Evaluation of biological fluid samples

Abstract

A method for evaluating a bodily fluid sample on a test strip may involve applying a periodic signal by a first electrode positioned at a first location within a microfluidic channel of the test strip, monitoring the applied periodic signal by a second electrode positioned at a second location within the microfluidic channel, and using a third electrode positioned at a third location within the microfluidic channel as a reference electrode. The method may also include collecting a bodily fluid sample in the microfluidic channel, continuing to apply the periodic signal, monitor the periodic signal, and use the third electrode as a reference electrode while collecting the bodily fluid sample, and determining that the bodily fluid sample is sufficient for analysis based at least in part on the applied and monitored periodic signals.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Provisional Patent Application No. 62 / 967,694, filed on January 30, 2020, entitled "BIOLOGICAL FLUID SAMPLE ASSESSMENT". The disclosure of this priority application is hereby incorporated by reference in its entirety into this application.

[0002] This application describes biomedical systems and methods. More specifically, this application describes methods and systems for assessing a biological fluid sample to determine whether it is sufficient for testing.

Background Art

[0003] Proper hydration within the human body is essential for the health of body organs and for the proper functioning of body organs. Water is lost from the body during breathing, sweating, and urination. Even a few percent loss of body fluid can have an adverse effect on cardiovascular function, heat dissipation, and exercise performance. Dehydration can cause headache, dizziness, fainting, and in extreme cases, mental confusion, unconsciousness, or death. Hyponatremia ("water intoxication") can also have a harmful effect on body functions, especially when exercising, and in extreme cases can lead to death.

[0004] Dehydration is the excessive loss of body fluids. Physiologically speaking, dehydration can cause a lack of water within the living body. Dehydration can be caused by losing too much water, not taking in enough water, or both. Vomiting, diarrhea, and excessive sweating in a state of insufficient water intake are other causes of dehydration, which can be a concern especially for athletes and people working in hot and dry environments. There are three types of dehydration symptoms: hypotonic (mainly loss of electrolytes, especially sodium), hypertonic (mainly loss of water), and isotonic (equal loss of water and electrolytes). Isotonic dehydration is the most common, but distinguishing these three types of dehydration can be important for appropriate treatment.

[0005] When a subject feels thirsty enough to drink and tries to drink, the subject is often already in a dehydrated state. Therefore, relying on thirst as a feedback mechanism to trigger water intake may not be sufficient to maintain optimal hydration levels. For example, this is why marathon runners are told to "drink before you feel thirsty." At the same time, drinking too much water during endurance events like marathons can lead to hyponatremia, and in the past, this has caused many deaths. Unfortunately, at present, there is no practical and affordable non-invasive device for measuring an individual's hydration level. Measuring devices are typically large and / or expensive devices stored in a laboratory, and they measure the amount of water intake using blood or urine. For this reason, measuring the amount of water intake is impractical, invasive, and / or prohibitively expensive.

[0006] In addition, many other physiological parameters and the levels of various substances within the human or animal body are frequently examined or would be desirable to examine. Unfortunately, to measure these parameters, it is often necessary to collect other body substances such as blood, urine, or cerebrospinal fluid. Some physiological parameters involve even more invasive or costly measurement techniques.

[0007] Therefore, it would be highly beneficial to have a practical and affordable non-invasive system and method for measuring a person's hydration level. It would also be highly desirable to have a practical and affordable non-invasive system and method for examining other parameters within the body.

[0008] Point-of-care testing (POCT) systems enable the measurement of biomarkers (e.g., metabolites, hormones, and electrolytes) in biological samples outside of a laboratory, such as in a clinic or a personal residence. POCT is an attractive alternative to laboratory testing, particularly for frequent or routine tests, by reducing labor and transportation costs.

[0009] Conventional laboratory testing allows for extensive sample handling and processing to standardize sample characteristics and remove contaminants prior to analysis. In contrast, POCT is difficult, if not impossible, to perform extensive sample processing due to equipment, cost, and time requirements. Thus, ideally, POCT would use unprocessed samples rather than processed samples.

[0010] For some biological fluids, viscosity is tightly regulated by the body. For example, blood viscosity is typically 3-4 centipoise (cP). In contrast, saliva viscosity is less regulated and can range from 1-10 cP depending on an individual's physiological state, age, gender, health status, and diet. This variability can be standardized by laboratory processing (e.g., mucin precipitates when saliva is frozen and can then be removed by centrifugation), but it becomes a problem when designing tools to directly measure analytes in saliva through direct collection (collection from the mouth) or near-direct collection (collection from a recently collected sample).

[0011] One particular problem when analyzing saliva samples using a point-of-care system is the presence of air bubbles in the saliva sample. This is especially true for individuals with dry mouths or highly viscous saliva. Air bubbles can cause voids within the fluid channels of the sample analysis device, which can result in blockages or abnormal measurements. Another problem is that the flow of more viscous saliva is non-uniform, which can result in incomplete filling of the sampling fluidics.

[0012] Therefore, it would be desirable to develop devices, systems, and methods for evaluating whether a body fluid sample is suitable for measurement and analysis. Ideally, such devices, systems, and methods are sufficiently user-friendly and cost-effective to enable use by untrained users in point-of-care environments such as the home, office, gym, or the like.

Summary of the Invention

Problems to be Solved by the Invention

[0013] This application describes devices, systems, and methods that use the continuous application of a periodic signal before and during sample collection by an electrode. This method also provides continuous monitoring of sample collection by a second electrode. Some embodiments also provide an evaluation of signal variations during sample collection. Typically, this method requires a period of signal consistency within a set range before the start of measurement. These features help confirm not only that the sample has completed the circuit between the two electrodes before the start of measurement, but also that no fluid is being collected anymore and the collected fluid is no longer moving within the sampling fluidics.

Means for Solving the Problems

[0014] In one aspect of the present disclosure, a method for evaluating a body fluid sample on a test strip includes applying a periodic signal by a first electrode disposed at a first location within a microfluidic channel of the test strip, monitoring the applied periodic signal by a second electrode disposed at a second location within the microfluidic channel, and using a third electrode disposed at a third location within the microfluidic channel as a reference electrode, wherein each of the first electrode, the second electrode, and the third electrode has a fixed function. The method further includes collecting a body fluid sample within the microfluidic channel, applying the periodic signal while collecting the body fluid sample, monitoring the periodic signal, and continuing to use the third electrode as a reference electrode, and determining that the body fluid sample is sufficient for analysis based at least in part on the application and monitoring of the periodic signal.

[0015] In some embodiments, the periodic signal varies in response to the volume of the body fluid sample and the movement of the body fluid sample through the microfluidic channel, and a stable period of the monitored periodic signal is required before determining that the body fluid sample is sufficient. The method may further include starting the analysis of the body fluid sample based on the determining step. Some embodiments may include, prior to the determining step, determining that the body fluid sample is insufficient for analysis and instructing the user to continue collecting the body fluid sample on the test strip. For example, the determining that the body fluid sample is insufficient may include identifying an unstable period or a stable period of the monitored periodic signal outside an acceptable range. The instruction to the user may include providing an auditory signal, a vibration, and / or a visual signal in a body fluid analysis device directly connected to the test strip or in a separate device wirelessly connected to the body fluid analysis device. In various embodiments, the body fluid sample may be any suitable body fluid, including but not limited to saliva, sweat, blood, or urine.

[0016] In another aspect of the present disclosure, a method for evaluating a body fluid sample on a test strip involves applying a periodic signal by a first electrode disposed in a first arrangement within a microfluidic channel of the test strip, monitoring the applied periodic signal by a second electrode disposed in a second arrangement within the microfluidic channel, and using a third electrode disposed in a third arrangement within the microfluidic channel as a reference electrode, wherein each of the first electrode, the second electrode, and the third electrode has a reconfigurable function. The method further involves collecting a body fluid sample within the microfluidic channel, while collecting the body fluid sample, continuing to apply the periodic signal, monitor the periodic signal, and use the third electrode as a reference electrode, while collecting the body fluid sample, switching the configuration of the first electrode, the second electrode, and the third electrode, and determining that at least in part based on the applied periodic signal and the monitored periodic signal, the body fluid sample is sufficient for analysis. In some embodiments, the method may further involve determining at least one of a sample flow rate and a sample viscosity by comparing signals generated by different electrode configurations.

[0017] In another aspect of the present disclosure, a method for evaluating the consistency of measurements of a body fluid sample on a test strip having at least four electrodes and reducing sensitivity involves applying a periodic signal with at least some of the at least four electrodes, wherein the at least four electrodes are disposed in different arrangements within a microfluidic sample chamber of the test strip, monitoring the periodic signal with at least some of the at least four electrodes, collecting a body fluid sample on the test strip, identifying a stable period of the monitored signal, and based on the identified stable period, starting the measurement of the body fluid sample.

[0018] Optionally, this method may also include determining the sample flow rate and viscosity by comparing signals generated by various sets of electrodes. This method may also include recommending to the user a method for collecting a body fluid sample, based at least in part on the signal being monitored.

[0019] These and other aspects and embodiments are described in more detail below in connection with the accompanying drawings.

Brief Description of the Drawings

[0020]

Figure 1A

Figure 1B

Figure 1C

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4A

Figure 4B

Figure 5

DETAILED DESCRIPTION OF THE INVENTION

[0021] The assignee of the present application has previously filed patent applications describing systems, methods, and devices for examining, measuring, and analyzing saliva to measure a subject's hydration level, and further for measuring other substances (e.g., sweat) and / or physiological parameters in a human or animal subject. These previous patent applications include U.S. Patent Application No. 16 / 197,530, filed November 21, 2018 (U.S. Publication No. 2019 / 0150836), titled "Saliva Testing System", U.S. Patent Application No. 62 / 744,389, filed October 11, 2018, titled "Ion Selective Sensor", and U.S. Patent Application No. 62 / 872,339, filed July 10, 2019, titled "Saliva Test Strip and Method". All of these patent applications are incorporated herein by reference and may be referred to herein as "incorporated applications".

[0022] The present application adds technology to the incorporated applications by describing methods, devices, and systems for determining whether a body fluid sample has completely and stably filled a collection frit on a test strip. This determination is made before starting the measurement of the fluid sample to ensure that the measurement is not performed on an inappropriate sample.

[0023] One solution to the problems described above in the Background section is a body fluid analysis test strip, which is part of a body fluid analysis system, and is configured to address these issues (e.g., fluidics size, shape, and / or material) and enhance the operation of the body analysis system for a given fluid such as saliva. The assignee of the present application has described such test strips in the co-pending U.S. Provisional Patent Application No. 62 / 872,339, referenced above.

[0024] Another possible solution to some of the problems of point-of-care testing of saliva and other body fluids would be for a part of the body fluid analysis system that determines whether the collected sample is sufficient for testing. Typically, the start of measurement is triggered on a disposable test strip when the sample fluid bridges the gap between two electrodes, thereby completing the circuit and indicating that sufficient sample has entered the test strip. The electrodes are typically placed at opposite ends (i.e., the ends of the strip where the sample is collected) from the sampling fluidics of the test strip. This solution is suitable for more consistent fluids such as blood, where the flow through the test strip fluidics is relatively uniform and predictable.

[0025] However, since the viscosity of saliva is variable (and potentially high), bridging between the two electrodes on the test strip may occur without the channel being completely filled (see Figure 1B), or may be essentially transient. As such, additional time may be required for the sample fluid to sufficiently fill the test strip to enable measurement of the sample. For users of such test strips / test systems, it can be very difficult to determine whether sufficient saliva has been collected on a given test strip to enable accurate measurement.

[0026] This application describes various embodiments and features of methods, devices, and systems for analyzing samples of saliva or other body fluids (e.g., sweat, blood, etc.). In particular, the embodiments described herein provide a method for evaluating a saliva sample to determine whether it is sufficient to enable accurate measurement of the sample (and whether the microfluidics of the test strip is sufficiently filled). The following disclosure focuses on the analysis of saliva, but the embodiments described below, or modifications thereof, can be used for the analysis of any other body fluid such as sweat, blood, urine, or the like.

[0027] Referring to FIGS. 1A - 1C, the tip of a saliva analysis test strip 10 is shown in three different states of fluid sample collection. FIG. 1A shows the test strip 10 in a state where its microfluidic channel 12 is empty - in other words, a state where no fluid sample has been collected. Also shown are the three electrodes 14 of the test strip 10.

[0028] FIG. 1B shows the test strip 10 with the microfluidic channel 12 partially filled with a saliva sample 16 (or, in an alternative embodiment, another body fluid sample). As described above, the image of FIG. 1B demonstrates one of the problems with using a typical test strip 10 in point - of - care saliva analysis - namely, that even if the sample 16 is not sufficient to fill the channel 12, it may still bridge across the electrodes 14. FIG. 1C shows the channel 12 completely filled with the saliva sample 16. Here too, with a typical test strip 10, it may be difficult or impossible to distinguish between the partial filling of FIG. 1B and the complete filling of FIG. 1C.

[0029] Next, referring to FIGS. 2A and 2B, an embodiment of a method for evaluating a saliva sample 26 on a test strip 20 is illustrated. In this embodiment, the test strip 10 includes a substrate, a microfluidic channel 22 (or "collection microfluidics"), and three electrodes 24a, 24b, 24c (alternative embodiments may include more than three). The electrodes 24a, 24b, 24c have fixed functions and are arranged in different positions along the length of the microfluidic channel 22 of the test strip. Before and during sample measurement, the first electrode 24a applies a periodic signal, the second electrode 24b monitors the signal, and the third electrode 24c acts as a reference electrode. The monitored signal is evaluated by a handheld sample analysis device (not shown) coupled to the test strip 20. When the saliva sample 26 is collected within the microfluidic channel 22, it may bridge all three electrodes 24a, 24b, 24c, but may continue to shift within the microfluidic channel 22. FIG. 2B shows a line graph illustrating this sample shift as an unstable period 30. After the sample 26 stops shifting, the line on the graph 28 stabilizes during a stable period 32. The handheld analysis device monitors the electrode signal and waits for the stable period 32. In this embodiment, the measurement of the sample 26 by the analysis device begins only after a period of consistency of the monitored signal within a predetermined range of acceptable variation - i.e., the stable period 32.

[0030] Next, referring to FIGS. 3A and 3B, in an alternative embodiment, the electrodes 44a - 44d of the test strip 40 having the microfluidic channel 42 do not have a fixed function, but instead rapidly reconfigure their function upon sample collection. In this embodiment, the test strip 40 comprises four electrodes 44a - 44d, although alternative embodiments may have any other suitable number. At any given time, one of the electrodes 44a - 44d applies a periodic signal, another of the electrodes 44a - 44d monitors this signal, and the remaining electrodes 44a - 44d serve as a reference. However, which of the electrodes 44a - 44d has each function can be changed frequently, even several times per second. Referring to FIG. 3B, as shown in the line graphs 45, 46, 47, a period of coherence of the monitored signals within and between electrode configurations is required before the start of measurement. In addition to the advantages of the method described above, this embodiment of the method enables determination of the sample flow rate and viscosity by evaluating the sample's time of flight. These parameters can optionally be used in a saliva measurement algorithm, for example, to adjust sample analysis results for flow rate and / or viscosity.

[0031] In another embodiment illustrated in FIGS. 4A and 4B, the biological fluid analysis test strip 50 includes a microfluidic channel 52 and a plurality of sets of concentric electrodes 54a - 54d within the microfluidic channel 52. Each set of electrodes 54a - 54d is configured to independently evaluate signal fluctuations during sample collection. As shown in the line graphs 55, 56, 57 of FIG. 4B, a period of coherence of the monitored signals of each set of electrodes 54a - 54d is required prior to the start of sample measurement, within a predetermined range of acceptable fluctuations. The differences between the signals measured by each set of electrodes 54a - 54d during sample collection can be used to evaluate the sample's flow rate and viscosity. Additionally, this electrode structure can reduce the sensitivity of sample measurements to the volume of the sample within the microfluidic channel 52 or local variations within the microfluidic channel 52.

[0032] For all method embodiments described herein, in-process signal monitoring before and during sample collection can be used to convey to the user the current state of the sample being collected (e.g., sufficient liquid, insufficient liquid, poor sample) through noise, vibration, and / or visual signals on the inspection system or connected device.

[0033] Figure 5 illustrates a method 60 for collecting a saliva (or other body fluid) sample using a test strip inserted into a saliva analysis device. Figure 5 depicts the above-described series of method steps 62 and the corresponding series of instructions 64 provided to the user on the display screen 69 of the handheld body fluid analysis device 61. First, following method step 62, according to this embodiment, the user first initiates the inspection system 66 (e.g., the handheld device 61). After the test strip 63 is inserted into the handheld device 61 and a sample is collected on the test strip 63, the system initiates fluid detection 70. If the fluid signal is not stable, fluid detection continues 74 until a stable signal is detected. If none is detected, the user is notified that the sample is insufficient. After a stable fluid signal is obtained, sample measurement is initiated 78. Finally, the measurement data is processed and the system displays one or more results of the fluid sample measurement 82 (saliva or other fluid).

[0034] Next, a series of instructions 64 are described while focusing on how this method would appear to a user of the handheld device 61. After initiation, the first step 68 of the handheld device 61 is to display an instruction on the display screen 69 to instruct the user to insert the test strip 63 into the device 61. In the next step 72, the user has inserted the test strip 63 and is instructed on the screen 69 to collect a sample. Then, in the sample collection step 76, the user collects a saliva (or other body fluid) sample 65, for example, by placing the free end of the test strip 63 against the user's tongue to directly collect saliva. If the collection of the sample fluid is insufficient, a visual signal is displayed on the screen of an analysis device (not shown), indicating that the collection of the sample is insufficient. When the sample is collected, the "Collect Sample" signal remains displayed on the screen, continuously prompting the user to continue collecting more saliva with the test strip 63. After sufficient liquid has been collected and consistency has been confirmed by one of the methods described above, a sound 67 is emitted from the device, and the message displayed on the screen changes 80 to reflect that a sufficient sample has been collected. These notifications inform the user that they can stop collecting saliva on the test strip 63. Next, the analysis device performs its measurement as shown on the screen. When the analysis is complete, the results are displayed on the device 84.

[0035] While the foregoing description is considered to be complete and accurate, various changes may be made to any of the embodiments and features described herein without departing from the scope of the invention. For example, in any given embodiment, the order of the method steps may be changed, one or more method steps may be eliminated, and / or one or more method steps may be added.

Description of the Reference Numerals

[0036] 10 Saliva analysis test strip 12 Microfluidic channel 14 Electrode 16 Saliva sample 20 Test strip 22 Microfluidic channel 24a, 24b, 24c Electrodes 26 Saliva sample 28 Graph 32 Stabilization period 40 Test strip 42 Microfluidic channel 44a - 44d Electrodes 50 Body fluid analysis test strip 52 Microfluidic channel 54a - 54d Concentric electrodes 55, 56, 57 Line graph 60 Method 61 Handheld body fluid analysis device 62 Method step 63 Test strip 64 Instruction 65 Saliva (or other body fluid) sample 66 Inspection system 67 Sound 69 Display screen 70 Fluid detection 82 Fluid sample measurement 84 Device

Claims

1. A method for evaluating a body fluid sample on a test strip, comprising: applying a periodic signal by a first electrode disposed at a first location within a microfluidic channel of the test strip; monitoring the applied periodic signal by a second electrode disposed at a second location within the microfluidic channel; using a third electrode disposed at a third location within the microfluidic channel as a reference electrode, wherein the functions of each of the first electrode, the second electrode, and the third electrode are fixed; collecting the body fluid sample within the microfluidic channel while applying the periodic signal, monitoring the periodic signal, and continuing to use the third electrode as a reference electrode; determining that the body fluid sample is sufficient for analysis by identifying a stable period of the monitored periodic signal, at least in part based on the application and monitoring of the periodic signal.

2. The method of claim 1, wherein the periodic signal varies in response to the volume of the body fluid sample and the movement of the body fluid sample through the microfluidic channel, and the stable period of the monitored periodic signal is required before determining that the body fluid sample is sufficient.

3. The method of claim 1, further comprising starting analysis of the body fluid sample based on the determining step.

4. Before the determining step, determining that the body fluid sample is insufficient for analysis; and instructing a user to further collect the body fluid sample on the test strip.

5. The method of claim 4, wherein the step of determining that the body fluid sample is insufficient comprises identifying either an unstable period or a stable period of the monitored periodic signal outside an acceptable range.

6. The method of claim 4, wherein the step of instructing the user comprises providing at least one of an audible signal, a vibration, or a visual signal in a body fluid analysis device directly connected to the test strip or in a separate device wirelessly connected to the body fluid analysis device.

7. The method according to claim 1, further comprising the step of instructing the user that the body fluid sample is sufficient by providing at least one of an auditory signal, a vibration, or a visual signal in a body fluid analysis device directly connected to the test strip or in a separate device wirelessly connected to the body fluid analysis device.

8. The method according to claim 1, wherein the body fluid sample includes a body fluid selected from the group consisting of saliva, sweat, blood, and urine.

9. A method for evaluating a body fluid sample on a test strip, comprising: applying a periodic signal by a first electrode disposed at a first location within a microfluidic channel of the test strip; monitoring the applied periodic signal by a second electrode disposed at a second location within the microfluidic channel; using a third electrode disposed at a third location within the microfluidic channel as a reference electrode, wherein the functions of each of the first electrode, the second electrode, and the third electrode are reconfigurable; collecting the body fluid sample within the microfluidic channel while continuing to apply the periodic signal, monitor the periodic signal, and use the third electrode as a reference electrode; reconfiguring the functions of the first electrode, the second electrode, and the third electrode while collecting the body fluid sample; determining that the body fluid sample is sufficient for analysis by identifying a stable period of the monitored periodic signal, at least in part based on the applied and monitored periodic signal. The method according to claim 9, further comprising determining at least one of a sample flow rate and a sample viscosity by comparing signals generated by different electrode configurations in which the function of each electrode is reconfigured.

11. Before the step of determining, determining that the body fluid sample is insufficient for analysis; The method according to claim 9, further comprising instructing the user to collect more of the body fluid sample on the test strip.

12. A method for evaluating a body fluid sample on a test strip having at least four electrodes, comprising: Applying a periodic signal to at least some of the at least four electrodes, wherein the at least four electrodes are arranged in different positions within the microfluidic sample chamber of the test strip; Monitoring the periodic signal at at least some of the at least four electrodes; Collecting the body fluid sample on the test strip; Identifying a stable period of the monitored signal; Based on the identified stable period, starting the measurement of the body fluid sample. A method comprising these steps. **Claim 13** The method according to claim 12, further comprising determining sample flow rate and viscosity by comparing signals generated by different sets of electrodes. **Claim 14** The method according to claim 12, further comprising recommending to the user a method for collecting the body fluid sample based at least in part on the monitored signal.

Images