Abbott Freestyle PRT03831-xxx - Manual (Page 172)

18 Appendix B: Specifications
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Measuring Glucose in Interstitial Fluid
FreeStyle Navigator system measures glucose in the interstitial fluid (ISF) by means of a sensor that is
inserted about 5 mm under the skin. Interstitial fluid is the fluid between the body’s cells. Physiologic
differences between the interstitial fluid and capillary blood may result in differences in glucose
measurements. Differences in glucose measurement between interstitial fluid and your finger may be
observed during times of rapid change in blood glucose, e.g. after eating, dosing insulin, or exercising.
Movement of nutrients, oxygen and glucose from the blood into the cells happen across the ISF.
Therefore, if the glucose in the bloodstream rises (e.g. during meals), that rise is not seen in the ISF
until later. Similarly, if glucose levels in the ISF drop (for example during exercise, the cells consume
glucose rapidly) that drop is not seen in the bloodstream until later.
On average, glucose levels in the ISF lag the glucose levels in capillary blood by 14 minutes. This is a
physiological phenomenon that can vary from one person to another.
Precision
Data from two sensors inserted at different insertion sites was used to calculate the between sensor
reproducibility. Based on 312953 pairs of data sets, the average between sensor reproducibility was 10%.
Sensor Insertion, Calibration and Sensor Wear
Home Use Study: Sensor insertion, calibration and sensor wear were evaluated in a Home Use Study
where 137 participants used the product on their own in a home environment. The participants wore
8 sensors during the study period of 40 days. They wore the sensors either on the arm or abdomen.
During the first 20 days of the study, continuous glucose results were not visible to the participants.
During the following 20 days, participants had access to the glucose measurements. In addition to
required calibration tests, the participants performed 4 finger stick measurements a day using the
built-in FreeStyle meter. The following information is based on the findings from this study.
When used as directed, 96.8% of the total sensor insertions were successful. 92.6% of the sensors were
calibrated successfully and began producing glucose results within 12 hours after sensor insertion. The
median time for a successful first calibration was 10.1 hours. The median duration of wear of
calibrated sensors was 120 hours. 83% of sensor wears lasted at least 108.3 hours. The median wear
time for sensors inserted on the arm was 0.4 hours longer than for sensors inserted on the abdomen.
Skin Interaction
Based on the examination of 124 study participants at a 21-day follow up, the following incidence of
skin issues were observed in 304 site exams.
Moderate to severe itching – 1.6% of the time
Moderate bruising – 0.3% of the time
Moderate erythema – 1.0% of the time
Moderate pain – 0.3% of the time
Rate of mild incidences for any individual category of skin issues above including edema, rash,
induration, bleeding and others was less than 5%.
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162 Section 18
Appendix B: Specifications