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.