title: A two-step screening, measurement of HbA1c in association with FPG, may be useful in predicting diabetes.
abstract: BACKGROUND
  We compared the usefulness of fasting plasma glucose (FPG), or hemoglobin A1c (HbA1c), or both in predicting type 2 diabetes.
  
  
  METHODS
  This retrospective cohort study investigated 9,322 Japanese adults (4,786 men and 4,536 women), aged 19-69 yrs, free of diabetes at baseline. Usefulness was assessed by predictive values (PV), sensitivity, specificity, and the area under the receiver operating characteristic curve (AUROC) maximised under the best cut-off point.
  
  
  RESULTS
  During the average 6 years of follow-up, 221 men (4.6%) and 92 women (2%) developed diabetes. The best cut-off points for FPG (i.e., 5.67 mmol/l for men and 5.5 mmol/l for women) gave excellent AUROC, and the highest positive PV (13% for men and 9% for women) in predicting diabetes. In high risk subjects with FPG 6.1-6.9 mmol/l, 119 men (26.8%) and 39 women (28.3%) developed diabetes. Under the best cut-off points of FPG 6.39 mmol/l and A1c 5.8, AUROC and positive PV for FPG slightly decreased indicating FPG became less useful and were statistically indistinguishable from those for HbA1c in men. In fact, HbA1c was the most useful in women: HbA1c of 6.0% gave the highest positive likelihood ratio of 2.74 and larger AUROC than did FPG. Although AUROC for HbA1c was acceptable and indistinguishable from that for the combined use, HbA1c had higher specificity and positive LR than did the combined use.
  
  
  CONCLUSIONS
  This study demonstrated that FPG was the most useful to predict diabetes in the general population. However, in subjects with FPG 6.1-6.9 mmol/l, FPG became less useful and diagnostic performance of FPG was indistinguishable from that of HbA1c in men whereas HbA1c was the most useful in women. Thus, a two-step screening, measurement of HbA1c in association with FPG, may be useful in predicting diabetes.
authors.affiliation: Teikyo University School of Medicine, Department of Hygiene and Public Health, Tokyo, Japan. kyoko@med.teikyo-u.ac.jp
authors.forename: Kyoko
authors.initials: K
authors.lastname: Nomura
authors.forename: Kazuo
authors.initials: K
authors.lastname: Inoue
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Akimoto
mesh_terms: D000328:Adult; D000368:Aged; D001774:Blood Chemical Analysis / Q000379:methods* / Q000592:standards; D001786:Blood Glucose / Q000032:analysis*; D003920:Diabetes Mellitus / Q000097:blood* / Q000175:diagnosis*; D005215:Fasting; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D012189:Retrospective Studies; D012306:Risk; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human