Accuracy of the GlucoWatch G2 Biographer and the Continuous Glucose Monitoring System During Hypoglycemia
Experience of the Diabetes Research in Children Network
- *The Diabetes Research in Children Network (DirecNet) Study Group
OBJECTIVE—The goal of this study was to assess the accuracy of the GlucoWatch G2 Biographer (GW2B) and the continuous glucose monitoring system (CGMS) during hypoglycemia in children and adolescents with type 1 diabetes.
RESEARCH DESIGN AND METHODS—During a 24-h clinical research center stay, 91 children and adolescents with type 1 diabetes (aged 3.5–17.7 years) wore one or two CGMSs, and 89 of these subjects wore one or two GW2Bs. Frequent serum glucose determinations were made during the day, overnight, and during insulin-induced hypoglycemia resulting in 192 GW2B reference pairs and 401 CGMS reference pairs during hypoglycemia (reference glucose ≤60 mg/dl).
RESULTS—During hypoglycemia, the median absolute difference between the 192 GW2B reference glucose pairs was 26 mg/dl and between the 401 CGMS reference glucose pairs was 19 mg/dl with 31 and 42%, respectively, of the sensor values within 15 mg/dl of the reference glucose. Sensitivity to detect hypoglycemia when the GW2B alarm level was set to 60 mg/dl was 23% with a false-alarm rate of 51%. Analyses suggested that modified CGMS sensors that became available in November 2002 might be more accurate than the original CGMS sensors (median absolute difference 15 vs. 20 mg/dl).
CONCLUSIONS—These data show that the GW2B and the CGMS do not reliably detect hypoglycemia. Both of these devices perform better at higher glucose levels, suggesting they may be more useful in reducing HbA1c levels than in detecting hypoglycemia.
- CGMS, continuous glucose monitoring system
- CRC, clinical research center
- DirecNet, Diabetes Research in Children Network
- GW2B, GlucoWatch G2 Biographer
Address correspondence and reprint requests to Eva Tsalikian, MD, c/o DirecNet Coordinating Center, Jaeb Center for Health Research, 15310 Amberly Dr., Suite 350, Tampa, FL 33647. E-mail:.
Received for publication 3 September 2003 and accepted in revised form 11 November 2003.
*A complete list of the DirecNet Study Group appears in the appendix.
B.A.B. has received honorarium from Medtronic MiniMed and research support from Medtronic MiniMed and Cygnus. D.M.W. has received consulting fees and research support from and serves as an advisor to Lifescan and MiniMed. J.M.B. is the president elect of the Santa Clara County Chapter of the American Association of Diabetes Educators and as such has attended meetings and dinners sponsored by Lifescan, Medtronic MiniMed, and other such companies; is a paid speaker for Lifescan; was a paid research subject for Cygnus; was a paid consultant for Medtronic MiniMed; and has a consultant agreement with Therasense. E.L.K. was a paid consultant for Medtronic-Minimed; was employed as a research study assistant by Cygnus; and received a stipend for participating in a study for Cygnus. W.V.T. is on the advisory board at and received honorarium and grant support from Medtronic MiniMed. E.A.D. has received honorarium from Medtronic MiniMed.
A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
See accompanying editorial, p. 834.
- DIABETES CARE