Analyte sensor with lag compensation
In particular embodiments, methods, devices and systems including calibrating analyte data associated with a monitored analyte level received from an analyte sensor based on a reference measurement, determining a lag time constant associated with the calibrated analyte data, and performing lag correction of the calibrated analyte data based on the determined time lag constant are disclosed.
1. A system for monitoring an analyte using an in vivo sensor, the system comprising:
an analyte sensor configured for positioning in contact with bodily fluid under a skin surface;
a display;
a processor; and
a memory operatively coupled to the processor, the memory storing instructions which, when executed by the processor, causes the processor to:
obtain a plurality of analyte sensor data associated with a monitored analyte level from the analyte sensor;
obtain one or more measured reference analyte data;
generate a first subset of data pairs, each pair of the first subset comprising a reference analyte data and one or more of the plurality of analyte sensor data;
determine a sensor sensitivity for the analyte sensor using the first subset of data pairs;
obtain a plurality of calibrated sensor data by calibrating the plurality of analyte sensor data using the sensor sensitivity;
generate a second subset of data pairs, each pair of the second subset comprising a reference analyte data and one or more of the plurality of calibrated sensor data;
estimate a time lag constant based on the second subset of data pairs;
estimate a lag corrected analyte level for the analyte sensor based on the estimated time lag constant; and
output data for the lad corrected analyte level on the display as part of a graphical user interface.
2. The system of claim 1 , further comprising instructions which, when executed by the processor, cause the processor to generate the first subset by including only pairs associated with analyte sensor data having an absolute rate of change that is below a predetermined threshold.
3. The system of claim 2 , wherein the predetermined threshold is about 6% change in an analyte estimate per minute.
4. The system of claim 1 , further comprising instructions which, when executed by the processor, cause the processor to obtain a plurality of time lag constants, to obtain a combined time lag constant based on the plurality of time lag constants and the estimated time lag constant, and to calibrate continuous glucose data from the analyte sensor using the combined time lag constant.
5. The system of claim 1 , further comprising instructions which, when executed by the processor, cause the processor to determine the sensor sensitivity using the first subset of data pairs by, for each data pair of the first subset, forming a ratio for the reference data and the one or more of the plurality of analyte sensor data associated with the data pair.
6. The system of claim 1 , further comprising instructions which, when executed by the processor, cause the processor to generate the second subset by at least including only pairs associated with calibrated analyte sensor data having an absolute rate of change exceeding a predetermined threshold.
7. The system of claim 1 , further comprising instructions which, when executed by the processor, cause the processor to generate the first subset by at least excluding pairs associated with a reference below a predetermined analyte level threshold.
8. The system of claim 1 , further comprising instructions which, when executed by the processor, cause the processor to modify the plurality of calibrated sensor data based on the estimated time lag constant.
9. An apparatus for calibrating an analyte sensor, comprising:
a communication component configured to receive signals associated with a monitored analyte level from the analyte sensor in contact with bodily fluid under a skin surface;
a display;
one or more processors operatively coupled to the communication component and configured to process the received signals; and
a memory for storing instructions which, when executed by the one or more processors, causes the one or more processors to:
obtain a plurality of analyte sensor data associated with the monitored analyte level from the analyte sensor in contact with the bodily fluid;
obtain one or more measured reference analyte data;
generate a first subset of data pairs, each pair of the first subset comprising a reference analyte data and one or more of the plurality of analyte sensor data;
determine a sensor sensitivity for the analyte sensor using the first subset of data pairs;
obtain a plurality of calibrated sensor data by calibrating the plurality of analyte sensor data using the sensor sensitivity;
generate a second subset of data pairs, each pair of the second subset comprising a reference analyte data and one or more of the plurality of calibrated sensor data;
estimate a time lag constant based on the second subset of data pairs;
estimate a lag corrected analyte level for the analyte sensor based on the estimated time lag constant; and
output data for the lag corrected analyte level on the display as part of a graphical user interface.
10. The apparatus of claim 9 , further comprising instructions which, when executed by the one or more processors, cause the one or more processors to generate the first subset by including only pairs associated with analyte sensor data having an absolute rate of change that is below a predetermined threshold.
11. The apparatus of claim 10 , wherein the predetermined threshold is about 6% change in an analyte estimate per minute.
12. The apparatus of claim 9 , further comprising instructions which, when executed by the one or more processors, cause the one or more processors to obtain a plurality of time lag constants, to obtain a combined time lag constant based on the plurality of time lag constants and the estimated time lag constant, and to calibrate continuous glucose data from the analyte sensor using the combined time lag constant.
13. The apparatus of claim 9 , further comprising instructions which, when executed by the one or more processors, cause the one or more processors to determine the sensor sensitivity using the first subset of data pairs by, for each data pair of the first subset, forming a ratio for the reference data and the one or more of the plurality of analyte sensor data associated with the data pair.
14. The apparatus of claim 9 , further comprising instructions which, when executed by the one or more processors, cause the one or more processors to generate the second subset by at least including only pairs associated with calibrated analyte sensor data having an absolute rate of change exceeding a predetermined threshold.
15. The apparatus of claim 9 , further comprising instructions which, when executed by the one or more processors, cause the one or more processors to generate the first subset by at least excluding pairs associated with a reference below a predetermined analyte level threshold.
16. The apparatus of claim 9 , further comprising instructions which, when executed by the one or more processors, cause the one or more processors to modify the plurality of calibrated sensor data based on the estimated time lag constant.