title: Influence of the glycation gap on the diagnosis of type 2 diabetes.
abstract: OBJECTIVE
  The results of using HbA1C-based criteria for diagnosis of type 2 diabetes and prediabetes have been reported to differ from those obtained using fasting plasma glucose (FPG) or an oral glucose tolerance test (OGTT). We aimed to determine whether these discrepancies might be due to the influence of the glycation gap.
  
  
  METHODS
  For 430 patients without previously diagnosed diabetes for whom an OGTT had been requested in normal clinical practice, FPG, fructosamine and HbA1C were measured at the time of the test and again 1 month later. Glycaemia/diabetes status was classified as normoglycaemia, prediabetes or diabetes using both HbA1C-based and FPG/OGTT-based criteria, and their glycation gaps GG were calculated.
  
  
  RESULTS
  The specificity of an HbA1C level of 6.5 % (48 mmol/mol) for diagnosis of FPG/OGTT-defined type 2 diabetes was 99 %, but its sensitivity was less than 37 %. HbA1C-diabetic patients had higher average blood glucose levels than FPG/OGTT-diabetic patients. With either set of criteria, high-GG patients were disproportionately numerous among those classified as diabetic and were disproportionately infrequent among those classified as normoglycaemic, but the effect was greater for the HbA1C criteria.
  
  
  CONCLUSIONS
  The differences between HbA1C-based and FPG/OGTT-based diagnoses are largely due to the influence of the glycation gap, which may also influence the early stages of FPG/OGTT-defined diabetes.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Santiago de Compostela, Santiago de Compostela, Spain, ssegade@telefonica.net.
authors.forename: Santiago
authors.initials: S
authors.lastname: Rodriguez-Segade
authors.forename: Javier
authors.initials: J
authors.lastname: Rodriguez
authors.forename: José M
authors.initials: JM
authors.lastname: García-López
authors.forename: Felipe F
authors.initials: FF
authors.lastname: Casanueva
authors.forename: Ian C
authors.initials: IC
authors.lastname: Coleman
authors.forename: Carmen
authors.initials: C
authors.lastname: Alonso de la Peña
authors.forename: Félix
authors.initials: F
authors.lastname: Camiña
mesh_terms: D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000378:metabolism*; D005215:Fasting / Q000097:blood / Q000378:metabolism; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin