User Manual

Performance Characteristics 85
Accuracy of Guardian RT Readings
In this study, YSI measurements (taken every half hour) were paired with the corresponding Guardian RT
reading (taken every 5 minutes). Pairing was done by selecting the Guardian RT value closest in time to the
YSI test result. Agreement was analyzed by comparing paired glucose measurements.
Agreement between the matched pair was estimated by evaluating the difference between the Guardian
RT reading and the YSI measurement. The difference between them was calculated as a percentage of the
YSI (Mean Absolute Percent Difference). The bias was also calculated, and it is defined as the overall
difference between the Guardian RT glucose values and the YSI values. The paired glucose measurements
are summarized in Table 5.1.
Table 5.1
The accuracy of the Guardian RT was also evaluated by calculating the percentage of Guardian RT
readings within 20% and within 30% of the YSI reading (or within 20 mg/dl (1.1 mmol/l) in the low glucose
range). Results are shown in Table 5.2
Table 5.2
*For the Low glucose range, 40-80 mg/dl (2.2-4.4 mmol/l), the value shown is the percent within 20 mg/dl (1.1 mmol/l).
Number of Paired Glucose Measurements 3941
Mean Absolute Percent Difference (+ SD) 19.7 + 18.4%
Bias -15.0 mg/dl (-0.8 mmol/l)
Plasma Glucose
Range (mg/dl)
Plasma Glucose
Range (mmol/l)
Number of
Paired Readings
Percent
Within 20%
Percent
Within 30%
Overall 3941 62% 79%
40-80* 2.2-4.4 356 68% 68%
>80-120 >4.4-6.7 769 60% 77%
>120-240 >6.7-13.3 2362 62% 81%
>240 >13.3 454 61% 82%