Analyte measurement method and system with error trapping
Described and illustrated herein are systems and exemplary methods of operating an analyte measurement system having a meter and a test strip. The methods and systems describe herein allow for trapping various errors during calculation of the analyte due to variations in the structure and materials making up the test strip and ambient temperatures.
1. A method for determining a glucose concentration with a system having a test strip and a meter having a test circuit including a microprocessor, the method comprising:
initiating a chemical reaction between a reference electrode and a second working electrode coated with a reagent layer and between the reference electrode and a first working electrode coated with a reagent layer of the test strip;
measuring a primary test current and a secondary test current on one of the first and second working electrodes;
determining whether a difference between the primary test current and secondary test current is less than zero;
if the difference between the primary test current and secondary test current is less than zero, then deriving a glucose concentration based on a plurality of test currents in which the plurality of measured test currents comprises first, second, third, fourth, and fifth test currents and K comprises a value from about 1.0 to about 2.0, and wherein the deriving comprises calculating a value representative of glucose concentration with an equation of the form:
G
=
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
-
intercept
slope
where:
G comprises the glucose concentration;
I i comprises the first test current;
I 2 comprises the second test current;
I 3 comprises the third test current;
I 4 comprises the fourth test current;
I 5 comprises the fifth test current;
a comprises a first tuning parameter and b comprises a second tuning parameter;
intercept comprises an intercept value determined from a linear regression of a plot of
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
versus a reference glucose concentration; and
slope comprises a slope value determined from a linear regression of a plot of
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
versus the reference glucose concentration; and
if the difference between the primary test current and secondary test current is not less than zero, then returning an error.
2. The method of claim 1 , in which the primary test current comprises a current being sampled at about an initiation of the measuring step.
3. The method of claim 1 , in which the secondary test current comprises a current being sampled at about 0.8 seconds after the initiation of the measuring step.
4. The method of claim 1 , in which K comprises a value from about 1 to about 1.4.
5. The method of claim 1 , in which K comprises a value of about 1.4.
6. The method of claim 1 , in which the first test current comprises a test current measured from about 0.98 to about 1.00 seconds after initiation of the measuring.
7. The method of claim 1 , in which the second current comprises a test current measured from about 1.98 to about 2.00 seconds after initiation of the measuring.
8. The method of claim 1 , in which the third current comprises a test current measured from about 2.43 to about 2.45 seconds after initiation of the measuring.
9. The method of claim 1 , in which the fourth current comprises a test current measured from about 2.61 to about 2.63 seconds after initiation of the measuring.
10. The method of claim 1 , in which the fifth current comprises a test current measured from about 2.70 to about 2.72 seconds after initiation of the measuring.
11. The method of claim 1 , in which first tuning parameter comprises a value from about 9.9 to about 10.2 and second tuning parameter comprises a value from about 10.8 to about 11.2.
12. A method for determining a glucose concentration with a system having a test strip and a meter having a test circuit including a microprocessor, the method comprising:
initiating a chemical reaction between a reference electrode and a second working electrode coated with a reagent layer and between the reference electrode and a first working electrode coated with a reagent layer of the test strip;
sampling a plurality of test currents after a blood sample is applied to the test strip;
determining a current ratio from respective tertiary test currents sampled from each of the second and first working electrodes;
querying as to whether the current ratio of the second working electrode to the first working electrode is less than about K, and if the current ratio of the second working electrode to the first working electrode is less than about K, then deriving a glucose concentration based on the plurality of test currents in which the plurality of measured or sampled test currents comprises first, second, third, fourth, and fifth test currents and K comprises a constant and wherein the deriving comprises calculating a value representative of glucose concentration with an equation of the form:
G
=
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
-
intercept
slope
where:
G comprises the glucose concentration;
I i comprises the first test current;
I 2 comprises the second test current;
I 3 comprises the third test current;
I 4 comprises the fourth test current;
I 5 comprises the fifth test current;
a comprises a first tuning parameter and b comprises a second tuning parameter;
intercept comprises an intercept value determined from a linear regression of a plot of
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
versus a reference glucose concentration; and
slope comprises a slope value determined from a linear regression of a plot of
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
versus the reference glucose concentration; and
if the current ratio of the second working electrode to the first working electrode is not less than about K, then returning an error.
13. The method of claim 12 , in which the first test current comprises a test current measured from about 0.98 to about 1.00 seconds after initiation of the measuring.
14. The method of claim 12 , in which the second current comprises a test current measured from about 1.98 to about 2.00 seconds after initiation of the measuring.
15. The method of claim 12 , in which the third current comprises a test current measured from about 2.43 to about 2.45 seconds after initiation of the measuring.
16. The method of claim 12 , in which the fourth current comprises a test current measured from about 2.61 to about 2.63 seconds after initiation of the measuring.
17. The method of claim 12 , in which the fifth current comprises a test current measured from about 2.70 to about 2.72 seconds after initiation of the measuring.
18. The method of claim 12 , in which first tuning parameter comprises a value from about 9.9 to about 10.2 and second tuning parameter comprises a value from about 10.8 to about 11.2.
19. A method for determining a glucose concentration with a system having a test strip and a meter having a test circuit including a microprocessor, the method comprising:
initiating a chemical reaction between a reference electrode and a second working electrode coated with a reagent layer and between the reference electrode and a first working electrode coated with a reagent layer of the test strip;
measuring a primary test current and a secondary test current on one of the first and second working electrodes;
determining whether a difference between the primary test current and secondary test current is less than zero;
determining a current ratio from respective tertiary test currents sampled from each of the second and first working electrodes;
evaluating whether a current ratio from respective tertiary test currents sampled from each of the second and first working electrodes is greater than about K, in which K comprises a constant; and
upon either or both of the difference being less than zero or the current ratio being greater than about K, returning an error otherwise deriving a glucose concentration based on the plurality of test currents in which the plurality of measured or sampled test currents comprises first, second, third, fourth, and fifth test currents, K is between about 1.0 and 1.4, and wherein the deriving comprises calculating a value representative of glucose concentration with an equation of the form:
G
=
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
-
intercept
slope
where:
G comprises the glucose concentration;
I 1 comprises the first test current;
I 2 comprises the second test current;
I 3 comprises the third test current;
I 4 comprises the fourth test current;
I 5 comprises the fifth test current;
a comprises a first tuning parameter and b comprises a second tuning parameter;
intercept comprises an intercept value determined from a linear regression of a plot of
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
versus a reference glucose concentration; and
slope comprises a slope value determined from a linear regression of a plot of
[
(
I
1
I
2
)
(
a
-
b
I
3
I
4
)
x
I
5
]
versus the reference glucose concentration.
20. The method of claim 19 , in which the first test current comprises a test current measured from about 0.98 to about 1.00 seconds after initiation of the measuring.
21. The method of claim 19 , in which the second current comprises a test current measured from about 1.98 to about 2.00 seconds after initiation of the measuring.
22. The method of claim 19 , in which the third current comprises a test current measured from about 2.43 to about 2.45 seconds after initiation of the measuring.
23. The method of claim 19 , in which the fourth current comprises a test current measured from about 2.61 to about 2.63 seconds after initiation of the measuring.
24. The method of claim 19 , in which the fifth current comprises a test current measured from about 2.70 to about 2.72 seconds after initiation of the measuring.
25. The method of claim 19 , in which first tuning parameter comprises a value from about 9.9 to about 10.2 and second tuning parameter comprises a value from about 10.8 to about 11.2.