title: Relationship between A1C and glucose levels in the general Dutch population: the new Hoorn study.
abstract: OBJECTIVE
  To investigate the relationship among A1C, fasting plasma glucose (FPG), and 2-h postload plasma glucose in the Dutch general population and to evaluate the results of using A1C for screening and diagnosis of diabetes.
  
  
  METHODS
  In 2006-2007, 2,753 participants of the New Hoorn Study, aged 40-65 years, who were randomly selected from the population of Hoorn, the Netherlands, underwent an oral glucose tolerance test (OGTT). Glucose status (normal glucose metabolism [NGM], intermediate hyperglycemia, newly diagnosed diabetes, and known diabetes) was defined by the 2006 World Health Organization criteria. Spearman correlations were used to investigate the agreement between markers of hyperglycemia, and a receiver operating characteristic (ROC) curve was calculated to evaluate the use of A1C to identify newly diagnosed diabetes.
  
  
  RESULTS
  In the total population, the correlations between fasting plasma glucose and A1C and between 2-h postload plasma glucose and A1C were 0.46 and 0.33, respectively. In patients with known diabetes, these correlations were 0.71 and 0.79. An A1C level of > or =5.8%, representing 12% of the population, had the highest combination of sensitivity (72%) and specificity (91%) for identifying newly diagnosed diabetes. This cutoff point would identify 72% of the patients with newly diagnosed diabetes and include 30% of the individuals with intermediate hyperglycemia.
  
  
  CONCLUSIONS
  In patients with known diabetes, correlations between glucose and A1C are strong; however, moderate correlations were found in the general population. In addition, based on the diagnostic properties of A1C defined by ROC curve analysis, the advantage of A1C compared with OGTT for the diagnosis of diabetes is limited.
authors.affiliation: EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands. e.vantriet@vumc.nl
authors.forename: Esther
authors.initials: E
authors.lastname: van 't Riet
authors.forename: Marjan
authors.initials: M
authors.lastname: Alssema
authors.forename: Josina M
authors.initials: JM
authors.lastname: Rijkelijkhuizen
authors.forename: Piet J
authors.initials: PJ
authors.lastname: Kostense
authors.forename: Giel
authors.initials: G
authors.lastname: Nijpels
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Dekker
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D003920:Diabetes Mellitus / Q000097:blood* / Q000175:diagnosis / Q000378:metabolism*; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D044465:White People
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin