The Accuracy of the FreeStyle Navigator Continuous Glucose Monitoring System in Children With Type 1 Diabetes

Jaeb Center for Health Research, Tampa, Florida, United States
Diabetes Care (Impact Factor: 8.42). 01/2007; 30(1):59-64. DOI: 10.2337/dc06-1407
Source: PubMed


To evaluate the accuracy and precision of the FreeStyle Navigator continuous glucose monitoring system in children with type 1 diabetes.
In 30 children with type 1 diabetes (mean age 11.2 +/- 4.1 years), the Navigator glucose values were compared with reference serum glucose values of blood samples obtained in an inpatient clinical research center and measured in a central laboratory using a hexokinase enzymatic method and in an outpatient setting with a FreeStyle meter. Median absolute difference (AD) and median relative absolute difference (RAD) were computed for sensor-reference and sensor-sensor pairs.
The median AD and RAD were 17 mg/dl and 12%, respectively, for 1,811 inpatient sensor-reference pairs and 20 mg/dl and 14%, respectively, for 8,639 outpatient pairs. The median RAD between two simultaneous Navigator measurements (n = 1,971) was 13%. Ninety-one percent of sensors in the inpatient setting and 81% of sensors in the outpatient setting had a median RAD < or = 20%.
The Navigator's accuracy does not yet approach the accuracy of current-generation home glucose meters, but it is sufficient to believe that the device has the potential to be an important adjunct to treatment of youth with type 1 diabetes.

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    • "In this series of experiments, as previously (12), the overnight glucose target was set at 6.6 mmol/L (120 mg/dL) to provide a margin of error. The median error of currently available real-time continuous glucose monitors is between 10 and 16% when plasma glucose levels are between 70 and 180 mg/dL (9,10,26,27). A sensor error overreading the plasma glucose by 33% would drive the true glucose to only 90 mg/dL. "
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    ABSTRACT: OBJECTIVE A key milestone in progress towards providing an efficacious and safe closed-loop artificial pancreas system for outpatient use is the development of fully automated, portable devices with fault detection capabilities to ensure patient safety. The ability to remotely monitor the operation of the closed-loop system would facilitate future physician-supervised home studies. RESEARCH DESIGN AND METHODS This study was designed to investigate the efficacy and safety of a fully automated, portable, closed-loop system. The Medtronic Portable Glucose Control System (PGCS) consists of two subcutaneous glucose sensors, a control algorithm based on proportional-integral-derivative with insulin feedback operating from a BlackBerry Storm smartphone platform, Bluetooth radiofrequency translator, and an off-the-shelf Medtronic Paradigm Veo insulin pump. Participants with type 1 diabetes using insulin pump therapy underwent two consecutive nights of in-clinic, overnight, closed-loop control after a baseline open-loop assessment. RESULTS Eight participants attended for 16 overnight studies. The PGCS maintained mean overnight plasma glucose levels of 6.4 ± 1.7 mmol/L (115 ± 31 mg/dL). The proportion of time with venous plasma glucose <3.9, between 3.9 and 8 (70 and 144 mg/dL), and >8 mmol/L was 7, 78, and 15%, respectively. The proportion of time the sensor glucose values were maintained between 3.9 and 8 mmol/L was greater for closed-loop than open-loop (84.5 vs. 46.7%; P < 0.0001), and time spent <3.3 mmol/L was also reduced (0.9 vs. 3%; P < 0.0001). CONCLUSIONS These results suggest that the PGCS, an automated closed-loop device, is safe and effective in achieving overnight glucose control in patients with type 1 diabetes.
    Diabetes care 08/2012; 35(11):2182-7. DOI:10.2337/dc12-0761 · 8.42 Impact Factor
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    • "We found that the iPro device tended to overestimate blood glucose concentrations when subjects were deemed to be hypoglycemic, as measured by capillary finger stick/glucometer readings (i.e., 50% of the time in 26 paired valued). This overestimation in blood glucose levels with CGM was likely due to the lagging of sensor reported glucose changes behind blood glucose changes during exercise, as has been reported previously [22, 23]. It is worth noting that blood glucose meters also have approximately a 20% variance compared to plasma glucose as measured by a clinical devise, such as a YSI analyzer, and these paired values would be susceptible to variance in both the iPro and glucometer readings. "
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    International Journal of Pediatrics 08/2010; 2010(2). DOI:10.1155/2010/216167
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    • "The reader is referred to guidelines for sensor accuracy assessment and comparison proposed by Wentholt et al. [15]. The precision of Table 2 Characteristics of continuous glucose sensing systems CGMS Gold Paradigm and Guardian RT Dexcom STS Abbot Freestyle Navigator Accuracy Reference [5] Reference [6] Reference [7] Reference [8] [9] "
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    Clinical biochemistry 11/2008; 42(3):136-42. DOI:10.1016/j.clinbiochem.2008.09.112 · 2.28 Impact Factor
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