title: Evidence for consistency of the glycation gap in diabetes.
abstract: OBJECTIVE
  Discordance between HbA(1c) and fructosamine estimations in the assessment of glycemia is often encountered. A number of mechanisms might explain such discordance, but whether it is consistent is uncertain. This study aims to coanalyze paired glycosylated hemoglobin (HbA(1c))-fructosamine estimations by using fructosamine to determine a predicted HbA(1c), to calculate a glycation gap (G-gap) and to determine whether the G-gap is consistent over time.
  
  
  METHODS
  We included 2,263 individuals with diabetes who had at least two paired HbA(1c)-fructosamine estimations that were separated by 10 ± 8 months. Of these, 1,217 individuals had a third pair. The G-gap was calculated as G-gap = HbA(1c) minus the standardized fructosamine-derived HbA(1c) equivalent (FHbA(1c)). The hypothesis that the G-gap would remain consistent in individuals over time was tested.
  
  
  RESULTS
  The G-gaps were similar in the first, second, and third paired samples (0.0 ± 1.2, 0.0 ± 1.3, and 0.0 ± 1.3, respectively). Despite significant changes in the HbA(1c) and fructosamine, the G-gap did not differ in absolute or relative terms and showed no significant within-subject variability. The direction of the G-gap remained consistent.
  
  
  CONCLUSIONS
  The G-gap appears consistent over time; thus, by inference any key underlying mechanisms are likely to be consistent. G-gap calculation may be a method of exploring and evaluating any such underlying mechanisms.
authors.affiliation: Wolverhampton Diabetes Centre, New Cross Hospital, Wolverhampton, UK. ananth.nayak@nhs.net
authors.forename: Ananth U
authors.initials: AU
authors.lastname: Nayak
authors.forename: Martin R
authors.initials: MR
authors.lastname: Holland
authors.forename: David R
authors.initials: DR
authors.lastname: Macdonald
authors.forename: Alan
authors.initials: A
authors.lastname: Nevill
authors.forename: Baldev M
authors.initials: BM
authors.lastname: Singh
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003920:Diabetes Mellitus / Q000097:blood / Q000378:metabolism*; D005260:Female; D019270:Fructosamine / Q000097:blood / Q000378:metabolism; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D019270:Fructosamine; D006442:Glycated Hemoglobin