title: High variability of glycated hemoglobin concentrations in patients with IDDM followed over 9 years. What is the best index of long-term glycemic control?
abstract: OBJECTIVE
  To determine variability of long-term glycemic control in patients with IDDM.
  
  
  METHODS
  A retrospective analysis of HbA1 among 122 IDDM patients followed over 9 years.
  
  
  RESULTS
  Annual group mean HbA1 ranged from 8.4 to 9.3% with large standard deviations (1.7-2.0%), indicating marked variability among individuals. Fluctuations of more than +/- 1% HbA1 occurred in 50% of the patients year to year, and over 9 years the minimum-maximum range was > 3 and > 5% HbA1 in 55 and 11% of patients, respectively. In any one year, 22-43% of patients had HbA1 < 8%, but over 9 years only 3.3% were consistently < 8%. Groups divided according to baseline HbA1 of < 8, 8-10, and > 10% were significantly separated over 9 years by frequency distribution analysis of individual mean HbA1 but were indistinguishable when analyzed by individual HbA1 interquartile range (measure of variability).
  
  
  CONCLUSIONS
  High variability of long-term glycemic control is a marked feature of IDDM, the extent of which may be relevant to microvascular risk.
authors.affiliation: Department of Endocrinology, Charing Cross Hospital, London, U.K.
authors.forename: B M
authors.initials: BM
authors.lastname: Singh
authors.forename: C
authors.initials: C
authors.lastname: McNamara
authors.forename: P H
authors.initials: PH
authors.lastname: Wise
mesh_terms: D000328:Adult; D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000378:metabolism; D005260:Female; D005500:Follow-Up Studies; D006442:Glycated Hemoglobin / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D006442:Glycated Hemoglobin