Accuracy of the SEVEN continuous glucose monitoring system: comparison with frequently sampled venous glucose measurements.

BACKGROUND: The purpose of this study was to compare the accuracy of measurements obtained from the DexCom SEVEN system with Yellow Springs Instrument (YSI) laboratory measurements of venous blood glucose.

METHODS: Seventy-two subjects with insulin-requiring diabetes, aged 18-71, were enrolled in a multicenter, prospective single-arm study. All participants wore the SEVEN continuous glucose monitoring (CGM) system for one, 7-day wear period. Calibration with capillary finger stick measurements was performed 2 hours after sensor insertion and once every 12 hours thereafter. A subset of subjects (28) wore two systems simultaneously to assess precision. All subjects participated in one, 10-hour in-clinic session on day 1, 4, or 7 of the study to compare CGM measurements against a laboratory method (YSI analyzer) using venous measurements taken once every 20 minutes. Carbohydrate consumption and insulin dosing were adjusted in order to obtain a broad range of glucose values.

RESULTS: Comparison of CGM measurements with the laboratory reference method (n = 2318) gave mean and median absolute relative differences (ARDs) of 16.7 and 13.2%, respectively. The percentage was 70.4% in the clinically accurate Clarke error grid A zone and 27.5% in the benign error B zone. Performance of the SEVEN system was consistent over time with mean and median ARD lowest on day 7 as compared to YSI (13.3 and 10.2%, respectively). Average sensor time lag was 5 minutes.

CONCLUSIONS: Measurements of the DexCom SEVEN system were found to be consistent and accurate compared with venous measurements made using a laboratory reference method over 7 days of wear.