Continuous Blood Glucose Monitoring Shows No Effect on Long-Term Glucose Control

Emma Hitt, PhD

July 09, 2007

July 9, 2007 — A comparison of 2 minimally invasive continuous blood glucose monitoring (CBGM) devices indicates that neither machine is significantly better than either controls or the other device in helping to achieve long-term glucose control in insulin-treated patients with diabetes mellitus.

The new findings, from the Minimally Invasive Technology Role and Evaluation (MITRE) study, were presented at the American Diabetes Association 67th Scientific Sessions, in Chicago, Illinois.

"These findings were surprising to us because we thought that providing continuous blood glucose information would be helpful and would lead to improvements in HbA1c," Stanton Newman, DPhil, from the University College London, England, told Medscape.

The researchers evaluated the efficacy of 2 minimally invasive CBGM devices in a study of more than 400 patients with type 1 or type 2 diabetes treated with insulin. Of the patients, 102 were randomly assigned to the Continuous Glucose Monitoring System (CGMS), manufactured by Minimed, and 100 patients were assigned to the Biographer, manufactured by Animas. The remaining patients were assigned to either a standard control group or an "attention" control group to control for the potential effect of increased contact with healthcare professionals in patients receiving CBGM.

The CGMS is connected via a wire to a subcutaneous sensor and can be worn for up to 72 hours, taking recordings every 5 minutes; the Biographer attaches to the skin and extracts fluid electro-osmotically for 12 to 15 hours, taking recordings every 10 minutes.

The primary endpoint was long-term glucose control, as indicated by changes in glycosylated hemoglobin (HbA1c) levels for 18 months. Patients entering into the study had a mean baseline HbA1c level ranging from 7.0% to 15.5%.

All 4 patient groups demonstrated a decline in mean HbA1c, especially during the first few months of the study. By month 18, the percentage of patients who had a relative reduction of at least 12.5% was 15% in the Biographer group, 27% in the CGMS group, 24% in the standard control, and 27% in the attention control group. The relative decline in HbA1c from baseline ranged from 1% to 4.6%.

None of these differences was significantly different from baseline or the results of the other groups. "These results suggest that the use of the CGMS conferred a small benefit, but only in the short term," the authors stated in their abstract. Furthermore, these short-term changes in the CGMS were not significant in comparison to the attention control group.

According to Dr. Newman, it is important to further establish whether specific subgroups of patients do show benefits with CBGM. "Future studies that are appropriately powered and designed are essential if we are going to understand the benefits or these devices or lack thereof," he noted.

However, Simon Heller, BA, MB BChir, DM, FRCP, professor of clinical diabetes and director of research and development with the Sheffield Teaching Hospitals Foundation Trust, in England, told Medscape that "many clinicians have not yet worked out how to use information generated by these devices, so it is to be expected that in this well-designed trial there would be no real effect.

"We need to learn more about how to use this new technology and, perhaps with pilot studies, explore the best way to help both patients and clinicians get the most out of the data generated," Dr. Heller added. "At the moment, these devices should be primarily used as research tools and should not be sold directly to patients."

The study was funded by the National Institute for Health Research (NIHR) Health Technology Assessment Programme. The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the NIHR. Steven J. Hurel, PHD, FRCP, one of the authors, sits on an advisory panel for Lifescan, manufacturer of OneTouch glucose meters. Dr. Heller has received speaker fees from Menarini, Roche, and Medtronic.

American Diabetes Association 67th Scientific Sessions: Abstract 0115-OR. Presented June 23, 2007.

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