FreeStyle Libre System: The New Continuous Glucose Monitor

DECEMBER 26, 2017
The FreeStyle Libre is a continuous blood glucose monitor on the market for type 1 and diabetics produced by Abbott, the manufacturer of the FreeStyle meter lines. The main difference between the FreeStyle Libre system from most blood glucose meters on the market is that it uses a sensor that is left on the body for a continuous reading, rather than getting traditional finger stick blood glucose readings throughout the day.
Upon the first fill, each patient requires a reader, along with sensors. Each sensor can be worn for up to 10 days, requiring 3 sensors for a 1-month supply. FreeStyle estimates that the Libre meter has a mean lifespan of 3 years. FreeStyle Libre is used with a sensor that is placed on the back of the upper arm, and a sensor filament is inserted into the skin and measures glucose readings based on interstitial fluid.
Readings are taken by swiping the reader system over the sensor for a painless 1-second scan. For each scan, users get a blood glucose reading, a trend, and an 8-hour history. The sensor continuously measures the glucose level every 60 seconds and stores the readings every 15 minutes, requiring it to be scanned every 8 hours. The reading device can then use that data to provide daily patterns, the percentage of time that the blood glucose was within the target range, and the number of low-glucose events. The reading device stores 90 days of glucose data to allow accurate readings to present to health care professionals in coordination of their A1c, which is a 3-month average of the patient’s blood glucose.
According to the IMPACT Trial of type 1 diabetics, patients used the device by scanning an average of 15.1 times per day, compared with testing with traditional blood glucose finger sticks averaging 5.6 times per day. In the REPLACE Trial of type 2 diabetics, patients used the device by scanning an average of 8.3 times, while averaging 3 times per day with traditional blood glucose finger stick testing. Both trials resulted in about a 3 times increase in glucose monitoring. Both trials also were able to show an increased time in the blood glucose target range and reduced hypoglycemia by limiting hypoglycemic events by 38% in type 1 diabetics and 43% in type 2 diabetics.
Patients can also download software for their Mac or personal computers called LibreView that is a cloud-based diabetes management system for tracking blood glucose levels. LibreView allows patients to upload data and create easy-to-read glucose reports for both patients and health care professionals. LibreView monitors average glucose, along with the standard deviation for assessing the variability of the glucose readings, as well as the tests per day, glucose history, and even insulin data, if the patient logs their insulin into the feature on the meter. The reports are available to assess daily readings, daily logs, mealtime patterns, weekly summary, and snapshots. 
Upon assessing the reports, the snapshot has a great function that breaks down the patient’s average glucose and testing for 14 days, along with the time in target, including the percentage of time that the patient was in their target range, above, or below their glucose goals. The glucose history within the snapshot provides a 90-day history of the 15-day glucose average, hypo events and the average tests per day to simplify the main focus of monitoring blood glucose and allows the patient to set reasonable and achievable goals to stay within target ranges. The daily log provided monitors the 14-day history of the readings taken to track the times that each reading occurred, hyperglycemic events, hypoglycemic events, and the daily average blood glucose. This report is helpful to assess the blood glucose trends for patients, because it allows them to visually note the times of the day that they may be consistently high, low, or within range to monitor their food or insulin intake to more appropriately manage their diabetes.
Patients and health care providers can use the LibreView resource immediately, because the system is compatible with other meters available in various countries from major manufacturers, including Accu-Chek Aviva, Accu-Chek Compact Plus, Accu-Chek Nano, Bayer Breeze2, Bayer Contour, Bayer Contour Next EZ, Bayer Contour Next USB, FreeStyle Freedom Lite, FreeStyle InsuLinx, FreeStyle Libre Pro, FreeStyle Lite, FreeStyle Optium, FreeStyle Optium Neo, FreeStyle Papillon InsuLinx, FreeStyle Papillon Lite, FreeStyle Precision, FreeStyle Vision, LinreLink Mobile App, OneTouch Ultra, OneTouch UltraEasy, OneTouch UltraMini, OneTouch Ultra2, OneTouch Verio IQ, and Optium Xido Neo.
The main competitors of the FreeStyle Libre system are the Dexcom CGM and Medtronic. The FreeStyle Libre is advertising that its sensor is 48% smaller than the Dexcom G5 transmitter and sensor; the FreeStyle Libre round sensor is 35 mm x 5 mm, while the Dexcom G5 sensor is 13 mm x 0.25 mm x 0.25 mm; and the transmitter is 38 mm x 23 mm x 13 mm. The FreeStyle Libre sensor is about the size of 2 quarters stacked together. The FreeStyle Libre sensor conveniently can be worn when exercising, showering, or swimming, because the sensor is water-resistant. Although the FreeStyle Libre sensor can be worn for 10 days, the Dexcom G53 sensor can only be worn for 7 days and requires finger stick calibrations every 12 hours to maintain system accuracy, while the FreeStyle Libre does not require calibration.
The FreeStyle Libre system is also surpassing the Dexcom CGM and the Medtronic, because the glucose readings are not being affected by acetaminophen, according to in vitro studies. While taking acetaminophen, both the Dexcom and Medtronic readings were significantly increased, while the FreeStyle Libre System remained constant. Once acetaminophen surpassed 5 mg/dL, FreeStyle Libre was the only system to keep constant blood glucose. During the study, the baseline blood glucose was 91 mg/dL and about 11 mg/dL; the Medtronic increased the blood glucose to >113 mg/dL and the Dexcom increased the readings >139 mg/dL, while the FreeStyle Libre system remained at 91 mg/dL.
Some warnings and limitations noted by Abbott include not being approved for use in critically ill patients, those on dialysis, and pregnant women. The sensor is approved for placement on the back of the arm. No alternative administration sites have been approved. Additionally, the reader does not have alerts for low blood glucose, unless the sensor is scanned so that the patient still needs to watch for signs and symptoms of blood glucose being low. The sensor is contraindicated to be worn during a CT scan, diathermy treatment, MRI, or X-ray.
Overall, FreeStyle Libre is a continuous blood glucose monitoring system that has easy-to-use resources for both patients and providers to accurately monitor blood glucose. The trails completed using the FreeStyle Libre by comparison to traditional finger sticks to monitor blood glucose overall show patients checking their blood glucose more frequently and having greater control in their blood glucose to remain in the target ranges, with fewer hypoglycemic events. Patients who are technologically inclined can download LibreView to create easy-to-interpret reports displaying their glucose readings.  

Abbott. LibreView professional support. Accessed December 26, 2017.

Abbott. Discover the FreeStyle Libre system. Accessed December 26, 2017.
Abbott. CGM, reinvented. Accessed December 26, 2017.

Brittany Myers-O'Shea, PharmD
Brittany Myers-O'Shea, PharmD, is a Pharmacy Manager of a high volume store for a large retail chain in the Northeast. She graduated from MCPHS University Boston in 2015. Her professional interests include pharmacy legislation, compounding, optimizing patient safety outcomes, and promoting vaccination awareness and education.
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