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The FreeStyle Libre glucose monitoring system (Abbott Diabetes Care) is accurate and safe in a pediatric population, new data show.
 
Findings from the first-ever study of the "flash" monitoring system in children and teens, showing good agreement between it and finger-stick blood glucose results, were published online January 31 in the Archives of Disease in Childhood by Julie Edge, MB ChB, paediatric endocrinology and diabetes, Oxford Children's Hospital, United Kingdom, and colleagues.
 
The FreeStyle Libre System comprises a small round glucose sensor worn for up to 14 days on the back of the upper arm and a scanner device that the patient waves (or "flashes") over the sensor to obtain a reading of interstitial fluid glucose levels. The scans display both historical and current glucose trends, and the data can be downloaded. Glucose measurements can be taken through clothing, and the sensor is water-resistant and can be worn while swimming and bathing.
 
The system was granted a CE Mark in Europe in 2014 as a replacement for finger-stick glucose monitoring in people with diabetes (any type) down to 4 years of age. The patient-use version awaits US Food and Drug Administration approval, but a blinded, professional version is already approved for use in the United States.
 
The system offers potential advantages over traditional continuous glucose monitoring (CGM) systems, including longer wear (14 vs 7 days or fewer) and no need for calibration, Dr Edge and colleagues note. And although the system doesn't include alarms for low or high glucose, it can alert the user to hypo- or hyperglycemia and pending excursions when detected following a scan.
 
Data on use of the Freestyle Libre system in adults have been published and were reported at the European Association for the Study of Diabetes meeting last year; these newly published results are the first to compare the system with finger-stick testing of blood glucose in children, despite it being already approved for use down to age 4 in the European Union.
 
CGM and Finger-Stick Testing Can Be Problematic in Kids
Dr Edge and colleagues note in their paper that monitoring of blood glucose levels in children and adolescents by finger-prick testing can be challenging, due to unpredictable and increased frequency of food intake, variable patterns of physical activity, and psychological and hormonal changes during adolescence, among other issues. This in turn can lead to greater glycemic variability, wider glycemic excursions, and more frequent hypoglycemia than seen in adults.
 
And monitoring glucose via CGM is problematic in children and adolescents too, for a number of reasons, they note. The FreeStyle Libre System "potentially resolves many of the issues that affect adherence with CGM," they point out.
 
A blinded version of the FreeStyle Libre system was used in the current prospective, single-arm study, involving 89 children aged 4 to 17 years with type 1 diabetes in 9 UK diabetes centers. Participants were asked to perform four capillary blood glucose tests daily, each immediately followed by a sensor reading. The data were unmasked on the third and final visit, at 12 to 15 days.
 
Overall, for 5493 paired results, the mean absolute relative difference between blood glucose measurements and the Freestyle Libre sensor was 13.9%, with 83.8% of results in zone A and 99.4% in zones A or B of the "consensus error grid," a model developed to assess continuous glucose monitoring accuracy.
 
Participants' glucose levels were in the target range of 3.9 to 10.0 mmol/L (70–180 mg/dL) approximately 50% of the time. They spent an average of 2.2 hours per day in hypoglycemia and 9.6 hours/day in hyperglycemia.
 
The sensor detected hypoglycemia (capillary blood glucose < 3.9 mmol/L) 70% of the time, rising to 84% when pending alerts were included, and hyperglycemia (> 13.3 mmol/L, or > 240 mg/dL) 85% of the time, rising to 94% when pending alerts were considered.
 
And there was little "lag" effect — when sensor results differ more from finger-stick readings when the glucose is increasing or decreasing.
 
Accuracy was not affected by method of insulin administration (pump or multiple daily injections), sensor lot, or daytime vs nighttime use, or by patient characteristics such as age, body weight, or sex.
 
Freestyle Libre System Rated Highly by Questionnaire Respondents
Five device-related adverse events were reported in five (6%) participants, including allergic reaction, blister, pink mark/scabbing, and abrasion on sensor removal. Four of these were mild and one was moderate. All were resolved at study completion.
 
Moderate erythema occurred 11.6% of the time, mild erythema and pain 13.6% and 4.1%, respectively, and mild instances of bleeding, bruising, itching, and edema each occurred on less than 3% of occasions.
 
On questionnaires, 84% to 97.5% of participants rated the sensor application, wear, and use favorably, while 68% to 96% gave the device itself high ratings.
 
The Freestyle Libre system is unique among interstitial fluid glucose monitoring systems "in that it can be worn for up to 14 days and does not require user calibration," Dr Edge and colleagues note in their discussion.
 
But they note their research examined outcomes only for 14 days, and so "further studies are needed to determine whether improved outcomes can be achieved with prolonged use of the system."
 
Arch Dis Child. Published online January 31, 2017. 
 
From www.medscape.com
 
ABSTRACT
An alternative sensor-based method for glucose monitoring in children and young people with diabetes
 
Objective
To determine accuracy, safety and acceptability of the FreeStyle Libre Flash Glucose Monitoring System in the paediatric population.
Design, setting and patients Eighty-nine study participants, aged 4–17 years, with type 1 diabetes were enrolled across 9 diabetes centres in the UK. A factory calibrated sensor was inserted on the back of the upper arm and used for up to 14 days. Sensor glucose measurements were compared with capillary blood glucose (BG) measurements. Sensor results were masked to participants.
 
Results
Clinical accuracy of sensor results versus BG results was demonstrated, with 83.8% of results in zone A and 99.4% of results in zones A and B of the consensus error grid. Overall mean absolute relative difference (MARD) was 13.9%. Sensor accuracy was unaffected by patient factors such as age, body weight, sex, method of insulin administration or time of use (day vs night). Participants were in the target glucose range (3.9–10.0 mmol/L) ∼50% of the time (mean 12.1 hours/day), with an average of 2.2 hours/day and 9.5 hours/day in hypoglycaemia and hyperglycaemia, respectively. Sensor application, wear/use of the device and comparison to self-monitoring of blood glucose were rated favourably by most participants/caregivers (84.3–100%). Five device related adverse events were reported across a range of participant ages.
 
Conclusions
Accuracy, safety and user acceptability of the FreeStyle Libre System were demonstrated for the paediatric population. Accuracy of the system was unaffected by subject characteristics, making it suitable for a broad range of children and young people with diabetes.
Trial registration number NCT02388815
 
What this study adds?
The FreeStyle Libre System is safe and accurate when used by children and young people with diabetes (4–17 years).
This new sensor-based glucose monitoring technology, requiring no user calibration, was highly acceptable to participants/caregivers. It is anticipated that the system could support enhanced diabetes management.
Glycaemic variability data for this UK population of 4–17-year-olds show that these children/young people spent on average approximately 50% of the time in euglycaemia.
 
Read the full article free
 
Introduction
The benefit of good glycaemic control to complications of diabetes is well recognised and self-monitoring of glucose levels is central to improving and maintaining good glycaemic control.
 
This can be challenging in children and young people due to unpredictable and increased frequency of food intake, variable patterns of physical activity, increased rates of intercurrent illness, and psychological and hormonal challenges of adolescence; all of which can lead to greater glycaemic variability, wider glycaemic excursions and more frequent hypoglycaemia than seen in adults.3–5 Currently, self-monitoring of glucose for children and young people involves a fingerprick, four or more times daily.3 ,6 The burden of self-monitoring of blood glucose (SMBG) for patients is well known, and includes: pain, inconvenience, disturbance for night-time tests and embarrassment.7–9
 
Continuous glucose monitoring (CGM) overcomes some of the burden of SMBG and provides a continuum of glucose data, including visibility of night-time glucose, rather than the discrete snapshots obtained by SMBG. A recent review of data from randomised controlled trials on CGM use in the paediatric population concluded that CGM use is safe and efficacious.10 However, CGM use in paediatrics has yielded mixed results on glycaemic control outcomes. Some studies demonstrated improved outcomes11–17 and associated increased benefit with increased use of CGM.16–19 Others showed little difference when comparing outcomes following use of CGM and SMBG; in these the lack of clinical benefit was often attributed to poor adherence to CGM use and reduced sensor wear.4 ,19–22
 
CGM is underused in children and young people, perhaps in part due to the lack of compelling evidence of the benefit it may provide. Barriers to CGM use include: sensor insertion on a weekly basis; skin reactions, discomfort/pain at the insertion site; frequent alarms especially at night (often turned off due to alarm fatigue); the need for multiple SMBG tests for calibration; interference with activities; poor sensor-receiver connectivity causing loss of data; high cost and limited reimbursement.4 ,19 ,23–25 It has been proposed that reducing these barriers could lead to increased uptake of continuous sensing by children and young people.25
 
The FreeStyle Libre System (Abbott Diabetes Care) used in this study potentially resolves many of the issues that affect adherence with CGM. It provides comprehensive glucose data (similar to CGM systems), increased sensor wear duration (up to 14 days, increasing the time between sensor applications), and has no requirement for fingerprick calibrations.
 
The reader, which displays glucose results after scanning over the small sensor worn on the back of the arm, does not need to be kept close to the sensor and has no automatic alarms (but can alert the user to hypo/hyperglycaemia and pending excursions when detected following a scan).
 
Scanning can be performed as often as is needed, after each scan the reader displays current sensor glucose, a trend arrow and 8-hour glucose history. The sensor automatically stores glucose data every 15 min. Device software can be used to generate summary glucose reports for review by the patient at home or in clinic with their healthcare professional (HCP).
 
These features were not available during the study; the device was masked to participants and HCPs. The system is designed to replace SMBG testing for self-management of diabetes, except during rapidly changing glucose, to confirm hypoglycaemia, or if symptoms do not match system results.
 
This study is the first to report accuracy, safety and acceptability of the FreeStyle Libre System in children and young people.
 
Accuracy of the blood glucose (BG) feature of the system is not under evaluation here; regulatory approval/Conformité Européenne (European Conformity marking of the device confirms this feature meets the required industry standards for performance. At the time of the study, the device was approved for use by adults; it has subsequently been approved for use with children (with supervision from a caregiver).
 
Discussion
This study was the first to evaluate performance and usability of the FreeStyle Libre System in children and has demonstrated good agreement between sensor and BG results. The system is unique among ISF glucose monitoring sensors in that it can be worn for up to 14 days and does not require user calibration. Comparison of accuracy data from this study to that from other paediatric studies using ISF glucose sensors demonstrated that the factory calibrated system provided similar accuracy to systems requiring daily fingerprick calibrations (table 2). The lack of user calibration eliminates potential variations in sensor systems that may be introduced through errors in BG results used for calibration, calibration at inappropriate times (during rapidly changing glucose), missing calibrations or use of sensor rather than BG values for calibration.31–33
 
Comparison of results from this study to those from a study where adults used the system34shows: MARD versus capillary BG of 13.9% and 11.4%; percentage in CEG zone A of 83.8% and 86.7%; and percentage in CEG zones A and B of 99.4% and 99.7%, in children and adults, respectively. This trend is similar to that reported for other ISF systems: Dexcom G4 Platinum had MARD versus capillary BG of 15% and 14.0% in children and adults, respectively.4 ,35 Similarly, Dexcom G4 Platinum with software 505 algorithm had MARD versus capillary BG of 13% and 11.3% in children and adults, respectively.
 
This study has confirmed that sensor accuracy is robust to patient characteristics such as age, body weight, method of insulin administration and sex. Accuracy of the system along with its robustness to differing patient characteristics, are sufficient to recommend its use to paediatric patients as support in optimising their glycaemic control. The study identified that there were 20/622 occasions where hypoglycaemia measured in capillary testing was not detected by the sensor and CEG analysis identified that there may be altered clinical action based on the sensor result. The product labelling advises patients to use a BG meter to check the sensor result if symptoms do not match the sensor result.
 
This study, providing the first glucose variability data for a paediatric population in the UK, and others,7 ,13 ,14 ,17 ,21 ,36 show there is significant opportunity to improve glycaemic control in children and young people with diabetes. Several studies have associated improved outcomes with increased sensor wear.16–19 A sensor with a longer wear period, that does not require fingerprick calibration, may support more frequent sensor use, and thus help improve clinical outcomes in children and young people.
 
SMBG provides single, intermittent results, which may not capture intervals of extreme variability or nocturnal events. In comparison, the system displays the current glucose result, the last 8 hours of glucose data (including night-time results without any disturbance to the child) and trend information when the sensor is scanned—providing significantly more data to guide treatment for this challenging population than routine SMBG.
 
This study has demonstrated safety and user acceptability of the system. Device related AEs occurred in 6% of participants, the same rate was observed in adults.34 The AEs were reported by participants aged 6–15 years, and thus were not concentrated in a particular age group. Anticipated sensor application/insertion site symptoms (pain, bleeding, bruising, erythema, itching, oedema) were reported in 44% of participants (63% of which were mild in severity), this is similar to the rate observed in adults,34 where 36% of participants experienced skin issues (p=0.337). Erythema was the symptom noted most frequently and, as with other anticipated AEs, was not associated with particular age groups. Despite these symptoms, results of the user questionnaires were similar for boys and girls and were largely favourable, culminating in 96.3% of respondents stating they would recommend the system to someone else with diabetes.
 
A limitation of this study is the single body site used. Additional studies are needed to determine suitability of additional body sites for sensor wear and longer-term studies are needed to evaluate whether this system can provide improved adherence with sensor wear and improved glycaemic outcomes with continued use over time. Exploring alternate reference methods and more detailed analysis of the glycaemic variability data using subgroups (eg, age) may be of interest.
 
Conclusions
This prospective study has clearly demonstrated the accuracy, safety and user acceptability of the FreeStyle Libre System for the paediatric population. Accuracy was unaffected by subject characteristics, making the system potentially suitable for a broad range of children and young people with diabetes. It is anticipated that the provision of comprehensive glucose data for up to 14 days, from a system that is easy to use, with reduced pain and burden for the user since there is no requirement for fingerprick calibration, could support enhanced diabetes management. Further studies are needed to determine whether improved outcomes can be achieved with prolonged use of the system.
 
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