Implications for nursing practice and research

• ■ Use of real-time continuous blood glucose monitoring (RT-CGM) as part of treatment of type 1 diabetes results in decreased HbA1c levels when compared with self-monitoring of blood glucose (SMBG).

• ■ The improvement in glycaemic control with RT-CGM use was especially pronounced in patients with poorer glycaemic control and in those who used the technology more frequently.

• ■ Use of RT-CGM may decrease exposure to hypoglycaemia in some patients.

• ■ This model is able to predict cost-effectiveness of RT-CGM in the clinical setting based on glycaemic control, sensor usage and age of patient.

Context

In patients with type 1 diabetes (T1DM), tight glycaemic control is associated with profound reductions in risks for long-term diabetes complications.1 Attaining glycaemic control usually requires intensive insulin therapy regimens and frequent SMBG for determining appropriate insulin doses in response to the many factors that affect blood glucose levels. Regular SMBG is an effective tool for maintaining blood glucose control, but only in those patients who perform SMBG with adequate frequency. Usual premeal SMBG regimens may also miss postprandial blood glucose excursions or nocturnal hypoglycaemia.

Real-time continuous glucose monitoring (RT-CGM) uses sensors that continuously measure glucose concentrations in interstitial fluids over 3–7 days. The monitor provides a visual display of the glucose levels, and can be set to alarm when levels go too high or too low, thus alerting the wearer to potential acute problems before they occur.

Mounting evidence suggests that the use of RT-CGM may be more effective than SMBG in reducing HbA1c levels in patients with T1DM. Pickup et al hypothesised that the clinical effectiveness of RT-CGM would be best in those patients who were in the worst glycaemic control and in those who used the RT-CGM sensors more frequently.

Findings

Six RCTs were included in the meta-analysis, resulting in a sample of 892 patients who were randomly allocated to RT-CGM (n=449) or SMBG (n=443). The overall reduction in HbA1c was 0.30% (95% CI) among patients allocated to the RT-CGM versus the SMBG groups. The largest effects were in patients who used the sensors more frequently and had the highest baseline HbA1c. Every 1-day increase in sensor usage per week resulted in a 0.15% decrease in HbA1c. With every 1% increase in baseline HbA1c, there was an increase in the effects of RT-CGM, resulting in a 0.126% decrease in HbA1c. The authors also reported an additional reduction of 0.05% in HbA1c for each 25 years increase in the age of patients who used the RT-CGM. Among patients using RT-CGM, there was a modest (23%) reduction in exposure to hypoglycaemia, but this was unrelated to increased sensor usage.

Commentary

RT-CGM has been available for over a decade, however, its use in clinical settings has been limited by a lack of evidence to support its effectiveness for improving glycaemic control. The rigorous meta-analysis by the authors offers strong support for use of RT-CGM in patients with T1DM. They were able to provide a model for predicting the reduction in HbA1c based on current HbA1c level, amount of sensors used, and, to a lesser degree, age of the patient. A key finding is that those patients with the poorest control benefitted the most from RT-CGM. Too often, patients with poor glycaemic control are also those who do not test their blood glucose levels regularly. This lack of glucose information thwarts the ability of both patient and provider to make informed adjustments to insulin doses, and thus their capacity to prevent high or low blood glucose excursions. Additionally, the patient is not able to learn from the experiential data gained through knowledge of blood glucose levels in relationship to food intake, physical activity or illness. Use of the RT-CGM would allow the infrequent tester to see immediate results from his or her behaviours and make glucose data-based decisions rather than guesses. While patients with T1DM continue to wait for a cure, or the more likely, artificial pancreas, use of RT-CGM in conjunction with intensive insulin therapy can help them to attain and maintain the best possible blood glucose control and avoid or delay the long-term complications associated with diabetes.