HK1175840B - Method for measuring analyte concentration in a liquid sample - Google Patents

Description

Method for measuring analyte concentration in liquid sample

Background

Recently, there has been a trend to monitor various health conditions by the patient himself. For example, diabetics traditionally monitor blood glucose levels multiple times per day. Due to its nature, glucose monitoring requires a high degree of accuracy in the reported glucose values, with little or no interference from other substances contained in the sample. Other types of body fluid tests require similar features.

The most common techniques for measuring glucose levels in blood or interstitial fluid utilize electrochemical techniques. Electrochemical detection of glucose is typically based on measurement of an electrical signal or property proportional to the analyte concentration. The signal is generated by a direct or indirect redox reaction occurring on the surface of the electrode or in the direct vicinity thereof. Some conventional electrochemical techniques include amperometry, coulometry, and/or impedance measurement. However, there are several drawbacks to these techniques. Due to the diffusion-controlled nature of the measurement signal, amperometric measurement techniques typically require long measurement times and may be susceptible to interference from varying hematocrit levels. While these problems can be solved using impedance measurement techniques, impedance techniques typically require complex and expensive equipment. Equipment costs are always a concern for home diagnostic test settings and settings in other medical areas.

Accordingly, improvements in this area are needed.

Disclosure of Invention

One aspect relates to a method for determining a glucose concentration in a body fluid. The body fluid in the biosensor is analyzed by differential pulse voltammetry, and the biosensor includes at least a reagent covering the working electrode. The instrument applies short, high frequency voltage pulses to the body fluid in the biosensor to maintain the diffusion layer within the reagent of the working electrode, and the voltage of the pulses is incrementally increased. The instrument determines a glucose concentration of the body fluid based on a response to the pulse within a voltage window below the peak diffusion limited current, and the instrument outputs a glucose concentration result.

Another aspect relates to a method of analyzing glucose concentration in a body fluid by differential pulse voltammetry. One or more pulses are applied to the body fluid within a voltage window below the peak diffusion limited current. The glucose concentration is determined based on the response to the pulse in the voltage window.

Yet another aspect relates to a method of analyzing an analyte concentration in a bodily fluid, such as, for example, whole blood, serum, plasma, urine, etc., by applying one or more voltage pulses in a limiting voltage window below a peak diffusion limited current to the bodily fluid. The voltage pulse is short to maintain the diffusion layer within the reagent of the working electrode. The analyte concentration is determined based on the response to the pulse in the threshold voltage window. Potential analytes include glucose, cholesterol, triglycerides, lactate, and the like, as known to those skilled in the art.

Further forms, objects, features, aspects, benefits, advantages, and embodiments of the present invention will become apparent from the detailed description and drawings provided herein.

Drawings

FIG. 1 is a diagram of a blood glucose monitoring system capable of using the differential pulse voltammetry techniques described herein, according to one embodiment.

FIG. 2 shows an example of a voltage signal that may be applied to a body fluid sample according to the described differential pulse voltammetry technique.

Fig. 3 shows an example of another differential pulse voltammetry waveform, which shows the evolution of the signal over time.

FIG. 4 is a differential pulse voltammogram of control solutions containing 66, 97, 220, 403, 648 and 709 mg/dl glucose, with the potentials reported against an Ag/AgCl reference electrode.

FIG. 5A is a differential pulse voltammogram of blood containing a target glucose concentration of 20 mg/dl and hematocrit levels of 25, 45, and 65 percent, with the potentials being compared to an Ag/AgCl reference electrode.

FIG. 5B is a differential pulse voltammogram of blood containing a target glucose concentration of 50 mg/dl and hematocrit levels of 25, 45, and 65 percent, with the potentials being compared to an Ag/AgCl reference electrode.

FIG. 5C is a differential pulse voltammogram of blood containing a target glucose concentration of 100 mg/dl and hematocrit levels of 25, 45, and 65 percent, with the potentials being compared to an Ag/AgCl reference electrode.

FIG. 5D is a differential pulse voltammogram of blood containing a target glucose concentration of 250 mg/dl and hematocrit levels of 25, 45, and 65 percent, with the potentials being compared to an Ag/AgCl reference electrode.

FIG. 5E is a differential pulse voltammogram of blood containing a target glucose concentration of 500 mg/dl and hematocrit levels of 25, 45, and 65 percent, with the potentials being compared to an Ag/AgCl reference electrode.

FIG. 6A is a graph showing current as a function of glucose concentration at-0.05V, where the results of 10 measurements performed with the same solution in a three-electrode mode were averaged.

Fig. 6B is a graph showing current as a function of glucose concentration at 0.0V, where the results of 10 measurements performed with the same solution in a three-electrode mode were averaged.

Fig. 7A is a graph showing current as a function of glucose concentration at 0.1V, where the results of 10 measurements performed with the same solution in a two-electrode mode were averaged.

Fig. 7B is a graph showing current as a function of glucose concentration at 0.2V, where the results of 10 measurements performed with the same solution in a two-electrode mode were averaged.

Fig. 8A is a graph showing current as a function of glucose concentration at 0.15V for experiments performed in the two-electrode mode, where the pre-pulse length was doubled to 0.05 seconds.

Fig. 8B is a graph showing current as a function of glucose concentration at 0.15V for experiments performed in the two-electrode mode, where the pre-pulse length and pulse length were doubled to 0.05 seconds.

Fig. 8C is a graph showing current as a function of glucose concentration at a shorter potential range (0.05 to 0.25V) with respect to experiments performed in the two-electrode mode.

FIG. 9 is a graph comparing predicted glucose concentrations against actual glucose concentrations using 3 calibration parameters at hematocrit levels of 25 percent, 45 percent, and 65 percent.

FIG. 10 is a graph comparing predicted glucose concentrations against actual glucose concentrations using 15 calibration parameters at hematocrit levels of 25 percent, 45 percent, and 65 percent.

Detailed Description

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. One embodiment of the invention is shown in great detail, however, it will be apparent to those skilled in the relevant art that some features that are not relevant to the present invention may not be shown for the sake of clarity.

The body fluid analysis techniques and systems described herein address the issue of hematocrit interference when rapidly detecting analyte concentrations. This problem is solved by using a pulsed voltammetry technique, in which short high frequency voltage pulses are applied to maintain the diffusion layer within the reagent of the working electrode, and the pulses are sequentially increased within a limiting voltage window (or range) below the voltage that creates the peak diffusion limited current. The glucose concentration is then determined using readings below the peak diffusion limited current. With this technique, the glucose concentration can be determined relatively quickly (e.g., within 5 seconds) and is generally independent of the hematocrit level of the fluid being analyzed. Although not specific, it is theorized that the relatively short pulse ensures that the diffusion layer remains in the reagent layer such that an observed current is generated by the analyte diffusing within the reagent layer. Therefore, interference by red blood cells is small.

This technique can be used to analyze glucose concentrations using two-electrode or three-electrode (or more) electrochemical-type test strips. The potential window may vary depending on the electrode arrangement. By using only Direct Current (DC) excitation at low potentials, electronics and other systems in the instrument can be simplified and short measurement times can be achieved. For example, the test may be completed within 5 seconds (or less) of drop detection. In addition, the low applied potential may eliminate the contribution of common interferents to the current response, providing more accurate results.

An example of a glucose monitoring system 30 configured to measure analyte levels using a Differential Pulse Voltammetry (DPV) technique as described herein is shown in fig. 1. The system 30 includes a biosensor 32 and an instrument 34, the biosensor 32 being a test strip in the illustrated example. As shown, the test strip 32 is attached to an instrument 34 and provides the analytical results on an output device 36. Biosensors and instruments are well known in the art and for the sake of clarity they will not be discussed in detail below. As previously mentioned, there are some difficulties in rapidly and inexpensively analyzing fluid samples using conventional electrochemical analysis techniques, where the blood samples used have varying hematocrit. The present inventors have discovered a unique technique and system for addressing the problem of hematocrit interference when rapidly detecting analyte concentrations. In particular, the DPV technique is used, in which short high-frequency voltage pulses are applied in a limiting voltage window or range below the peak diffusion-limited current. The resulting response signal is then used to determine an analyte concentration such as a glucose level. Using this technique, the glucose concentration may be determined relatively quickly with little hematocrit interference, and the electronics in the instrument 34 may be relatively inexpensive.

FIG. 2 is a graph 40 illustrating an example of an applied potential waveform for analyzing a fluid sample using, for example, the glucose monitoring system 30 of FIG. 1. Fig. 40 shows the potential waveform applied by the instrument 34 to the test strip 32 during analysis. In one example, a solution containing glucose, such as blood, is applied to the test strip 32 and a potential waveform as shown in fig. 1 is applied after the solution diffuses through the capillary in the electrochemical region containing the electrodes and reagents. As can be seen in fig. 1, when a body fluid is initially applied to the test strip 32, there is a quiet time or incubation period that allows sufficient time for the enzymatic reaction to occur. In the example shown, the incubation period is about 3 seconds, but in other examples, the incubation period may be longer or shorter. For example, a 2 second incubation period or no incubation period at all may be included.

After the incubation period, the instrument 34 applies a series of pulses at increasing potentials. In one example, a 50 millivolt (mV) pulse is applied for 25 milliseconds (msec) and repeated every 25 msec. For each pulse, the baseline pulse is increased in increments of 4 mV in this example. In one particular example, the pulses have the form of a symmetrical wave superimposed on a staircase waveform, where the period of the symmetrical wave is the same as the time step of the staircase wave.

Other types of waveforms may be used for analyzing the body fluid. For example, graph 42 of FIG. 3 shows an example of a waveform in which a 50 mV pulse is applied and increased in 4 mV increments in a potential window of-100 mV to 300 mV.

During analysis, the instrument 34 measures the system response as the difference between the current at the end of the pulse and the current just prior to the application of the pulse. In other words, the signal current is the difference between the currents sampled at the end of the positive pulse. FIG. 4 is a graph 44 showing differential pulse voltammograms of control solutions with various glucose concentrations using this technique. In particular, graph 44 in FIG. 4 shows a voltammogram for control solutions having glucose concentrations of 66, 97, 220, 403, 648, and 709 mg/dl. The potential window was 400 mV and the duration of the test lasted 5 seconds. For one exemplary reagent chemistry, glucose in the blood is converted to gluconolactone, and at the same time, the electrons generated by the reaction participate in the reduction of the catalyst. By applying an increasing positive potential, the oxidation of the reduced form of the catalyst is induced. By pulsing the potential to have more positive values, the current increase is proportional to the amount of reduction catalyst that is converted to glucose in the sample, respectively. When the rate of diffusion of the electroactive species to the electrode is lower than the rate of the redox reaction, the current peak at a potential close to the standard redox potential of the oxidation/reduction couple of the catalyst is followed by a drop in current. This diffusion limiting effect can be seen in the peaking of the curves shown in fig. 4, where the relative height of the peaks generally increases with increasing glucose concentration.

As previously mentioned, variations in hematocrit levels can adversely affect glucose concentration readings, and therefore, there is a need to reduce the effects of hematocrit. To understand this problem, blood samples with hematocrit content adjusted to 25 percent, 45 percent, and 65 percent with various glucose concentrations of 25, 50, 100, 250, and 500 mg/dl were analyzed. FIGS. 5A, 5B, 5C, 5D, and 5E contain graphs 46, 48, 50, 52, and 54, which show differential pulse voltammograms for blood samples having hematocrit concentrations of 25 percent, 45 percent, and 65 percent, respectively, at glucose concentrations of 25, 50, 100, 250, and 500 mg/dl, respectively. In all graphs, the maximum peak diffusion limited current is at about 70 mV. By comparing samples with different hematocrit levels but the same glucose content, it can be observed that the peak current decreases as the percent hematocrit increases. This accounts for the hematocrit effect, where the measured glucose concentration deviates from the actual glucose concentration in a sample with a blood cell (hematocrit) content. Surprisingly, it was observed that the effect of hematocrit can be minimized in the potential range below the peak diffusion limited current. In particular, as can be seen in the graphs, the hematocrit effect is negligible in the potential window of-100 mV to 0 mV. The hematocrit effect is minimal even in the potential range of-100 mV to 10 mV. Thus, it was observed that measuring readings below the peak diffusion limited current using a pulsed voltammetry technique, in which short high frequency voltage pulses are used, helps to improve glucose concentration readings at varying hematocrit levels.

To further reflect this improvement, fig. 6A shows a graph 56 showing current at-0.05 mV as a function of glucose concentration at hematocrit levels of 25 percent, 45 percent, and 65 percent, and fig. 6B shows a graph 58 showing current at 0 mV as a function of glucose concentration at hematocrit levels of 25 percent, 45 percent, and 65 percent. As should be appreciated, the measurements in these graphs 56, 58 are both made using the pulsed voltammetry technique described above, where the current is measured below the diffusion limited peak current (i.e., within the potential window described above). The test was conducted for the system described above in which the test strip 32 had three electrodes (i.e., the working electrode, the counter electrode, and the reference electrode). In particular, the potential was measured against an Ag/AgCl reference electrode. In fig. 6A and 6B, the arrow columns indicate ± 1 standard deviation. The current values of ten measurements performed with the same solution were averaged, with hematocrit levels varying between 25 percent, 45 percent, and 65 percent. As can be seen, there is considerable overlap in the average readings at all the hematocrit levels shown, as well as the glucose concentration.

As described above, it is theorized that the relatively short, high frequency voltage pulses help maintain the diffusion layer within the reagent, thereby reducing the hematocrit effect. Using the previous 50 and 0 mV examples, the applied potentials correspond to measurement times of 0.625 and 1.25 seconds, respectively, which exclude incubation times. Assuming radial diffusion, the diffusion layer thickness (d) at 0.625 seconds can be calculated according to the following equation 1:

d=sqrt(2Dt)formula 1

Wherein:

d= thickness of diffusion layer

D= diffusion coefficient

tTime.

5*10^-6 cm²The diffusion coefficient (D)/sec is characteristic of most analytes in aqueous solutions. Using equation 1, the diffusion layer thickness (d) at 0.625 seconds (t) is 25 micrometers (μm). As previously described, the pulses were applied in 25 millisecond pulses. By applying a 25 millisecond pulse according to equation 1, only a 5 micron diffusion layer will be sampled. Thus, the response current generated by the analyte diffuses into the reagent layer where red blood cells are less likely to be present. By taking measurements based on a voltage window below the redox potential of the oxidation/reduction pair (i.e., operating without crossing the potential), the kinetics of the reaction will become a limiting factor, which in turn minimizes the contribution from diffusion. As can be seen from these results, the technique is able to accurately predict glucose in the 20 to 500 mg/dl concentration range within the minimal contribution from hematocrit and to detect glucose quickly.

In the previous example, the test strip 32 was a three-electrode configuration, i.e., working, counter, and reference electrode mode, in which an external Ag/AgCl reference electrode was used. It will be appreciated that the technique may be adapted to use only two electrodes. For example, the test strips 32 may comprise Aviva brand test strips manufactured by Roche Diagnostics, Inc. When using a two-electrode strip 32, the parameters are adjusted by changing the potential window to 0.5-0.55 volts. Fig. 7A contains a graph 60 showing current at 0.1 volts as a function of glucose concentration at 25 percent, 45 percent, and 65 percent hematocrit levels. FIG. 7B shows a graph 62 illustrating the resulting current as a function of glucose concentration at 0.2 volts using the two-electrode mode for hematocrit levels of 25 percent, 45 percent, and 65 percent. For both fig. 7A and 7B, the pulse length and pulse interval are the same as above, and so are the pulse voltages and voltage step sizes. That is, the pulse length and pulse interval are 25 msec and the pulse voltage is 50 mV with a step size of 4 mV. The potential window is from 0.5 to 0.55 volts. Although the responses shown in fig. 7A and 7B for the two-electrode mode appear to be less stable than the three-electrode mode, the graphs still show good sensitivity to glucose concentration. Like the previous example, by measuring the response at a low potential within the first few seconds of its measurement, the hematocrit effect is reduced. In other words, by applying and measuring pulses below the peak diffusion limited current, the hematocrit effect is reduced.

Other experimental conditions provided similar results to those described above. Fig. 8A, 8B, and 8C show graphs 64, 66, 68 showing current as a function of glucose concentration at 0.15 volts for experiments performed using the two-electrode type test strip 32. In the results shown in fig. 8A, the pulse sequence was modified in which the pre-pulse or pulse interval length was doubled from 25 milliseconds to 50 milliseconds (0.05 seconds). The error bars in fig. 8A represent ± 1 sample standard deviation units and the current values of ten measurements performed with the same solution were averaged. The current was measured for hematocrit levels of 25 percent, 45 percent, and 65 percent. As can be seen in fig. 8B, the pre-pulse length and the pulse length are each doubled to a length of 0.5 seconds, respectively. In this particular example, the sampling rate was adjusted so that the duration of the experiment was constant. As can be seen in the current response in fig. 8B, the current response was similar at all hematocrits (25 percent, 45 percent, and 65 percent). Similarly, the error bars represent ± 1 sample standard deviation units and the current values for ten measurements performed with the solution are averaged. Fig. 8C shows the current response, where a shorter potential range of 0.05 to 0.25 volts was used, which in turn further reduced the test time. From the results shown in fig. 8A, 8B, and 8C, as well as other examples, it should be appreciated that the technique is capable of predicting glucose concentrations in the 20 to 500 ml/dl concentration range with minimal hematocrit interference.

The accuracy of this technique can be further improved by incorporating calibration parameters. In particular, by using calibration parameters instead of a single potential constant, the accuracy of the technique can be further improved. The graph 70 of fig. 9 shows the results of a non-linear regression technique using three calibration parameters. In particular, the curve compares the predicted glucose concentration to the actual glucose concentration using 3 calibration parameters at 25 percent, 45 percent, and 65 percent hematocrit levels. The three calibration parameter examples provided in fig. 9 provide excellent correlation between predicted glucose concentration and measured glucose concentration. In particular, using linear regression, the fitting coefficient (R)²) Is 0.9692. In a similar analysis using 15 calibration parameters, shown in graph 72 of FIG. 10, the fitting coefficient (R) is²) To 0.9962 for comparing the predicted and actual glucose concentrations used in the above technique at 25 percent, 45 percent and 65 percent hematocrit levels.

A specific example of such a technique for measuring the glucose concentration in blood will now be described. Initially, there is a 2 second quiet time for sufficient time to allow the enzymatic reaction to occur when applying the bodily fluid to the test strip 32 for analysis. After this quiet period, the instrument 34 pulses the potential to an ever increasing potential within a potential window below the maximum (diffusion limited) current response. In one particular form, a 50 mV pulse is applied for 25 milliseconds and is repeated every 25 milliseconds. For each pulse, the baseline pulse was increased by 4 mV. Again, the potential range or window in which the pulse is applied may vary depending on the nature of the test strip, but the window is below the peak response current. The instrument 34 measures the response as the difference between the current at the end of the pulse and the current just before the pulse is applied. By measuring the current just before the pulse is applied, the effect of the charging current can be reduced. The meter 34 compares the response (below the peak current) to the response for known glucose concentrations to determine the measured glucose level. The meter 34 provides the measured glucose level to the user on an output device 36, such as a display.

In one example, only a few pulses of about 150 mV are applied (in a two-electrode mode), and the glucose concentration is determined based on the response current at one potential. However, the detection accuracy can be further improved by performing the measurement at three different potentials. In yet another example, the same accuracy can be achieved when measuring over a narrow potential window, but with an improvement in measurement time. In the example for a three electrode system, 50 mV pulses are applied in 4 mV increments to cover the range of-100 to 300 mV (400 mV total).

As will be appreciated, the above-described techniques provide a simple diagnostic method for use in DC-type excitation signals. Furthermore, short sample measurement times and low potentials are allowed. In alternative embodiments, it is contemplated that the detection time may be further reduced to below 5 seconds when a single potential measurement is performed. It should also be appreciated that the applied lower potential below the peak diffusion limited current eliminates potential contributions from common interferers.

It should be appreciated that potentiostats and instruments may be used interchangeably to perform the techniques described herein. While many of the test results discussed above were generated using a potentiostat, it should be recognized that instruments may be used instead, particularly in a home diagnostic setting. The instrument 34 may include components such as a display, speaker, processor, memory, power source such as a battery, and/or electrical contact pins for connecting to the test strip 32. However, it should be appreciated that other types of electronic devices may utilize these measurement techniques in addition to the illustrated instruments. In one particular example, Aviva brand test strips sold by Roche Diagnostics are used, but it should be appreciated that the above-described technique is suitable for use in other types of test strips 32. For example, these techniques may be used to analyze glucose concentrations using two-electrode or three-electrode (or more) electrochemical-type test strips. The potential window may vary depending on the electrode arrangement. In one particular form, Aviva @teststrips were used with this technique. The technique provides an alternative measurement method for determining blood glucose concentrations to compare to the current technique for the Aviva ® type system. By using only DC excitation at low potentials, the electronics and other systems in the instrument can be simplified and short measurement times can be achieved. For example, the test may be completed within 5 seconds of drop detection. In addition, the low applied potential may eliminate the contribution of common interferents to the current response, providing more accurate results.

As used in the specification and claims, the following definitions apply:

the term "differential pulse voltammetry" is used in a broad sense and is meant to include electrical measurement techniques in which a series of regular voltage pulses are superimposed on a linear or step-wise sweep. The current is measured immediately before and after each potential change and the current differential is plotted as a function of the potential. The waveform of the pulse may be a square wave or may include other shape types of pulses.

The term "diffusion layer" includes the region, typically near the working electrode, where the concentration of the analyte being measured is different from the volumetric concentration of the solution. This diffusion layer expansion leads to T^1/2The proportional current drops. Diffusion is the movement of material from a region of high concentration to a region of lower concentration. Peaking currents are observed due to the combined effect of the decrease in electrical surface concentration and the spread of the diffusion layer over time.

The language used in the claims and specification has its plain and ordinary meaning only, unless otherwise explicitly defined above. The words in the above definitions have their plain and ordinary meaning only. These plain and ordinary meanings include all consistent dictionary definitions from the recently published Webster dictionary and the Random House dictionary.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes, equivalents, and modifications that come within the spirit of the invention as defined by the following claims are desired to be protected. All publications, patents, and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference in its entirety.

The following is a list of preferred embodiments of the invention:

1. a method, comprising:

analyzing the glucose concentration in a body fluid received in a biosensor (32) by differential pulse voltammetry, wherein the biosensor (32) comprises at least a reagent covering a working electrode, the analyzing comprising

Applying short high frequency voltage pulses to the bodily fluid in the biosensor (32) to maintain a diffusion layer within the reagent of the working electrode, wherein the voltage of the pulses is incrementally increased,

determining a glucose concentration of the body fluid based on a response to the pulse within a voltage window below a peak diffusion limited current, an

Outputting a glucose concentration result from the determination.

2. The method of embodiment 1, wherein the voltage window is from-0.05V to 0V.

3. The method of embodiment 1, wherein the voltage window is no greater than 300 mV.

4. The method of embodiment 1, wherein the voltage window is a single reading.

5. The method of embodiment 1, wherein the voltage window is 0.05V to 0.25V.

6. The method of embodiment 1, wherein during the applying, the pulses have a pulse length of 25 milliseconds, a pulse interval of 25 milliseconds, a pulse voltage of 50 mV, and a voltage step of 4 mV.

7. The method of embodiment 1, wherein during the applying, the pulses have a pulse interval of 50 milliseconds.

8. The method of embodiment 1, wherein during the applying, the pulses have a pulse length of 50 milliseconds.

9. The method of embodiment 1, further comprising:

wherein the instrument (34) executes the output glucose concentration result;

detecting dosing of the body fluid in the biosensor (32) with the instrument (34) prior to the applying; and

wherein no more than 5 seconds elapse between said detecting the dosing of the body fluid and said outputting a glucose concentration result.

10. The method of embodiment 1, further comprising:

detecting dosing of the bodily fluid in the biosensor (32) prior to the applying; and

the body fluid was allowed to incubate for 2 seconds prior to the application.

11. The method of embodiment 1, wherein there is no incubation period.

12. The method of embodiment 1, wherein the determining comprises measuring a difference between the current at the end of each pulse and the current just before each pulse.

13. The method of embodiment 1, wherein the determining comprises adjusting the response based on one or more calibration parameters.

14. The method of embodiment 1, wherein the biosensor (32) has a two-electrode configuration.

15. The method of embodiment 1, wherein the biosensor (32) has a three-electrode configuration.

16. A method, comprising:

analyzing glucose concentration in a body fluid using differential pulse voltammetry, wherein said analyzing comprises

Applying one or more pulses to the body fluid within a voltage window below a peak diffusion limited current, an

Determining a glucose concentration based on a response to the pulse in the voltage window.

17. The method of embodiment 16, wherein the voltage window is from-0.05V to 0V.

18. The method of embodiment 16, wherein the voltage window is no greater than 300 mV.

19. The method of embodiment 16, wherein the voltage window is a single reading.

20. The method of embodiment 16, wherein the voltage window is 0.05V to 0.25V.

21. The method of embodiment 16, wherein during the applying, the pulses have a pulse length of 25 milliseconds, a pulse interval of 25 milliseconds, a pulse voltage of 50 mV, and a voltage step of 4 mV.

22. The method of embodiment 16, wherein during the applying, the pulses have a pulse interval of 50 milliseconds.

23. The method of embodiment 22, wherein during the applying, the pulses have a pulse length of 50 milliseconds.

24. The method of embodiment 16, further comprising:

detecting dosing of the body fluid in a biosensor (32) prior to the applying;

outputting, with an instrument (34), a result from the determining of the glucose concentration; and

wherein no more than 5 seconds elapse between said detecting the dosing of the body fluid and said outputting a glucose concentration result.

25. A method, comprising:

analyzing an analyte concentration in a bodily fluid with an instrument (34), wherein the analyzing comprises:

applying one or more voltage pulses to the body fluid in a limiting voltage window below a peak diffusion limited current with the instrument (34);

wherein the voltage pulse is short to maintain the diffusion layer within the reagent of the working electrode;

determining, with the instrument (34), a glucose concentration based on a response to the pulse in the limiting voltage window; and

outputting the glucose concentration from the determination with the instrument (34).

26. The method of embodiment 25, wherein the voltage window is from-0.05V to 0V.

27. The method of embodiment 25, wherein the voltage window is no greater than 300 mV.

28. The method of embodiment 25, wherein the voltage window is 0.05V to 0.25V.

29. The method of embodiment 25, wherein during the applying, the pulses have a pulse length of 25 milliseconds, a pulse interval of 25 milliseconds, a pulse voltage of 50 mV, and a voltage step of 4 mV.

30. The method of embodiment 25, further comprising:

detecting dosing of the body fluid in a biosensor prior to the applying; and

wherein no more than 5 seconds elapse between said detecting the dosing of the body fluid and said outputting a glucose concentration result with the instrument.

31. The method of embodiment 25, wherein the determining comprises adjusting the response based on one or more calibration parameters.

Claims (17)

1. A method for determining a glucose concentration in a body fluid, comprising:

analyzing glucose concentration in a body fluid using differential pulse voltammetry, wherein said analyzing comprises

Applying a voltage pulse to the body fluid within a voltage window below a peak diffusion limited current, an

Determining a glucose concentration based on a response to the pulse in the voltage window.

2. The method of claim 1, further comprising:

analyzing a glucose concentration in a body fluid received in a biosensor (32), wherein the biosensor (32) comprises at least a reagent covering a working electrode, the analyzing comprising

In an analyzing step, a short high frequency voltage pulse is applied to the body fluid in the biosensor (32) to maintain a diffusion layer within the reagent of the working electrode, wherein the voltage of the pulse is incrementally increased, and

outputting a glucose concentration result from the determination.

3. The method of claim 1, further comprising:

analyzing the glucose concentration in the body fluid with an instrument (34), wherein the analyzing comprises:

applying, with the instrument (34), a voltage pulse in a limiting voltage window below a peak diffusion limited current to the body fluid in an analyzing step;

wherein the voltage pulse is short to maintain the diffusion layer within the reagent of the working electrode;

in the determining step, determining with the instrument (34) a glucose concentration based on the response to the pulse in the limiting voltage window; and

outputting the glucose concentration from the determination with the instrument (34).

4. The method of claim 1, 2 or 3, wherein the voltage window is from-0.05V to 0V.

5. The method of claim 1, 2, or 3, wherein the voltage window is no greater than 300 mV.

6. The method of claim 1 or 2, wherein the voltage window is a single reading.

7. The method of claim 1, 2 or 3, wherein the voltage window is 0.05V to 0.25V.

8. The method of claim 1, 2, or 3, wherein during the applying, the pulses have a pulse length of 25 milliseconds, a pulse interval of 25 milliseconds, a pulse voltage of 50 mV, and a voltage step of 4 mV.

9. The method of claim 1 or 2, wherein during the applying, the pulses have a pulse interval of 50 milliseconds.

10. The method of claim 9, wherein during the applying, the pulses have a pulse length of 50 milliseconds.

11. The method of claim 2, further comprising:

wherein the instrument (34) executes the output glucose concentration result;

detecting dosing of the body fluid in the biosensor (32) with the instrument (34) prior to the applying; and

wherein no more than 5 seconds elapse between said detecting the dosing of the body fluid and said outputting a glucose concentration result.

12. The method of claim 2, further comprising:

detecting dosing of the bodily fluid in the biosensor (32) prior to the applying; and

the body fluid was allowed to incubate for 2 seconds prior to the application.

13. The method of claim 2, wherein there is no incubation period.

14. The method of claim 2, wherein the determining comprises measuring a difference between the current at the end of each pulse and the current immediately before each pulse.

15. The method of claim 2 or 3, wherein the determining comprises adjusting the response based on one or more calibration parameters.

16. The method of claim 1, further comprising:

detecting dosing of the body fluid in a biosensor (32) prior to the applying;

outputting, with an instrument (34), a result from the determining of the glucose concentration; and

wherein no more than 5 seconds elapse between said detecting the dosing of the body fluid and said outputting a glucose concentration result.

17. The method of claim 3, further comprising:

detecting dosing of the body fluid in a biosensor prior to the applying; and

wherein no more than 5 seconds elapse between said detecting the dosing of the bodily fluid and said outputting an analyte concentration with the instrument.