Accurate analyte measurements for electrochemical test strip based on sensed physical characteristic(s) of the sample containing the analyte and derived biosensor parameters
Various embodiments for a method that allow for a more accurate analyte concentration with a biosensor by determining at least one physical characteristic, typically hematocrit, of the sample containing the analyte and deriving from this characteristic a parameter relating to the biosensor to attain accurate glucose concentration.
1. A method of determining an analyte concentration from a fluid sample with a biosensor having at least two electrodes and a reagent disposed on at least one of the electrodes, the method comprising:
starting an analyte test sequence upon deposition of a sample on the biosensor;
applying a first signal to the sample to determine a physical characteristic of the sample wherein the physical characteristic is hematocrit level;
driving a second signal to the sample to cause a chemical transformation of the sample;
measuring at least one output signal from the sample;
obtaining a biosensor parametric factor from a look-up table or matrix based on the determined hematocrit level; and
calculating an analyte concentration based on the biosensor parametric factor and the at least one output signal measured at one of a plurality of predetermined time positions from the start of the test sequence based on the relationship:
G
1
=
[
I
E
-
P
1
P
2
*
x
2
]
where G 1 is the analyte concentration;
I E represents a total output signal of the electrodes of the biosensor measured at the one of the plurality of predetermined time positions;
P 1 represents a known batch intercept of the biosensor;
P 2 represents a known batch slope of the biosensor; and
x 1 represents the biosensor parametric factor based on the determined hematocrit level of the sample; and
annunciating the analyte concentration.
2. The method of claim 1 , in which the applying of the first signal and the driving of the second signal may be in sequential order.
3. The method of claim 1 , in which the applying of the first signal overlaps with the driving of the second signal.
4. The method of claim 1 , in which the applying of the first signal comprises directing an alternating signal to the sample so that the hematocrit level of the sample may be determined from an output of the alternating signal.
5. The method of claim 4 , in which the physical characteristic comprises an impedance characteristic representative of hematocrit level of the sample and the analyte comprises glucose.
6. The method of claim 5 , in which the applying of the first signal comprises including a step of driving first and second alternating signals at different respective frequencies in which a first frequency may be lower than the second frequency.
7. The method of claim 6 , in which the first frequency may be at least one order of magnitude lower than the second frequency.
8. The method of claim 7 , in which the first frequency comprises any frequency in the range of about 10 kHz to about 250 kHz.
9. The method of claim 1 , in which the one of the plurality of predetermined time positions for measuring at least one output signal during the test sequence may be about 2.5 seconds after a start of the test sequence.
10. The method of claim 9 , in which the one of the plurality of predetermined time positions comprises a time interval that overlaps a time point of 2.5 seconds after the start of the test sequence.
11. The method of claim 1 , in which another one of the plurality of predetermined time positions for measuring at least one output signal during the test sequence may be a time point of about 5 seconds after a start of the test sequence.
12. The method of claim 1 , in which one of the plurality of predetermined time positions comprises any time point at less than five seconds from a start of the test sequence.
13. The method of claim 12 , in which the another one of the plurality of predetermined time positions comprises any time point at less than ten seconds from a start of the test sequence.
14. The method of claim 13 , in which the one of the plurality of predetermined time positions comprises a time interval overlapping a time point of 2.5 seconds after the start of the test sequence and the another of the plurality of predetermined time positions comprises a time interval overlapping a time point of 5 seconds after the start of the test sequence.
15. The method of claim 1 , in which the at least two electrodes and at least two other electrodes are disposed in the same chamber provided on the substrate.
16. The method of claim 1 , in which the at least two electrodes comprise two electrodes to measure the hematocrit level and the analyte concentration.
17. The method of claim 1 , in which the at least two electrodes comprise a first set of at least two electrodes to determine the hematocrit level of the sample and a second set of at least two other electrodes to determine the analyte concentration.
18. The method of claim 17 , in which all of the electrodes are disposed on a same plane defined by a substrate of the biosensor.
19. The method of claim 16 , in which a third electrode may be disposed proximate the first set of at least two electrodes and connected to the second set of at least two other electrodes.
20. The system method of claim 18 , in which a reagent may be disposed proximate the second set of at least two other electrodes and no reagent may be disposed on the first set of at least two electrodes.