GLUCOSE MONITORING IN DIABETES
A key goal in diabetes management is good glycaemic control to reduce the risk of complications, such as loss of vision, nerve damage, kidney failure, amputations, and cardiovascular disease.1,2
International guidelines recommend that glycaemic targets be tailored to individual patients (Table 1).3-5
TABLE 1: FACTORS TO CONSIDER WHEN ESTABLISHING INDIVIDUAL BLOOD GLUCOSE TARGETS
Comorbid health conditions
Duration of diabetes
Risk of low or high glucose levels (hypoglycaemia and hyperglycaemia)
Frequency and intensity of physical activity Patient motivation and adherence
Monitoring glucose levels is critically important to ensure good glycaemic control, particularly since glucose levels can vary from hour-to-hour.6 The hemoglobin A1c test is important for monitoring and diagnosing patients with diabetes by providing an average glycaemic level over several months.7 However, hemoglobin A1c does not accurately portray daily glucose variability and hypoglycaemic events.6 To date, patients have relied on self-monitoring of blood glucose (SMBG) or continuous glucose monitoring (CGM) to assess daily variations in blood glucose levels.
SELF-MONITORING BLOOD GLUCOSE
The development of SMBG was considered a breakthrough because it provided an instant assessment of glycaemic control.8 Current guidelines from professional organisations recommend SMBG for most patients with type 1 diabetes and those with type 2 diabetes who are treated with insulin.3 Most patients should perform SMBG 6 to 8 times per day,3 although the optimal frequency and timing of SMBG is debated.9
CONTINUOUS GLUCOSE MONITORING
CGM was introduced in 1999 as a new technology to measure glucose levels in interstitial fluid that exists between the cells of the body. The CGM system is composed of a disposable sensor, a transmitter, and a monitor that is about the size of a mobile phone. The sensor is inserted just beneath the skin of the abdomen or the upper arm and can remain in place for 3 to 7 days. Glucose readings are transmitted from the sensor to a monitor that is worn by the patient. The monitor displays real-time glucose levels and some also emit an alarm when glucose levels fall too low or rise too high.10 Real-time CGM has been recommended for patients over 8 years with type 1 diabetes to help lower or maintain hemoglobin A1c levels.11
BENEFITS AND LIMITATIONS OF CURRENT BLOOD GLUCOSE MONITORING METHODS
There is evidence to suggest a positive relationship between SMBG and glycaemic control among patients with type 1 diabetes. A higher number of SMBG measurements per day has been associated with better glycaemic control and a lower hemoglobin A1c level. However results are conflicting about the the benefits of SMBG for individuals with type 2 diabetes who are not treated with insulin.3,13.
Few patients consistently perform SMBG14-16 and those who do test several times each day frequently fail to capture information about levels that are too high or too low between tests17; leading to a non-accurate or unreliable picture of glucose control.6
Benefits of CGM include the ability to identify trends and track patterns in glucose levels, improve the detection of hypoglycaemia and hyperglycaemia, and provide information to guide treatment decision-making.
Many patients are able to reduce hemoglobin A1c levels while not experiencing a higher rate of hypoglycaemic episodes.6 In addition, CGM is associated with improved quality of life, greater convenience, reduced worry about diabetes, and improved diabetes control.18
However, it is estimated that CGM devices may be inaccurate up to 21% of the time, particularly during hypoglycaemic events and rapid changes in blood glucose levels.19 CGM is primarily used by patients with type 1 diabetes, but the reliability and validity of CGM for patients with type 2 diabetes is yet to be established.6
Patients must clip the monitor to their belt or waistband, which compromises their ability to discreetly monitor glucose levels. In addition, a lack of research on the role of CGM in the management of hypoglycaemia and the need for reimbursement are considered significant barriers to routine use of CGM in Europe.6,20
UNMET NEEDS IN ROUTINE BLOOD GLUCOSE MONITORING
Despite the benefits of glucose monitoring, a recent study shows that around four out of 10 people do not test their blood as often as recommended by a doctor or nurse.21 Lack of information and knowledge of glucose testing, motivational barriers, and limited behavioral skills have been found to be associated with lower frequency of blood glucose monitoring.21,22
ADDRESSING BARRIERS TO ROUTINE BLOOD GLUCOSE MONITORING
When used appropriately and consistently, both SMBG and CGM provide important insights for physicians and patients about
1) trends in glucose levels over time,
2) factors associated with glucose levels that are not within an acceptable range,
3) risk of hypoglycaemia, and
4) cues to manage high and low glucose levels. This information can help identify the need for treatment modifications, support patients’ efforts to better manage their lifestyle and medications, and enhance patient safety.
This reinforces the importance of continued efforts to reduce or eliminate barriers to routine monitoring. New interventions to support the integration of glucose monitoring into the routines of everyday life, with an emphasis on pain-free techniques, are required. Technological advances have the potential to significantly improve patients’ glycaemic control, reduce hypoglycaemic episodes, and enhance quality of life. These should ensure that patients have access to discreet methods of testing that are easy and convenient to perform, including the availability of small, disposable sensors. Innovative glucose monitoring systems should provide an historical perspective on glucose readings and projections for future trends and direction in glucose levels.
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