ADVANCED ANALYTE SENSOR CALIBRATION AND ERROR DETECTION

• US 20120265036A1
• Filed: 04/13/2012
• Published: 10/18/2012
• Est. Priority Date: 04/15/2011
• Status: Abandoned Application

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Estes, Michael J., Simpson, Peter C., Kamath, Apurv Ullas
• Application Number:
  US13/446,866
• Publication Number:
  US 20120265036A1
• Time in Patent Office: Days
• US Class Current: 600/309
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2560/0276 Determining malfunction
• CPC Class Codes: A61B 2560/04 Constructional details of apparatus
• CPC Class Codes: A61B 2562/085 combined with means for recording calibration data
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14503 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors A61B5/1459, A61B5/1464, A61B5/1473, A61B5/1482, A61B5/14865 take precedence
• CPC Class Codes: A61B 5/1451 for interstitial fluid
• CPC Class Codes: A61B 5/14517 for sweat
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: A61B 5/14735 comprising an immobilised reagent
• CPC Class Codes: A61B 5/1486 using enzyme electrodes, e.g. with immobilised oxidase
• 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
• CPC Class Codes: A61B 5/15003 for venous or arterial blood
• CPC Class Codes: A61B 5/150992 Blood sampling from a fluid line external to a patient, such as a catheter line, combined with an infusion line; blood sampling from indwelling needle sets, e.g. sealable ports, luer couplings, valves tubing connectors and couplings A61M39/00
• CPC Class Codes: A61B 5/155 : Devices specially adapted for continuous or multiple sampling, e.g. at predetermined intervals devices loaded with multiple lancets simultaneously A61B5/15146
• CPC Class Codes: A61B 5/157 : Devices characterised by integrated means for measuring characteristics of blood
• CPC Class Codes: A61B 5/412 : Detecting or monitoring sepsis
• CPC Class Codes: A61B 5/4839 : combined with drug delivery
• CPC Class Codes: A61B 5/6848 : Needles
• CPC Class Codes: A61B 5/6849 : in combination with a needle set
• CPC Class Codes: A61B 5/6866 : Extracorporeal blood circuits, e.g. dialysis circuits
• CPC Class Codes: A61B 5/7257 : using Fourier transforms
• CPC Class Codes: A61B 5/7267 : involving training the classification device
• CPC Class Codes: A61B 5/7275 : Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 5/743 : Displaying an image simultaneously with additional graphical information, e.g. symbols, charts, function plots
• CPC Class Codes: A61M 2005/14296 : Pharmacokinetic models
• CPC Class Codes: A61M 2230/201 : Glucose concentration
• CPC Class Codes: A61M 5/14 : Infusion devices, e.g. infusing by gravity; Blood infusion; Accessories therefor
• CPC Class Codes: A61M 5/16804 : Flow controllers
• CPC Class Codes: A61M 5/1723 : using feedback of body parameters, e.g. blood-sugar, pressure measurement of body parameters A61B5/00
• CPC Class Codes: C12Q 1/001 : Enzyme electrodes
• CPC Class Codes: C12Q 1/006 : for glucose
• CPC Class Codes: G01D 18/00 : Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G01N 27/026 : Dielectric impedance spectroscopy electrochemical impedance spectroscopy for measuring corrosion G01N17/02
• CPC Class Codes: G01N 27/3274 : Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771
• CPC Class Codes: G01N 33/49 : Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80
• CPC Class Codes: G16H 10/40 : for data related to laboratory analysis, e.g. patient specimen analysis
• CPC Class Codes: G16H 20/17 : delivered via infusion or injection
• CPC Class Codes: G16H 40/40 : for the management of medical equipment or devices, e.g. scheduling maintenance or upgrades
• CPC Class Codes: G16H 40/63 : for local operation
• CPC Class Codes: H05K 999/00 : dummy group
• CPC Class Codes: H05K 999/99 : dummy group
• CPC Class Codes: Y02A 90/10 : Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

Systems and methods for processing sensor data and self-calibration are provided. In some embodiments, systems and methods are provided which are capable of calibrating a continuous analyte sensor based on an initial sensitivity, and then continuously performing self-calibration without using, or with reduced use of, reference measurements. In certain embodiments, a sensitivity of the analyte sensor is determined by applying an estimative algorithm that is a function of certain parameters. Also described herein are systems and methods for determining a property of an analyte sensor using a stimulus signal. The sensor property can be used to compensate sensor data for sensitivity drift, or determine another property associated with the sensor, such as temperature, sensor membrane damage, moisture ingress in sensor electronics, and scaling factors.

Claims

1. A method for calibrating sensor data generated by a continuous analyte sensor, comprising:

generating sensor data using a continuous analyte sensor;

iteratively determining, with an electronic device, a sensitivity value of the continuous analyte sensor as a function of time by applying a priori information comprising sensor sensitivity information; and

calibrating the sensor data based at least in part on the determined sensitivity value.

2. The method of claim 1, wherein calibrating the sensor data is performed iteratively throughout a substantially entire sensor session.

3. The method of claim 1, wherein iteratively determining a sensitivity value is performed at regular intervals or performed at irregular intervals, as determined by the a priori information.

4. The method of claim 1, wherein iteratively determining a sensitivity value is performed throughout a substantially entire sensor session.

5. The method of claim 1, wherein determining a sensitivity value is performed in substantially real time.

6. The method of claim 1, wherein the a priori information is associated with at least one predetermined sensitivity value that is associated with a predetermined time after start of a sensor session.

7. The method of claim 6, wherein the at least one predetermined sensitivity value is associated with a correlation between a sensitivity determined from in vitro analyte concentration measurements and a sensitivity determined from in vivo analyte concentration measurements at the predetermined time.

8. The method of claim 1, wherein the a priori information is associated with a predetermined sensitivity function that uses time as input.

9. The method of claim 8, wherein time corresponds to time after start of a sensor session.

10. The method of claim 8, wherein time corresponds to at least one of time of manufacture or time since manufacture.

11. The method of claim 1, wherein the sensitivity value of the continuous analyte sensor is also a function of at least one other parameter.

12. The method of claim 11, wherein the at least one other parameter is selected from the group consisting of:

temperature, pH, level or duration of hydration, curing condition, an analyte concentration of a fluid surrounding the continuous analyte sensor during startup of the sensor, and combinations thereof.

13. The method of claim 1, wherein calibrating the sensor data is performed without using reference blood glucose data.

14. The method of claim 1, wherein the electronic device is configured to provide a level of accuracy corresponding to a mean absolute relative difference of no more than about 10% over a sensor session of at least about 3 days, and wherein reference measurements associated with calculation of the mean absolute relative difference are determined by analysis of blood.

15. The method of claim 14, wherein the sensor session is at least about 4 days.

16. The method of claim 14, wherein the sensor session is at least about 5 days.

17. The method of claim 14, wherein the sensor session is at least about 6 days.

18. The method of claim 14, wherein the sensor session is at least about 7 days.

19. The method of claim 14, wherein the sensor session is at least about 10 days.

20. The method of claim 14, wherein the mean absolute relative difference is no more than about 7% over the sensor session.

21. The method of claim 14, wherein the mean absolute relative difference is no more than about 5% over the sensor session.

22. The method of claim 14, wherein the mean absolute relative difference is no more than about 3% over the sensor session.

23. The method of claim 1, wherein the a priori information is associated with a calibration code.

24. The method of claim 1, wherein the a priori sensitivity information is stored in the sensor electronics prior to use of the sensor.

25. A method for calibrating sensor data generated by a continuous analyte sensor, the method comprising:

generating sensor data using a continuous analyte sensor;

determining, with an electronic device, a plurality of different sensitivity values of the continuous analyte sensor as a function of time and of sensitivity information associated with a priori information; and

calibrating the sensor data based at least in part on at least one of the plurality of different sensitivity values.

26. The method of claim 25, wherein calibrating the continuous analyte sensor is performed iteratively throughout a substantially entire sensor session.

27. The method of claim 25, wherein the plurality of different sensitivity values are stored in a lookup table in computer memory.

28. The method of claim 25, wherein determining a plurality of different sensitivity values is performed once throughout a substantially entire sensor session.

29. The method of claim 25, wherein the a priori information is associated with at least one predetermined sensitivity value that is associated with a predetermined time after start of a sensor session.

31. The method of claim 25, wherein the a priori information is associated with a predetermined sensitivity function that uses time as input.

32. The method of claim 25, wherein time corresponds to time after start of a sensor session.

33. The method of claim 25, wherein time corresponds to time of manufacture or time since manufacture.

34. The method of claim 25, wherein the plurality of sensitivity values are also a function of at least one parameter other than time.

35. The method of claim 25, wherein the at least one other parameter is selected from the group consisting of:

temperature, pH, level or duration of hydration, curing condition, an analyte concentration of a fluid surrounding the continuous analyte sensor during startup of the sensor, and combinations thereof.

36. The method of claim 25, wherein calibrating the continuous analyte sensor is performed without using reference blood glucose data.

37. The method of claim 25, wherein the electronic device is configured to provide a level of accuracy corresponding to a mean absolute relative difference of no more than about 10% over a sensor session of at least about 3 days;

and wherein reference measurements associated with calculation of the mean absolute relative difference are determined by analysis of blood.

38. The method of claim 37, wherein the sensor session is at least about 4 days.

39. The method of claim 37, wherein the sensor session is at least about 5 days.

40. The method of claim 37, wherein the sensor session is at least about 6 days.

41. The method of claim 37, wherein the sensor session is at least about 7 days.

42. The method of claim 37, wherein the sensor session is at least about 10 days.

43. The method of claim 37, wherein the mean absolute relative difference is no more than about 7% over the sensor session.

44. The method of claim 37, wherein the mean absolute relative difference is no more than about 5% over the sensor session.

45. The method of claim 37, wherein the mean absolute relative difference is no more than about 3% over the sensor session.

46. The method of claim 37, wherein the a priori information is associated with a calibration code.

30. The method of 29, wherein the at least one predetermined sensitivity value is associated with a correlation between a sensitivity determined from in vitro analyte concentration measurements and a sensitivity determined from in vivo analyte concentration measurements at the predetermined time.

47. A method for processing data from a continuous analyte sensor, the method comprising:

receiving, with an electronic device, sensor data from a continuous analyte sensor, the sensor data comprising at least one sensor data point;

iteratively determining a sensitivity value of the continuous analyte sensor as a function of time and of an at least one predetermined sensitivity value associated with a predetermined time after start of a sensor session;

forming a conversion function based at least in part on the sensitivity value; and

determining an analyte output value by applying the conversion function to the at least one sensor data point.

48. The method of claim 47, wherein iteratively determining a sensitivity of the continuous analyte sensor is performed continuously.

49. The method of claim 47, wherein iteratively determining a sensitivity is performed in substantially real time.

50. The method of claim 47, wherein the at least one predetermined sensitivity value is set at a manufacturing facility for the continuous analyte sensor.

51. The method of claim 47, further comprising:

receiving at least one calibration code; and

applying the at least one calibration code to the electronic device at a predetermined time after start of the sensor session.

52. The method of claim 51, wherein iteratively determining a sensitivity is performed at regular intervals or performed at irregular intervals, as determined by the at least one calibration code.

53. The method of claim 52, wherein the at least one calibration code is associated with the at least one predetermined sensitivity.

54. The method of claim 52, wherein the at least one calibration code is associated with a predetermined sensitivity function that uses time of the function of time as input.

55. The method of claim 47, wherein time corresponds to time after start of the sensor session.

56. The method of claim 47, wherein time corresponds to time of manufacture or time since manufacture.

57. The method of claim 47, wherein the sensitivity value of the continuous analyte sensor is also a function of at least one other parameter.

58. The method of claim 57, wherein the at least one other parameter is selected from the group consisting of:

temperature, pH, level or duration of hydration, curing condition, an analyte concentration of a fluid surrounding the continuous analyte sensor during startup of the sensor, and combinations thereof.

59. A method for calibrating a continuous analyte sensor, the method comprising:

receiving sensor data from a continuous analyte sensor;

forming or receiving a predetermined sensitivity profile corresponding to a change in sensor sensitivity to an analyte over a substantially entire sensor session, wherein the predetermined sensitivity profile is a function of at least one predetermined sensitivity value associated with a predetermined time after start of the sensor session; and

applying, with an electronic device, the sensitivity profile in real-time calibrations.

60. The method of claim 59, wherein the at least one predetermined sensitivity value, the predetermined sensitivity profile, or both are set at a manufacturing facility for the continuous analyte sensor.

61. The method of claim 59, further comprising:

receiving at least one calibration code; and

applying the at least one calibration code to the electronic device at a predetermined time after start of the sensor session.

62. The method of claim 61, wherein the at least one calibration code is associated with the at least one predetermined sensitivity.

63. The method of claim 61, wherein the at least one calibration code is associated with a predetermined sensitivity function that uses time as input.

64. The method of claim 59, wherein the sensitivity profile is a function of time.

65. The method of claim 64, wherein time corresponds to time after start of the sensor session.

66. The method of claim 64, wherein time corresponds to time of manufacture or time since manufacture.

67. The method of claim 59, wherein the sensitivity value is a function of time, the predetermined sensitivity value, and at least one parameter selected from the group consisting of:

temperature, pH, level or duration of hydration, curing condition, an analyte concentration of a fluid surrounding the continuous analyte sensor during startup of the sensor, and combinations thereof.

68. A method for processing data from a continuous analyte sensor, the method comprising:

receiving, with an electronic device, sensor data from a continuous analyte sensor, the sensor data comprising at least one sensor data point;

receiving or forming a sensitivity profile corresponding to a change in sensor sensitivity over a substantially entire sensor session;

forming a conversion function based at least in part on the sensitivity profile; and

determining an analyte output value by applying the conversion function to the at least one sensor data point.

69. The method of claim 68, wherein the sensitivity profile is set at a manufacturing facility for the continuous analyte sensor.

70. The method of claim 68, further comprising:

receiving at least one calibration code; and

applying the at least one calibration code to the electronic device at a predetermined time after start of the sensor session.

71. The method of claim 70, wherein the at least one calibration code is associated with the at least one predetermined sensitivity.

72. The method of claim 70, wherein the at least one calibration code is associated with the sensitivity profile.

73. The method of claim 68, wherein the sensitivity profile is a function of time.

74. The method of claim 73, wherein time corresponds to time after start of the sensor session.

75. The method of claim 73, wherein time corresponds to time of manufacture or time since manufacture.

76. The method of claim 68, wherein the sensitivity is a function of time and at least one parameter is selected from the group consisting of:

temperature, pH, level or duration of hydration, curing condition, an analyte concentration of a fluid surrounding the continuous analyte sensor during startup of the sensor, and combinations thereof.

77. A system for monitoring analyte concentration in a host, the system comprising:

a continuous analyte sensor configured to measure analyte concentration in a host and to provide factory-calibrated sensor data, the factory-calibrated sensor data being calibrated without reference blood glucose data;

wherein the system is configured to provide a level of accuracy corresponding to a mean absolute relative difference of no more than about 10% over a sensor session of at least about 3 days, wherein reference measurements associated with calculation of the mean absolute relative difference are determined by analysis of blood.

78. The system of claim 77, wherein the sensor session is at least about 4 days.

79. The system of claim 77, wherein the sensor session is at least about 5 days.

80. The system of claim 77, wherein the sensor session is at least about 6 days.

81. The system of claim 77, wherein the sensor session is at least about 7 days.

82. The method of claim 77, wherein the sensor session is at least about 10 days.

83. The system of claim 77, wherein the mean absolute relative difference is no more than about 7% over the sensor session.

84. The system of claim 77, wherein the mean absolute relative difference is no more than about 5% over the sensor session.

85. The system of claim 77, wherein the mean absolute relative difference is no more than about 3% over the sensor session.