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The Bigfoot Unity
™
Diabetes Management System User Guide | Appendix C
Accuracy
Accuracy of the Libre 2 Sensor was measured by comparing paired
continuous glucose monitoring (CGM) and YSI blood glucose values.
The percentage of total Libre 2 Sensor 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 9.8% for the comparison with YSI reference.
Table 1a: Overall Accuracy to YSI
Subject Group
Number
of CGM-
Reference
Pairs
Number
of
Subjects
Percent Within
±20% /
±20 mg/dL
Percent Within
±20% /
±20 mg/dL
on Day 1
Percent Within
±20% /
±20 mg/dL in
first 12 hours
MARD
(%)
Adults
18735
144
92.4
87.5
81.7
9.2
Pediatrics
(age 12 – 17)
5086
86
91.5
83.3
80.1
9.8
The accuracy of different CGM glucose ranges versus YSI reference
was assessed by calculating the percentage of Libre 2 Sensor readings
that were within 15%, 20%, and 40% for reference values ≥ 70 mg/dL,
and within 15 mg/dL, 20 mg/dL, and 40 mg/dL for values < 70 mg/dL.
For blood glucose values < 70 mg/dL, the difference in mg/dL between
the CGM and YSI blood glucose values was calculated. For values
≥ 70 mg/dL, the relative difference (%) to the YSI blood glucose values
was calculated. The results categorized within CGM glucose ranges
are presented in
Tables 1b and 1c
. The results categorized within YSI
glucose ranges are presented in
Tables 1d and 1e
.
the Libre 2 Sensor measures glucose (40 – 400 mg/dL). The Pediatric
results below apply to the 87 pediatrics in the FreeStyle Libre 2 study
who were aged 12 – 17 years old; 35 subjects were analyzed during
the beginning of the Sensor wear period (day 1 or 2), 35 subjects were
analyzed during the early middle period (day 7 or 8), 34 subjects were
analyzed during the late middle period (day 9 or 12), and 42 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.
