Analyte measurement technique and system
View Patent ↗Described are methods and systems to apply a plurality of test voltages to the test strip and measure a current transient output resulting from an electrochemical reaction in a test chamber of the test strip so that highly accurate glucose concentration can be determined.
1. A method of determining blood glucose concentration with a glucose measurement system that includes a test strip and test meter, the test meter having a microcontroller programmed to apply a plurality of test voltages to the test strip and measure a current transient output resulting from an electrochemical reaction in a test chamber of the test strip, the method comprising:
inserting the test strip into a strip port connector of the test meter to connect at least two electrodes of the test strip to a strip measurement circuit;
initiating a test sequence after deposition of a sample;
applying a first voltage and measuring a first current for a first time duration;
switching the first voltage to a second voltage different than the first voltage;
changing the second voltage to a third voltage different from the second voltage;
measuring a second current output of a current transient from the electrodes after the changing from the second voltage to the third voltage;
estimating a third current that approximates a steady state current output of a current transient after the third voltage is maintained at the electrodes;
calculating a blood glucose concentration based on the first, second and third current outputs of the current transients with an equation of the form:
G
1
=
(
i
2
corr
′
i
L
′
)
′
p
(
a
′
i
2
corr
′
-
zgr
′
)
+
d
;
where: G 1 is proportional to glucose concentration;
i
R
=
∑
t
=
4.4
t
=
5
i
(
t
)
;
i
L
′
=
(
∑
t
~
1.4
sec
s
t
~
4
sec
s
i
(
t
)
)
-
41
(
i
2
)
;
i
2
corr
′
=
(
i
4.1
+
b
′
i
5
-
c
i
1.1
i
4.1
+
b
′
i
5
)
i
R
where:
a′ is approximately 0.14, b′ is approximately 4.9, c is approximately 4.24, d is approximately 11.28, p′ is approximately 0.548, and zgr′ is approximately 9.38;
i 4.1 comprises the current measured during application of the third voltage;
i 5 comprises the current measured during application of the third voltage;
i 1.1 comprises the current measured during application of the second voltage; and
i 2 comprises the current measured during application of the second voltage.
2. The method of claim 1 , in which the measuring of the first current output comprises measuring a current output of the at least two electrodes at about 1.1 seconds after initiation of the test sequence.
3. The method of claim 2 , in which the measuring of the second current output comprises measuring a current output of the at least two electrodes at about 4.1 seconds after initiation of the test sequence.
4. The method of claim 2 , in which the estimating of the steady state current output comprises measuring a current output of the at least two electrodes at about 5 seconds after initiation of the test sequence.
5. A blood glucose measurement system comprising:
an analyte test strip including:
a substrate having a reagent disposed thereon;
at least two electrodes proximate the reagent in test chamber;
an analyte meter including:
a strip port connector disposed to connect to the two electrodes;
a power supply; and
a microcontroller electrically coupled to the strip port connector and the power supply, the microcontroller programmed to determine a glucose concentration G 1 based on a hematocrit compensation factor and initial glucose proportional current in which the hematocrit compensation factor comprises a ratio that includes the initial glucose proportional current so that at least 97% of corrected test results are within respective bias criterion of ±10 mg/dL at 65 mg/dL, 240 mg/dL, or at 450 mg/dL as compared to reference YSI data; ±12 mg/dL at 65 mg/dL, 240 mg/dL, or 450 mg/dL as compared to reference YSI data; and ±15 mg/dL at 65 mg/dL, 240 mg/dL, or 450 mg/dL as compared to reference YSI data;
the test meter comprising a strip port connector of the test meter to connect at least two electrodes of the test strip to a strip measurement circuit, the strip measurement circuit having a microcontroller programmed to:
apply a plurality of test voltages to the test strip and measure a current transient output resulting from an electrochemical reaction in a test chamber of the test strip;
initiate a test sequence after deposition of a sample by applying a first voltage for a first time duration and measuring a first current;
switch the first voltage to a second voltage different than the first voltage;
change the second voltage to a third voltage different from the second voltage;
measure a second current output of a current transient from the electrodes after the changing from the second voltage to the third voltage;
estimate a third current that approximates a steady state current output of a current transient after the third voltage is maintained at the electrodes;
calculate a blood glucose concentration based on the first, second and third current outputs of the current transients with an equation of the form:
G
1
=
(
i
2
corr
′
i
L
′
)
′
p
(
a
′
i
2
corr
′
-
zgr
′
)
+
d
;
Where: G 1 is proportional to glucose concentration;
i
R
=
∑
t
=
4.4
t
=
5
i
(
t
)
;
i
L
′
=
(
∑
t
~
1.4
sec
s
t
~
4
sec
s
i
(
t
)
)
-
41
(
i
2
)
;
i
2
corr
′
=
(
i
4.1
+
b
′
i
5
-
c
i
1.1
i
4.1
+
b
′
i
5
)
i
R
where:
a′ is approximately 0.14, b′ is approximately 4.9, c is approximately 4.24, d is approximately 11.28, p′ is approximately 0.548, and zgr′ is approximately 9.38;
i 4.1 comprises the current measured during application of the third voltage;
i 5 comprises the current measured during application of the third voltage;
i 1.1 comprises the current measured during application of the second voltage; and
i 2 comprises the current measured during application of the second voltage.