Investigators:
- Tim Wysocki, PhD
- Nelly Mauras, MD
- Larry A. Fox, MD
- Keisha Bird, MSN, RN
- Kimberly Englert, BSN, RN
Background
Nemours Children's Clinic was selected as one of five clinical centers to participate in an NIH-funded (U10-HD/DK 41918) cooperative research network on the use of continuous glucose sensors in children and adolescents with type 1 diabetes. The other clinical centers in this Diabetes Research in Children Network (DirecNet) are at Yale University, the University of Iowa, Stanford University, and the University of Colorado, and the data coordinating center is at the Jaeb Center for Health Research in Tampa. The principal investigators and co-investigators from each DirecNet site form a steering committee that designs, implements, analyzes and disseminates the results of studies that are performed for the purpose of evaluating the clinical application of current and future continuous glucose sensors in the management of diabetes in children and adolescents.
What We're Doing
Thus far, five DirectNet studies have been completed:
Evaluation during a clinical research center admission of the accuracy of the two FDA-approved continuous glucose sensors: The Cygnus GlucoWatch Biographer and the Medtronic-Minimed Continuous Glucose Monitoring System (CGMS). A sample of 89 3- to 17-year-old children with type 1 diabetes was studied. Frequent comparisons with reference lab determinations of glucose levels were performed during "steady state" glucose levels and during IV insulin challenge and high carbohydrate meal challenge tests.
Repetition of the above study with a sample of 15 7- to 17-year-old children who did not have diabetes. The IV Insulin and high carbohydrate meal challenge tests were not performed with this sample.
A pilot and feasibility study was completed with 15 7- to 17-year-old children with type 1 diabetes in preparation for a randomized controlled trial of the use of the Glucowatch Biographer. The primary purpose of the pilot study was to evaluate the feasibility of the data collection protocols, which employed extensive reliance on patients and parents to download glucose sensor, glucose meter, and hypoglycemia diary data directly to the coordinating center using home PCs that were provided for their use during the study.
A randomized controlled trial of the clinical use of the Glucowatch G2 Biographer in the management of childhood type 1 diabetes. A sample of 200 patients was randomized to Glucowatch or Standard Care for 6 months. The trial indicated no glycemic benefit to Glucowatch use. A continuous glucose monitor satisfaction scale was validated in this trial.
A study of the effect of exercise on the development on hypoglycemia in 50 children with diabetes was completed.
NIH funding of DirecNet has been approved through August of 2006 and is potentially renewable thereafter. Other studies currently ongoing:
A pilot study to evaluate the Navigator (Therasense, Inc.) continuous glucose sensor is in progress. The pilot study will be followed by a larger randomized controlled trial of clinical use of this device.
A study is in progress evaluating the effect of basal insulin during exercise on hypoglycemia in 55 children on insulin pump therapy.
Some of What We've Found
The initial inpatient accuracy studies showed that neither the GlucoWatch nor the CGMS was as accurate as available home glucose meters in estimating point-by-point blood glucose levels. However, both devices may retain adequate utility in terms of detecting blood glucose profiles that are predictive of hypoglycemia and hyperglycemia, thus permitting prevention and/or earlier correction of these unwanted fluctuations.
The study of accuracy of the sensors in normal children confirmed that 24-hour blood glucose profiles of youths without diabetes remained in a very tightly controlled range between 70-120 mg/dl and there was no evidence to substantiate the possibility of nocturnal hypoglycemia in any of these participants. The accuracy of the two continuous glucose sensors was felt to be inadequate to enable collection of normative data on blood glucose variability in a large sample of youths in their natural environments.
The pilot and feasibility study showed that download of study data from home PCs to the data coordinating center was technically feasible, that participants used the system effectively, and that adherence with this aspect of the protocol was adequate to permit its use in a planned randomized controlled trial.