title: Optimal sampling intervals to assess long-term glycemic control using continuous glucose monitoring.
abstract: OBJECTIVE
  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
  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.
authors.affiliation: Jaeb Center for Health Research, Tampa, Florida, USA.
authors.forename: Dongyuan
authors.initials: D
authors.lastname: Xing
authors.forename: Craig
authors.initials: C
authors.lastname: Kollman
authors.forename: Roy W
authors.initials: RW
authors.lastname: Beck
authors.forename: William V
authors.initials: WV
authors.lastname: Tamborlane
authors.forename: Lori
authors.initials: L
authors.lastname: Laffel
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Buckingham
authors.forename: Darrell M
authors.initials: DM
authors.lastname: Wilson
authors.forename: Stuart
authors.initials: S
authors.lastname: Weinzimer
authors.forename: Rosanna
authors.initials: R
authors.lastname: Fiallo-Scharer
authors.forename: Katrina J
authors.initials: KJ
authors.lastname: Ruedy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D015190:Blood Glucose Self-Monitoring / Q000379:methods* / Q000592:standards; D002648:Child; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D013997:Time Factors; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin