Page 139 - Glucose Monitoring Devices

140 CHAPTER 7 Clinical impact of CGM use

CGM efficacy
Given the recent availability of CGM and limited long-term complication data, het-
erogeneous outcomes of glycemic control have been adopted as measures of clinical
efficacy. These include HbA1c, time in range, time spent in hypo- or hyperglycemia,
and various metrics of glycemic variability.

Retrospective CGM studies
Without immediate access to CGM data, retrospective (blinded) CGM users are un-
able to make real-time therapeutic changes and study outcomes derived from this
population are largely based on interventions following retrospective data analysis.

Observational trials
Observational retrospective studies have reported significant HbA1c reductions
across various age groups in individuals with T1DM, with some studies maintaining
insulin dose neutrality [42e44]. Although critiqued for low participant numbers, not
showing significant hypoglycemia reduction, and no comparative control arm, these
studies reinforce the value of CGM in identifying glucose trends and facilitating
effective therapeutic intervention.
Randomized controlled trials
Apart from a 3-month randomized controlled crossover study reporting a significant
reduction in HbA1c during the retrospective CGM phase [45], randomized
controlled trials (RCTs) have largely failed to establish superior glycemic control
using retrospective CGM. A large 12-week trial of 128 randomized T1DM children
found no significant difference in HbA1c change when comparing retrospective
CGM against SMBG [46]. Similarly, a 3-month adult trial comparing adjunctive
blinded CGM against SMBG failed to show a difference in the improvement of
HbA1c despite identifying half the cases of asymptomatic hypoglycemia [47]. Inter-
estingly, the control arms in both studies saw participants performing SMBG more
than the clinically recommended 4 times a day, an achievement most individuals
would find challenging under normal circumstances. These shortcomings are heavily
biased toward SMBG when comparing against CGM and must be considered before
transferring outcomes into real-world clinical settings.

Real-time CGM studies
Real-time CGM (RT-CGM) provides users with immediate access to glucose levels,
rate and direction of change, and glycemic profile patterns.

Observational
Observational studies following adults and children using RT-CGM also report
improvement in glycemic control and highlight the benefits of dynamic therapeutic
modification. Reduced time spent in hypo- and hyperglycemia has been successfully