Page 138 - Glucose Monitoring Devices

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Clinical application of CGM

Alerts
An additional benefit of CGM is the ability to alert users when glycemia veers
outside target parameters. This function encourages timely intervention to avoid
labile swings (variability) in blood glucose and severe hypo- and hyperglycemia.
Hypoglycemia is normally heralded by autonomic and eventually neuroglyco-
penic symptoms prompting a capillary glucose measurement and appropriate
treatment once confirmed. Impaired awareness of hypoglycemia describes the
failure to identify a significant decline in blood glucose or the failure to elicit
autonomic symptoms before neuroglycopenia. With a prevalence of just under
20% in adults with T1DM [38], the CGM alarm feature provides a safety mech-
anism to prevent forthcoming hypoglycemia in this large vulnerable group. Most
global health organizations recommend physical activity as part of a diabetes
care plan [30,39]. Unfortunately for many people with diabetes exercise is fraught
with fear of hypoglycemia resulting in an avoidance of physical activity or
additional calorie intake as a precautionary step. As an adjunct to capillary glucose
testing, CGM can alert users of impending hypoglycemia during exercise and
mitigate the risk by facilitating appropriate insulin dosing before and after
exercise.

Clinical application of CGM
In clinical settings, CGM can be used as a permanent adjunct to facilitate daily
glucose monitoring or as a short-term investigative tool to identify trends and
optimize treatment. Incongruence between HbA1c and capillary glucose
measurements is a common clinical scenario and often represents periods of
hypo- and hyperglycemia missed by SMBG. CGM fills the gaps missed by
SMBG and sheds light on blood glucose levels when users are asleep or unable
to perform capillary glucose monitoring. Permanent CGM use is currently prior-
itized for vulnerable individuals with hypoglycemia unawareness and individuals
struggling to improve glucose control despite optimizing all other avenues of
treatment. The UK NICE guidelines reserve long-term CGM application for those
willing to comply with use for at least 70% of the time, committed to calibrating
when required, and struggling with any of the following: severe hypoglycemia,
complete hypoglycemia unawareness, frequent asymptomatic hypoglycemia,
extreme fear of hypoglycemia and a HbA1c >9% despite 10 times daily
SMBG [40]. Although this list of indications may appear prescriptive their subjec-
tivity allows clinical discretion to take precedent if necessary. The ADA recom-
mends CGM be considered in both T1DM and T2DM where individuals
are failing to achieve treatment goals despite being on intensive insulin
therapy, with greater precedent reserved for those experiencing troublesome hypo-
glycemia [41].