System and method for measuring an analyte in a sample
Methods of determining a corrected analyte concentration in view of some error source are provided herein. The methods can be utilized for the determination of various analytes and/or various sources of error. In one example, the method can be configured to determine a corrected glucose concentration in view of an extreme level of hematocrit found within the sample. In other embodiments, methods are provided for identifying various system errors and/or defects. For example, such errors can include partial-fill or double-fill situations, high track resistance, and/or sample leakage. Systems are also provided for determining a corrected analyte concentration and/or detecting some system error.
1. A system for determining a corrected glucose concentration of a sample, comprising:
an electrochemical cell having at least two electrodes including a first electrode and a second electrode, the electrochemical cell being sized and configured to receive the sample, the electrochemical cell further configured to determine an initial glucose concentration and also configured to generate a pre-determined voltage between the first and second electrodes for a pre-determined amount of time, and further configured to measure at least one resulting current of the sample during the pre-determined time; and
a processor programmed for receiving a set of data from the electrochemical cell, the data including the initial glucose concentration, at least one applied voltage, and at least one resulting current, the processor further programmed to utilize this data to determine a corrected glucose concentration, said electrochemical cell being further configured to measure a hematocrit level of the sample, and in which the processor receives and utilizes the measured hematocrit level to determine a correction term based on the measured hematocrit level and the initial glucose concentration, the processor being further programmed to utilize the correction term as data in determining the corrected glucose concentration.
2. The system of claim 1 , wherein the processor utilizes a set of equations to determine the correction term depending on the measured hematocrit level and the initial glucose concentration.
3. The system of claim 2 , wherein an equation of the set of equations utilized by the processor is selected to calculate the corrected glucose concentration based on at least one of: a comparison of the measured hematocrit level to one or more predetermined hematocrit levels and a comparison of the initial glucose concentration to one or more predetermined glucose concentration levels.
4. The system of claim 2 , wherein the processor is programmed to calculate the correction term Corr using a first function, the first function being utilized if the hematocrit level H is less than a lower predetermined hematocrit level H L and if the initial glucose concentration G 1 is less than an upper predetermined glucose concentration value G U .
5. The system of claim 4 , wherein the first function is one of the set of equations, the equation being
Corr= K 1 ( H L −H ) G 1
where Corr is the correction value, K 1 is a first constant, H L is the lower predetermined hematocrit level, H is the hematocrit level, and G 1 is the initial glucose concentration.
6. The system of claim 5 , wherein the corrected glucose concentration G 2 is determined by the equation G 2 =G 1 +Corr if the initial glucose concentration G 1 is less than a glucose threshold.
7. The system of claim 5 , wherein the corrected glucose concentration G 2 is determined by the equation
G
2
=
G
1
(
1
+
Corr
100
)
if the initial glucose concentration G 1 is greater than a glucose threshold.
8. The system of claim 2 , wherein the processor is programmed to calculate the correction value Corr using a second function, the second function being utilized if the hematocrit level H is less than a lower predetermined hematocrit level H L and if the initial glucose concentration G 1 is greater than an upper predetermined glucose concentration value G U .
9. The system of claim 8 , wherein the second function is one of the set of equations, the equation being
Corr= K 2 ( H L −H )( G max −G 1 )
where Corr is the correction value, K 2 is a second constant, H L is the lower predetermined hematocrit level, H is the hematocrit level, G max is a predetermined maximum glucose concentration, and G 1 is the initial glucose concentration.
10. The system of claim 1 , wherein the corrected glucose concentration G 2 is determined to be substantially equal to the initial glucose concentration G 1 if the hematocrit level H is greater than an upper predetermined hematocrit level H U and if the first glucose concentration G 1 is less than a lower predetermined glucose concentration G L .
11. The system of claim 2 , wherein the processor is programmed to calculate the correction value Corr using a utilized third function if the measured hematocrit level H is greater than an upper predetermined hematocrit level H U and if the initial glucose concentration G 1 is greater than the lower predetermined glucose concentration G L .
12. The system of claim 11 , wherein the third function is one of the set of equations, the equation being
Corr= K 4 ( H−H U )( G 1 −G L )
where Corr is the correction value, K 4 is a fourth constant, H is the hematocrit level, H U is the upper predetermined hematocrit level, G 1 is the initial glucose concentration, and G L is the lower predetermined glucose concentration.
13. The system of claim 1 , wherein the hematocrit level H is based on at least one resulting current determined during a first time interval T 1 and a second time interval T 2 .
14. The system of claim 1 , wherein the first electrode and the second electrode have an opposing face arrangement.