System and methods for processing analyte sensor data

• US 7,986,986 B2
• Filed: 03/23/2010
• Issued: 07/26/2011
• Est. Priority Date: 08/01/2003
• Status: Expired due to Term

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Brauker, James, Goode, Paul V., Kamath, Apurv U., Carr-Brendel, Victoria E.
• Primary Examiner(s): Mallari; Patricia C
• Assistant Examiner(s): D'ANGELO, MICHAEL J
• Application Number:
  US12/730,108
• Publication Number:
  US 20100179405A1
• Time in Patent Office: 490 Days
• Field of Search: 600345-347, 600/365
• US Class Current: 600/347
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: A61B 5/1495 Calibrating or testing of in-vivo probes

Abstract

Systems and methods for processing sensor analyte data, including initiating calibration, updating calibration, evaluating clinical acceptability of reference and sensor analyte data, and evaluating the quality of sensor calibration. During initial calibration, the analyte sensor data is evaluated over a period of time to determine stability of the sensor. The sensor may be calibrated using a calibration set of one or more matched sensor and reference analyte data pairs. The calibration may be updated after evaluating the calibration set for best calibration based on inclusion criteria with newly received reference analyte data. Fail-safe mechanisms are provided based on clinical acceptability of reference and analyte data and quality of sensor calibration. Algorithms provide for optimized prospective and retrospective analysis of estimated blood analyte data from an analyte sensor.

Claims

1. A method for determining a stability of substantially continuous glucose sensor, the method comprising:

receiving reference data from a reference glucose monitor, including a reference data point;

receiving a data stream from a continuous glucose sensor, including one or more sensor data points;

pairing the reference data point with a substantially time-corresponding sensor data point of said one or more sensor data points, whereby a matched data pair is formed;

determining a sensitivity of the continuous glucose sensor based on the matched data pair;

determining, using electronic circuitry, a level of stability of the continuous glucose sensor, wherein the level of stability is based on a variability of the sensitivity over time; and

prohibiting display of real-time glucose information in response to the level of stability not meeting one or more predetermined criteria.

2. The method of claim 1, wherein the determining a level of stability further comprises comparing the one or more sensor data points.

3. The method of claim 2, wherein the comparing includes comparing the one or more sensor data points to a template.

4. The method of claim 1, wherein the determining a level of stability further comprises determining a baseline drift or offset.

5. The method of claim 1, wherein the determining a level of stability is performed over an initial instability time period.

6. The method of claim 5, wherein the determining a level of stability further comprises monitoring a frequency content of the sensor data stream over a predetermined amount of time.

7. The method of claim 5, wherein the initial instability time period is between about one minute and six weeks.

8. The method of claim 7, wherein the initial instability time period is between about one hour and one day.

9. The method of claim 1, wherein the determining the level of stability further comprises evaluating pH, oxygen, hypochlorite, interfering species, correlation of matched pairs, R value, baseline drift, baseline offset, and/or an amplitude of the data stream.

10. The method of claim 1, further comprising providing output in response to the level of stability meeting the one or more predetermined criteria, wherein the output is audible, visual, tactile, and/or a wireless transmission.

11. The method of claim 10, wherein the providing output comprises at least one of a numeric estimated glucose value, a directional trend of glucose concentration, and a graphical representation of an estimated glucose value.

12. The method of claim 10, wherein the providing output comprises sending the one or more sensor data points to an insulin pump in response to the level of stability meeting the one or more predetermined criteria.

13. The method of claim 1, wherein the reference glucose monitor comprises a blood glucose test.

14. The method of claim 1, wherein the receiving reference data from a reference glucose monitor comprises receiving an internal wired communication.

15. The method of claim 1, wherein the level of stability of the substantially continuous glucose sensor is further based on a determination of an amplitude of the sensitivity.

16. The method of claim 1, wherein the determining a level of stability of the substantially continuous glucose sensor further comprises determining a physiological stability of host tissue surrounding the continuous glucose sensor when subcutaneously implanted in a host.

17. The method of claim 1, further comprising implanting the continuous sensor in a host, wherein the determining a level of stability of the substantially continuous glucose sensor is further based on environmental information provided by the host.

18. The method of claim 1, further comprising repeating the receiving steps to receive additional reference data comprising one or more additional reference data points and additional sensor data comprising one or more additional sensor data points.

19. The method of claim 18, further comprising repeating the determining steps on one of the additional reference data point and a substantially time-corresponding sensor data point of the one or more additional sensor data points.

20. The method of claim 1, wherein the one or more sensor data points are time-lag compensated sensor data values.

21. The method of claim 20, wherein the substantially time-corresponding sensor data point is a time-lag compensated sensor data value.

22. The method of claim 1, further comprising converting at least a portion of the sensor data into calibrated sensor data using a conversion function and outputting the calibrated sensor data in response to the level of stability meeting the one or more predetermined criteria.

23. The method of claim 22, wherein the conversion function is based on the matched data pair.

24. The method of claim 22, wherein the conversion function is based on at least two matched data pairs including the matched data pair.

25. The method of claim 22, further comprising discarding a least concordant matched data pair from a plurality of matched data pairs when forming the conversion function.

26. The method of claim 1, further comprising displaying an indication of instability in response to the level of stability not meeting the one or more predetermined criteria.

27. The method of claim 1, further comprising displaying a status associated with the level of stability.

28. The method of claim 1, further comprising waiting a predetermined time period prior to determining the level of stability.

29. A system for determining a stability of continuous glucose sensor, comprising:

a reference input module configured to receive reference data from a reference glucose monitor, including a reference data point;

a sensor data module operatively connected to a continuous glucose sensor configured to receive a data stream from the continuous glucose sensor, including one or more sensor data points; and

electronic circuitry programmed to pair the reference data point with a substantially time-corresponding sensor data point of said one or more sensor data points to form a matched data pair, wherein the electronic circuitry is programmed to determine a sensitivity of the continuous glucose sensor based on the matched data pair., wherein the electronic circuitry is programmed to determine a level of stability of the continuous glucose sensor, wherein the level of stability is based on a variability of the sensitivity over time; and

wherein the electronic circuitry is programmed to prohibit display of real-time glucose information in response to the level of stability not meeting one or more predetermined criteria.

30. The system of claim 29, wherein the electronic circuitry is further programmed to determine the level of stability based on a comparison of the sensor data points.

31. The system of claim 29, wherein the electronic circuitry is further programmed to determine the level of stability based on a comparison of the sensor data points to a template.

32. The system of claim 29, wherein the electronic circuitry is further programmed to determine a level of stability by evaluating baseline drift and/or offset.

33. The system of claim 29, wherein the electronic circuitry is further programmed to determine a level of stability by monitoring a frequency content of the sensor data stream over a predetermined amount of time.

34. The system of claim 29, wherein the electronic circuitry is further programmed to evaluate pH, oxygen, hypochlorite, interfering species, correlation of matched pairs, R value, baseline drift, baseline offset, and/or an amplitude of the data stream.

35. The system of claim 29, wherein the electronic circuitry is programmed to provide output in response to the level of stability meeting the one or more predetermined criteria, wherein the output is audible, visual, tactile, and/or a wireless transmission.

36. The system of claim 35, wherein the output comprises at least one of a numeric estimated glucose value, a directional trend of glucose concentration, and/or a graphical representation of an estimated glucose value.

37. The system of claim 35, wherein the electronic circuitry is programmed to send the output to an insulin pump in response to the level of stability meeting the one or more predetermined criteria.

38. The system of claim 29, wherein the reference glucose monitor comprises a blood glucose test.

39. The system of claim 29, wherein the reference glucose monitor is physically connected to the system, and wherein the reference input module is configured to receive the reference data as a communication from the reference glucose monitor.

40. The system of claim 29, wherein the electronic circuitry is further programmed to determine a level of stability by evaluating an amplitude of the sensitivity associated with the continuous glucose sensor.

41. The system of claim 29, wherein the electronic circuitry is further programmed to determine a level of stability by evaluating a physiological stability of host tissue surrounding the continuous glucose sensor when subcutaneously implanted in a host.

42. The system of claim 29, wherein the continuous glucose sensor is configured for implantation in a host, and wherein the processor module is configured to determine a level of stability by obtaining environmental information from the host.

43. The system of claim 29, wherein the electronic circuitry is configured to repeat the programming on additional reference data comprising one or more additional reference data points and additional sensor data comprising one or more additional sensor data points.

44. The system of claim 29, wherein the one or more sensor data points are time-lag compensated sensor data values.

45. The system of claim 44, wherein the substantially time-corresponding sensor data point is a time-lag compensated sensor data value.

46. The system of claim 29, wherein the electronic circuitry is programmed to convert at least a portion of the sensor data into calibrated sensor data using a conversion function, and wherein the electronic circuitry is further programmed to output the calibrated sensor data in response to the level of stability meeting the one or more predetermined criteria.

47. The system of claim 46, wherein the conversion function is based the matched data pair.

48. The system of claim 46, wherein the conversion function is based on at least two matched data pairs including the matched data pair.

49. The system of claim 46, wherein the electronic circuitry is programmed to discard a least concordant matched data pair from a plurality of matched data pairs when forming the conversion function.

50. The system of claim 29, wherein the electronic circuitry is further configured to display an indication of instability in response to the level of stability not meeting the one or more predetermined criteria.

51. The system of claim 29, wherein the electronic circuitry is further configured to display a status associated with the level of stability.

52. The system of claim 29, wherein the electronic circuitry is further configured to wait a predetermined time period prior to determining the level of stability.

53. The system of claim 29, wherein the electronic circuitry is programmed to determine the stability during an initial instability time period.

54. The system of claim 53, wherein the initial instability time period is between about one minute and six weeks.

55. The system of claim 53, wherein the initial instability time period is between about one hour and one day.