Diagnostic Tests

What Physicians Need to Know

Flash Continuous Glucose Monitoring (FreeStyle Libre 14-Day System) for Self-Management of Diabetes Mellitus

 

Am Fam Physician. 2021 Jun 1;103(11):688-690.

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TestIndicationPopulationCost*

Flash continuous glucose monitoring (FreeStyle Libre 14-day system)

Monitoring blood glucose in self-management of diabetes mellitus

Adults with type 1 diabetes or insulin-treated type 2 diabetes, and children with type 1 diabetes

$75 for a reader $135 per month for sensors


*—The fair price represents the reasonable out-of-pocket cost based on price comparisons. Actual cost will vary with insurance and by region. Information obtained at https://www.goodrx.com and https://provider.myfreestyle.com/ (accessed April 21, 2021; zip code: 66211).

TestIndicationPopulationCost*

Flash continuous glucose monitoring (FreeStyle Libre 14-day system)

Monitoring blood glucose in self-management of diabetes mellitus

Adults with type 1 diabetes or insulin-treated type 2 diabetes, and children with type 1 diabetes

$75 for a reader $135 per month for sensors


*—The fair price represents the reasonable out-of-pocket cost based on price comparisons. Actual cost will vary with insurance and by region. Information obtained at https://www.goodrx.com and https://provider.myfreestyle.com/ (accessed April 21, 2021; zip code: 66211).

Continuous glucose monitors (CGMs) are used for the self-management of diabetes mellitus and have a subcutaneously inserted sensor that measures glucose in the interstitial fluid and transmits the result to a receiver. The FreeStyle Libre 14-day system is an intermittently scanned or “flash” CGM that was approved by the U.S. Food and Drug Administration in 2017. It displays glucose values when the sensor is scanned with the receiver. The sensor is placed on the posterior upper arm, lasts 14 days, and is factory calibrated. FreeStyle Libre displays eight-hour glucose trends but does not have any alarms.1,2 Real-time CGMs measure glucose every one to five minutes and issue alarms when glucose values are too high or low. Some brands may need to be calibrated by self-monitoring of capillary blood glucose (SMBG), which uses a finger stick and test strips.1,2

Accuracy

FreeStyle Libre is accurate in adults and children (mean absolute relative difference = 11.4% and 13.9%, respectively), with capillary blood glucose as the reference standard.3,4 Its accuracy is stable throughout the 14-day lifespan of the sensor but is lower during hypoglycemia and exercise and after a glucose load.3,5,6

Benefit

A systematic review and meta-analysis of 15 randomized controlled trials (RCTs) evaluated the impact of CGMs (including real-time and flash CGMs) on glycemic control compared with usual care using SMBG (n = 2,477).7 It included three studies of FreeStyle Libre in adults; two of the studies evaluated adults with type 1 diabetes and one study evaluated adults with insulin-treated type 2 diabetes. In general, CGMs produced a pooled A1C reduction of −0.17% (95% CI, −0.29% to −0.06%), greater time in euglycemic range (70.74 minutes per day; 95% CI, 46.73 to 94.76), less time in hyperglycemia (−30.26 minutes per day; 95% CI, −58.15 to −2.38), and less time in hypoglycemia (−27.16 minutes per day; 95% CI, −42.08 to −12.25). A subanalysis of the FreeStyle Libre trials (n = 626) found similar effects on time in euglycemic range, hyperglycemia, and hypoglycemia, but no statistically significant A1C reduction.

A meta-analysis of 12 studies (three RCTs, five prospective cohorts, three retrospective cohorts, one not reported; n = 2,173) evaluating the use of FreeStyle Libre in adults and children with type 1 diabetes or insulin-treated type 2 diabetes showed that the use of FreeStyle Libre reduced A1C levels by −0.26% (95% CI, −0.43% to −0.09%) compared with baseline. Compared with SMBG, however, A1C reduction was no longer significant.8

ADULTS WITH TYPE 1 DIABETES

An RCT of adults with well-controlled type 1 diabetes

Address correspondence to Hiu Ying Joanna Choi, MD, at Hiuyingjoanna.choi@tuhs.temple.edu. Reprints are not available from the author.

Author disclosure: No relevant financial affiliations.

References

show all references

1. American Diabetes Association. 7. Diabetes technology: Standards of Medical Care in Diabetes-2021. Diabetes Care. 2021;44(suppl 1):S85–S99....

2. Leelarathna L, Wilmot EG. Flash forward: a review of flash glucose monitoring. Diabet Med. 2018;35(4):472–482.

3. Bailey T, Bode BW, Christiansen MP, et al. The performance and usability of a factory-calibrated flash glucose monitoring system. Diabetes Technol Ther. 2015;17(11):787–794.

4. Edge J, Acerini C, Campbell F, et al. An alternative sensor-based method for glucose monitoring in children and young people with diabetes. Arch Dis Child. 2017;102(6):543–549.

5. Moser O, Eckstein ML, McCarthy O, et al. Performance of the FreeStyle Libre flash glucose monitoring (flash GM) system in individuals with type 1 diabetes: secondary outcome analysis of a randomized crossover trial. Diabetes Obes Metab. 2019;21(11):2505–2512.

6. Fokkert MJ, van Dijk PR, Edens MA, et al. Performance of the FreeStyle Libre Flash glucose monitoring system in patients with type 1 and 2 diabetes mellitus. BMJ Open Diabetes Res Care. 2017;5(1):e000320.

7. Maiorino MI, Signoriello S, Maio A, et al. Effects of continuous glucose monitoring on metrics of glycemic control in diabetes: a systematic review with meta-analysis of randomized controlled trials. Diabetes Care. 2020;43(5):1146–1156.

8. Castellana M, Parisi C, Di Molfetta S, et al. Efficacy and safety of flash glucose monitoring in patients with type 1 and type 2 diabetes: a systematic review and meta-analysis. BMJ Open Diabetes Res Care. 2020;8(1):e001092.

9. Bolinder J, Antuna R, Geelhoed-Duijvestijn P, et al. Novel glucose-sensing technology and hypoglycaemia in type 1 diabetes: a multicentre, non-masked, randomised controlled trial. Lancet. 2016;388(10057):2254–2263.

10. Charleer S, De Block C, Van Huffel L, et al. Quality of life and glucose control after 1 year of nationwide reimbursement of intermittently scanned continuous glucose monitoring in adults living with type 1 diabetes (FUTURE): a prospective observational real-world cohort study. Diabetes Care. 2020;43(2):389–397.

11. Gordon I, Rutherford C, Makarounas-Kirchmann K, et al. Meta-analysis of average change in laboratory-measured HbA1c among people with type 1 diabetes mellitus using the 14 day flash glucose monitoring system. Diabetes Res Clin Pract. 2020;164:108158.

12. Piona C, Dovc K, Mutlu GY, et al. Non-adjunctive flash glucose monitoring system use during summer-camp in children with type 1 diabetes: the free-summer study. Pediatr Diabetes. 2018;19(7):1285–1293.

13. Messaaoui A, Tenoutasse S, Crenier L. Flash glucose monitoring accepted in daily life of children and adolescents with type 1 diabetes and reduction of severe hypoglycemia in real-life use. Diabetes Technol Ther. 2019;21(6):329–335.

14. Yaron M, Roitman E, Aharon-Hananel G, et al. Effect of flash glucose monitoring technology on glycemic control and treatment satisfaction in patients with type 2 diabetes. Diabetes Care. 2019;42(7):1178–1184.

15. Haak T, Hanaire H, Ajjan R, et al. Flash glucose-sensing technology as a replacement for blood glucose monitoring for the management of insulin-treated type 2 diabetes: a multicenter, open-label randomized controlled trial. Diabetes Ther. 2017;8(1):55–73.

16. Vergier J, Samper M, Dalla-Vale F, et al. Evaluation of flash glucose monitoring after long-term use: a pediatric survey. Prim Care Diabetes. 2019;13(1):63–70.

17. Abbott Laboratories. FreeStyle Libre 14-Day System. Accessed February 21, 2021. https://provider.myfreestyle.com

18. GoodRx. Accessed February 21, 2021. https://www.goodrx.com

This series is coordinated by Kenny Lin, MD, MPH, deputy editor.

A collection of Diagnostic Tests published in AFP is available at https://www.aafp.org/afp/diagnostic.

 

 

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