Modal plots of diurnal glucose during masked and unmasked use of the FreeStyle Navigator Continuous Glucose Monitoring System®

The FreeStyle Navigator® Continuous Glucose Monitoring System, an investigational device, was evaluated in a multi-center study under home use conditions over 40 days of continuous sensor wear. The FreeStyle Navigator system consists of a disposable subcutaneous sensor that can be worn up to 5 days, a reusable transmitter attached to the sensor, and a handheld receiver with a built-in FreeStyle blood glucose (BG) meter. Real-time data and alarms were masked for the first 20 days and were unmasked for the next 20 days. The objective of this analysis was to compare glucose patterns during masked and unmasked use of FreeStyle Navigator by subject groups divided by mean glucose levels.

In total, 123 insulin-requiring subjects with type 1 or type 2 diabetes (age 49±13 years) completed the study. There were 119 subjects with at least 100 hours of FreeStyle Navigator sensor data in both study phases employed in these analyses.

Subjects were categorized into four groups based on their mean glucose level during the first 20 days (masked phase), A: <135mg/dL (16 subjects), B: 135–170mg/dL (50 subjects), C: 171–205mg/dL (37 subjects), and D: >205mg/dL (16 subjects). These groups equate to HbA1c of <6%, 6–7%, 7–8% and >8% respectively.

Modal day graphs for the masked and the unmasked phases were constructed separately, whereby each modal profile point was statistically summarized for the time interval from one half hour before to one half hour after the time point. For example, for the 10 AM modal point, continuous data from 9:30 to 10:30 AM were included.

Results from these plots demonstrate that the two extreme groups based on mean glucose may have benefited the most from unmasked FreeStyle Navigator use even after a very short period of time. The highest baseline glucose group D had substantially lower average glucose values throughout the 24 hour day during the unmasked phase, with notable differences from 6PM to midnight. The lowest baseline glucose group A appears to have benefited from unmasked FreeStyle Navigator use by having a more stable overall 24 hour modal profile, but at generally similar average values. Group B showed similar modal glucose profiles in the two study phases. For group C, the subjects appeared to have improved glycemic profiles throughout the day with more stable and lower average values from mid morning (10 AM) to 1 AM, and slightly higher 1 AM to 6 AM glucose values keeping, perhaps, more subjects from approaching the hypoglycemic range during sleep.

These encouraging findings based on examination of the comparative modal plots with subject categorization by mean glucose level, from such a short initial study with FreeStyle Navigator, are similar to those reported for other continuous glucose monitoring systems.