Accuracy of the 5-Day FreeStyle Navigator Continuous Glucose Monitoring System

Accuracy of the 5-Day FreeStyle Navigator Continuous Glucose Monitoring System Comparison with frequent laboratory reference measurements Richard L. Weinstein , MD 1 , Sherwyn L. Schwartz , MD 2 , Ronald L. Brazg , MD 3 , Jolyon R. Bugler , MS 4 , Thomas A. Peyser , PHD 4 and Geoffrey V. McGarraugh , MS 4 1 Diablo Clinical Research, Walnut Creek, California 2 Diabetes and Glandular Disease Clinic, San Antonio, Texas 3 Rainier Clinical Research Center, Renton, Washington 4 Abbott Diabetes Care, Alameda, California Address correspondence and reprint requests to Richard L. Weinstein, MD, Diablo Clinical Research, 2255 Ygnacio Valley Rd., Suite M, Walnut Creek, CA 94598. E-mail: rweinstein{at}diabloclinical.com Abstract 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. RESEARCH DESIGN AND 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 (