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Randomized Controlled Trial
. 2011 Mar;13(3):351-8.
doi: 10.1089/dia.2010.0156. Epub 2011 Feb 7.

Optimal sampling intervals to assess long-term glycemic control using continuous glucose monitoring

Dongyuan Xing  1 , Craig Kollman, Roy W Beck, William V Tamborlane, Lori Laffel, Bruce A Buckingham, Darrell M Wilson, Stuart Weinzimer, Rosanna Fiallo-Scharer, Katrina J Ruedy; Juvenile Diabetes Research Foundation Continuous Glucose Monitoring Study Group
Collaborators, Affiliations
Randomized Controlled Trial

Optimal sampling intervals to assess long-term glycemic control using continuous glucose monitoring

Dongyuan Xing et al. Diabetes Technol Ther. 2011 Mar.

Abstract

Aims and hypothesis: The optimal duration and frequency of short-term continuous glucose monitoring (CGM) to reflect long-term glycemia have not been determined. The Juvenile Diabetes Research Foundation CGM randomized trials provided a large dataset of longitudinal CGM data for this type of analysis.

Methods: The analysis included 185 subjects who had 334 3-month intervals of CGM data meeting specific criteria. For various glucose indices, correlations (r²) were computed for the entire 3-month interval versus selected sampling periods ranging from 3 to 15 days. Other computed agreement measures included median relative absolute difference, values within ± 10% and ± 20% of full value, and median absolute difference.

Results: As would be expected, the more days of glucose data that were sampled, the higher the correlation with the full 3 months of data. For 3 days of sampling, the r² value ranged from 0.32 to 0.47, evaluating mean glucose, percentage of values 71-180 mg/dL, percentage of values > 180 mg/dL, percentage of values ≤ 70 mg/dL, and coefficient of variation; in contrast, for 15 days of sampling, the r² values ranged from 0.66 to 0.75. The results were similar when the analysis intervals were stratified by age group (8-14, 15-24, and ≥ 25 years), by baseline hemoglobin A1c level (< 7.0% and ≥ 7.0%), and by CGM device type.

Conclusions and interpretation: Our data suggest that a 12-15-day period of monitoring every 3 months may be needed to optimally assess overall glucose control. Shorter periods of sampling can be useful, but the correlation with 3-month measures of glycemic control is lower.

Trial registration: ClinicalTrials.gov NCT00406133.

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Figures

FIG. 1.
FIG. 1.
Examples of sampled versus full continuous glucose monitoring data over a 3-month interval (n = 334 from 185 subjects). The scatterplots represent data in the (A) 3-day and (B) 15-day samplings of percentage in target range (71–180 mg/dL) compared with the value over a 3-month interval. Each data point denotes one 3-month analysis interval (up to four per subject). RAD, relative absolute difference.
FIG. 2.
FIG. 2.
The r2 value for the sampled period compared with the 3-month interval. The r2 values between continuous glucose monitoring (CGM) data over the sampled period and the average over the entire 3 months were plotted. Each r2 value was calculated from 334 analysis intervals from 185 subjects.
See this image and copyright information in PMC

References

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