Continuous glucose monitoring: reliable measurements for up to 4 days with the SCGM1 system

Abstract

Continuous glucose monitoring allows patients with diabetes to check their metabolic status throughout the day, including rarely monitored time periods, such as postprandial and nocturnal periods. The performance of a prototype of the novel SCGM1 System (Roche Diagnostics GmbH, Mannheim, Germany) employing the microdialysis technique was evaluated. Forty-two patients with type 1 diabetes participated in the study [29 males/13 females, age 34 +/- 9 years, duration of diabetes 16 +/- 11 years, glycated hemoglobin 7.7 +/- 1.2% (mean +/- SD)]. Forty-seven experiments were performed at four different investigational sites. A microdialysis catheter was inserted into the subcutaneous tissue of the patient's abdominal wall. Glucose was extracted from the interstitial fluid, and glucose levels were determined and stored by the SCGM1 System continuously for the duration of the experiment. Capillary blood glucose was measured frequently (at least 10 times per day) and used for linear retrospective calibration. The patients were instructed to maintain their normal diet and insulin therapy. Thirty experiments (mean duration 103 +/- 18 h) were analyzed in detail. The mean deviation of the calibrated glucose sensor values from the capillary blood glucose values (expressed as percent predicted error sum of squares) was <12.5% in 25 and <20% for all of the 30 experiments analyzed. The percent median absolute difference between the calibrated values and the reference values was <10% in 28 experiments, with a median of 5.8% for all 30 experiments. The error grid analysis of all 30 experiments showed that 99.5% of all 1,195 pairs' values were in zones A and B with only 0.2% in zone C and 0.3% in zone D. Thus the microdialysis technique employed by the SCGM1 System allows precise and accurate continuous glucose monitoring over prolonged periods of time. It appears also that effective monitoring of acute metabolic deteriorations is possible.