User Manual

90 Chapter 5
The Low Glucose Alert
The Low Glucose Alert was evaluated for its ability to detect glucose levels at 70 mg/dl (3.9 mmol/l), or
below, using the YSI 2300 STAT Plus glucose analyzer. As a reference, with the Low Glucose Alert set at 70
mg/dl (3.8 mmol/l), 49% (100/205) of low glucose events were detected by the Guardian RT. Better
detection of low blood glucose can be obtained by setting the Low Glucose Alert level higher. For
example, setting the Low Glucose Alert at 90 mg/dl (5.0 mmol/l), instead of 70 mg/dl (3.9 mmol/l),
increases the ability to detect low blood glucose levels from 49% to 82% (Table 5.5).
Sometimes the Guardian RT will alert when the blood glucose levels are not low. When the Guardian RT
Low Alert was set at 70 mg/dl (3.9 mmol/l) in this study, 43% of the results were considered false alerts
(actual blood glucose values are greater than 85 mg/dl (4.7 mmol/l)). This percentage may be
exaggerated because blood glucose may be dropping when the Guardian RT alerts. Table 5.5 shows the
percent of Low Glucose readings correctly identified by the Guardian RT for specific settings.
Table 5.5
* True Alert Rates are the % of times when the glucose level was at or below the alert setting and the alert sounded.
** False Alerts Rates are the % of times when the Guardian RT Sensor alarmed but the blood glucose level was greater
than the alert setting.
Increasing the Low Alert settings will improve the ability to detect low blood glucose events, but it will
also increase the frequency of Guardian RT false alerts for blood glucose levels not below the target
value. You should consider this trade-off between the improved ability to detect true low blood glucose
versus the increased number of false alerts when setting the low alert threshold.
Guardian RT Low
Alert Setting
(mg/dl)
Guardian RT Low
Alert Setting
(mmol/l)
True Alert Rate* False Alert Rate**
70 3.9 49% 60%
80 4.4 68% 64%
90 5.0 82% 75%
100 5.6 90% 79%