PT  - JOURNAL ARTICLE
AU  - , 
TI  - Hemoglobin A<sub>1c</sub> and Mean Glucose in Patients With Type 1 Diabetes
AID  - 10.2337/dc10-1054
DP  - 2011 Mar 01
TA  - Diabetes Care
PG  - 540--544
VI  - 34
IP  - 3
4099  - http://care.diabetesjournals.org/content/34/3/540.short
4100  - http://care.diabetesjournals.org/content/34/3/540.full
SO  - Diabetes Care2011 Mar 01; 34
AB  - OBJECTIVE To determine the relationship between mean sensor glucose concentrations and hemoglobin A1c (HbA1c) values measured in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications laboratory at the University of Minnesota in a cohort of subjects with type 1 diabetes from the Juvenile Diabetes Research Foundation continuous glucose monitoring randomized trial.RESEARCH DESIGN AND METHODS Near-continuous glucose sensor data (≥4 days/week) were collected for 3 months before a central laboratory–measured HbA1c was performed for 252 subjects aged 8–74 years, the majority of whom had stable HbA1c values (77% within ±0.4% of the patient mean).RESULTS The slope (95% CI) for mean sensor glucose concentration (area under the curve) versus a centrally measured HbA1c was 24.4 mg/dL (22.0–26.7) for each 1% change in HbA1c, with an intercept of −16.2 mg/dL (−32.9 to 0.6). Although the slope did not vary with age or sex, there was substantial individual variability, with mean sensor glucose concentrations ranging from 128 to 187 mg/dL for an HbA1c of 6.9–7.1%. The root mean square of the errors between the actual mean sensor glucose concentration versus the value calculated using the regression equation was 14.3 mg/dL, whereas the median absolute difference was 10.1 mg/dL.CONCLUSIONS There is substantial individual variability between the measured versus calculated mean glucose concentrations. Consequently, estimated average glucose concentrations calculated from measured HbA1c values should be used with caution.