
Effects of calibration frequency
The average bias when Guardian RT was calibrated ~ 3.5 times a day was -20.5 ± 41 mg/dl (LL: -22.40 mg/dl
and UL: -18.63 mg/dl). In those calibrated ~ 5 times a day, the bias was -10.2 mg/dl ± 36 mg/dl (LL: -11.74
mg/dl and UL: -8.66 mg/dl). When comparing Guardian RT units that were calibrated less often to those
calibrated more often, the following alarm performance was observed:
• Specificity increased 2-4 percent in the hypoglycemic range and decreased 0-2 percent in the
hyperglycemic range
• Sensitivity increased between 5-9 percent across the hyperglycemic range, and decreased 7-16 percent
when the alarm was set to 80 mg/dl or below, and decreased 3-7 percent when set between 85 and 100
mg/dl
Stratified error grid analysis also shows better performance in the hypoglycemic range when fewer
calibrations are performed, i.e., 62 percent of data points are in Zone A when fewer calibrations were
performed, whereas 58 percent were in Zone A when more calibrations were performed.
Sensor accuracy
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ಘAppendix A
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