RU2793144C1 - Method for determining analyte concentration in a sample - Google Patents

Abstract

FIELD: measurement system.

SUBSTANCE: methods for determining the concentration of an analyte in a liquid sample of a physiological fluid. Method for determining analyte concentration in a fluid sample of a physiological fluid, the method comprising the steps of applying the sample to a biosensor, the biosensor comprising an electrochemical cell having electrodes; applying a predetermined voltage waveform including the first predetermined voltage applied for at least the first time interval and the second predetermined voltage applied for the second time interval to the biosensor electrodes; measuring at least the first current values during the first time interval and the second current values during the second time interval, in which the current i_pb, representing the transition from the first predetermined voltage to the second predetermined voltage, occurs during the initial part of the second time interval; determining the time of the turning point during the first time interval in which the measured first current values pass from the first profile to the second profile; and calculating the analyte concentration in the sample based on the determined turning point time and at least one current value from the first and the second measured current values, wherein the first measured current values transition from the first profile to the second profile due to the presence of an interference in the fluid sample, and wherein the turning point time occurs before the occurrence of i_pb.

EFFECT: increase of the accuracy of analyte concentration measurements carried out in presence of interferents in a sample of physiological fluid.

19 cl, 22 dwg, 7 tbl

Description

The field of technology to which the invention belongs

[0001] This application is generally directed to systems for measuring the level of an analyte, and more specifically, to methods for determining the concentration of an analyte in a sample, for example, blood glucose, while the analyte includes a physical characteristic or property that is inappropriately changes the concentration measurement, such as an interference factor such as hematocrit, uric acid, or other interference.

State of the art

[0002] The detection of an analyte in bodily fluids, such as blood or blood-derived products, is of ever-increasing importance to today's society. Quantitative assays for analyte detection find use in a variety of applications including clinical laboratory testing, home testing, etc., and the results of such testing play a prominent role in periodic diagnosis and monitoring in a variety of disease states. Analytes of interest include glucose for diabetes control and cholesterol, among others. In response to the growing importance of analyte detection, a variety of testing protocols and devices have been developed for clinical and home use.

[0003] One method that is used to detect an analyte in a liquid sample is an electrochemical method. In such a method, an aqueous liquid sample, such as a blood sample, is deposited on a biosensor and filled into an electrochemical cell sample receiving chamber that includes two electrodes, such as a counter electrode and a working electrode. The analyte is allowed to react with the redox reagent to form an oxidizable (or reducible) substance in an amount corresponding to the concentration of the analyte. The amount of oxidizable (or reduced) substance present is then estimated electrochemically and related to the amount of analyte present in the sample to be deposited.

[0004] However, any analyte level measurement system may be subject to various modes of inefficiency and/or error. For example, interferences present in body fluids can lead to inaccurate analyte level measurements. As one specific example, the presence of uric acid in the blood can interfere with glucose measurements, leading to erroneous results. In some cases, these erroneous results can potentially mislead the researcher into prescribing the wrong dosage of drugs, with potentially catastrophic results. Therefore, there is the greatest possible need to improve the accuracy of analyte concentration measurements performed in the presence of interferents in a physiological fluid sample.

Brief description of the drawings

[0005] Therefore, the manner in which the disclosure features can be understood is set forth in the detailed description with reference to specific embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings only illustrate specific embodiments and, as such, should not be construed as limiting its scope, as the scope of the disclosed subject matter covers other embodiments as well. The drawings are not necessarily drawn to scale, with emphasis generally placed on illustrating features of particular embodiments. In the drawings, like numbers are used to indicate like parts in different views.

[0006] FIG. 1 illustrates a perspective view of an analyte level measurement system including a test meter and a biosensor (test strip) in accordance with the aspects set forth herein;

[0007] FIG. 2 is an upward view of the circuit board located in the test meter of FIG. 1 illustrating various components, in accordance with the aspects set forth herein;

[0008] FIG. 3A is a perspective view of an assembled test strip suitable for use in the analyte level measurement system of FIG. 1 and 2;

[0009] FIG. 3B is an exploded perspective view of the test strip of FIG. 3A;

[0010] FIG. 3C is an expanded perspective view of the proximal portion of the test strip of FIG. 3A and 3B;

[0011] FIG. 3D is a bottom plan view of the test strip of FIG. 3A-3C;

[0012] FIG. 3E is a vertical sectional side view of the test strip of FIG. 3A-3D;

[0013] FIG. 3F is a top plan view of the test strip of FIG. 3A-3E;

[0014] FIG. 3G is a partial side elevational view of the proximal portion of the test strip of FIG. 3A-3F;

[0015] FIG. 4 is a simplified circuit diagram showing a test meter in electrical communication with portions of a test strip, such as the test strip illustrated in FIG. 3A-3F;

[0016] FIG. 5A shows an example of a test waveform applied by the test meter of FIG. 4 to the working and counter electrodes of the test strip during the prescribed time intervals to determine the analyte in the sample applied to the test strip;

[0017] FIG. 5B illustrates the measured current over time based on the waveform of FIG. 5A for nominal test strip;

[0018] FIG. 5C illustrates the initiation of the test waveform of FIG. 5A based on the determination that the sample fills the test strip illustrated in FIG. 3A-3F;

[0019] FIG. 5D is a flowchart showing a method for determining an analyte concentration in a test strip;

[0020] FIG. 6A illustrates a redox reaction in two electrodes stimulated by applying an electrical potential between the electrodes;

[0021] FIG. 6B illustrates initiation based on determining that a sample is being applied to the test strip illustrated in FIG. 3A-3F;

[0022] FIG. 6C illustrates a plot of current versus time measured after application of an electrical potential, including a turning point at which the current profile transitions, for example, from a profile other than the Cottrell profile, for example, to a Cottrell profile;

[0023] FIG. 6D illustrates measured current values of the test strip illustrated in FIG. 3A-3F based on the test waveform of FIG. 5A initiated as illustrated in FIG. 6b;

[0024] FIG. 6E illustrates measured current values of the test strip illustrated in FIG. 3A-3F, based on another waveform initiated as illustrated in FIG. 6b;

[0025] FIG. 6F and 6G are flowcharts representing methods for determining the concentration of an analyte in a sample, in accordance with the aspects set forth herein; And

[0026] FIG. 6H illustrates an experimental validation of an improved measurement of analyte concentration in the presence of an interferent, in accordance with the aspects set forth herein.

Detailed description of the invention

[0027] The following detailed description should be read with reference to the drawings, with similar elements in the various drawings being identically numbered. The drawings, which are not necessarily to scale, illustrate selected embodiments and are not intended to limit the scope of the invention. The detailed description illustrates, by way of example and not limitation, the principles of the invention. This description is intended to clearly enable those skilled in the art to make and use the invention and describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is currently considered to be the best mode for carrying out the invention.

[0028] As used herein, the terms "about" or "approximately" for any numerical values or ranges indicate a suitable dimensional tolerance that enables a portion or combination of components to function for their intended purpose as described herein. In addition, as used herein, the terms "patient," "disease carrier," "user," and "subject" mean any human or animal under study and are not intended to limit systems or methods to human use, although patient use of the technologies in question -human is the preferred embodiment.

[0029] The present disclosure relates, in part, to technologies for determining the concentration of an analyte using a biosensor, such as a disposable test strip. A biased measurement (eg, higher than the actual measurement) can result in an incorrectly high dose of insulin administered to a patient, leading to a serious impact on the patient's health. Testing shows that analytes that have certain interferences, such as uric acid or ascorbic acid present in the sample, can undergo oxidation and therefore change the current response compared to a sample with fewer interferences. In an attempt to find ways to improve the accuracy of blood glucose measurements, technology is provided herein to more accurately account for interference, including improved measurement techniques and/or correction for physical property measurements affected by interferences. Therefore, various aspects of the method for determining the concentration of an analyte in a sample are presented in this document. In one example of the present technology, a measurement technique is applied to a sample and the analyte concentration is determined by correcting for the presence of an interferent. In another example, an estimated physical property is calculated and then one of a variety of different linear models is selected with the ability to calculate an analyte concentration based on the physical property and other parameters.

[0030] Generally speaking, and according to at least one embodiment, a method is provided for determining the concentration of an analyte in a liquid sample. The sample is applied to a biosensor, which includes an electrochemical cell having electrodes. The predetermined voltage waveform is applied for at least the first and second time intervals. At least the first and second current values are measured during the first and second time intervals, respectively. The turning point time is determined during the first time interval in which the measured first current values pass from the first to the second profile. The analyte concentration in the sample is calculated based on the determined turning point time and at least one measured current value.

[0031] In one embodiment, the calculation step is based on the determined turning point time and at least one current value from the measured first current values and at least one current value from the measured second current values. In another embodiment, the calculation step is based on the value of the current at the turning point at the time of the turning point.

, в котором:[0032] In one particular implementation, calculating the analyte concentration includes using an equation of the form

, in which:

- G _basic is the concentration of the analyte (in mg/dl);

- a _{i, j} are coefficients;

- x ₀ is a constant (for example, equal to 1);

- x ₁ is t _Turn , the turning point time (in seconds);

- x ₂ is i _r , the sum of at least some of the measured second current values of the second time interval (in microamps);

- x ₃ is one of the first values of the current in the first time interval (in microamps);

- x ₄ is i _Turn , the value of the current in t _Turn (in microamps);

- x ₅ is the inversion of one of the first current values in the first time interval (in 1/microamps);

- x ₆ is the inversion of one of the first current values in the first time interval (in 1/microamps); And

- c is a predefined constant.

, в котором:[0033] In another particular implementation, the predetermined voltage waveform is further applied during a third time interval, wherein the measurement step further comprises measuring third current values during the third time interval, and wherein the calculation step is based on the defined turning point time and at least one current value from the measured first, second and third current values. In such a case, the calculation of the analyte concentration may involve the use of an equation of the form

, in which:

- G _basic is the concentration of the analyte (in mg/dL);

- a _{i, j} are predetermined coefficients;

- x ₀ is a constant (for example, equal to 1);

- x ₁ is t _Turn , the turning point time (in seconds);

- x ₂ is i _r , the sum of at least some of the measured third current values of the third time interval (in microamps);

- x ₃ is one of the second values of the current in the second time interval (in microamps);

- x ₄ is i _pb close to the peak of the second current values in the second time interval (in microamps);

- x ₅ is the inversion of one of the first current values in the first time interval (in 1/microamps);

- x ₆ is the inversion of one of the second current values in the second time interval (in 1/microamps); And

- c is a predefined constant.

, в котором:[0034] In a further specific implementation, using the waveform outlined in FIG. 5A and in the resultant current transient shown in FIG. 5B, the calculation of the analyte concentration comprises using an equation of the form

, in which:

- G _basic is the concentration of the analyte (in milligrams per deciliter);

- t _Turn is the turning point time (in seconds);

(в микроамперах);-

(in microamps);

- i _pc is the current close to the negative peak of the third current values in the third time interval (in microamps);

- i _pb is the current close to the peak of the second current values in the second time interval (in microamps);

- i _ss is the steady state of the third current values in the third time interval;

- i _r is the sum of at least some of the measured second current values of the third time interval (in microamps); And

- a, b, p and z _gr are predefined coefficients.

[0035] In one example, the method further includes excitation, after applying the sample to the biosensor, initiating current between the electrodes of the electrochemical cell, measuring values of the initiating voltage during excitation of the initiating current; and triggering a predetermined voltage waveform when the measured trigger voltage falls below the trigger threshold voltage.

[0036] In another example, the trigger current is between 500-700 nA and the trigger threshold voltage is between 800-1100 mV.

[0037] Upon initiation of a predetermined voltage waveform, current values transition from the first profile to the second profile. The first profile may deviate from the Cottrell profile and the second profile essentially follows the Cottrell profile. In another aspect, the interferent undergoes oxidation in a bare electrode of the electrochemical cell electrodes. In an additional aspect, the interference contains uric acid or ascorbic acid.

[0038] In one example, the electrochemical cell electrodes comprise a bare electrode and an electrode at least partially coated with a reagent. The electrodes of the electrochemical cell may be collocated, or the electrodes may be coplanar. The measurement of the first and second current values is carried out at a frequency between 50-200 Hz.

[0039] In another aspect, the probe is applied to a biosensor including an electrochemical cell having electrodes. The predetermined voltage waveform is applied for at least the first and second time intervals. At least the first and second current values are measured during the first and second time intervals, respectively. The turning point time is determined during the first time interval in which the measured first current values pass from the first to the second profile. The physical characteristic of the sample (eg hematocrit) is evaluated based on the measured current values. The concentration is calculated using one of a number of specific models (for example, first, second, third, etc. models) if the estimated physical property of the sample is in a specific range (for example, in the first, second, third, etc. ranges) .

[0040] In one embodiment, the first model comprises first coefficients and the second model comprises second coefficients, wherein the first coefficients and second coefficients are determined by linear optimization. In another embodiment, the physical characteristic estimation comprises using turning point time.

, и вычисление концентрации аналита с использованием второй модели содержит использование уравнения формы:[0041] In one specific example, calculating the analyte concentration using the first model comprises using an equation of the form

, and the calculation of the analyte concentration using the second model contains the use of an equation of the form:

, в котором:

, in which:

является концентрацией аналита, вычисленной с использованием первой модели (в мг/дл);-

is the analyte concentration calculated using the first model (in mg/dl);

являются предварительно определенными коэффициентами первой модели;-

are predetermined coefficients of the first model;

являются константами (например, равными 1);-

are constants (for example, equal to 1);

являются предикторами первой модели на основе измеренных значений тока;-

are predictors of the first model based on the measured current values;

- c ₁ is a predefined constant of the first model;

является концентрацией аналита, вычисленной с использованием второй модели (в мг/дл);-

is the analyte concentration calculated using the second model (in mg/dl);

являются предварительно определенными коэффициентами второй модели;-

are predetermined coefficients of the second model;

являются предикторами второй модели на основе измеренных значений тока; и-

are predictors of the second model based on the measured current values; And

- c ₂ is a predefined constant of the second model.

[0042] The above embodiments are intended to be merely examples. It should be apparent from the following explanation that other embodiments are within the scope of the disclosed subject matter.

[0043] Specific working examples are described below with respect to FIGS. 1-6H.

[0044] FIG. 1 illustrates a diabetes monitoring system that includes a portable test meter 10 and a biosensor, the second of which is provided in the form of a disposable test strip 62 that is capable of detecting blood glucose. For the purposes of the following explanation, the portable test meter 10 is referred to synonymously throughout this document as "analyte monitoring and measurement unit", "glucose meter", "meter", and/or "meter instrument unit". Although not shown in this view and in at least one embodiment, the portable test meter can be combined with an insulin delivery device, an additional analyte testing device, and a drug delivery device. The portable test meter 10 may be connected to a remote computer or remote server via a cable or suitable wireless technology such as, for example, GSM, CDMA, Bluetooth, Wi-Fi, and the like. Such analyte level measurement systems are described in U.S. Patent No. 8709232 B2, issued April 29, 2014, entitled "Analyte Measurement Technique and System", and in International Patent Publication No. WO 2012/012341 A1, issued January 26, 2012, entitled " System and Method for Measuring the Analyte in the Sample", each of which is referenced in its entirety in this document.

[0045] Still referring to FIG. 1, the portable test meter 10 is defined by a housing 11 having a plurality of user interface buttons (16, 18 and 20) which are located on the facing surface. A display 14 is provided in addition to a strip port port 22 that is configured to receive a biosensor (test strip 62). The buttons (16, 18 and 20) of the user interface may be configured to allow data entry, menu navigation, and execution of various commands. It should be obvious that the configuration and functionality of the user interface buttons 16, 18 and 20 of the portable test meter 10 is intended to be exemplary, and modifications and variations are possible. According to this particular embodiment, the user interface button 18 may be in the form of a toggle switch. The data may include values representing the concentration of an analyte and/or information that is associated with a person's daily lifestyle. Information that is related to daily life may include diet, medication use, preventive health check-ups, and a person's general health and exercise levels.

[0046] As shown in FIG. 2 and shown in a simplified schematic form, the electronic components of the portable test meter 10 may be located on a circuit board 34 contained in the interior of the case 11, FIG. 1. According to this embodiment, the electronic components include a strip port connector 23, an operational amplifier circuit 35, a microcontroller 38, a display connector 14a, a non-volatile memory 40, a clock generator 42, and a first wireless module 46. On the opposite bottom surface of the circuit board 34 , the electronic components may include a battery connector (not shown) and a data port 13 . It should be understood that the relative position of various electronic components may vary, and the configuration described herein is exemplary.

[0047] Microcontroller 38 may be electrically coupled to strip port connector 23 aligned with strip port port opening 22 (FIG. 1), operational amplification circuit 35, first wireless module 46, display 14, non-volatile memory 40, clock generator 42 at least one battery (not shown), data port 13 and user interface buttons (16, 18 and 20).

[0048] The operational amplifier circuit 35 may include two or more operational amplifiers configured to provide part of a potentiostat function and a current measurement function. The function of a potentiostat may mean applying a test voltage between at least two electrodes of the test strip. The current function may mean measuring the test current resulting from the applied test voltage. Current measurement can be performed using a current-to-voltage converter. Microcontroller 38 may take the form of a mixed signal microprocessor (MSP) 430, such as, for example, an MSP from Texas Instruments (TI). The MSP 430 can also be configured to perform part of the potentiostat function and the current measurement function. In addition, these 430 may also include volatile and non-volatile storage. In another embodiment, many electronic components may be integrated with the microcontroller in the form of an application specific integrated circuit (ASIC).

[0049] Strip port connector 23 may be configured to form an electrical connection to test strip 62. Display connector 14a may be configured to connect to display 14. For purposes of this description, display 14 may be in the form of a liquid crystal display for reporting measured glucose levels. and to facilitate the entry of lifestyle-related information. The display 14 may optionally include a backlight. The communication port 13 can receive a suitable connector connected to the connection lead, thereby allowing the test meter 10 to be connected to an external device such as a personal computer (not shown). For the purposes of this description, communication port 13 may be any port that provides data communication capability, such as, for example, a serial, USB, or parallel port. The communication port 13 can be accessed through the case 11 of the portable test meter 10. The clock generator 42 can be configured to store the current time associated with the geographic area in which the user is located, as well as to measure the time. The test meter 10 may be configured to be electrically coupled to a power supply source such as, for example, at least one built-in battery (not shown).

[0050] FIG. 3A-3G show different types of test strip 62 suitable for use with the methods and systems described herein. In an exemplary embodiment, test strip 62 is defined by an elongate body extending from distal end 80 to opposite proximal end 82 and having transverse edges 56, 58 as illustrated in FIG. 3A. As shown in FIG. 3B, the test strip 62 also includes a first electrode layer 66, a second electrode layer 64, and a spacer 60 placed midway between the two electrode layers 64 and 66 at the distal end 80 of the test strip 62. The first electrode layer 66 may include a first electrode 66 , a first connection track 76 and a first pad 67, with the first connection track 76 electrically connecting the first electrode 66 to the first pad 67 as shown in FIG. 3B and 3C. It should be noted that the first electrode 66 forms part of the first electrode layer 66, which is immediately below the reagent layer 72, as indicated by FIG. 3A and 3B. Similarly, the second electrode layer 64 may include a second electrode 64, a second connection track 78, and a second pad 63, with the second connection track 78 electrically connecting the second electrode 64 to the second pad 63, as shown in FIG. 3A-3C. It should be noted that the second electrode 64 forms part of the second electrode layer 64, which is located above the reagent layer 72, as best shown in FIG. 3B and 3C.

[0051] As shown, a sample receiving chamber 61 (eg, an electrochemical cell) is defined by a first electrode 66, a second electrode 64, and a spacer 60, near the distal end 80 of the test strip 62, as shown in FIG. 3B-3E. The first electrode 66 and the second electrode 64 may define the bottom and top of the sample receiving chamber 61, respectively, as illustrated in FIG. 3g. The cut-out area 68 of the spacer 60 may define the side walls of the sample receiving chamber 61, as illustrated in FIG. 3g. In one aspect, sample receiving chamber 61 may include ports 70 that provide an exemplary inlet and/or vent, as shown in FIG. 3A-3C. For example, one of ports 70 may provide fluid sample inlet and the other port 70 may provide air outlet.

[0052] In an exemplary embodiment, the sample receiving chamber 61 may have a small volume. For example, chamber 61 may have a volume ranging from about 0.1 microliters to about 5 microliters, from about 0.2 microliters to about 3 microliters, or preferably from about 0.3 microliters to about 1 microliter. To provide a small sample volume, recess 68 may have an area ranging from about 0.01 cm ² to about 0.2 cm ² , from about 0.02 cm ² to about 0.15 cm ² , or preferably from about 0 .03 cm ² to approximately 0.08 cm ² . In addition, the first electrode 66 and the second electrode 64 can be spaced apart from about 1 micron to about 500 microns, preferably between about 10 microns and about 400 microns, and more preferably between about 40 microns and about 200 microns. The relatively small electrode spacing may also allow redox cycling to occur in which the oxidized mediator formed in the first electrode 66 may diffuse into the second electrode 64 so that it becomes reduced and then diffuse back into the first electrode 66 so that it becomes oxidized again. Those skilled in the art will appreciate that various such volumes, areas, and/or spacings of the electrodes are within the spirit and scope of the present disclosure.

[0053] In one embodiment, the first electrode 66 and the second electrode 64 may include an electrode layer. The electrode layer may include a conductive material formed from materials such as gold, palladium, carbon, silver, platinum, tin oxide, iridium, indium, or combinations thereof (eg, indium-doped tin oxide). In addition, the electrode layers may be formed by arranging the conductive material on an insulating sheet (not shown) through a sputtering process, non-electrolyte plating, or screen printing. In one exemplary embodiment, first electrode 66 and second electrode 64 may include electrode layers made of palladium-plated and gold-plated, respectively. Suitable materials that can be used as spacer 60 include a variety of insulating materials such as, for example, plastics (eg, PET, PETG, polyimide, polycarbonate, polystyrene), silicon, ceramics, glass, adhesives, and combinations thereof.

[0054] In one embodiment, spacer 60 may be in the form of a double-sided adhesive applied to opposite sides of the polyester sheet, wherein the adhesive may be pressure sensitive or heat activated. Applicants note that various other materials for first electrode layer 66, second electrode layer 64, and/or spacer 60 are within the spirit and scope of the present disclosure.

[0055] The first electrode 66 or the second electrode 64 may function as a working electrode depending on the absolute value and/or polarity of at least one applied test voltage. The working electrode can measure the ultimate test current, which is proportional to the concentration of the reduced mediator. For example, if the current-limiting particles are a reduced mediator (eg, potassium ferrocyanide), then it can be oxidized in the first electrode 66 provided that the test voltage is sufficiently greater than the potential of the redox mediator with respect to the second electrode 64. In this situation, the first electrode 66 functions as a working electrode, and the second electrode 64 functions as a counter/reference electrode. Applicants note that it is possible to refer to the counter/reference electrode as simply "reference electrode" or "counter electrode". Limit oxidation occurs when all of the reduced mediator is depleted at the working electrode surface so that the measured oxidation current is proportional to the flux of reduced mediator diffusing from the bulk solution to the working electrode surface. The term "basic volume of solution" as used herein means the part of the solution at a sufficiently large distance from the working electrode, and the recovered mediator is not located in the depleted zone. It should be noted that, unless otherwise noted for the test strip 62, all potentials applied by the test meter 10 are hereinafter referred to with respect to the second electrode 64.

[0056] Similarly, if the test voltage is sufficiently less than the potential of the redox mediator, then the reduced mediator may be oxidized in the second electrode 64 as a current limit. In such a situation, the second electrode 64 functions as a working electrode, and the first electrode 66 functions as a counter/reference electrode.

[0057] Initially, the assay may include introducing an amount of sample fluid into the sample receiving chamber 61 through one of the ports 70. In one aspect, the port 70 and/or the sample receiving chamber 61 may be configured such that capillary action causes liquid sample to fill the chamber 61 for receiving samples. The first electrode 66 and/or the second electrode 64 may be coated with a hydrophilic reagent to promote capillarity of the sample receiving chamber 61. For example, thiol-derivative reagents having a hydrophilic moiety, such as 2-mercaptoethanesulfonic acid, can be applied to the first electrode and/or the second electrode.

[0058] In the above analysis of the test strip 62, the reagent layer 72 may include glucose dehydrogenase (GDH) based on the PQQ cofactor and ferricyanide. In another embodiment, the PQQ cofactor enzymatic GDH may be replaced with the FAD cofactor enzymatic GDH. When blood or control solution is dispensed into the sample reaction chamber 61, glucose is oxidized by GDH _(ox) and, in the process, converts GDH _(ox) to GDH _(red) as shown in chemistry T.1 below. It should be noted that GDH _(ox) means the oxidized state of GDH, and GDH _(red) means the reduced state of GDH.

[0059] T.1. D-glucose+GDH _(ox) → gluconic acid+GDH _(red)

[0060] GDH _(red) is then reduced back to its active oxidized state by ferricyanide (ie, an oxidized mediator or Fe(CN) ₆ ^3- , such as potassium ferricyanide) as shown in chemistry T.2 below. During the regeneration of GDH _(ox) , ferrocyanide (i.e. reduced mediator or Fe(CN) ₆ ^4- , such as potassium ferrocyanide) is formed from the reaction as shown in T.2:

[0061] T.2. GDH _(red) +2Fe(CN) ₆ ^3- → GDH _(ox) +2Fe(CN) ₆ ^4-

[0062] FIG. 4 provides a simplified schematic view showing the test meter 10 interacting with the first pad 67a, 67b and the second pad 63 of the test strip 62. The second pad 63 may be used to make an electrical connection to the test meter 10 via U- shaped recess 65 as illustrated in FIG. 3b. In one embodiment, test meter 10 may include a second electrode connector 101, first electrode connectors (102a, 102b), a test voltage determination unit 106, a current measurement unit 107, a processor 212, a memory unit 210, and a video display 202, as schematically shown in FIG. 4. The first pad 67 may include two prongs, referred to as 67a and 67b. In one exemplary embodiment, the first electrode connectors 102a and 102b are individually connected to teeth 67a and 67b, respectively. The second electrode connector 101 may be connected to the second pad 63. The test meter 10 may measure the resistance or electrical continuity between the teeth 67a and 67b to determine whether or not the test strip 62 is electrically connected to the test meter 10.

[0063] In one embodiment, test meter 10 may apply a test voltage and/or current between first pad 67 and second pad 63. After test meter 10 recognizes that strip 62 is inserted, test meter 10 turns on and initiates liquid detection mode. In one embodiment, the liquid detection mode instructs the test meter 10 to apply a constant current of approximately 1 microampere between the first electrode 66 and the second electrode 64. Since the test strip 62 is dry, the test meter 10 measures a relatively large voltage. When the fluid sample bridges the gap between the first electrode 66 and the second electrode 64 during the dosing process, the test meter 10 should measure a decrease in measured voltage that is below a predetermined threshold, instructing the test meter 10 to automatically initiate a glucose test.

[0064] Referring to FIG. 5A-5D, the following describes a method for determining the concentration of an analyte using a test strip 62 and a test meter 10. As a general introduction, firstly, the application of test voltages and measurement of current values are explained, with further explanation of the measurement of analyte concentration.

[0065] First, with respect to applying voltages to the test strip, an exemplary test meter 10 and an exemplary test strip 62 are mentioned. The test meter 10 may include electronic circuitry that may be used to apply a plurality of voltages to the test strip. 62 and measure the transient current output resulting from the electrochemical reaction in the test chamber of test strip 62. Test meter 10 may also include a signal processor with an instruction set for a method for determining an analyte concentration in a fluid sample, as disclosed herein. In one embodiment, the analyte is blood glucose.

[0066] Continuing with the explanation of the application of the test voltages, FIG. 5A depicts an exemplary waveform consisting of a plurality of test voltages applied to test strip 62 for prescribed time intervals. The plurality of test voltages according to this waveform include a first test voltage E1 which is applied during the first time interval t ₁ , a second test voltage E2 which is applied during the second time interval t ₂ , and a third test voltage E3 which is applied during the third time interval t ₃ . The third voltage E3 may differ in the absolute value of the electromotive force, in polarity, or in combinations of what is indicated with respect to the second test voltage E2. In preferred embodiments and as shown, E3 may have the same absolute value as E2 but opposite polarity. The glucose test time interval t _G represents the amount of time to perform a glucose test (but not necessarily all calculations associated with a glucose test). The time interval t _G of the glucose test can vary from about 1.1 seconds to about 5 seconds. Additionally, as illustrated in FIG. 5A, the second test voltage E2 may include a direct (DC-) test voltage component and a superimposed alternating (AC-) or alternatively oscillating test voltage component applied for a short time interval. More specifically, the superimposed AC or fluctuating component of the test voltage may be applied for a time interval indicated by t _cap when the second time interval is initiated.

[0067] A plurality of test current values measured during any of the time intervals may be performed at a frequency ranging from about 1 measurement per microsecond to about one measurement per 100 milliseconds, and preferably at about 10 milliseconds. Although an embodiment is described using three test voltages in a serial manner, a glucose test may include various numbers of open circuit voltages and test voltages.

[0068] FIG. 5C illustrates the initiation of the test waveform of FIG. 5A based on the determination that the sample fills the test strip 62 illustrated in FIG. 3A-3F. For example, during a test cycle, the user may apply a blood sample to the test strip, and during the initial stages of application, the test strip 62 should begin to fill with sample. During this time, the signal can be quite noisy as the sample physically enters the electrochemical cell. To best determine when to start testing a sample, an initiating current of 500-700 nA can be applied between the electrodes and average voltage values can be measured, as illustrated in FIG. 5C. When the voltage value falls from approximately 3.0 V previously to a certain value, for example 0.5 V, the test waveform of FIG. 5A may be initiated and the test cycle may begin. Advantageously, waiting for the average voltage to drop below a predetermined threshold should allow time for the noisy signal to dissipate before testing.

[0069] FIG. 5D is a flowchart representing a method 500 for determining an analyte concentration in a test strip based on the waveform of FIG. 5A and measured currents as shown in FIG. 5b. In exemplary step 510, a glucose quantitation test is initiated by inserting test strip 62 into test meter 10 and by depositing a sample on test strip 62. At exemplary step 520, test meter 10 may apply a first test voltage E1 (e.g., approximately 20 mV in Fig. 5A) between the first electrode 66 and the second electrode 64 during the first time interval t ₁ (for example, 1 second in Fig. 5A). The first time interval t ₁ may range from about 0.1 seconds to about 3 seconds and preferably range from about 0.2 seconds to about 2 seconds and most preferably range from about 0.3 seconds to about 1.1 seconds.

[0070] The first time interval t ₁ may be long enough such that the sample receiving chamber 61 may be completely filled with sample, and also such that the reagent layer 72 may at least partially dissolve or solvate. In one aspect, the first test voltage E1 may be a value relatively close to the redox potential of the mediator, such that a relatively small amount of reduction or oxidation current is measured. Fig. 5B shows that a relatively small amount of current is observed during the first time interval t ₁ compared to the second and third time intervals t ₂ and t ₃ . For example, when using potassium ferricyanide and/or potassium ferrocyanide as mediator, the first test voltage E1 in FIG. 5A can range from about 1 mV to about 100 mV, preferably range from about 5 mV to about 50 mV, and most preferably range from about 10 mV to about 30 mV. Although applied voltages are specified as positive values in the preferred embodiments, identical voltages in the negative region can also be used to achieve the intended purpose of the claimed invention. During this interval, the first output current may be sampled by the processor to collect current values for this interval at step 530.

[0071] In exemplary step 540, after applying the first test voltage E1 (step 520) and sampling the output (step 530), test meter 10 applies a second test voltage E2 between first electrode 66 and second electrode 64 (e.g., approximately 300 millivolts in Fig. 5A) during the second time interval t ₂ (for example, approximately 3 seconds in Fig. 5A). The second test voltage E2 may be a different value from the first test voltage E1 and may be sufficiently negative with respect to the redox potential of the mediator such that the limiting oxidation current is measured at the second electrode 64. For example, when using potassium ferricyanide and/or potassium ferrocyanide as a mediator, the second test voltage E2 may range from about zero mV to about 600 mV, preferably range from about 100 mV to about 600 mV, and more preferably about 300 mV.

[0072] The second time interval t ₂ should be long enough such that the rate of formation of the reduced mediator (eg, potassium ferrocyanide) can be tracked based on the absolute value of the oxidation limit current. The recovered mediator is formed through enzymatic reactions with the reagent bed 72 . During the second time interval t ₂ , a marginal amount of the reduced mediator is oxidized in the second electrode 64 and an unlimited amount of the oxidized mediator is reduced in the first electrode 66 to form a concentration gradient between the first electrode 66 and the second electrode 64.

[0073] In an exemplary embodiment, the second time interval t ₂ should also be sufficiently long such that sufficient potassium ferricyanide can diffuse into the second electrode 64 or diffuse out of the reagent at the first electrode. A sufficient amount of potassium ferricyanide is required in the second electrode 64 so that the current limit can be measured to oxidize the potassium ferrocyanide in the first electrode 66 during the third test voltage E3. The second time interval t ₂ can be less than about 60 seconds and preferably can range from about 1.1 seconds to about 10 seconds, and more preferably range from about 2 seconds to about 5 seconds. Similarly, the time interval indicated as t _cap in FIG. 5A may also be extended by a range of times, but in one exemplary embodiment, it has a duration of approximately 20 milliseconds. In one exemplary embodiment, the superimposed AC component of the test voltage is applied from about 0.3 seconds to about 0.4 seconds after application of the second test voltage E2 and induces a sine wave having a frequency of about 109 Hz with an amplitude of about +/- 50 mV. During this interval, the second output current may be sampled by the processor to collect current values for this interval at step 550.

[0074] FIG. 5B shows a relatively small current i _pb after the start of the second time interval t ₂ , after which a gradual increase in the absolute value of the oxidation current is performed during the second time interval t ₂ . A small current i _pb arises from the oxidation of endogenous or exogenous reducing agents after the transition from the first voltage E1 to the second voltage E2, resulting in a gradual increase in the absolute value of the oxidation current during the second time interval t ₂ .

[0075] In exemplary step 560, after applying a second test voltage E2 (step 540) and sampling the output (step 550), test meter 10 applies a third test voltage E3 between first electrode 66 and second electrode 64 (e.g., approximately -300 millivolt in Fig. 5A) during the third time interval t ₃ (for example, 1 second in Fig. 5A). The third test voltage E3 may be a value sufficiently positive with respect to the redox potential of the mediator such that the limiting oxidation current is measured at the first electrode 66. For example, when using potassium ferricyanide and/or potassium ferrocyanide as the mediator, the third test voltage E3 may range from about zero mV to about -600 mV, preferably range from about -100 mV to about -600 mV, and more preferably about -300 mV.

[0076] After applying the third test voltage E3 at step 570, the current values are measured in the third time interval t ₃ . The third time interval t ₃ may be long enough to track the diffusion of the reduced mediator (eg, potassium ferrocyanide) around the first electrode 66 based on the absolute value of the oxidation current. During the third time interval t ₃ , a marginal amount of reduced mediator is oxidized in the first electrode 66 and an unlimited amount of oxidized mediator is reduced in the second electrode 64. The third time interval t ₃ may vary from about 0.1 seconds to about 5 seconds, and preferably ranges from about 0.3 seconds to about 3 seconds, and more preferably range from about 0.5 seconds to about 2 seconds.

[0077] FIG. 5B shows a relatively large current i _pc at the beginning of the third time interval t ₃ , after which a decrease is made to an almost steady state current i _ss for the nominal test strip. In one embodiment, the second test voltage E2 may have a first polarity, and the third test voltage E3 may have a second polarity that is opposite to the first polarity. In another embodiment, the second test voltage E2 may be sufficiently negative with respect to the redox potential of the mediator, and the third test voltage E3 may be sufficiently positive with respect to the redox potential of the mediator. The third test voltage E3 may be applied immediately after the second test voltage E2. However, those skilled in the art will appreciate that the absolute value and polarity of the second and third test voltages may be selected depending on the manner in which the analyte concentration is determined.

[0078] The following describes the determination of glucose concentration for the embodiments described herein, and as indicated at step 580 of FIG. 5D. Fig. 5A and 5B show the sequence of events in the test strip transient. Approximately 1.1 seconds after the initiation of the test sequence (and shortly after setting the second electrode as the working electrode due to the application of the second voltage E2), when the reagent has not yet reached the first electrode and current due to predominantly interfering reducing agents in the plasma (in the absence of a mediator in the second electrode 64), current measurements are taken. Between about 1.4 seconds and about 4 seconds, when (at least in the last part of this interval when the second voltage E2 is applied) the reduced mediator diffuses into the second electrode, the first glucose-proportional current, i _l , is measured. Shortly after setting the first electrode as the working electrode by applying the third voltage E3, 2 single-point measurements (at about 4.1 and 5 seconds according to this embodiment) and one integrated measurement of i _r are taken. Measurements sampled at 1.1, 4.1 and 5 seconds respectively according to this particular embodiment are used to correct i _r for additive current from interfering reducing agents (i2corr). The ratio of i _l to i _r is used to correct i2corr for hematocrit interfering effects.

[0079] In one embodiment, the following equation is then used to determine the glucose concentration:

, где:

, Where:

- G _basic is the analyte concentration;

- i _r is the sum of the third current values during the third time interval;

- i _i is the sum of the second current values during the second time interval;

; и-

; And

- a, b, p and z _gr are predefined coefficients.

.[0080] In one specific example,

.

[0081] In another example, different test strip chemistries can be used in which the times that appear in the current estimate vary according to the above general relationship. Additional details related to the applied waveform and determination of the test strip analyte concentration are provided in U.S. Patent No. 8709232 B2 and International Patent Publication No. WO 2012/012341 A1, previously referenced herein.

[0082] FIG. 6A-6H provide a working example of the technology described herein.

[0083] Starting with FIG. 6A, the underlying mechanism for measurement problems is identified. In FIG. 6A, redox reactions are illustrated for an electrochemical test strip, such as the self blood glucose test strip 62 of FIG. 1. The exemplary strip has two electrodes, a first electrode E1 and a second electrode E2. However, similar results are obtained with three or more electrodes, and the electrodes may be converging, coplanar, or other spaced configurations. The first electrode E1 is coated with a reagent layer that contains a redox mediator (M) and other materials (eg enzyme), while the second electrode E2 has a surface without a reagent coating layer. The first and second electrodes E1 and E2, respectively, are electrically connected to a potentiostat (not shown). In use, the first and second electrodes E1 and E2, respectively, are in contact with the entire blood sample, and an electrical potential (voltage) is applied between the two electrodes. This leads to redox reactions in both electrodes. The resulting current between the first and second electrodes E1 and E2 is measured as a function of time.

[0084] To conduct a test using a test strip, an electrical potential is applied between the first and second electrodes E1 and E2, and the resulting current is measured. The absolute value and polarity of the electrical potential are chosen to initiate the reduction(s) of the mediator(s) in the first electrode E1 and the oxidation(s) of the redox active substance in the second electrode E2.

[0085] The application of a blood sample to the strip sample chamber initiates physical and chemical processes/changes that depend on the physical characteristic (eg, hematocrit) and the redox active substance of the blood sample. The physical processes include reagent layer hydration, mediator dissolution, and bilayer charging (a process for neutralizing charge imbalances near electrode surfaces by rearranging charged particles in the blood). The chemical processes include the oxidation(s) of the redox active in the second electrode E2 and the reduction of the oxidized mediator _Mox in the first electrode E1 as shown in FIG. 1.

[0086] As a result of the physical and chemical processes noted above, the recorded current has a transient that has a unique pattern that deviates from the known Cottrell current decay profile, as illustrated in FIG. 6C. However, the initiation for sample filling described with respect to FIG. 5C must be too late to observe this unique pattern.

[0087] Thus, FIG. 6B illustrates early initiation based on determining that a sample is being applied to the test strip illustrated in FIG. 3A-3F. In this example, the user may apply a blood sample to a test strip, and during the initial stages of application, the test strip should begin to fill with sample, as noted above with respect to FIG. 5C, and an initiating current of 500-700 nA can be applied between the electrodes and voltage values can be measured. Unlike FIG. 5C, when the voltage value drops from approximately 3.0V to a higher predetermined value, such as 1.0V, the test waveform of FIG. 5A may be initiated and the test cycle may begin. Advantageously, this earlier initiation provides monitoring of a portion of the earlier electrochemical behavior, including observation of the turning point illustrated in FIG. 6C.

[0088] FIG. 6C illustrates a plot of current versus time measured after application of an electrical potential, including a turning point at which the current profile transitions, for example, from a non-Cottrell profile, for example, to a Cottrell profile. Fig. 6D illustrates measured current values of the test strip illustrated in FIG. 3A-3F based on the test waveform of FIG. 5A. Fig. 6E illustrates measured current values of the test strip illustrated in FIG. 3A-3F based on a different waveform. In this example, another waveform also exhibits a turning point, as described above.

[0089] In each of the current plots of FIG. 6C-6E, the turning point is marked and has the parameter i_turn current and parameter t_turn time. The turning point is the point at which the first low-level ripple transition ends and the second fade-out transition begins. The first transition part deviates from the Cottrell current decay profile, while the second transition part actually follows the Cottrell current decay profile. The second transition part is completed as soon as the current reaches a steady state or the redox mediator enters the second electrode E2 by diffusion from the reagent layer. The turning point may be identified by process(s)/algorithm(s), which may be developed using various mathematical approaches/technologies.

[0090] If not limited to the theory, the deviation of the transient current process from the attenuation of the Cottrell current, in particular, the first transient part, is likely to result from physical processes that play a predominant role at this stage when changing the active surface area of the first electrode E1 and / or the availability of a mediator for recovery in the first electrode E1. These physical processes are likely dependent on the diffusion of the blood sample. Regardless of the underlying physical mechanism, the time at which the transient current passes from the first transient to the second transient, t _Turn , is a function of diffusion.

[0091] On the other hand, if not limited by theory, at an early stage of the test using a test strip, the reduced mediator probably does not diffuse through the exemplary chamber to reach the surface of the second electrode E2. Therefore, the oxidation current is likely to be predominantly generated by the oxidation of the redox active substance. Simultaneously, the oxidation of the redox active is dependent on the mass transfer of the redox active in the liquid sample. Regardless of the underlying physical mechanism, i _Turn is a function of both the redox active and its diffusion.

[0092] Function for t_turnand function for i_turncan be derived from laboratory data obtained by testing liquid samples with a designated diffusion property and redox active substance(s). This makes it possible to determine diffusion-related features such as, for example, diffusion coefficient, hematocrit (which affects diffusion), coagulation or viscosity. To be able to measure the proportion of any redox active, the redox active(s) of interest must be calibrated as a function of time t_turn turn and additionally as a function of the current i_turn turn. Alternatively, the redox active substance(s) of interest can be represented by a mathematical function that depends on time t_turn turn and current i_turn turn. In any case, after the relationship between the redox active substance(s), the time t_turn turn and current i_turn turn known, it can be used in subsequent measurements to provide an indicator or estimate of the redox active substance or the proportion in the measured current carried out by the redox active substance.

[0093] The indicator of the redox active substance may be an indicator of the concentration of the substance in the sample. The indicator of the proportion contributed by the redox active substance may be the indicator of the proportion in the current. It can be used in subsequent steps or processes to correct all calculations based on current measurements when such calculations require the effects of a redox active to be eliminated. For example, uric acid interferes with electrochemical glucose measurements, and the invention enables the effects of uric acid to be identified and excluded from calculations of glucose levels.

[0094] FIG. 6F is a flowchart representing a method 600 for determining an analyte concentration. In the embodiment of FIG. 6F, method 600 applies the probe to the biosensor in step 610. The biosensor may be an electrochemical cell having electrodes, such as the test strip 62 of FIG. 1. In one example, the electrodes of an electrochemical cell comprise a bare electrode and an electrode at least partially coated with a reagent. In another example, the electrodes of the electrochemical cell are one of converging or coplanar. In one example, the method further includes excitation, after applying the sample to the biosensor, an initiating current between the electrodes of the electrochemical cell, measuring values of the initiating voltage during excitation of the initiating current; and triggering the voltage waveform when the measured trigger voltage falls below a predetermined trigger threshold voltage. In another example, the trigger current is between 500-700 nA and the trigger threshold voltage is between 800-1100 mV.

[0095] Next, method 600 applies the voltage waveform at 620 for at least a first time interval and a second time interval. For example, at 620, any of the waveforms of FIG. 5A, 6D or 6E may be applied to the test strip 62 of FIG. 1. In addition, any waveform may be applied and may include AC and/or DC components. In a further example, the first predetermined voltage is selected to facilitate oxidation of the interference from the applied sample.

[0096] Continuing, method 600 at 630 measures at least first current values during a first time interval and second current values during a second time interval. The waveform can also continue for the third, fourth, fifth, and so on. time intervals, with measurements of the corresponding, third, fourth, fifth, etc. current values. In an additional example, the measurement of the first and second current values is carried out at a frequency between 50-200 Hz.

[0097] The method 600 at 640 then determines the time of the turning point during the first time interval in which the measured first current values transition from the first profile to the second profile, for example, due to the presence of interference in the sample. As explained above, the turning point occurs during the initial stages due to the filling of the test strip 62 with sample. The current value can be measured during the turning point to determine the current at the turning point. In one embodiment, the first profile deviates from the Cottrell profile and the second profile substantially follows the Cottrell profile. In another embodiment, the interference is oxidized in the bare electrode of the electrochemical cell electrodes. In a further embodiment, the interference contains uric acid or ascorbic acid.

[0098] After determining the turning point time at step 640, the method 600 at step 650 calculates the analyte concentration in the sample based on the determined turning point time and at least one current value from the measured first and second current values.

[0099] For example, the calculation step may be based on the determined turning point time and at least one current value from the measured first current values and at least one current value from the measured second current values. In another embodiment, the calculation step is based on the value of the current at the turning point at the time of the turning point.

, в котором:[00100] In one particular implementation, calculating the analyte concentration includes using an equation of the form

, in which:

- G _basic is the concentration of the analyte (in mg/dL);

- a _{i, j} are coefficients;

- x ₀ is a constant;

- x ₁ is t _Turn , the turning point time (in seconds);

- x ₂ is i _r , the sum of at least some of the measured second current values of the second time interval (in microamps);

- x ₃ is one of the first values of the current in the first time interval (in microamps);

- x ₄ is i _Turn , the value of the current in t _Turn (in microamps);

- x ₅ is the inversion of one of the first current values in the first time interval (in 1/microamps);

- x ₆ is the inversion of one of the first current values in the first time interval (in 1/microamps); And

- c is a predefined constant.

изложены ниже в таблице 1.[00101] Specific examples of the application of the linear equation of the form

are set out in Table 1 below.

Table 1. Parameters used in the linear equation.

Waveform x _{1 x2} x _{3 x4 x5 x6} Fig. 6D t _Turn i _r i(2.2 s) i(1.1 s) 1/i(0.05 s) 1/i(1.0 s) Fig. 6E t _Turn i _r i(2.2 s) 0.00 i _Turn 1/i(1.0 s)

, в котором:[00102] In a further specific implementation, calculating the analyte concentration comprises using an equation of the form

, in which:

- G _basic is the concentration of the analyte (in milligrams per deciliter);

- t _Turn is the turning point time (in seconds);

(в микроамперах);-

(in microamps);

- i _pc is the current close to the negative peak of the third current values in the third time interval (in microamps);

- i _pb is the current close to the peak of the second current values in the second time interval (in microamps);

- i _ss is the steady state of the third current values in the third time interval;

- i _r is the sum of at least some of the measured third current values of the third time interval (in microamps); And

- a, b, p and z _gr are predefined coefficients.

[00103] FIG. 6G is a flowchart representing a method 601 for determining an analyte concentration. In the embodiment of FIG. 6G, method 601 applies the probe to the biosensor in step 610. The biosensor may include an electrochemical cell having electrodes, such as the test strip 62 of FIG. 1.

[00104] Next, the method 601 at 620 applies the voltage waveform for at least the first time interval and the second time interval. For example, at 620, any of the waveforms of FIG. 5A, 6D or 6E may be applied to the test strip 62 of FIG. 1.

[00105] Continuing, method 601 at 630 measures at least first current values during a first time interval and second current values during a second time interval.

[00106] The method 601 at step 640 then determines the time of the turning point during the first time interval in which the measured first current values transition from the first profile to the second profile, for example, due to the presence of interference in the sample.

[00107] After determining the turning point time at step 640, the method 601 at step 660 evaluates the physical characteristic of the sample, for example, based on one or more of the turning point time, the first measured current values, and the second measured current values.

[00108] In one case, if the estimated physical property of the sample is in the first range, the method 601 at step 670 calculates the analyte concentration in the sample using the first model, the first measured current values, and the second measured current values. If the estimated physical property of the sample is in the second range, the method 601 at step 670 calculates the analyte concentration in the sample using the second model based on the determined turning point time, the first measured current values, and the second measured current values.

, и вычисление концентрации аналита с использованием второй модели содержит использование уравнения формы:[00109] In one specific example, calculating the analyte concentration using the first model comprises using an equation of the form

, and the calculation of the analyte concentration using the second model contains the use of an equation of the form:

, в котором:

, in which:

является концентрацией аналита, вычисленной с использованием первой модели (в мг/дл);-

is the analyte concentration calculated using the first model (in mg/dL);

являются предварительно определенными коэффициентами первой модели;-

are predetermined coefficients of the first model;

являются константами (например, равными 1);-

are constants (for example, equal to 1);

являются предикторами первой модели на основе измеренных значений тока;-

are predictors of the first model based on the measured current values;

- c ₁ is a predefined constant of the first model;

является концентрацией аналита, вычисленной с использованием второй модели (в мг/дл);-

is the analyte concentration calculated using the second model (in mg/dL);

являются предварительно определенными коэффициентами второй модели;-

are predetermined coefficients of the second model;

являются предикторами второй модели на основе измеренных значений тока; и-

are predictors of the second model based on the measured current values; And

- c ₂ is a predefined constant of the second model.

[00110] In one embodiment, the first model contains the first coefficients and the second model contains the second coefficients, and the first coefficients and the second coefficients are determined by linear optimization. In another embodiment, the physical characteristic estimation comprises using turning point time.

[00111] The following is a working example of estimating one particular physical characteristic, namely hematocrit level, using the two waveforms of FIG. 6D or according to FIG. 6E.

, в котором оценки и коэффициенты линейной модели задаются посредством нижеприведенных таблиц 2-6, в зависимости от того, какая форма сигнала выбирается из таблицы 1.[00112] The first step is that a linear model is used to estimate hematocrit H. The model uses the following equation:

, in which the estimates and coefficients of the linear model are given by the following tables 2-6, depending on which waveform is selected from table 1.

Table 2. Linear model estimates for hematocrit

The waveform of FIG. 6D The waveform of FIG. 6E

ln(t _Turn ) ln(t _Turn )

log(i1,0) log(i1,0)

ln(i0.05) ln(i0.05)

i2,2 i2,2

i1,1 i _Turn

log(i _r ) log(i _r )

Table 3. Coefficients for the waveform of FIG. 6D

Member Coefficient Member Coefficient C 187 'x2:x5' 0.313 'x1' -1.47 'x2:x6' -4.17 'x2' 35.3 'x3:x5' 0.254 'x3' -21.7 'x3:x6' 1.45 'x4' 4.23 'x4:x5' -0.0938 'x5' -3.09 'x4:x6' -1.45 'x6' -49.4 'x5:x6' 0.532 'x1:x2' 3.65 'x1^2' -7.8 'x1:x3' -1.48 'x2^2' 1.87 'x1:x4' -0.311 'x3^2' -2.71 'x1:x5' -0.194 'x4^2' 0.213 'x1:x6' -3.47 'x5^2' 0.0436 'x2:x3' 2.76 'x6^2' 4.08 'x2:x4' 0.89

Table 4. Coefficients for the waveform of FIG. 6E

Member Coefficient Member Coefficient C 126 'x2:x6' -7.1 'x1' 4.2 'x3:x4' -0.644 'x2' 36.4 'x3:x5' -0.97 'x3' -51.7 'x3:x6' 3.08 'x4' -2.64 'x4:x5' -0.0703 'x5' -3.16 'x4:x6' -0.89 'x6' -32.9 'x5:x6' 0.193 'x1:x2' -3.17 'x1^2' -6.82 'x1:x3' -2.95 'x2^2' 5.75 'x1:x4' -1.28 'x3^2' -7.53 'x1:x6' -3.86 'x4^2' 0.252 'x2:x3' -3.36 'x5^2' -0.0278 'x2:x4' 1.98 'x6^2' 2.84 'x2:x5' -0.613

[00113] Then, after using the set of equations above to determine the estimated hematocrit H, the linear model glucose calculation is used with the following coefficients selected depending on which range H falls in, depending on which waveform selected.

[00114] FIG. 6H illustrates an experimental validation of an improved analyte concentration measurement in the presence of an interferent using the linear model of Table 1 with the waveform of FIG. 6d. In FIG. 6H, on the left side, the first three box plots illustrate an approximate blood glucose target of 70 mg/dL when uric acid peaks at 0, 2, and 4, respectively. The second three box plots illustrate an approximate blood glucose target of 300 mg/dL when uric acid peaks at 0, 2, and 4, respectively, as defined in Table 7 below. Each individual box plot contains all results at peak levels of 0, 2 and 4 ascorbic acid as given in Table 7.

Table 7. Determination of peak levels illustrated in FIG. 6H.

Level 0 Level 2 Level 4 Added uric acid (mg/dl) 0.00 11.91 23.81 Ascorbic acid added (mg/dl) 0.00 3.19 6.38

[00115] As illustrated in FIG. 6H, using the linear model of Tables 4 and 7 as described above, the present technology provides corrected analyte concentration measurements.

[00116] Although the invention is described in terms of specific variations and illustrative drawings, those skilled in the art will recognize that the invention is not limited to the described variations or drawings. In addition, if the methods and steps described above indicate certain events occurring in a certain order, those skilled in the art will recognize that the order of certain steps may be modified, and that such modifications correspond to variations of the invention. Additionally, some of the steps may be performed in parallel in a parallel process, if possible, and may also be performed sequentially as described above. Therefore, to the extent that there are variations of the invention that are within the spirit of the disclosure or are equivalent to the inventions contained in the claims, this patent should also cover those variations.

[00117] To the extent that the claims state the phrase "at least one of" with reference to a plurality of elements, it is intended to mean at least one or more of the listed elements and is not limited to at least one of each element. For example, "at least one of element A, element B, and element C" is intended to indicate only element A, or only element B, or only element C, or any combination of the above. "At least one of element A, element B, and element C" is not intended to be limited to at least one of element A, at least one of element B, and at least one of element C.

[00118] This written description uses examples to disclose the invention, including the optimal mode, as well as to enable those skilled in the art to practice the invention, including the formation and use of all devices or systems and implementation of all included methods. The patentable scope of the invention is defined by the claims and may include other examples that should be obvious to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have constructs that do not differ from the verbatim language of the claims, or if they include equivalent constructs with minor differences from the verbatim language of the claims.

[00119] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms are intended to also include the plural forms, unless the context clearly indicates otherwise. It should be further understood that the terms "comprise" (and any form of "comprise" such as "comprises" and "comprising"), "have" (and any form of "have" , such as "has" and "having"), "include" (and any form of "include", such as "includes" and "including") and "contain" (and any form of "contain" such as "contains" and "containing" are multiple linking verbs. As a result, a method or apparatus that "comprises", "has", "comprises", or "contains" one or more steps or elements has those one or more steps or elements, but is not limited to having only these one or more steps or elements. Similarly, a method step or device element that "comprises", "has", "includes", or "contains" one or more features, has those one or more features, but is not limited to having only those one or more signs. In addition, a device or structure that is configured in a particular way is at least configured in such a way, but may also be configured in ways that are not listed.

[00120] Respective structures, materials, acts, and equivalents of all means or step plus function elements in the following claims, if any, are intended to include any structure, material, or act to perform a function in combination with other claimed elements, as specifically stated in the claims. The description set forth herein is provided for purposes of illustration and description, but is not intended to be complete or limited to the form disclosed. Many modifications and changes should become apparent to those skilled in the art without departing from the scope and spirit of the disclosure. An embodiment is selected and described in order to best explain the principles of one or more of the aspects set forth herein and the practical application, and to enable others skilled in the art to understand one or more of the aspects described herein for various embodiments. with various modifications that suit the particular intended use case.

Claims (83)

1. A method for determining the concentration of an analyte in a fluid sample of a physiological fluid, the method comprising the steps of: - apply the sample to the biosensor, and the biosensor contains an electrochemical element having electrodes; applying a predetermined voltage waveform including a first predetermined voltage applied for at least a first time interval and a second predetermined voltage applied for a second time interval to the biosensor electrodes; - measuring at least the first current values during the first time interval and the second current values during the second time interval, in which the current i _pb , representing the transition from the first predetermined voltage to the second predetermined voltage, occurs during the initial part of the second time interval; - determine the time of the turning point during the first time interval in which the measured first current values pass from the first profile to the second profile; And - calculating the concentration of the analyte in the sample based on the determined turning point time and at least one current value from the measured first and second current values, the measured first current values moving from the first profile to the second profile due to the presence of an interference in the liquid sample, and moreover the turning point time occurs before the occurrence of i _pb . 2. The method of claim 1, wherein the step of calculating is based on the determined turning point time and at least one current value from the measured first current values and at least one current value from the measured second current values. 3. The method of claim 1, wherein the step of calculating is based on the value of current at the turning point measured during the turning point. 4. The method of claim 1, wherein the calculation of the analyte concentration comprises using an equation of the form

, in which: - G _basic is the concentration of the analyte (in mg/dL); - a _i,j are coefficients; - x ₀ is a constant; - x ₁ is t _Turn , the turning point time (in seconds); - x ₂ is i _r , the sum of at least some of the measured second current values of the second time interval (in microamps); - x ₃ is one of the first values of the current in the first time interval (in microamps); - x ₄ is i _Turn , the value of the current in t _Turn (in microamps); - x ₅ is the inversion of one of the first current values in the first time interval (in 1/microamps); - x ₆ is the inversion of one of the first current values in the first time interval (in 1/microamps); And - c is a predefined constant. 5. The method of claim 1, wherein the predetermined voltage waveform is further applied during a third time interval, the measurement further comprises measuring third current values during the third time interval, and the step of calculating is based on the determined turning point time and at least one current value from the measured first, second and third current values. 6. The method of claim 5, wherein the calculation of the analyte concentration comprises using an equation of the form

, in which: - G _basic is the concentration of the analyte (in mg/dL); - a _i,j are predetermined coefficients; - x ₀ is a constant; - x ₁ is t _Turn , the turning point time (in seconds); - x ₂ is i _r , the sum of at least some of the measured third current values of the third time interval (in microamps); - x ₃ is one of the second values of the current in the second time interval (in microamps); - x ₄ is i _pb close to the peak of the second current values in the second time interval (in microamps); - x ₅ is the inversion of one of the first current values in the first time interval (in 1/microamps); - x ₆ is the inversion of one of the first current values in the first time interval (in 1/microamps); And - c is a predefined constant. 7. The method of claim 5, wherein the calculation of the analyte concentration comprises using an equation of the form

, in which: - G _basic is the concentration of the analyte (in milligrams per deciliter); - t _Turn is the turning point time (in seconds); -

(in microamps); - i _pc is close to the negative peak of the third current values in the third time interval (in microamps); - i _pb is close to the peak of the second current values in the second time interval (in microamps); - i _ss is the steady state of the third current values in the third time interval; - i _r is the sum of at least some of the measured third current values of the third time interval (in microamps); And - a, b, p and z _gr are predefined coefficients. 8. The method of claim 1, further comprising the steps of: - excite, after applying the sample to the biosensor, initiating current between the electrodes of the electrochemical element; - measure the values of the initiating voltage during the excitation of the initiating current; And - initiate a predetermined voltage waveform when the measured initiating voltage falls below the initiating threshold voltage. 9. The method according to claim 8, wherein the initiating current is between 500-700 nA and the initiating threshold voltage is between 800-1100 mV. 10. The method of claim 1, wherein the first predetermined voltage is selected to facilitate oxidation of the interference from the applied sample. 11. The method of claim 1 wherein the first profile deviates from the Cottrell profile and the second profile substantially adheres to the Cottrell profile. 12. The method of claim. 1, in which the interference is subjected to oxidation in the uncoated electrode of the electrochemical cell. 13. The method according to p. 12, in which the interference contains uric acid or ascorbic acid. 14. The method of claim 1 wherein the electrodes of the electrochemical cell comprise a bare electrode and an electrode at least partially coated with a reagent. 15. The method of claim 1, wherein the electrodes of the electrochemical cell are one of inverted or coplanar. 16. The method according to claim 1, wherein the measurement of the first and second current values is carried out at a frequency between 50-200 Hz. 17. A method for determining the concentration of an analyte in a fluid sample of a physiological fluid, the method comprising the steps of: - apply the sample to the biosensor, and the biosensor contains an electrochemical element having electrodes; applying a predetermined voltage waveform for at least a first time interval and a second time interval; - measure at least the first current values during the first time interval and the second current values during the second time interval; - determine the time of the turning point during the first time interval in which the measured first current values pass from the first profile to the second profile; And - evaluate the physical characteristic of the sample on the basis of the turning point time, the first measured current values and the second measured current values; - if the estimated physical characteristic of the sample is in the first range, calculate the analyte concentration in the sample using the first model based on the first measured current values and the second measured current values; And - if the estimated physical property of the sample is in the second range, calculate the analyte concentration in the sample using the second model based on the determined turning point time, the first measured current values and the second measured current values, the first model containing the first coefficients and the second model containing the second coefficients , and the first coefficients and the second coefficients are determined by linear optimization. 18. The method of claim 17 wherein calculating the analyte concentration using the first model comprises using an equation of the form

, and the calculation of the analyte concentration using the second model contains the use of an equation of the form:

, in which: -

is the analyte concentration calculated using the first model (in mg/dl); -

are predetermined coefficients of the first model; - x ₀ ¹ and x ₀ ² are constants (for example, 1); -

are predictors of the first model based on the measured current values; - c ₁ is a predefined constant of the first model; -

is the analyte concentration calculated using the second model (in mg/dL); -

are predefined coefficients of the second model; -

are predictors of the second model based on the measured current values; And - c ₂ is a predefined constant of the second model. 19. The method of claim 17 wherein calculating the analyte concentration using the first model comprises using an equation of the form

, and the calculation of the analyte concentration using the second model contains the use of an equation of the form:

, in which: -

is the analyte concentration calculated using the first model (in mg/dl); -

And

are predetermined coefficients of the first model; -

is the analyte concentration calculated using the second model (in mg/dl); -

And

are predefined coefficients of the second model; -

(in microamperes); - i _pc is close to the negative peak of the third current values in the third time interval (in microamps); - i _pb is close to the peak of the second current values in the second time interval (in microamps); - i _ss is the steady state of the third current values in the third time interval; - i _r is the sum of at least some of the measured third current values of the third time interval (in microamps); And - b, c and p are predefined coefficients.

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