Automatic analyte sensor calibration and error detection
Systems and methods are provided that address the need to frequently calibrate analyte sensors, according to implementation. In more detail, systems and methods provide a preconnected analyte sensor system that physically combines an analyte sensor to measurement electronics during the manufacturing phase of the sensor and in some cases in subsequent life phases of the sensor, so as to allow an improved recognition of sensor environment over time to improve subsequent calibration of the sensor.
1. A method for self-calibration of an analyte sensor system that includes a glucose sensor operatively coupled to sensor electronics, the method comprising:
applying a bias voltage with the sensor electronics to generate sensor data, the analyte sensor system having an initial characteristic metric determined at a first time;
using the sensor electronics at a second time subsequent to the first time to determine a change to the initial characteristic metric of the analyte sensor system based at least in part on a humidity associated with the glucose sensor while the glucose sensor is within a sterile package;
storing a relationship between impedance and humidity in a memory associated with the sensor electronics;
monitoring the humidity associated with the glucose sensor while the glucose sensor is within the sterile package, wherein the humidity is monitored between the first time and second time, the monitoring comprising:
applying a stimulus signal to at least one of a first electrode or a second electrode of the glucose sensor while the glucose sensor is within the sterile package;
measuring a signal response to the stimulus signal applied while the glucose sensor is within the sterile package;
calculating the impedance based on the signal response to the stimulus signal applied while the glucose sensor is within the sterile package;
determining a value for the humidity within the sterile package based on the calculated impedance and the relationship between impedance and humidity stored in the memory; and
determining, based at least on the calculated impedance, a duration of exposure of the glucose sensor to the value for the humidity while the glucose sensor is within the sterile package;
using the sensor electronics to automatically calibrate, without user intervention, the analyte sensor system based at least in part on the value for the humidity and the duration of exposure of the glucose sensor to the value for the humidity while the glucose sensor is within the sterile package, the automatically calibrating comprising determining an updated calibration factor; and
automatically applying the updated calibration factor, without user intervention, to a signal generated by the first electrode and the second electrode to determine a glucose concentration during use of the glucose sensor, wherein the glucose sensor is used after removal of the glucose sensor from the sterile package and after at least the stimulus signal is applied to at least one of the first electrode or the second electrode of the glucose sensor while the glucose sensor is within the sterile package.
2. The method of claim 1 , wherein the first time is subsequent to sensor fabrication and the second time is prior to sensor use in vivo or subsequent to initiation of sensor use in vivo.
3. The method of claim 1 wherein the initial characteristic metric is determined by initially calibrating the glucose sensor while the glucose sensor is operatively coupled to a sensor interface that is configured to provide an electrical communication interface between the glucose sensor and each of a manufacturing station and the sensor electronics.
4. The method of claim 3 wherein the initial characteristic metric is further determined by measuring an in vitro sensitivity characteristics of the glucose sensor.
5. The method of claim 1 , wherein the initial characteristic metric is determined by initially calibrating the glucose sensor while the glucose sensor is operatively coupled to one or more components of the sensor electronics.
6. The method of claim 5 , wherein the one or more components includes a potentiostat.
7. The method of claim 5 , wherein the glucose sensor is continuously operatively coupled to the one or more components of the sensor electronics between the first time and the second time without interruption.
8. The method of claim 7 , wherein the first time is during a first portion of a manufacturing life phase of the glucose sensor and the second time is during a second portion of the manufacturing life phase that is subsequent to packaging the glucose sensor and the one or more components of the sensor electronics in the sterile package.
9. The method of claim 7 , wherein the first time is during a manufacturing life phase of the glucose sensor and the second time is during sensor use in vivo.
10. The method of claim 1 , wherein monitoring the humidity includes measuring the humidity using a humidity sensor included in the sterile package, the humidity sensor being operatively couplable to the sensor electronics.
11. The method of claim 1 , wherein determining the change to the initial characteristic metric includes determining the change through use of a mathematical function.
12. The method of claim 1 , further comprising selecting a user to receive the analyte sensor system based at least in part on one or more glucose sensor characteristics.
13. The method of claim 12 , wherein the one or more glucose sensor characteristics includes an updated characteristic metric that is derived from the determined change to the initial characteristic metric.
14. The method of claim 1 , wherein monitoring the humidity of the glucose sensor while in the sterile package includes determining if the humidity exceeds or falls below one or more threshold values.
15. The method of claim 1 , wherein the initial characteristic metric is reflective of an initial sensor sensitivity or baseline value, or is reflective of an initial sensor sensitivity profile.
16. The method of claim 1 , further comprising deriving an initial calibration factor from the initial characteristic metric.
17. The method of claim 1 , wherein the change to the initial characteristic metric is indicative of sensor failure.
18. The method of claim 1 , wherein the determining the change to the initial characteristic metric of the analyte sensor system is based at least in part on one or more manufacturing parameters.
19. The method of claim 18 , wherein the one or more manufacturing parameters are obtained from an identifier of the glucose sensor, and wherein the identifier is affixed to the glucose sensor, or is obtained by wirelessly interrogating the glucose sensor, or is associated with a manufacturing lot from which the glucose sensor was obtained.
20. The method of claim 18 , wherein the one or more manufacturing parameters are measured prior to the second time and prior to the first time.
21. The method of claim 1 , wherein the sterile package is not worn by a user.
22. The method of claim 1 , wherein the glucose sensor is only located in the sterile package during shipping and storage of the glucose sensor.