Underfill Detection System For A Biosensor

• US 20150144508A1
• Filed: 02/02/2015
• Published: 05/28/2015
• Est. Priority Date: 05/03/2006
• Status: Active Grant

• Current Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Original Assignee: Bayer Healthcare LLC (Bayer AG)
• Inventors: Wu, Huan-Ping, Nelson, Christine D.
• Granted Patent: US 9,939,406 B2
• Time in Patent Office: Days
• US Class Current: 205/792
• CPC Class Codes: G01N 2035/00108 Test strips, e.g. paper
• CPC Class Codes: G01N 27/327 Biochemical electrodes , e.g. electrical or mechanical details for in vitro measurements
• 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 27/4163 checking the operation of, or calibrating, the measuring apparatus G01N27/3274, G01N27/4175 and G01N33/0006 take precedence
• CPC Class Codes: G01N 35/00029 provided with flat sample substrates, e.g. slides G01N35/028 takes precedence
• CPC Class Codes: G01N 35/1016 Control of the volume dispensed or introduced
• CPC Class Codes: Y10T 436/10 Composition for standardization, calibration, simulation, stabilization, preparation or preservation; processes of use in preparation for chemical testing

Abstract

A biosensor has an underfill detection system that determines whether a sample of a biological fluid is large enough for an analysis of one or more analytes. The underfill detection system applies an excitation signal to the sample, which generates an output signal in response to the excitation signal. The underfill detection system switches the amplitude of the excitation signal. The transition of the excitation signal to a different amplitude changes the output signal when the sample is not large enough for an accurate and/or precise analysis. The underfill detection system measures and compares the output signal with one or more underfill thresholds to determine whether an underfill condition exists.

Claims

1-45. -45. (canceled)

46. A biosensor for determining an analyte concentration in a biological fluid, comprising:

a sensor strip having a sample interface on a base, where the sample interface is adjacent to a reservoir formed by the base;

a measuring device having a processor connected to a sensor interface, where the sensor interface has electrical communication with the sample interface; and

where the processor applies a test excitation signal to the sample interface,

where the processor switches the test excitation signal to at least one different amplitude during at least one of a start of the test excitation signal, a test pulse, and a transition from one test pulse to another test pulse,

where the processor measures a test output signal from the sample interface, and

where the processor compares the test output signal to at least one underfill threshold to determine if the sensor strip is underlined.

47. The biosensor of claim 46, where the processor applies a polling excitation signal to the sample.

48. The biosensor of claim 47, where the processor switches from the polling excitation signal to the test excitation signal when the polling output signal is equal to or greater than a polling threshold.

49. The biosensor of claim 47, where the processor applies the polling excitation signal during a polling period of less than 180 seconds, and where the processor applies the test excitation signal during a test period of less than 180 seconds.

50. The biosensor of claim 46, where the test excitation signal has a test pulse width less than about 5 sec and a test pulse interval less than about 15 sec.

51. The biosensor of claim 46, where the at least one different amplitude is lower than an original amplitude, and where the original and different amplitudes are selected from an output signal plateau in an electrochemical sensor system.

52. The biosensor of claim 51, where the output signal plateau includes excitation amplitudes that generate output signals within ±

5% of an average output signal.

53. The biosensor of claim 46, where the processor switches the test excitation signal to at least one different amplitude essentially during at least one of a start of the test excitation signal, a test pulse, and a transition from one test pulse to another test pulse.

54. The biosensor of claim 46, where the processor switches the test excitation signal to a first different amplitude during a test pulse, and where the processor switches the test excitation signal to a second different amplitude during a transition from one test pulse to another test pulse.

55. The biosensor of claim 46, where the processor reduces the amplitude of at least one test pulse in the test excitation signal below the amplitude of a polling pulse in the polling excitation signal.

56. The biosensor of claim 46, further comprising a display connected to the processor, where the processor shows an error signal on the display in response to an underfill condition.

57. The biosensor of claim 56, where the error signal requests the addition of biological fluid to the sample in response to the error signal.

58. The biosensor of claim 56, where the processor stops an analysis of an analyte in a sample in response to the error signal.

59. A method for detecting an underfill condition in a biosensor, comprising:

applying a test excitation signal to a sample of a biological fluid, where the test excitation signal includes at least first and second test pulses separated by a test relaxation;

measuring a first test output signal from the first test pulse;

measuring a second test output signal from the second test pulse;

comparing a difference between the first and second test output signals with at least one underfill threshold; and

detecting an underfill condition in the biosensor from the comparison of the difference with the at least one underfill threshold.

60. A method for detecting an underfill condition in a biosensor, comprising:

applying a test excitation signal to a sample of a biological fluid;

measuring a first test output signal from the sample;

measuring a second test output signal from the sample;

determining if at least one test output signal is equal to or less than a first underfill threshold;

determining if a difference between the first and second test output signals is equal to or greater than a second underfill threshold; and

detecting an underfill condition in the biosensor from at least one of the determinations.

61. A method for determining an analyte concentration in a biological fluid, comprising:

applying a test excitation signal to a sample of a biological fluid in a biosensor during a test period, the test excitation signal comprising a sequence of test pulses separated by test relaxations;

measuring at least one test output signal from the sample in response to the test excitation signal;

comparing the at least one test output signal with at least one underfill threshold; and

determining whether an underfill condition exists based on the comparison;

where, if an underfill condition does exist, the biosensor generates an error signal, and if an underfill condition does not exist, the biosensor proceeds with an analysis of the analyte in the biological fluid, the analysis comprising;

measuring an assay output signal from the sample, generated in response to the test excitation signal; and

correlating the assay output signal with a concentration of the analyte in the biological fluid to provide a determined analyte concentration;

where, when the method is performed with a plurality of samples, at least 98% of the determined analyte concentrations are within 15% of a reference value of the analyte concentration.

62. The method of claim 61, where, when the method is performed with a plurality of samples, at least 90% of the determined analyte concentrations are within 10% of a reference value of the analyte concentration.

63. The method of claim 61, where the test excitation signal comprises an applied potential, and the assay output signal is a current generated in response to the applied potential.

64. The method of claim 61, where if the biosensor is underfilled, the method further comprises

prompting a user to add more of the sample to the biosensor;

applying a second test excitation signal to the sample;

measuring a second test output signal from the sample;

determining whether the biosensor is underfilled by comparing the second test output signal with the at least one underfill threshold; and

if the biosensor is not underfilled, proceeding with the analysis of the analyte in the biological fluid.

65. A method for determining an analyte concentration in a sample of a biological fluid, comprising:

detecting an application of the sample to a biosensor, the detecting comprising

applying a polling excitation signal to a biosensor,

measuring a polling output current from the biosensor,

determining if the polling output current exceeds a polling threshold, and

measuring another polling output current from the biosensor after a first delay;

starting a time count;

applying a pulse sequence to the biosensor, the pulse sequence comprising

applying a first pulse,

measuring a first series of sensor currents in response the first pulse,

applying a second pulse,

measuring a second series of sensor currents in response the second pulse,

applying a third pulse after a second delay,

measuring a third series of sensor currents in response the third pulse,

applying a fourth pulse after a third delay,

measuring a fourth series of sensor currents in response the fourth pulse,

applying a fifth pulse after a fourth delay, and

measuring a fifth series of sensor currents in response the fifth pulse;

adjusting a slope value and an intercept value of a calibration for the biosensor for a temperature effect;

calculating a glucose concentration of the sample using the adjusted calibration; and

checking for underfill of the sample in the biosensor, the checking comprising

setting an error mode to “

underfill”

if a last measured current in the second series is less than a current threshold for underfill, or

setting an error mode to “

underfill”

if the difference of a last measured current in the first series and a first measured current in the second series is greater than a current delta threshold for underfill.