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Continuous Versus Flash Glucose Monitoring To Reduce Hypoglycemia In Type 1 Diabetes

Continuous glucose monitoring may reduce hypoglycemia fear.

The Dexcom G5 system was approved by the FDA in 2016 and was later permitted for use to replace finger-stick testing to determine insulin dose. The REPLACE-BG study proved its safety and effectiveness in adults with well-controlled type 1 diabetes at low risk for severe hypoglycemia. The FreeStyle Libre Pro System was also approved last year by the US FDA for use by physicians for monitoring glucose in patients with diabetes. It is the third “blinded” professional CGM system on the US market, joining the Dexcom G4 Platinum Professional Real-Time CGM and the Medtronic iPro2 Professional CGM, but it does not require finger-stick calibration, has no reusable components requiring disinfection, provides a longer period of data capture (14 days, compared with 7 for the Dexcom and 3 for Medtronic), and has a lower cost.

Previously studies revealed that CGMs could increase the time spent in and above glucose target range along with reduction in time below that same range in type 1 diabetes. Almost one-fourth of the adult patients had experienced reduction in awareness of hypoglycemia putting them at high-risk for severe hypoglycemia. In a recent UK study, real-time continuous glucose monitoring (CGM) has shown significant improvement in identifying and reducing the time spent in hypoglycemia in comparison to the flash glucose monitoring (FGM) in type 1 diabetes patients with impaired hypoglycemia awareness. According to Dr. Monika Reddy, the study showed that both CGM and FGM devices: G5 by Dexcom and Freestyle Libre by Abbott’s, respectively, presented significantly improved HbA1c levels and the amount of time spent in the target glucose range. However, she stressed on CGM being superior to FGM with beneficial impact on hypoglycemia outcomes and hypoglycemia awareness specifically in patients with type 1 diabetes experiencing impaired hypoglycemia awareness.

On the other hand, Dr. Dev Singh at Royal Wolverhampton NHS Trust, UK was not entirely convinced with the clinical use of the two devices when compared in the real world. He was concerned that comparing the two devices would not reflect the real world clinical use because FGM is a step up from what patients might be doing and not a high-tech device, like CGM. The FreeStyle Libre system consisted of a glucose sensor inserted into the back of the upper arm for up to 14 days and a scanner that users wave over the sensor to obtain readings and, just like conventional CGM, it measured interstitial fluid glucose levels in real time. Moreover, it provided longer sensor wear with no calibration required, and at a lower cost. However, it lacked an alarm for low and high glucose values, which gives CGM an upper hand. Singh summed up that the use of both devices would be applicable in different sort of patients with different tiers of problems, thus making it unfair to compare them head-to-head. The main concern was that both devices require different processes with one guiding to make appropriate decision, while the other tells what needs to be done.

Dr. Reddy’s study was a prospective, parallel-grouped, and randomized to CGM or FGM after a 2-week run-in. It involved 40 CGM-naive adults with type 1 diabetes and impaired hypoglycemia awareness. Baseline characteristics had no significant differences between the two groups; 60% of subjects were men with average age of 50 years old, and mean duration of diabetes was about 30 years. In the primary outcome, CGM was associated with a significant reduction, percentage time spent in hypoglycemia (<3.3 mmol/L or 60 mg/dL), from baseline to 8 weeks compared with a nonsignificant slight increase with the FreeStyle Libre. Although both groups had a significant increase in the time spent in the target glucose range with similar and significant reductions in HbA1c between baseline and 8-week follow-up, the CGM group experienced a significant reduction in the mean Gold score of impaired hypoglycemia awareness, whereas FGM users had no significant difference in the score. The Hypoglycemia Fear Survey-II (HFS-II) revealed the CGM group experienced a reduction in total score, from 59.2 to 50.5 (P = 0.01) and no significant difference in the flash monitoring group.

Past study results from over 50,000 users in the past studies support that the FreeStyle Libre significantly improved blood sugar control in type 1 diabetes in addition to improvement in HbA1c levels and the amount of time spent in the target glucose range as much as the G5 did, but when looking at the impact on hypoglycemia and hypoglycemia awareness specifically, the G5 takes the lead and the benefits for users go well and beyond what the Freestyle Libre can offer. The study investigated the hypoglycemia outcomes in a well-defined setting in a high-risk population, but the results were not applicable to all patients with diabetes and that the follow-up period was short as well.

In conclusion, the results were crucial to select the appropriate monitoring technology relevant to the patient in order to minimize cost and clinical impact of hypoglycemia, but adding the real-time CGM significantly reduced hypoglycemia fear over flash glucose monitoring.

Practice Pearls:

  • Impaired hypoglycemia awareness affects up to a third with type 1 diabetes patients.
  • The study showed that both CGM and flash monitoring had a significant increase in the time spent in the target glucose range with similar and significant reductions in HbA1c between baseline and 8-week follow-up.
  • Use of real-time CGM over the Freestyle Libre helps in significant reduction in hypoglycemia fear and worries of consequences.

References:

  1. Davenport, Liam. CGM vs flash monitoring in diabetes with hypoglycemia unawareness. Medscape. Mar 16, 2017.
  2. Diabetes UK Professional Conference 2017. March 10, 2017; Manchester, UK.
  3. Lutz H and Freckmann G. CGM versus FGM; or, continuous glucose monitoring is not flash glucose monitoring. Journal of Diabetes Science & Technology. 2015. 9(5):947-950.
  4. Tucker ME. FDA Approves Abbott’s FreeStyle Libre Pro System for Diabetes. Medscape. September 28, 2016.

Tenzing Dolkar, BSc., PharmD Candidate 2017, Lake Erie College of Osteopathic Medicine, School of Pharmacy