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Abstract

Click to add/remove this article to your list of 'My Favorites' A Comparison of the Original vs. Modified Continuous Glucose Monitoring System (CGMS™) Sensor Using Data from Two DirecNet Studies

Abstract Number: 1945-PO

Authors: MICHAEL TANSEY, ROY BECK, BRUCE BUCKINGHAM, NELLY MAURAS, ROSANNA FIALLO-SCHARER, DONGYUAN XING, CRAIG KOLLMAN, WILLIAM TAMBORLANE, KATRINA RUEDY, THE DIABETES RESEARCH IN CHILDREN NETWORK (DIRECNET) STUDY GROUP

Institutions: Iowa City, IA; Tampa, FL; Stanford, CA; Jacksonville, FL; Denver, CO; New Haven, CT

Results: The Continuous Glucose Monitoring System (“CGMS”; Medtronic MiniMed) was the first glucose sensor approved by the FDA, and has been used extensively in the management of individuals with diabetes. The Diabetes Research in Children Network (DirecNet) Study Group evaluated the accuracy of the original CGMS sensor in 78 children with type 1 diabetes who were hospitalized in a clinical research center for 24 hours. In this study, 5,658 CGMS sensor glucose values were compared with reference plasma glucose measurements performed in a central laboratory. During the course of the study, a modified version of the CGMS sensor became available and was tested in 14 subjects resulting in 1,120 sensor-reference glucose pairs. Accuracy was significantly improved with the modified version (median relative absolute difference (RAD) 11% vs. 19%; P<0.001).

DirecNet is currently conducting a randomized clinical trial (RCT) to assess the merits of the GlucoWatch G2® Biographer (Cygnus, Inc.). At baseline, each subject used a CGMS (modified version) and a One Touch® UltraSmart® (Lifescan, Inc.) home glucose meter as an outpatient prior to randomization. Excluding values used for calibration, this resulted in 886 CGMS-Ultra pairs from 107 subjects with a median RAD of 11%.

In both studies accuracy improved with increasing glucose level as shown below:

Median Relative Absolute Difference (RAD)
Inpatient StudyOutpatient Study
Reference GlucoseOriginal(N=5,658)Modified(N=1,120)Modified(N=886)
All19%11%11%
≤70 mg/dL38%29%18%
71-120 mg/dL23%14%14%
121-180 mg/dL19%14%9%
181-240 mg/dL16%11%11%
>240 mg/dL16%7%9%
These RCT data confirm the improved accuracy with the modified CGMS sensor originally observed in a small number of subjects. However, accuracy is still reduced in the hypoglycemic range.