title: Defining the relationship between plasma glucose and HbA(1c): analysis of glucose profiles and HbA(1c) in the Diabetes Control and Complications Trial.
abstract: OBJECTIVE
  To define the relationship between HbA(1c) and plasma glucose (PG) levels in patients with type 1 diabetes using data from the Diabetes Control and Complications Trial (DCCT).
  
  
  METHODS
  The DCCT was a multicenter, randomized clinical trial designed to compare intensive and conventional therapies and their relative effects on the development and progression of diabetic complications in patients with type 1 diabetes. Quarterly HbA(1c) and corresponding seven-point capillary blood glucose profiles (premeal, postmeal, and bedtime) obtained in the DCCT were analyzed to define the relationship between HbA(1c) and PG. Only data from complete profiles with corresponding HbA(1c) were used (n = 26,056). Of the 1,441 subjects who participated in the study, 2 were excluded due to missing data. Mean plasma glucose (MPG) was estimated by multiplying capillary blood glucose by 1.11. Linear regression analysis weighted by the number of observations per subject was used to correlate MPG and HbA(1c).
  
  
  RESULTS
  Linear regression analysis, using MPG and HbA(1c) summarized by patient (n = 1,439), produced a relationship of MPG (mmol/l) = (1.98 . HbA(1c)) - 4.29 or MPG (mg/dl) = (35.6 . HbA(1c)) - 77.3, r = 0.82). Among individual time points, afternoon and evening PG (postlunch, predinner, postdinner, and bedtime) showed higher correlations with HbA(1c) than the morning time points (prebreakfast, postbreakfast, and prelunch).
  
  
  CONCLUSIONS
  We have defined the relationship between HbA(1c) and PG as assessed in the DCCT. Knowing this relationship can help patients with diabetes and their healthcare providers set day-to-day targets for PG to achieve specific HbA(1c) goals.
authors.affiliation: Department of Child Health, University of Missouri School of Medicine, 1 Hospital Drive M772, Columbia, MO 65203, USA. rohlfingc@health.missouri.edu
authors.forename: Curt L
authors.initials: CL
authors.lastname: Rohlfing
authors.forename: Hsiao-Mei
authors.initials: HM
authors.lastname: Wiedmeyer
authors.forename: Randie R
authors.initials: RR
authors.lastname: Little
authors.forename: Jack D
authors.initials: JD
authors.lastname: England
authors.forename: Alethea
authors.initials: A
authors.lastname: Tennill
authors.forename: David E
authors.initials: DE
authors.lastname: Goldstein
mesh_terms: D001786:Blood Glucose / Q000378:metabolism*; D003922:Diabetes Mellitus, Type 1 / Q000150:complications / Q000175:diagnosis / Q000378:metabolism*; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D016014:Linear Models
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin