FreeStyle Libre: 'Convenient, Valuable Addition' to Glucose Monitoring

Miriam E. Tucker

January 02, 2020

The Abbott FreeStyle Libre glucose monitoring system improves some aspects of blood glucose control and quality of life in people with diabetes, two new prospective real-world studies suggest.

Findings from one of the studies, of more than 1000 individuals with diabetes from a nationwide Dutch registry, FLARE-NL, was published online December 9 in BMJ Open Diabetes Research and Care by Marion J. Fokkert, BAS, and colleagues.

The other study, FUTURE, of almost 2000 adults with type 1 diabetes at specialist centers in Belgium, was published online December 16 in Diabetes Care by Sara Charleer, PhD, and colleagues.

The Libre system — also known as intermittently scanned continuous glucose monitoring (CGM) or flash glucose monitoring — was first approved for patient use in Europe in 2014 and the United States in 2017.

It differs from real-time CGM systems in that results can only be obtained by the user scanning a sensor worn on the upper arm, rather than the data being automatically relayed to a receiver. It does not require fingerstick calibration.

A newer version (FreeStyle Libre 2) with alarms for high and low blood glucose levels is available in Europe but not yet in the United States.

In both studies, use of the first-generation Libre for up to 1 year reduced hypoglycemia and work absenteeism. In the Dutch study, there was also a significant reduction in A1c and diabetes-related hospitalization, and less reported disease burden.

In the Belgian study, Libre users — who scanned themselves, on average, 9.7 times per day — reported higher treatment satisfaction but A1c didn't change significantly.

This is "the largest real-life observational study to date investigating effectiveness of intermittently scanned CGM [Libre] under everyday conditions in a general population with type 1 diabetes," the authors emphasize.

Neither study was directly funded by Abbott.

Less Work Absenteeism and Hypoglycemia, and Lower A1c

The Dutch prospective nationwide registry study included 1365 adults, of whom 77% had type 1 diabetes, 16% had type 2 diabetes, and the rest had other forms of diabetes. Assessments were done at baseline and 6 and 12 months after starting to use the Libre.

Overall, average A1c levels dropped from 64.1 mmol/mol (8.0%) at baseline to 59.2 mmol/mol (7.6%) after 6 months (P < .001) and 60.1 mmol/mol (also 7.6%) at 12 months (P < .001).

By diabetes type, decreases in A1c ranged from –3.3 mmol/L for those with type 1 diabetes to –6.2 mmol/mol for those with type 2 diabetes.

Use of the Libre had the greatest impact among insulin-treated individuals with baseline A1c greater than 70 mmol/mol (8.5%) despite maximal efforts using fingerstick monitoring and intensive lifestyle interventions.

Patients with frequent unexpected hypoglycemia also experienced significant A1c improvements, while A1c remained stable in other groups, including individuals with hypoglycemic unawareness, those with contraindications to fingersticks (eg, musicians), or those for whom even rare hypoglycemic episodes could have severe consequences (eg, truck drivers). 

Significant improvements with the Libre were seen in scores on the Short Form Health Survey version 2 mental component (but not the physical component) and EuroQol 5D, both measures of health-related quality of life.

The percentage of individuals experiencing any hypoglycemic event dropped from 93.5% to 91.0% at 12 months (P < .05).

The percentage experiencing diabetes-related hospital admissions decreased from 13.7% to 4.7% (P < .05), and the percentage reporting work absenteeism was reduced from 18.5% to 7.7% (P < .05).

"A Valuable Addition to Treatment Options" 

"It can be concluded that a large proportion of persons with diabetes using FreeStyle Libre flash glucose monitoring experiences positive effects on a wide range of outcome parameters," Fokkert, of the Department of Clinical Chemistry, Isala Clinics, Zwolle, The Netherlands, and colleagues write.

These included, but were not limited to, the following:

  • No impediment to measuring glucose in the presence of strangers: Increased from 34.7% to 81.7% (P < .001).

  • Deciding what best to do after measuring glucose: Improved from 22.9% to 56.7% (P < .001).

  • Glucose measurement in a poorly illuminated space was achievable/workable: Increased from 49.4% to 88.6% (P < .001).

  • Measuring glucose before participating in traffic as a driver, usually and always: Improved from 40.9% to 75.4% (P < .001).

  • 37% reported participating in sports and exercising more frequently.

  • 95% reported a better understanding of their glucose fluctuations.

  • 77% experienced less hypoglycemia.

  • 78% experienced less severe hypoglycemia.

  • 92% found it easier to regulate glucose around a meal.

  • 80% adjusted insulin doses more frequently.

  • 62% reported that housemates and family members were less worried about their diabetes.

However, the researchers add that "these outcomes should not all be taken at face value" because of several study limitations, including the lack of a control group, use of patient-reported outcomes, missing data, and bias introduced by the fact that patients had to pay for half the cost of the Libre.

"Acknowledging the several limitations of this study, in our opinion the results are still convincing enough to allow the general conclusion that the [Libre] is a valuable addition to treatment options for specific target groups of patients with [diabetes], irrespective of the type of diabetes," the authors conclude.

They add that, in a follow-up study, they plan to combine the data as present in the current FLARE-NL registry with reimbursement data of the healthcare insurance company in the Netherlands to assess the actual effects of the FreeStyle Libre on healthcare costs (as represented by reimbursement data).

"This will allow an analysis with regards to diabetes-related hospital admission rate, but also allows for other comparisons," they write.

"Much More Convenient Than Classical Fingersticking"

Meanwhile in their article, Charleer, of University Hospitals Leuven and Antwerp University Hospital, Belgium, and coauthors explain that, in 2016, nationwide reimbursement of the Libre was introduced in Belgium for people with type 1 diabetes treated at specialist diabetes centers.

Subsequent to that, their prospective study involved 1913 individuals seen at three of those centers who used the device for 12 months.

Overall, quality of life was high at baseline, as assessed by scores on the 36-item Short-Form questionnaire (SF-36). Other study measures included the Problem Areas in Diabetes, Short Form (PAID-SF), Hypoglycemia Fear Survey (HFS-Worry), and Diabetes Treatment Satisfaction Questionnaire (DTSQ).

Scores on the SF-36, PAID-SF, and HFS-Worry remained stable overall, while DTSQ status satisfaction significantly increased from baseline to 12 months after adoption of the Libre (28.0 vs 30.4; P < .0001).

Overall, participants rated their satisfaction with the Libre at 8.4 on a scale of 10 at 6 and 12 months, with near-unanimous agreement that the system is "more convenient than fingerstick tests" (94.6% and 95.1% at 6 and 12 months, respectively). 

Overall, average A1c was slightly lower at 6 months than baseline (61 mmol/mol [7.7%] vs 62 mmol/mol [7.8%]; P < .0001) but returned to the baseline value by 12 months (P = .287).

And the proportion achieving A1c < 53 mmol/mol (< 7%) actually dropped from 20.8% to 18.3% at 12 months (P = .01). Similar patterns were seen regardless of scan frequency.

The authors speculate that the absence of overall A1c improvement might relate to "a more defensive attitude toward hypoglycemic events," such as more snacking and administering lower insulin doses in the face of greater perceived hypoglycemia.

However, time spent in hypoglycemia, < 3.9 mmol/L (< 70 mg/dL) and < 3.0 mmol/L (< 54 mg/dL), significantly decreased with the Libre from 5.1% and 4.0% in the first 2 weeks to 4.5% and 3.5% at 6 months (P < .0001) and remained at 4.5% and 3.5% at 12 months (P < .0001), respectively, independent of the number of scans per day.

This resulted in a continuous reduction of time in hypoglycemia of 16 minutes/day.

Fewer people reported severe hypoglycemic events requiring outside assistance (P < .0001), hypoglycemic comas (P = .001), and diabetes-related work absenteeism (P < .0001).

The proportion of participants admitted to the emergency room or hospital because of hypoglycemia or ketoacidosis also dropped from 3.3% in the prior year to 2.2% while using the Libre (P = .031).

However, in parallel with the reduction in time spent in hypoglycemia, there was less time spent in range, 3.9-10.0 mmol/L (70-180 mg/dL), at 12 months compared with 2 weeks after first use of the Libre (P = .004), and more time spent in hyperglycemia.

Hence, say the researchers, "continued efforts are needed to improve education about the use of [FreeStyle Libre] focusing on increasing time in range while decreasing both time in hyper- and hypoglycemia."

And despite reporting general satisfaction with the system, 64% of the 1913 users also reported a total of 3081 negative experiences with the device, most often pertaining to sensor loss (52% of comments) and accuracy (42% of comments).

"In conclusion," the authors write, the findings show that the Libre "can be successfully implemented with clinically relevant benefits."

BMJ Open Diabetes Res Care. 2019;7:e000809. Full text

Diabetes Care. Published online December 16, 2019. Abstract

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