.633 (95 % CI 0.615-0.651). The kappa coefficients between FPG and HbA1c for diagnosis of diabetes and intermediate hyperglycemia were 0.601 (P < 0.001) and 0.104 (P < 0.001). The Pearson's correlation coefficient of FPG and HbA1c was 0.640 (P < 0.001), but when we classified FPG as normal, intermediate hyperglycemia and diabetes, the coefficients became 0.07 (P = 0.002), 0.185 (P < 0.001) and 0.760 (P < 0.001), respectively.
  
  
  CONCLUSIONS
  The relationship between HbA1c and FPG changed according to the different FPG ranges. When FPG was higher, the relationship was stronger. HbA1c and FPG were highly consistent in diagnosing diabetes, but they were not in predicting intermediate hyperglycemia.
authors.affiliation: Department of Cardiology, The First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, People's Republic of China.
authors.forename: X
authors.initials: X
authors.lastname: Guan
authors.affiliation: Department of Clinical Epidemiology, Library, Shengjing Hospital of China Medical University, Shenyang, People's Republic of China.
authors.forename: L
authors.initials: L
authors.lastname: Zheng
authors.affiliation: Department of Cardiology, The First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, People's Republic of China.
authors.forename: G
authors.initials: G
authors.lastname: Sun
authors.affiliation: Department of Cardiology, The First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, People's Republic of China.
authors.forename: X
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Cardiology, The First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, People's Republic of China.
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Cardiology, The First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, People's Republic of China.
authors.forename: H
authors.initials: H
authors.lastname: Song
authors.affiliation: Department of Cardiology, The First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, People's Republic of China.
authors.forename: F
authors.initials: F
authors.lastname: Tian
authors.affiliation: Department of Cardiology, The First Hospital of China Medical University, 155 Nanjing North Street, Heping District, Shenyang, 110001, People's Republic of China. sunyingxian2013@163.com.
authors.forename: Y
authors.initials: Y
authors.lastname: Sun
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D005215:Fasting / Q000502:physiology*; D005260:Female; D018149:Glucose Intolerance / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D012372:ROC Curve
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human
keywords: Diabetes; Fasting plasma glucose (FPG); Hemoglobin A1c (HbA1c)