Freestyle Libre - Replacing Your Sensor

Agreement on Day 1 against YSI Reference
The accuracy of CGM versus YSI reference on the rst day of sensor wear was assessed by calculating
the percentage of System readings that were within 15%, 20%, 30% and 40% for reference values
80 mg/dL and above, and within 15 mg/dL, 20 mg/dL, 30 mg/dL and 40 mg/dL for values below
80 mg/dL by hourly intervals. The results are presented in Table 2.
Table 2: Number and Percent of Results within YSI Reference
Time Interval
(hours)
Number of CGM-
Reference Pairs
Within
±15% /
±15mg/dL
Within
±20% /
±20mg/dL
Within
±30% /
±30mg/dL
Within
±40% /
±40mg/dL
Outside
±40% /
±40mg/dL
(0-2) 81 69.1 87.7 100.0 100.0 0.0
(2-4) 318 73.9 84.6 97.2 99.7 0.3
(4-6) 374 76.7 88.0 97.3 99.7 0.3
(6-8) 369 79.9 90.8 99.2 100.0 0.0
Overall Accuracy against YSI reference
Accuracy was measured by comparing the absolute relative dierence between the System and
reference YSI glucose values. The absolute relative dierence measures the level of disagreement
between the System and the reference value, but does not tell you whether the System glucose
value was, on average, higher or lower than the reference glucose value. The Mean Absolute Relative
Dierence gives an indication of the average percent disagreement between the CGM
and the reference. Table 3 shows the overall absolute dierence measure. Overall the Mean Absolute
Relative Dierence was 9.7% for the comparison with YSI reference. The Median Absolute Relative
Dierence shows that half of the time the System was within 7.7% of the YSI reference.
Table 3: Dierence Measures with YSI Reference
Number of
CGM-Reference Pairs
Median Absolute Relative
Dierence
Mean Absolute Relative
Dierence
5772 7.7% 9.7%
Agreement with BG Levels
Agreement between the System and capillary blood glucose values (BG) as measured by the Reader’s
built-in meter was characterized by using paired System CGM and BG value. The accuracy of CGM
versus BG value was assessed by calculating the percentage of System readings that were within 15%,
20%, 30% and 40% for BG values 80 mg/dL and above, and within 15 mg/dL, 20 mg/dL, 30 mg/dL
and 40 mg/dL for values below 80 mg/dL. The results are presented in Table 4 for BG values. Overall
84.3% of results were within ±20 mg/dL / 20% of BG values.
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