Utility of CGMS as a Measure of Glycemic Control in Children with Type 1 Diabetes T1DM

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Utility of CGMS as a Measure of Glycemic Control
in Children with Type 1 Diabetes (T1DM)
Rosanna Fiallo-Scharer, MD for
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Background DirecNet

• Diabetes Research in Children Network
• NIH funded collaborative study group
• 5 clinical centers, central laboratory,
  coordinating center, and representatives from
  NICHD and NIDDK
  
• Objective to critically evaluate the clinical
  usefulness of current and future glucose sensors
  in children and adolescents
  

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DirecNet Outpatient Randomized Clinical Trial
(RCT)

• 6-month RCT to assess the merits of the
  GlucoWatch G2 Biographer (Cygnus Inc. Redwood
  City, CA) in children ages 7-17 years with type 1
  diabetes

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• Initial outpatient evaluations of glycemic
  control prior to randomization included
  
• 48-72 hr CGMS (Medtronic MiniMed) profile.
• 8-point SMBG testing while simultaneously
  wearing a CGMS for 2-3 days using the One Touch
  UltraSmart (Life scan) meter.
  
• HbA1c measured by HPLC in a central laboratory.
• Purpose To examine and compare the results
  obtained by these baseline measures of glycemic
  control in a large sample of children and
  adolescents with T1DM.

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Methods

• Analysis included 183 patients who completed the
  following
  
• At least 10 Ultra measurements during 2 days of
  8-point testing.
  
• 40 total hours of CGMS use.
• At least one day of overlap between 8-point
  testing and CGMS use.
  
• Ultra plasma glucose levels used as reference
  values for assessment of accuracy of hypoglycemic
  detection by the CGMS.
  

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• Demographic and Clinical Characteristics of 183
  Subjects
  
• Male/Female 52/48
• Age 12.5 2.8 years
• Minorities 14
• Duration of Diabetes 5.4 3.3 years
• Injections/Pump 54/46

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Number of Glucose Measurements

• Ultra 3,408
• CGMS 170,381

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Mean Ultra and CGMS glucose values
Ultra
CGMS
Mean ( SD) A1c value was 8.0 0.9
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Percent Glucose Values in Range, Below Range and
Above Range
Results were similar for pre- and post-prandial
and bedtime.
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Mean Glucose Values by Time of Day
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Mean Ultra Glucose Values by A1c With regression
line and 95 confidence limits
Spearman correlation 0.44 P-value 12
Mean CGMS Glucose Values by A1c With regression
line and 95 confidence limits
Spearman correlation 0.44 P-value 13
Slopes of Regression Lines

• 8-point testing
• 26 mg/dl per 1.0 change in A1c
• CGMS
• 22 mg/dl per 1.0 change in A1c

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CGMS and Ultra During Hypoglycemia
136 CGMS hypoglycemia episodes
Hypoglycemia two values ? 60 mg/dl without
an intermediate value 70 mg/dl
80 ULTRA hypoglycemia episodes
Hypoglycemia BG value ? 60 mg/dl
CGMS 70
10
Ultra 70
32
CGMS 61-70
11
Ultra 61-70
33
79
CGMS 60
Ultra 60
35
Sensitivity defined as CGMS 70 within 30
minutes False positive defined as Ultra 70.
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CGMS and Ultra During Overnight Hypoglycemia
17 CGMS episodes Hypoglycemia two values ? 60
mg/dl without
an intermediate value 70 mg/dl
5 ULTRA episodes Hypoglycemia BG value ? 60 m
g/dl
CGMS 70
40
Ultra 70
59
CGMS 61-70
20
29
Ultra 61-70
40
CGMS 60
Ultra 60
12
Sensitivity defined as CGMS 70 within 30
minutes False positive defined as Ultra 70.
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Summary

• 8-point testing and CGMS were similar in
  detection of hyperglycemia and normoglycemia, and
  in their correlation to A1c values.
  
• One-third of CGMS defined hypoglycemia episodes
  overall and over half overnight could not be
  confirmed by the home glucose meter.
  

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Conclusions

• 8-point testing and the CGMS provide useful
  short-term measure of glucose control in youth
  with type 1 diabetes
  
• Both methods have limitations for determining the
  true rate of hypoglycemia in these patients

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Conclusions

• Limitations of 8-point testing
• Compliance
• Limited number of values
• Limitations of CGMS
• Retrospective data
• Inaccuracy of low glucose measurements

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• Barbara Davis Center
• H. Peter Chase
• Rosanna Fiallo-Scharer
• Jennifer Fisher
• Barb Tallant
• University of Iowa
• Eva Tsalikian
• Michael Tansey
• Linda Larson
• Julie Coffey
• Amy Sheehan
• Nemours Childrens Clinic
• Tim Wysocki
• Nelly Mauras
• Larry Fox
• Keisha Bird
• Kelly Lofton

• Stanford University
• Bruce Buckingham
• Darrell Wilson
• Jennifer Block
• Paula Clinton
• Yale University
• William Tamborlane
• Stuart Weinzimer
• Elizabeth Doyle
• Kristin Sikes
• Amy Steffen
• Jaeb Center for Health Research
• Roy Beck
• Katrina Ruedy
• Craig Kollman
• Dongyuan Xing
• Cynthia Silvester