title: Screening with HbA1c identifies only one in two individuals with diagnosis of prediabetes at oral glucose tolerance test: findings in a real-world Caucasian population.
abstract: OBJECTIVE
  Discordance between HbA1c and OGTT in screening pre-diabetes may occur because of lack of laboratory standardization, distinct underlying pathophysiological processes or different ethnicity. We evaluated HbA1c efficacy for screening OGTT-defined IFG and IGT conditions in a large Caucasian population using the newly revised IFCC protocol.
  
  
  METHODS
  A total of 501 consecutive subjects were screened for pre-diabetic conditions with OGTT with 75 g of glucose. Testing for HbA1c, lipid profile and fasting insulin levels was also performed. For detecting differences between continuous variables, ANOVA followed by Tukey's honestly significant difference (HSD) post hoc test was used. Logistic regression and ROC curve analysis were also performed for assessing HbA1c screening efficacy.
  
  
  RESULTS
  ROC curve analysis showed that optimal HbA1c cut-off for detecting IFG was 5.6 % (sensitivity of 78 % and specificity of 63 %), while for IGT, the optimal cut-off was 5.9 % (sensitivity of 46 % and specificity of 84 %), with AUCs < 0.8. Screening with HbA1c identified 53.4 % of the 193 patients with IFG and/or IGT diagnosed at OGTT. As regards surrogate markers of insulin resistance, we observed a trend towards higher values of HOMA-IR and lower QUICKI values in subjects with IFG than in those with IGT. Patients with pre-diabetes at both tests had similar values of HOMA and QUICKI, compared with those with altered OGTT only.
  
  
  CONCLUSIONS
  IFCC-aligned HbA1c assay proved scarcely effective in detecting IFG and/or IGT in a large Caucasian population, identifying only half of the patients with abnormal OGTT. Moreover, adding HbA1c screening to OGTT may be of little benefit in identifying subjects with a worse metabolic profile.
authors.affiliation: Unit of Metabolic Diseases, Department of Medicine, University of Padova, Via Giustiniani, 2, 35100, Padua, Italy.
authors.forename: Nino Cristiano
authors.initials: NC
authors.lastname: Chilelli
authors.forename: Chiara
authors.initials: C
authors.lastname: Cosma
authors.forename: Eugenio
authors.initials: E
authors.lastname: Ragazzi
authors.forename: Silvia
authors.initials: S
authors.lastname: Burlina
authors.forename: Martina
authors.initials: M
authors.lastname: Zaninotto
authors.forename: Mario
authors.initials: M
authors.lastname: Plebani
authors.forename: Annunziata
authors.initials: A
authors.lastname: Lapolla
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000175:diagnosis; D019937:Diagnostic Techniques and Procedures; D005260:Female; D005951:Glucose Tolerance Test / Q000379:methods*; D006442:Glycated Hemoglobin / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood* / Q000175:diagnosis; D012372:ROC Curve; D044465:White People
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; D007328:Insulin