Analyte measurement method and system
Described and illustrated herein are systems and exemplary methods of operating an analyte measurement system having a meter and a test strip. In one embodiment, the method may be achieved by applying a first test voltage between a reference electrode and a second working electrode and applying a second test voltage between the reference electrode and a first working electrode; measuring a first test current, a second test current, a third test current and a fourth test current at the second working electrode after a blood sample containing an analyte is applied to the test strip; measuring a fifth test current at the first working electrode; estimating a hematocrit-corrected analyte concentration from the first, second, third, fourth and fifth test currents; and annunciating the hematocrit-corrected analyte concentration.
1. An analyte measurement system to measure a glucose concentration in physiological fluid of a user, the system comprising:
a test strip including a substrate having a reference electrode, a first working electrode and a second working electrode coated with a reagent layer having a mediator, the electrodes being connected to corresponding contact pads; and
an analyte meter having a signal processor and a test circuit in connection with a test strip port that receives the contact pads of the test strip so that the meter is configured to apply a test voltage after deposition of physiological fluid on the electrodes and determine a hematocrit-corrected glucose concentration from measured first, second, third, fourth and fifth test currents at first, second, third, fourth and fifth discrete intervals after application of the test voltage by the meter in which the signal processor is programmed with instructions to determine a ratio of the first test current to the second test current raised to a power term and multiplying the ratio by the fifth test current, where the power term is a function of a first tuning parameter and a second tuning parameter in order to determine the hematocrit-corrected analyte concentration.
2. The system of claim 1 , in which the first test current comprises a current measured from about 0.98 to about 1.00 seconds after initiation of the measuring; the second current comprises a current measured from about 1.09 to about 2.00 seconds after initiation of the measuring; the third current comprises a current measured from about 2.43 to about 2.45 seconds after initiation of the measuring; the fourth current comprises a current measured from about four 2.61 to about 2.63 seconds after initiation of the measuring; the fifth current comprises a current measured from about 2.70 to about 2.72 seconds after initiation of the measuring.
3. The system of claim 1 , in which the first test current is measured from about 3.37 to about 3.39 seconds after a reaction period of time; the second current is measured from about 3.46 to about 3.48 seconds after a reaction period of time; the third current is measured from about 3.54 to about 3.56 seconds after a reaction period of time; the fourth current is measured from about 4.05 to about 4.07 seconds after a reaction period of time; the fifth current is measured from about 4.08 to about 4.10 seconds after a reaction period of time.
4. The system of claim 1 , in which the reference electrode, the first electrode and the second electrodes are disposed on one plane.
5. The system of claim 1 , in which the signal processor is programmed to determine the glucose concentration from the first, second, third, fourth and fifth test currents with an equation of the form:
G
=
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
×
I
5
]
-
intercept
slope
in which:
G is the glucose concentration;
I 1 is the first test current;
I 2 is the second test current;
I 3 is the third test current;
I 4 is the fourth test current;
I 5 is the fifth test current;
a is the first tuning parameter; and
b is the second tuning parameter.
6. The system of claim 5 , in which the first tuning parameter is from about 9.9 to 10.2 and the second tuning parameter is from about 10.8 to 11.2.
7. An analyte measurement system to measure a glucose concentration in physiological fluid of a user, the system comprising:
a test strip including a substrate having a reference electrode, a first working electrode and a second working electrode coated with a reagent layer having a mediator, the electrodes being connected to corresponding contact pads; and
an analyte meter having a signal processor and a test circuit in connection with a test strip port that receives the contact pads of the test strip so that the meter is configured to apply a test voltage after deposition of physiological fluid on the electrodes and determine a hematocrit-corrected glucose concentration from measured first, second, third, fourth and fifth test currents so that at least 97% of plural samples are within an ISO (International Standards Organization) bias criteria of about ±20%, with at least 85% of the plural samples are within ISO bias criteria of about ±15%, and at least 69% of the samples are within ISO bias criteria of about ±10% in which the signal processor is programmed with instructions to determine a ratio of the first test current to the second test current raised to a power term and multiplying the ratio by the fifth test current, where the power term is a function of a first tuning parameter and a second tuning parameter in order to determine the hematocrit-corrected glucose concentration.
8. The system of claim 7 , in which the reference electrode, the first electrode and the second electrodes are disposed on one plane.