Accuracy of the 5-day FreeStyle Navigator Continuous Glucose Monitoring System: comparison with frequent laboratory reference measurements.
OBJECTIVE
The purpose of this study was to compare the accuracy of measurements of glucose in interstitial fluid made with the FreeStyle Navigator Continuous Glucose Monitoring System with Yellow Springs Instrument laboratory reference measurements of venous blood glucose.


METHODS
Fifty-eight subjects with type 1 diabetes, aged 18-64 years, were enrolled in a multicenter, prospective, single-arm study. Each subject wore two sensors simultaneously, which were calibrated with capillary fingerstick measurements at 10, 12, 24, and 72 h after insertion. Measurements from the FreeStyle Navigator system were collected at 1-min intervals and compared with venous measurements taken once every 15 min for 50 h over the 5-day period of sensor wear in an in-patient clinical research center. Periods of high rates of change of glucose were induced by insulin and glucose challenges.


RESULTS
Comparison of the FreeStyle Navigator measurements with the laboratory reference method (n = 20,362) gave mean and median absolute relative differences (ARDs) of 12.8 and 9.3%, respectively. The percentage in the clinically accurate Clarke error grid A zone was 81.7% and that in the in the benign error B zone was 16.7%. During low rates of change (< +/-1 mg x dl(-1) x min(-1)), the percentage in the A zone was higher (84.9%) and the mean and median ARDs were lower (11.7 and 8.5%, respectively).


CONCLUSIONS
Measurements with the FreeStyle Navigator system were found to be consistent and accurate compared with venous measurements made using a laboratory reference method over 5 days of sensor wear (82.5% in the A zone on day 1 and 80.9% on day 5).
Weinstein
Richard L
RL
Diablo Clinical Research, 2255 Ygnacio Valley Rd., Suite M, Walnut Creek, CA 94598, USA. rweinstein@diabloclinical.com
Schwartz
Sherwyn L
SL
Brazg
Ronald L
RL
Bugler
Jolyon R
JR
Peyser
Thomas A
TA
McGarraugh
Geoffrey V
GV
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D019411:Clinical Laboratory Techniques; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D005260:Female; D005947:Glucose / Q000032:analysis*; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D018670:Monitoring, Ambulatory / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D001786:Blood Glucose; D005947:Glucose