System and methods to account for interferents in a glucose biosensor
Various embodiments that allow for improved accuracy in the measurement of glucose with a glucose meter and a biosensor, principally, by using pulsed signal inputs to the biosensor and selecting at least one specific pulsed output from the biosensor to determine a glucose concentration that is less affected by interfering chemical substances that might be present in the fluid sample.
1. An analyte measurement system comprising:
a biosensor having at least two electrodes with a reagent disposed proximate the at least two electrodes;
an analyte meter comprising:
a power supply;
memory for storage of data; and
a microprocessor coupled to the power supply and memory, and the biosensor, the microprocessor configured to determine an analyte concentration in a physiological sample by:
application of positive and negative electrical pulses to the at least two electrodes that repeat in sequence as a positive pulse, negative pulse, positive pulse and negative pulse, in which a voltage of at least one positive electrical pulse is at a generally constant magnitude during at least one discrete interval, followed by a voltage of at least one negative electrical pulse at a generally constant magnitude during at least one discrete interval;
obtain at least one current output over a predetermined time period from the at least two electrodes for each of the plurality of electrical pulses other than the first electrical pulse; and
calculate an analyte concentration based on the at least one current output.
2. An analyte measurement system comprising:
a biosensor having at least two electrodes with a reagent disposed proximate the at least two electrodes;
an analyte meter comprising:
a power supply;
memory for storage of data; and
a microprocessor coupled to the power supply and memory, and the biosensor, the microprocessor configured to determine an analyte concentration in a physiological sample by:
application of positive and negative electrical pulses to the at least two electrodes that repeat in sequence as a positive pulse, negative pulse, positive pulse and negative pulse, in which the sequence of electrical pulses is applied over discrete intervals and during each interval, a voltage of each of the positive electrical pulses is at a generally constant magnitude, and a voltage of at least one negative electrical pulse at a generally constant magnitude;
obtain at least a first current output from the from the at least two electrodes for each of a first predetermined time period due to application of at least one positive electrical pulse in the sequence other than the first electrical pulse;
obtain at least a second current output from the at least two electrodes for each of a second predetermined time period due to application of at least one negative electrical pulse in the sequence; and
calculate an analyte concentration based on at least one of the first and second current outputs.
3. The system of claim 1 , in which the biosensor comprises a substrate on which the at least two electrodes are disposed, wherein the at least two electrodes comprise three electrodes, of which one of the three includes a reference electrode and two of the three are working electrodes.
4. The system of claim 1 , in which the at least one current output comprises a negative current output of the last electrical pulse.
5. The system of claim 4 , in which the microprocessor is configured to calculate the analyte concentration with an equation of the form:
G
N
=
(
I
N
-
Intercept
)
Slope
where
I N comprises a negative current output from the last electrical pulse of the sequence;
Slope comprises the value obtained from calibration testing of a batch of biosensors of which this particular biosensor comes from; and
Intercept comprises the value obtained from calibration testing of a batch of biosensors of which this particular biosensor comes from.
6. The system of claim 2 , in which the microprocessor is configured to calculate the analyte concentration with an equation of the form:
G
=
(
I
E
-
Intercept
)
Slope
where
I E comprises an average of the first current output I P and second current output I N ;
I P comprises at least one current output or an average current output of the first output currents measured from each positive pulse other than the first positive pulse;
I N comprises at least one current output or an average current output of the second output currents measured from each negative pulse in the sequence;
Slope comprises the value obtained from calibration testing of a batch of biosensors of which this particular biosensor comes from; and
Intercept comprises the value obtained from calibration testing of a batch of biosensors of which this particular biosensor comes from.
7. The system of claim 6 , in which the sequence comprises a number of k pulses and each of the first output currents and second output currents comprises an output current measured at a predetermined time within each of the k number of pulses.
8. The system of claim 7 , in which each of the first output currents comprises a summation of the positive output currents over a predetermined time duration during each pulse in the sequence of k pulses.
9. The system of claim 7 , in which each of the second output currents a summation of the negative output currents over a predetermined time duration during each pulse in the sequence of k pulses.
10. The system of claim 9 , in which the number k is at least 2.
11. The system of claim 5 , in which the microprocessor is configured to calculate the analyte concentration with an equation of the form:
G
P
=
(
I
P
-
Intercept
)
Slope
where
I P comprises an average of output currents measured from positive electrical pulses of the sequence other than the first positive electrical pulse in the sequence;
Slope comprises the value obtained from calibration testing of a batch of biosensors of which this particular biosensor comes from; and
Intercept comprises the value obtained from calibration testing of a batch of biosensors of which this particular biosensor comes from.
12. The system of claim 11 , in which the analyte concentration comprises an average of the sum of the analyte concentrations G p and G N .
13. The system of claim 3 , in which the sequence of pulses comprises a k number of pulses and the first current comprises an average of current outputs over the first predetermined time period within each pulse of the sequence of k pulses.
14. The system of claim 3 , in which the sequence of pulses comprises a k number of pulses, and the first current comprises a summation of current outputs over the first predetermined time period within each pulse of the sequence of k pulses in which k comprises any whole number of at least 2.
15. The system of claim 3 , in which the sequence of pulses comprises a k number of pulses, and the second current comprises an average of current outputs over the second predetermined time period within each pulse of the sequence of k pulses in which k comprises any whole number of at least 2.
16. The system of claim 3 , in which the sequence of pulses comprises a k number of pulses, and the second current comprises a summation of current outputs over the second predetermined time period within each pulse of the sequence of k pulses in which k comprises any whole number of at least 2.
17. The system of claim 3 , in which each of the first and second predetermined time periods comprises about the same duration of time.
18. The system of claim 3 , in which the first predetermined time period comprises about 200 milliseconds and the second predetermined time period comprises about 200 milliseconds.
19. The system of claim 3 , in which the magnitude of the positive electrical pulse comprises about 400 millivolts and the magnitude of the negative electrical pulse comprises about negative 400 millivolts.
20. The system of claim 3 , in which the duration of the positive electrical pulse comprises about any duration from about 0.5 seconds to about 5 seconds.
21. The system of claim 3 , in which the duration of the negative electrical pulse comprises about any duration from about 0.5 seconds to about 5 seconds.
22. A method to determine analyte concentration in a physiological sample with analyte meter having a microprocessor coupled to a power supply and memory and a biosensor having a reagent disposed on at least two electrodes, the method comprising:
depositing a physiological fluid sample on the reagent proximate the at least two electrodes of the biosensor;
applying a plurality of positive and negative electrical pulses to the at least two electrodes that repeat in sequence as a positive pulse, negative pulse, positive pulse and negative pulse with a positive electrical pulse being first in the sequence and at least one positive electrical pulse being next to the last pulse in the sequence, the applying step includes:
driving the plurality of positive electrical pulses of the sequence over discrete time intervals and during each interval, a voltage of each of the positive electrical pulses is at a generally constant magnitude, and
driving a plurality of negative electrical pulses of the sequence over at least one discrete time interval and during the at least one discrete interval, a voltage of the at least one negative electrical pulse is at a generally constant magnitude;
measuring a first current output over a first predetermined time duration from the at least two electrodes due to application of at least one positive electrical pulse in the sequence other than the first positive electrical pulse;
measuring a second current output over a second predetermined time period from the at least two electrodes due to application of at least one negative electrical pulse in the sequence;
determining a analyte concentration based on at least one of the first and second current outputs; and
annunciating the analyte concentration from the determining step.
23. The method of claim 22 , in which the determining step comprises calculation of the analyte concentration with an equation of the form:
G
=
(
I
E
-
Intercept
)
Slope
and where:
I E comprises an average of the first current output I P and second current output I N ;
I P comprises an average current output of the first output currents measured from each positive pulse other than the first positive pulse;
I N comprises an average current output of the second output currents measured from each negative pulse in the sequence;
Slope comprises the value obtained from calibration testing of a batch of biosensors of which this particular biosensor comes from; and
Intercept comprises the value obtained from calibration testing of a batch of biosensors of which this particular biosensor comes from.