Calibration of Sensors or Measuring Systems

• US 20070168145A1
• Filed: 07/26/2006
• Published: 07/19/2007
• Est. Priority Date: 01/27/2004
• Status: Active Grant

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Roche Diagnostics International AG (Roche Holding AG)
• Inventors: Beyer, Uwe, Haueter, Ulrich, Krieftewirth, Michael
• Granted Patent: US 8,880,371 B2
• Time in Patent Office: Days
• US Class Current: 702/85
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 33/5438 Electrodes

Abstract

A method for adjusting a sensor, continuous sensor or automatic measuring system in an interstitium including the steps of adjusting the steepness of a measuring curve and a standard offset (standard axis intercept) prior to the use of the sensor, continuous sensor or measuring system, and adapting the offset by a point calibration by using a reference measure or value during the use. The present invention encompasses sensors, continuous sensors or automatic measuring systems calibrated or adjusted in accordance with the method, and in some embodiments, the offset adjusted prior to use is rectified according to the difference between a value determined by the sensor, continuous sensor or measuring system taking into account the standard steepness and the reference value.

Claims

1. A method for calibrating continuous sensors or automatic measuring systems in the interstitium, comprising the steps of setting a gradient of a measuring curve and a standard offset prior to use, and adapting the offset during use by a one-point calibration with the aid of a reference measurement.

2. The method as claimed in claim 1, wherein the reference measurement is carried out only for a function test of the measuring system.

3. The method as claimed in claim 1, wherein the offset is adapted with the aid of the mean deviation between the measuring curve, measured by taking account of the standard gradient of the measuring system or sensor, and at least two reference values.

4. The method as claimed in claim 1, wherein at least the sensitive zone of a sensor included in the measuring system is located subcutaneously in the tissue of the test subject.

5. The method as claimed in claim 1, wherein the values of a reference measuring instrument are transmitted to the measuring system in a wireless fashion, preferably by radio or infrared radiation, or via a cable.

6. The method as claimed in claim 1, wherein an analyte is glucose.

7. The method as claimed in claim 6, wherein the offset correction is executed by the sensor or measuring system with a suitable algorithm by using a daily mean, determined by taking account of the preset calibration parameters, and an average long-term glucose value for a patient, which is calculated from the values of the patient for the glycosylated hemoglobin.

8. A method for calibrating continuously measuring sensors or automatic measuring systems for glucose in the interstitium, wherein, to compensate a physiologically conditioned deviation in a glucose content between a location of a reference measurement and a location of the sensor measurement, a trend signal of a glucose value is used as additional information in a calibration of the measuring system or sensor.

9. The method according to claim 8, wherein the trend signal comprises the first mathematical derivative of the glucose value.

10. The method as claimed in claim 8, wherein, depending on the extant trend signal, the measuring system or the sensor detects and proposes a suitable period for the calibration with the aid of a glucose reference measurement or sensor measurement.

11. The method as claimed in claim 10, wherein the trend signal present at the instant of the reference measurement or sensor measurement is used with a suitable algorithm to calculate the time offset of the sensor signal relative to the reference measurement, and to take it into account.

12. A measuring system or sensor for carrying out a calibration method comprising the steps of setting a gradient of a measuring curve and a standard offset prior to use, and adapting the offset during use by a one-point calibration with the aid of a reference measurement.

13. A measuring system or sensor for carrying out a calibration method, wherein, to compensate a physiologically conditioned deviation in a glucose content between a location of a reference measurement and a location of a sensor measurement, a trend signal of a glucose value is used as additional information in the calibration of the measuring system or sensor.

14. A measuring system for determining a value of a biochemical parameter, the measuring system comprising:

a) a measuring sensor (2, R_m, R_ref), having a known gradient and a known offset, for recording a measured value in vivo in a temporally sequential or continuous fashion, and outputting measuring sensor values (P1, P2), the measured values of the measured variable or formed from the measured values, and

b) a data acquisition device that receives the measuring sensor values and at least one reference value and forms characteristic values of the parameter from the measuring sensor values, wherein

c) for the purpose of an automatic self-calibration of the measuring system, the data acquisition device compares one of the characteristic values with the at least one reference value or a value calculated therefrom, and the offset of the measuring sensor is adjusted in accordance with the result of the comparison by a one-point calibration.

15. The measuring system as claimed in claim 14, wherein the data acquisition device forms a difference between the characteristic value on which the calibration is based and the at least one reference value, and adjusts the offset in accordance with the difference.

16. The measuring system as claimed in claim 14, the measuring sensor is a viscosimetric affinity sensor.

17. The measuring system as claimed in claim 14, wherein the measuring sensor comprises a dialysis probe.

18. The measuring system as claimed in claim 14, wherein the measuring sensor comprises a probe that can be placed in a body and a conveyor device by which a liquid can be conveyed through, only into or only out of the probe.

19. The measuring system as claimed in claim 14, wherein the measuring sensor comprises a flow resistance zone (R_ref) and the measured variable recorded by the measuring sensor is a pressure of a fluid flowing through the flow resistance zone.

20. The measuring system according to claim 19, wherein the flow resistance zone comprises a flow resistance capillary.

21. The measuring system as claimed in claim 19, wherein a pressure is measured at an upstream inlet and a downstream outlet of the flow resistance zone (R_ref), and the pressure values are transmitted to the data acquisition device.

22. The measuring system as claimed in claim 14, wherein the measuring sensor comprises a dialysis chamber through which a sensitive liquid can flow, a flow resistance zone arranged upstream of the dialysis chamber, a flow resistance zone arranged downstream of the dialysis chamber, a pressure transmitter upstream of one of the flow resistance zones, and a pressure transmitter downstream of that one of the flow resistance zones, one of the pressure transmitters being arranged between the flow resistance zones, wherein pressure values recorded by the pressure transmitters are transmitted to the data acquisition device.

23. The measuring system as claimed in claim 22, wherein the data acquisition device calculates from the pressure values a relative fluidity F_r using

F_r=(P1−

P2)/(P2+α

(P1−

P2).

P1 being the pressure value of the upstream pressure transmitter, P2 being the pressure value of the downstream pressure transmitter and a being a linearization coefficient.

24. The measuring system as claimed in claim 23, the data acquisition device calculates a concentration of a substance in a fluid from the relative fluidity F_r by using the formula

[KONZ]=gain*F_r+offset.

25. The measuring system as claimed in claim 24, wherein the data acquisition device calculates a trend using measuring sensor values, and determines an instant for the calibration from the calculated trend.

26. The measuring system as claimed in claim 14, wherein the measuring sensor is a glycose sensor and the at least one reference value is a long-term glycose value, and wherein the data acquisition device creates a long-term glucose value from the at least one reference value and calculates a daily mean or a multiple daily mean of the parameter from the measuring sensor values, and the correction of the offset is corrected in accordance with the result of the comparison of the daily mean or multiple daily mean with the long-term glucose value.

27. The measuring system as claimed in claim 14, wherein the data acquisition unit comprises a data memory for a number of the measuring sensor values, and a clock to assign the measuring sensor values the respective instant of their recording.

28. The measuring system as claimed in claim 14 further comprising a reference unit for recording the measured variable or another measured variable, and for outputting the at least one reference value determined from the measured variable or the other measured variable.

29. The measuring system as claimed in claim 28, wherein the reference unit automatically transmits the at least one reference value to the data acquisition device in a wireless fashion or by wire per data transmission.

30. The measuring system as claimed in claim 14, wherein the data acquisition device creates a mean from a number of reference values of a single reference unit or a number of reference units, and uses the mean in the calibration.