Although individuals with diabetes often feel burdened by the need to control their blood sugar through multiple measures, including diet and medication, glucose monitoring is also an essential component in the management of their disease. This is especially true for patients with type 1 diabetes and type 2 diabetes who require insulin treatment. Various studies have shown the benefit of achieving good glycemic control1,2, but with intensification of therapy, patients are at risk for hypoglycemia. This risk can be mitigated, however, with the adjuvant use of devices that monitor blood sugar levels.
Glucometers were first developed and used in the 1970s and only became widely available in the 1980s3. Self-monitoring of blood glucose (SMBG) has been shown to improve glycaemic control4-6. Research on the use of SMBG in non-insulin-dependent patients with type 2 diabetes shows some studies finding positive results7-9, while others did not report any benefit from SMBG10. Monitoring technology continued to evolve with the introduction of continuous glucose monitoring (CGM) in 1999. The earliest CGM devices, which measure glucose in the interstitial fluid, stored the glucose data over a period of three days. However, patients were “blinded” to the results and were able to review their data only retrospectively with their health care provider. Such devices also required calibration with fingerstick blood glucose measurements. Newer devices allow patients to view their results in real time, with programmable alerts for high or low glucose levels. Moreover, some devices are paired with insulin pumps creating a closed loop system. To date there are two such systems available: Medtronic’s MiniMed 670G and Tandem’s Control-IQ hybrid closed loop system. The latter system was approved by the FDA late last year. In terms of CGM versus SMBG, the Multiple Daily Injections and Continuous Glucose Monitoring in Diabetes (DIaMonD) study found that in patients with type 1 diabetes treated with insulin injections, CGM improved mean glycated hemoglobin (HbA1c) by 1.0% at 24 weeks from baseline. There was an additional 76 minutes increase in time in range for users and reduction in glycemic variability11. The second arm of this trial focused on use of CGM in patients with type 2 diabetes who were receiving multiple daily injections of insulin. In this population, use of CGM led to a reduction of mean HbA1c from 8.5% to 7.7% at 24 weeks (adjusted difference in mean change in HbA1c was 0.3%). Improvement in HbA1c was more pronounced in those with higher baseline HbA1c (at least 9%), with a reduction of 1.4% versus 0.7%11. Several trials in patients with type 1 diabetes have also demonstrated reductions in hypoglycemic events with the use of CGM13-15.
Another exciting addition to the glucose monitoring “toolbox” is flash glucose monitoringA which is a hybrid between conventional glucometers and CGM. This device, which measures interstitial fluid glucose and provides a reading when the sensor is scanned with a handheld device, can show a history of glucose data collected over the previous eight hours. Unlike older CGM devices, flash monitoring does not require calibration with blood glucose testing; moreover, the sensor device can be attached for a two-week period. The use of flash glucose monitoring has been shown to reduce hypoglycemia events. In patients with type 1 diabetes assessed in the Novel Glucose-Sensing Technology and Hypoglycemia in Type 1 Diabetes: a Multicentre, Non-masked, Randomised Controlled Trial (IMPACT), the use of flash glucose monitoring resulted in a 38% reduction in duration of hypoglycemia, 40% reduction in duration of nocturnal hypoglycemia and 50% reduction of serious hypoglycemia. There was no significant change in HbA1C (baseline of 6.7%) and the need for finger prick testing was lowered by 91%16. Similar reductions in hypoglycemia events with flash glucose monitoring devices were seen in patients with type 2 diabetes who were taking insulin 17. A retrospective analysis of real-world data in a cohort of type 1 diabetes patients found that users of flash glucose monitoring had an HbA1c reduction of 0.6%; reduction in HbA1c was better in those with higher baseline HbA1c18. Another device that deserves a mention is the Eversense CGM System, which monitors the patient’s glucose level continuously for up to 90 days via a sensor that is implanted subcutaneously. Glucose is measured with the aid of a light-emitting diode that passes through the sensor membrane. A clinical trial of the device is currently underway.
With the expansion in technologies that assist patients in monitoring their glucose levels, it is vital for health care providers to understand how such devices can be incorporated into disease management. For some patients, cost may be a barrier to use of this technology, hence conventional glucometers still have a role to play. However, for individuals who would benefit from these devices, for instance those with recurrent hypoglycemia, initiatives should be undertaken to facilitate access.
Pei Lin Chan, MBBS (IMU), MRCP (UK)
Read previous columns from Dr. Chan.