System and method for measuring an analyte in a sample
Methods for calculating an analyte concentration of a sample are provided. In one exemplary embodiment the method includes steps that are directed toward accounting for inaccuracies that occur as a result of temperature variations in a sample, a meter, or the surrounding environment. In another exemplary embodiment the method includes steps that are directed toward determining whether an adequate sample is provided in a meter because insufficient samples can result in inaccuracies. The methods that are provided can be incorporated into a variety of mechanisms, but they are primarily directed toward glucose meters for blood samples and toward meters for controls solutions.
1. A method for measuring a temperature corrected glucose concentration over a temperature range, the method comprising the steps of:
applying in a test meter a first test voltage for a first time between a first electrode and a second electrode in communication with a sample disposed on a test strip within the test meter, the first time interval being sufficient to oxidize a reduced mediator at the second electrode;
following the application of the first test voltage, applying a second test voltage for a second time interval between the first electrode and the second electrode sufficient to oxidize the reduced mediator at the first electrode;
calculating a first glucose concentration based on test current values during the first time interval and the second time interval;
measuring a temperature value using a temperature reading device incorporated into the test meter that receives the test strip; and
calculating a temperature corrected glucose concentration based on the first glucose concentration and the temperature value, wherein the step of calculating the temperature corrected concentration includes the additional steps of:
calculating a correction value based on the temperature value and the first glucose concentration; and
calculating a temperature corrected concentration based on the first glucose concentration and the correction value, wherein the correction value is calculated with a first function if the temperature value is greater than a first temperature threshold, and wherein the correction value is calculated with a second function if the temperature value is not greater than a first temperature threshold, and in which the first function is a first equation, the first equation being:
Corr 2 =−K 1 ( T−T RT )+ K 2 ×G 1 ( T−T RT )
Where Corr 2 is the correction value, K 1 is a first constant, T is a temperature value, T RT is a room temperature value, K 2 is a second constant and G 1 is the first glucose concentration.
2. The method of claim 1 , in which the correction value is about zero when the temperature value is about equal to room temperature value.
3. The method of claim 2 , in which the room temperature is about 22 degrees Celsius.
4. The method of claim 1 , further comprising the additional steps of:
determining whether the applied sample is a control solution; and
calculating the correction value with a third function if the applied sample is control solution.
5. A method for measuring a temperature corrected glucose concentration over a temperature range, the method comprising the steps of:
applying in a test meter a first test voltage for a first time between a first electrode and a second electrode in communication with a sample disposed on a test strip within the test meter, the first time interval being sufficient to oxidize a reduced mediator at the second electrode;
following the application of the first test voltage, applying a second test voltage for a second time interval between the first electrode and the second electrode sufficient to oxidize the reduced mediator at the first electrode;
calculating a first glucose concentration based on test current values during the first time interval and the second time interval;
measuring a temperature value using a temperature reading device incorporated into the test meter that receives the test strip; and
calculating a temperature corrected glucose concentration based on the first glucose concentration and the temperature value, wherein the step of calculating the temperature corrected concentration includes the additional steps of:
calculating a correction value based on the temperature value and the first glucose concentration; and
calculating a temperature corrected concentration based on the first glucose concentration and the correction value, wherein the correction value is calculated with a first function if the temperature value is greater than a first temperature threshold, and wherein the correction value is calculated with a second function if the temperature value is not greater than a first temperature threshold, and in which the second function is a second equation, the second equation being:
Corr 2 =−K 3 ( T−T RT )+ K 4 ×G 1 ( T−T RT )+ K 5 ×G 1 ( T−T 1 )+ K 6 ×G 1 ( T−T 1 )
where Corr 2 is the correction value, K 3 is a third constant, T is a temperature value, T RT is a room temperature value, K 4 is a fourth constant, G 1 is a first glucose concentration, K 5 is a fifth constant, T 1 is a first temperature threshold and K 6 is a sixth constant.
6. The method of claim 5 , in which the correction value is about zero when the temperature value is about equal to room temperature value.
7. The method of claim 6 , in which the room temperature is about 22 degrees Celsius.
8. The method of claim 5 , said method further comprising the additional steps of:
determining whether the applied sample is a control solution; and
calculating the correction value with a third function if the applied sample is control solution.
9. The method of claim 1 or 5 , in which the step of calculating the temperature corrected concentration further comprises:
adding the correction value to the first glucose concentration to give the temperature corrected concentration if the first glucose concentration is less than a glucose threshold.
10. The method of claim 1 or 5 , in which the step of calculating the temperature corrected concentration further comprises:
dividing the correction value by one hundred and adding one to give an intermediate term; and
multiplying the intermediate term times the first glucose concentration to give a temperature corrected concentration.
11. The method of claim 1 or 5 that further comprises the following step,
determining if the correction value is greater than a threshold value, then setting the correction value to the threshold value, where the threshold value is about ten.
12. A method for measuring a temperature corrected glucose concentration over a temperature range, the method comprising the steps of:
applying in a test meter a first test voltage for a first time between a first electrode and a second electrode in communication with a sample disposed on a test strip within the test meter, the first time interval being sufficient to oxidize a reduced mediator at the second electrode;
following the application of the first test voltage, applying a second test voltage for a second time interval between the first electrode and the second electrode sufficient to oxidize the reduced mediator at the first electrode;
calculating a first glucose concentration based on test current values during the first time interval and the second time interval;
measuring a temperature value using a temperature reading device incorporated into the test meter that receives the test strip; and
calculating a temperature corrected glucose concentration based on the first glucose concentration and the temperature value, wherein the step of calculating the temperature corrected concentration includes the additional steps of:
calculating a correction value based on the temperature value and the first glucose concentration;
calculating a temperature corrected concentration based on the first glucose concentration and the correction value, wherein the correction value is calculated with a first function if the temperature value is greater than a first temperature threshold, wherein the correction value is calculated with a second function if the temperature value is not greater than a first temperature threshold, said method further including the steps of
determining whether the applied sample is a control solution; and
calculating the correction value with a third function if the applied sample is a control solution, and in which the third function is a third equation, the third equation being:
Corr 2 =−K 7 ( T−T RT )+ K 8 ×G 1 ( T−T RT )
where Corr 2 is the correction value, K 7 is a first constant, T is a temperature value, T RT is a room temperature value, K 8 is a second constant and G 1 is the first glucose concentration.