Contamination determination of biosensors used in analyte measurement systems
A method for determining contamination of a biosensor in which the biosensor is loaded into a test meter and a sample is then applied. First and second predetermined test voltages are applied between spaced electrodes of the biosensor for respective first and second predetermined time intervals. First and second current values are measured during the respective first and second predetermined time intervals. Reference values are determined based on the measured first and second current values. Based on one or more of the reference values, a determination of contamination is made. Reporting of the analyte concentration of the sample can be suppressed based on the determination.
1. A method for determining the presence of contamination of a biosensor, the method comprising:
loading the biosensor into a test meter and applying a sample having an analyte of interest to the biosensor, the biosensor having an electrochemical cell defined by a pair of spaced electrodes;
applying a first predetermined voltage between the spaced electrodes of the electrochemical cell for a first predetermined time interval, and a second predetermined voltage between the spaced electrodes during a second predetermined time interval after the first predetermined time interval;
measuring first current values during the first predetermined time interval at a frequency of about 1 measurement per millisecond to 1 measurement per 100 milliseconds;
determining a first reference value that is a sum of the first current values measured during the first predetermined time interval;
measuring second current values during the second predetermined time interval;
determining a second reference value based on a peak current value measured during the second predetermined time interval and a third reference value based on the rate of change in current values measured after the peak current value during the second time interval;
determining whether the biosensor is contaminated based on one or more of the first through the third reference values; and
suppressing reporting of the concentration of the analyte in the sample upon the determination that the biosensor is contaminated based on the one or more of the first through the third reference values, and
wherein the concentration of the analyte in the sample is calculated based upon the sum of second current values measured in the second time interval and the sum of third current values measured in a third predetermined time interval.
2. The method of claim 1 , wherein determining the biosensor is contaminated is based on all of the first through the third reference values.
3. The method of claim 1 , wherein the first reference value comprises a sum of the first current values between about 0.2 seconds and 0.75 seconds after applying the first predetermined voltage, and the determining the biosensor is contaminated is based on the first reference value being greater than about 6.5 μA.
4. The method of claim 1 , wherein the second reference value is based on the peak current value measured during the second predetermined time interval being less than about 12.5 μA.
5. The method of claim 4 , wherein the peak current value is measured at about 0.05 seconds after applying the second predetermined voltage.
6. The method of claim 1 , wherein the third reference value comprises a difference between a measured current value at about 0.1 seconds after applying the second predetermined voltage and the peak current value measured during the second predetermined time interval, and the determining the biosensor is contaminated is based on the third reference value being between about −3.5 μA and 0 μA.
7. The method of claim 1 , further comprising determining a fourth reference value based on a magnitude of the difference between a highest measured current value and a lowest measured current value during the first predetermined time interval, and determining the biosensor is contaminated is further based on the fourth reference value.
8. The method of claim 7 , wherein the fourth reference value comprises the magnitude of the difference between the highest measured current value and the lowest measured current value between about 0.2 seconds and 0.75 seconds after applying the first predetermined voltage, and determining the biosensor is contaminated is based on the measured second reference value being greater than about 0.57 μA.
9. The method of claim 1 , further comprising determining a fifth reference value based on a minimum measured current value during the first predetermined time interval, and determining the biosensor is contaminated is further based on the fifth reference value.
10. The method of claim 9 , wherein the fifth reference value comprises a minimum of the current values between about 0.2 seconds and 0.75 seconds after applying the first predetermined voltage, and determining the biosensor is contaminated is based on the fifth reference value being greater than about 0 μA.
11. The method of claim 1 , wherein calculating the analyte concentration comprises using an equation of the form
G
basic
=
(
i
r
i
l
)
p
·
(
a
·
i
2
corr
-
z
gr
)
,
in which:
G basic is the analyte concentration;
i r is the sum of the third current values during the third time interval;
i l is the sum of the second current values during the second time interval;
i
2
corr
=
i
pc
+
b
i
ss
-
2
i
pb
i
pc
+
b
i
ss
·
i
r
;
and
a, b, p and z gr are predetermined coefficients.