Defining the relationship between plasma glucose and HbA(1c): analysis of glucose profiles and HbA(1c) in the Diabetes Control and Complications Trial.
Level 3 - non-randomized controlled study
Secondary observational correlation analysis of prospective multicenter trial data
PubMed 11815495 · doi:10.2337/diacare.25.2.275
What was done
Quarterly HbA1c measurements and corresponding seven-point capillary blood glucose profiles (premeal, postmeal, bedtime) from the Diabetes Control and Complications Trial (DCCT) were analyzed in patients with type 1 diabetes. Complete profiles with paired HbA1c (n = 26,056) across 1,439 participants were evaluated. Mean plasma glucose (MPG) was calculated by multiplying capillary values by 1.11, and weighted linear regression was used to correlate MPG with HbA1c.
What was found
Linear regression derived the formula MPG (mg/dl) = (35.6 × HbA1c) - 77.3, or MPG (mmol/l) = (1.98 × HbA1c) - 4.29, with a correlation coefficient of r = 0.82. Afternoon and evening glucose measurements (postlunch, predinner, postdinner, bedtime) showed higher correlations with HbA1c than morning measurements (prebreakfast, postbreakfast, prelunch).
Why it matters
This establishes a quantitative linear relationship between day-to-day mean plasma glucose and HbA1c in type 1 diabetes, providing empirical guidance to translate target HbA1c goals into daily blood glucose targets.
Limits
The study is restricted to individuals with type 1 diabetes, so findings may not directly generalize to type 2 diabetes. Glucose profiling relied on episodic 7-point capillary self-monitoring rather than continuous glucose monitoring, and plasma glucose was derived using a fixed mathematical multiplier (1.11) rather than direct laboratory plasma measurement.
Cited by
- supports A hemoglobin A1c level of 5.0% corresponds to an average blood glucose level of approximately 100 mg/dL, while 5.5% corresponds to approximately 115 mg/dL.