The accuracy benefit of multiple amperometric glucose sensors in people with type 1 diabetes

Abstract

Objective: To improve glucose sensor accuracy in subjects with type 1 diabetes by using multiple sensors and to assess whether the benefit of redundancy is affected by intersensor distance.

Research design and methods: Nineteen adults with type 1 diabetes wore four Dexcom SEVEN PLUS subcutaneous glucose sensors during two 9-h studies. One pair of sensors was worn on each side of the abdomen, with each sensor pair placed at a predetermined distance apart and 20 cm away from the opposite pair. Arterialized venous blood glucose levels were measured every 15 min, and sensor glucose values were recorded every 5 min. Sensors were calibrated once at the beginning of the study.

Results: The use of four sensors significantly reduced very large errors compared with one sensor (0.4 vs. 2.6% of errors ≥50% from reference glucose, P < 0.001) and also improved overall accuracy (mean absolute relative difference, 11.6 vs. 14.8%, P < 0.001). Using only two sensors also significantly improved very large errors and accuracy. Intersensor distance did not affect the function of sensor pairs.

Conclusions: Sensor accuracy is significantly improved with the use of multiple sensors compared with the use of a single sensor. The benefit of redundancy is present even when sensors are positioned very closely together (7 mm). These findings are relevant to the design of an artificial pancreas device.

Figure 1

Summary of very large errors, defined as sensor values ≥50% away from the reference venous blood glucose. Each study visit is depicted separately. The percentages of very large errors when the four sensors are averaged are shown by black open circles, and values for each single sensor are shown by gray Xs. Note the significant decrease in very large errors with the use of four sensors.

Figure 2

An example of two X-ray images taken during one of the studies. Note that the sensors are positioned very closely on the right side of the subject’s abdomen and are much farther apart on the left side.

Figure 3

Graph of intersensor distance versus the difference between the signed differences of each sensor in a pair compared with the reference blood glucose. If close proximity caused sensor entrainment, one would expect the value on the y axis to be low. Note that there is no significant correlation between intersensor distance and the difference between the signed differences of each sensor in a pair.