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Continuous glucose monitoring used to adjust diabetes therapy improves glycosylated hemoglobin: a pilot study

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Abstract

A 5-week pilot study was conducted to determine if continuous glucose monitoring could be used to improve glycemic control. A total of nine subjects with type 1 diabetes and HbA1c values greater than 8.5% completed the study. Subjects wore a continuous glucose monitor for two 1-week periods during the study. After each sensor use, changes to diet, insulin dosage and self-monitored blood glucose (SMBG) schedule were made. HbA1c decreased from 9.9% (S.D.=1.1%) at baseline to 8.8% (S.D.=1.0%) 5 weeks after baseline (P=0.0006), but daily insulin usage was unchanged over the same period of time (P=0.428). The glucose sensors performed accurately, with a median correlation of 0.92 and a mean absolute difference of 19.1% (S.D.=9.0%). The continuous glucose profiles allowed identification of glucose patterns and excursions that helped direct changes in therapy. These treatment changes would not have been made on the basis of meter data alone and were effective in improving glucose control. Additional studies are needed to validate these findings. This pilot study highlights the potential for continuous glucose monitoring to provide the valuable information necessary to make therapy adjustments that can dramatically improve patients’ glycemic control and reduce the risk of long-term complications.

Introduction

The benefits of intensive management of type 1 diabetes have been well established and include reduced long-term complications [1] and reduced cost to the health care system [2]. Current guidelines target a glycosylated hemoglobin (HbA1c) of 7.0% or lower as the goal of intensive insulin therapy [3]. This goal remains elusive for a large subset of type 1 patients. A potentially significant technological ally in the struggle to achieve tight control is the recent availability of continuous glucose monitoring [4]. Continuous glucose measurement allows the identification of glycemic excursions and general patterns of glucose levels in a manner not available with periodic blood glucose meter readings. Knowledge of these excursions and patterns may be used to make appropriate changes in diabetes management.

The present study was undertaken to determine if glucose profiles generated by the Continuous Glucose Monitoring System (CGMS, MiniMed, Sylmar, CA 91342, USA) [4] can be used to refine the diabetes treatment regimens of subjects with poor glycemic control. The CGMS is comprised of a disposable subcutaneous glucose sensing device connected by a cable to a pager-sized glucose monitor. The system takes a glucose measurement every 10 s and stores an average value every 5 min, for a total of 288 measurements each day. A communication device enables the data stored in the monitor to be downloaded and reviewed on a personal computer (Fig. 1). The CGMS was expected to help identify periods of significant glycemic excursion which would allow the physician to suggest specific changes in the timing and dosage of insulin infusion or injections, dietary changes and changes in the timing and frequency of blood glucose measurements. These changes were expected to result in a lowering of HbA1c values. The pilot study results were also intended to aid in determining the design, procedures and size of a subsequent randomized study of the CGMS.

Section snippets

Subjects

Subjects were selected from patients being treated by one of the authors (B.W.B.). Medical records were reviewed to identify patients with a recent HbA1c of 8.5% or greater. All subjects had to have type 1 diabetes and had to be performing intensive management for a minimum of 6 months. A total of 12 subjects were evaluated for participation in the study. Of these subjects, two were ineligible due to baseline HbA1c values below 8.5%. Of the 10 subjects eligible for the study, five were being

Sensor performance

The CGMS performed reliably and accurately during the 5-week pilot study. Agreement between the sensor glucose readings and SMBG readings was quite high, with a median correlation of 0.92 and intra-use mean absolute difference (%) of 19.1±9.0.

Clinical outcomes

HbA1c values improved significantly over the 5-week study period, decreasing from 9.9±1.0 at baseline to 8.8±1.0 at week 5 (P=0.0006), while daily insulin usage remained constant over the same period of time (53.2±24.2 units/day at baseline to 55.5±24.0

Discussion

These pilot results suggest that continuous glucose monitoring can provide useful information to the health care team about a patient’s pattern of blood glucose trends and excursions. This information can then be used to refine and adjust patients’ diabetes management, resulting in improved glycemic control. A decrease of 1.1 HbA1c percentage points in only 5 weeks points to the robustness of the changes in therapy. This improvement was achieved even though these subjects were already

Acknowledgements

Funds for this research were provided by MiniMed Inc., Sylmar, CA 91342, USA. FastTake™ Glucose Meters and Strips were provided by LifeScan, Inc., Milpitas, CA 95035. The authors wish to thank Kelly McCulloch, study coordinator and Suzanne Parks, R.N. for their assistance in developing and conducting the study, Lily Jeng, M.A. for her help in analyzing the data, and Paul C. Davidson, M.D. for his review and comments on this manuscript.

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