System and method for measuring an analyte in a sample
Inventors
Hodges, Alastair M. • Chatelier, Ronald C.
Assignees
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Publication Number
US-9784707-B2
Publication Date
2017-10-10
Expiration Date
Abstract
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.
Core Innovation
The method provides determining whether a test strip is sufficiently filled with a sample and distinguishing the sample as a control solution or a physiological sample. The test strip includes a first electrode coated with a reagent layer and a second electrode not having a reagent layer coating, and liquid detection triggers electrical test steps between the first and second electrodes.
A first DC test voltage is selected to minimize disturbances of a distribution of a reduced mediator within the test strip, where the reduced mediator is a reaction product of the sample and the reagent layer at the first electrode. The first DC test voltage is applied once liquid is detected to distinguish between a control solution and a physiological sample.
A second test voltage is then applied directly after the first voltage step, including a DC voltage component with a larger absolute magnitude than the first DC test voltage and a superimposed AC voltage component. The capacitance value is measured by processing a portion of the test currents resulting from the AC voltage component, and the resulting capacitance value is compared to a predetermined threshold to determine whether the test strip is sufficiently filled.
Claims Coverage
The partial content includes one independent claim. The independent claim centers on a two-step DC/second DC+AC electrical sequence between a coated first electrode and an uncoated second electrode, followed by capacitance-based sufficient-fill determination and control/physiological sample discrimination.
Determining sufficient fill and discriminating control vs physiological sample with a two-electrode strip
A method for determining whether a test strip is sufficiently filled with a sample and distinguishing the sample as a control solution or a physiological sample, where the test strip comprises a first electrode coated with a reagent layer and a second electrode not having a reagent layer coating, and the method applies a sequence of test voltages and uses a capacitance threshold decision.
Minimized disturbance DC test voltage for control vs physiological discrimination
Selecting a first DC test voltage to minimize disturbances of a distribution of a reduced mediator within the test strip, and applying the selected first DC test voltage between the first electrode and the second electrode once liquid is detected to distinguish between a control solution and a physiological sample.
Two-step DC/AC capacitance measurement with limiting test current and timing selection
Measuring a capacitance value by applying a second test voltage between the first electrode and the second electrode directly after the first voltage step, where the second test voltage includes a DC voltage component with a larger absolute magnitude than the first DC test voltage and a superimposed AC voltage component applied for a predetermined time interval; the predetermined time interval is selected to allow sufficient time for sample fill and at least partial dissolution before applying the AC voltage component and to minimize perturbing a subsequent analyte concentration measurement.
Capacitance extraction from AC/DC current portions around zero crossing or AC maximum
Processing a portion of the test currents resulting from the AC voltage component into the capacitance value by summing portions of the test currents resulting from the AC voltage component and the DC voltage component only between about a half wavelength before and about a half wavelength after one of a zero voltage crossing point or a maximum AC voltage component.
Threshold comparison for sufficient fill decision
Utilizing the measured capacitance value to determine whether the test strip is sufficiently filled by determining that the test strip is sufficiently filled if the capacitance value is greater than a predetermined threshold and determining that the test strip is not sufficiently filled if the capacitance value is less than a predetermined threshold.
The independent claim combines a reduced-mediator-disturbance-minimized first DC step for distinguishing control solution versus physiological sample after liquid detection, and a timed second DC+AC step with capacitance extraction from current portions around a defined voltage event, followed by threshold comparison to decide sufficient fill.
Stated Advantages
Enables determining whether the test strip is sufficiently filled with the sample by using a measured capacitance value and a predetermined threshold.
Distinguishes the sample as a control solution or a physiological sample using the first DC test voltage step after liquid is detected.
Minimizes perturbing a subsequent analyte concentration measurement by selecting the timing of the AC voltage component and its application interval.
Documented Applications
Electrochemical test systems using a test strip with opposing electrodes for distinguishing control solution versus physiological sample and determining whether the test strip is sufficiently filled.
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