Accuracy - Abbott FreeStyle Libre 2 User Manual

manipulated per the study protocol to raise or lower glucose. This was done to assess performance
of the System over the range that the System measures glucose (40 – 400 mg/dL). 48 subjects were
analyzed during the beginning of the Sensor wear period (day 1 or 2), 50 subjects were analyzed
during the early middle period (day 7 or 8), 51 subjects were analyzed during the late middle period
(day 9 or 12), and 51 subjects were analyzed during the end period (day 13 or 14). All subjects tested
their blood glucose using fingerstick capillary samples at least four times during each day of the
study.

Accuracy

Accuracy of the System was measured by comparing paired System Glucose Measurement (CGM) and
YSI blood glucose values. The percentage of total System readings that were within 20 mg/dL for YSI
blood glucose values < 70 mg/dL or 20% of YSI for blood glucose values ≥ 70 mg/dL is displayed in
Table 1a. The Mean Absolute Relative Difference (MARD) gives an indication of the average percent
disagreement between the CGM and the reference. For example, in the Adult study, 92.4% of the
readings fell within ± 20 mg/dL of YSI blood glucose values < 70 mg/dL and within ± 20% of YSI
blood glucose values ≥ 70 mg/dL. The total number of data pairs considered in the analysis was
18,735. In the Adult study, the Mean Absolute Relative Difference was 9.2% for the comparison
with YSI reference. In the Pediatric study, the Mean Absolute Relative Difference was 9.7% for the
comparison with YSI reference.
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