HK1073886A - Diagnostic test strip for collecting and detecting an analyte in a fluid sample and method for using same - Google Patents

Description

Diagnostic test strip for collecting and detecting an analyte in a liquid sample and method of using the same

Technical Field

The present invention relates generally to diagnostic devices and, more particularly, to a diagnostic test strip for use in determining the concentration of an analyte in a liquid sample.

Background

Test strips containing reagents, such as biosensors, are often used in assays to determine the concentration of an analyte in a liquid sample. Testing and self-testing the concentration of glucose in blood is one common use of test strips. One method of obtaining a blood sample and analyzing the sample to determine the glucose level is to use a lancing device and a separate blood collection device. In obtaining a blood sample, a drop of blood is taken from the fingertip with a lancing device, and the blood is collected with a test strip and then analyzed by a test device that determines the concentration of glucose in the blood. Test strips are also used to determine the presence or concentration of a variety of other analytes (e.g., fructosamine, hemoglobin, cholesterol, glucose, alcohol, drugs including illicit drugs, etc.) in various body fluids (e.g., blood, interstitial fluid, saliva, urine, etc.).

One disadvantage associated with the use of physically separate lancing and collection devices is that the patient/user must operate two different sets of instruments, which require the user/patient to take the collection device (e.g., the test strip) to the punctured skin site to collect a sample. Since the user must align the sample to be collected with the collection device, more sample than is necessary is often produced and collected to ensure accuracy of the analysis. In other cases, not enough sample is collected for accurate analysis due to incorrect placement of the collection device. The problem is further compounded if the user is not well-sighted or dexterous. Because the test system requires a relatively small amount of blood for analysis, it is difficult to place a collection instrument for proper collection.

The topography of the skin can affect the formation of blood droplets at the needle-prick site on the skin. Many individuals use hand sanitizers, have oily or sweaty skin, or do not completely dry their hands after washing their hands, which can also affect the formation of blood droplets. It is not always the case that the user cleans the skin site to be punctured with alcohol. These changes increase the wettability of the skin surface, causing the droplets to spread in an uncontrolled and unpredictable manner, thereby making sampling difficult.

In addition, alternative sites for taking blood samples, such as the forearm, are complicated by the presence of body hair, as the sample (e.g., blood) tends to be "wicked" by body hair growing in this part of the body. Cleaning the needle-punched site with alcohol also does not improve this wicking problem. Accordingly, there is a need for a lancing and collection device that is cooperatively positioned at the lancing and collection site to accurately collect a blood sample for analysis.

Disclosure of Invention

Summary of The Invention

According to one embodiment of the present invention, a test strip for use in the determination of an analyte in a liquid sample is disclosed. The test strip includes a base having a top and a bottom; a collection chamber extending between the top and bottom of the substrate; a volume ring disposed at the bottom of the base and surrounding the collection chamber; and a capillary channel formed on top of the substrate having an inlet in fluid communication with the collection chamber, the test element being placed in the capillary channel. A lid is attached to the top of the base and covers the collection chamber, test membrane, and at least a portion of the capillary channel.

The above summary of the present invention is not intended to represent each embodiment, or every aspect, of the present invention. Other features and advantages of the invention will become apparent from the following detailed description, the accompanying drawings, and the claims.

Brief Description of Drawings

FIG. 1 is a top perspective view of a portion of a test strip according to one embodiment of the present invention;

FIG. 2 is a lower perspective view of the test strip of FIG. 1;

FIG. 3 is a perspective view of a test strip with a lancing and collection device according to one embodiment of the present invention;

FIG. 4 is a side view of a lancing and collection device and an end cap according to another embodiment of the present invention;

FIGS. 5a-5f are enlarged perspective and side views of the front end of the lancing and collection device illustrating various points during lancing of a subject's skin and subsequent sampling in accordance with one embodiment of the present invention;

FIG. 6 is a top perspective view of a test strip according to one embodiment of the present invention.

While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Description of the illustrated embodiments

Turning now to the drawings, and first to FIGS. 1 and 2, a test strip 10 is shown according to one embodiment of the present invention. Test strip 10 includes a base 12 and a cover 14. Substrate 12 has a lower surface 13 and an upper surface 15. Substrate 12 includes a collection chamber 16, a capillary channel 18 containing a test zone 19, and a volume ring 24. Capillary channel 18 extends outwardly from test zone 19 to form an optional vent 22. The cover 14 covers the collection chamber 16 and the capillary channel 18 including the test zone 19. According to one embodiment of the present invention, a cover 14 is attached to the base 12. A test element 20 containing reagents used in the assay is placed in the test zone of the capillary channel 18. According to one embodiment of the invention, test strip 10 can be incorporated into a lancing and collection device 26 (FIG. 4), which is described in detail below in connection with FIGS. 4-5 f.

Collection chamber 16, and capillary channel 18 including test zones and vent holes 22 (if any), may be embossed on top surface 15 of substrate 12 by mechanical or other suitable manufacturing methods, but may also be formed during the molding of substrate 12. In the illustrated embodiment, collection chamber 16 is a cylindrical bore through base 12. The inlet of capillary channel 18 is formed in the side wall of collection chamber 16. Capillary channel 18 is in fluid communication with collection chamber 16 and test zone 19 containing test element 20. The collection chamber 16, the capillary channel 18 containing the test zones 19, or a combination thereof may be coated with a hydrophilic material to facilitate the flow of the liquid sample. In addition, according to one embodiment of the present invention, the capillary passage 18 is sized to provide underfill-type protection.

In one embodiment of the invention, the test element 20 is attached to the cover 14 with an adhesive that is substantially transparent, and the reading of the test element 20 can be optically read through the cover 14. In the embodiment where the test element 20 is attached to the lid 14, the test zone 19 of the capillary channel 18 is sized to provide a slight separation between the bottom of the test zone 19 and the bottom of the test element 20 so that the liquid sample will be exposed to more surface area of the test element 20. Similarly, the test zone 19 of the capillary channel 18 is sized to provide spacing around the test element 20, as shown in FIG. 1. In an alternative embodiment of the invention, the test element may be attached to the substrate 12.

In taking a body fluid sample such as blood from a subject, the lower surface 13 of the base 12 is placed on the skin of the subject. A volume ring 24, which surrounds the collection chamber 16 and extends downwardly from the lower surface 13 of the base 12, contacts the skin of the subject. As will be described in more detail below, the skin of the subject is punctured within the periphery of the acquisition chamber 16. The containment ring 24 inhibits the sample from spreading over the skin and retains the sample within the perimeter of the collection chamber 16. The containment ring 24 is formed during the molding of the base 12 and projects upwardly above the lower surface 13 or is attached to the lower surface 13 of the base 12 during manufacture.

The substrate 12 may be constructed of any suitable material, such as polycarbonate, polypropylene, polystyrene, and the like. The lid 14 is constructed of any material suitable for the nature of the item being analyzed. For example, if optical analysis is desired, the cover 14 may be constructed of a substantially optically transparent material such as polyethylene terephthalate (PET) or polycarbonate. Alternatively, for applications where opacity of the lid 14 is not a concern, the lid 14 may be constructed of polycarbonate, polypropylene, polystyrene, and polyethylene terephthalate (PET). The material of the cap is substantially non-porous so that the cap does not absorb the sample; rather, the cap directs the sample to the inlet of the capillary passage 18, as described below.

According to another embodiment of the present invention, test strip 10 can be implemented into a variety of lancing devices. Lancing devices that can be used with various embodiments of the present invention include U.S. patent 6,152,942 (vacuum assisted lancing device); 5,350,392 (automatic cocking lancing device); and 6,364,889 (electronic lancing devices); each of which is incorporated herein by reference in its entirety. The test strip 10 with lancing device 26 is implemented such that the lancing device 26 punctures the skin of the subject and collects a body fluid sample at the lancing site.

Referring to fig. 3, we present the front end of lancing and collecting device 26 implementing test strip 10 according to one embodiment of the present invention. Test strip 10 can have a variety of shapes and configurations to conform to the design of a variety of appliances, operating as described above. For example, when the test strip 10 shown in fig. 3 is substantially the same size as the cross-section of the end cap 30, the test strip 10 can be substantially rectangular as shown in fig. 1-2. The test strip 10 can be connected to an end cap 30 that can be removably attached to the lancing device 26. As described below, the lancing and collection device 26 includes a lancet 28 for puncturing the cover 14 and the skin of a subject.

Referring to fig. 4, a lancing and collection device 26 implementing test strip 10 is shown according to one embodiment of the present invention. The lancet assembly includes a housing 32 that encases a lancet assembly 31 having a piston 34 for driving the lancet 28. A top end 36 of the piston 34 extends from the housing 32. In using the lancet 28 to pierce the skin of a subject, a user grasps the housing 32 of the device 26 and presses the top end 36 of the piston 34, pressing the piston 34 into the housing 32 of the device 26, to propel the lancet 28 downwardly into the skin of the subject. A lancet holder (not shown) is disposed within housing 32. The lancet 28 is movably attached to the lancet holder so that the lancet 28 can be removed and discarded after use. A piston 34 is attached to the housing 32 at an end opposite the lancet holder. Piston 34 thus drives the lancet holder which in turn drives lancet 28.

The end cap 30 is attached to the forward end 40 of the device 26 opposite the piston 34. The edge 42 of the end cap 30 is movably attached to the front end 40 of the piston 34. (according to an embodiment of the vacuum-assisted lancing device 26, the front end 40 includes an O-ring to form an air-tight seal between the end cap 30 and the front end 40.) the open end 44 of the end cap 30 includes an aperture 46 through which the lancet 28 punctures the skin of the subject. In one embodiment of the invention, an opening 45 is provided in the side wall of end cap 30 for insertion and removal of test strip 10. In another embodiment of the invention, test strip 10 is fixedly attached to a disposable end cap 30, and removal of end cap 30 removes the used test strip 10.

During lancing of the subject's skin, the open end 44 of the endcap 30 is placed on a portion of the subject's skin (e.g., forearm, finger, etc.). Depressing the piston 34 urges the lancet 28 from a retracted position, wherein the lancet 28 is fully contained by the end cap 30, to a lancing position, wherein the lancet 28 extends from the aperture 46 in the end cap 30. The user pushes the piston 34 to activate a spring (not shown) in the housing 32 of the lancet assembly 31 to rapidly advance the lancet 28 into the skin of the subject. The lancet assembly 31 includes a second spring (not shown) for urging the lancet 28 back to the retracted position.

In the embodiment shown in fig. 4, the lancet kit 31 further comprises an instrument 48 for reading the test strip 10 (not shown) and determining the concentration of the analyte in the sample. The instrument 48 includes a display 50 for communicating the results of the analysis to a user. In embodiments of the invention that do not include such an instrument, a separate device is used to read the test strip 10.

In accordance with one embodiment of the present invention, the lancing device 26 is vacuum-assisted as described in U.S. patent 5,152,942 (incorporated by reference above) to facilitate the production of a blood sample at a lancing site on the skin of a test subject. In such embodiments, the edge 42 of the end cap 30 forms a hermetic seal with an O-ring as described above. And by pressing the end cap towards the skin an airtight seal is created between the open end 44 of the end cap 30 and the skin of the subject. The lancet set 31 includes a vacuum element (not shown), such as a diaphragm or bellows, that can expel air from the lancet set and the end cap 30 to create a vacuum in the end cap 30. During operation of the lancet, the vacuum element is triggered to evacuate air from the end cap 30 by the user releasing the piston 36.

As discussed above, the test element 20 contains reagents for determining the concentration of an analyte of interest in a sample. The reagent is designed to react with an analyte in the sample. The reaction is indicative of the concentration of the analyte in the sample and can be measured by a suitable sensor. The particular reagent incorporated into the test element 20 depends on the type of assay used for the analyte and for determining the concentration of the analyte.

According to one embodiment of the present invention, the reagents used in the test element 20 may be designed as reagents known in the art that produce a colorimetric reaction indicative of the concentration of the analyte. The degree of color change is determined by an optical read head or detector to determine the concentration of the analyte. In accordance with one embodiment of the present invention, a photodetector is mounted in the end cap 30 of the device 26 for reading the test strip. Colorimetric tests are described in detail in U.S. Pat. No. 6,181,41781 (entitled colorimeter reading head with light-sensing plate; 5,518,689 (entitled scattered light reflectance reading head), and 5,611,999 (entitled scattered light reflectance reading head), each of which is incorporated herein by reference in its entirety.

Alternatively, the reagents used in the test element 20 can be designed as reagents known in the art that produce an electrochemical reaction indicative of the concentration of the analyte in the sample. In an electrochemical assay, the reagent is designed to react with the analyte to produce an oxidation current on the electrodes placed in the test zone 19 that is proportional to the glucose concentration in the user's blood. The resulting current may be measured with an instrument, such as an instrument incorporated into instrument 48. Electrochemical testing is described in U.S. Pat. No. 5,120,20 (entitled "biosensor and method for making same"); 5,660,791 ("liquid test sensors for metering instruments"); 5,759,364 (topic electrochemical biosensor); and 5,798,031 (entitled electrochemical biosensor), each of which is incorporated herein by reference in its entirety.

Turning now to FIG. 5a, we will describe the operation of lancing and collection device 26 according to one embodiment of the present invention. The lancing and collection device 26 is placed on the skin S of the subject. The volume ring 24 contacts the skin S of the subject. In the embodiment of the present invention in which the lancing and collecting device 26 is of a vacuum assist type, the skin S of the subject is sucked by vacuum to be brought into contact with the volume ring 24.

In fig. 5a, the lancet 28 is shown just before it penetrates the skin of the subject. In operation, the lancet 28 passes through (e.g., pierces) the cap 14 as it approaches the skin S of the subject. When the skin S of the subject contacts the volume ring 24, the user presses the piston 36, which triggers the lancet assembly 31 (fig. 4). Upon triggering, the lancet 28 pierces the cap 14, then continues through the acquisition chamber 16 and pierces the skin S of the subject. The puncture site on the subject's skin is defined by the collection chamber 16 (i.e., within the perimeter of the collection chamber 16).

Referring to fig. 5b, the device 26 is shown after piercing the cap 14 and when puncturing the skin S of the subject. After the skin S of the subject is punctured, the lancet 28 is retracted from the skin S of the subject as shown in fig. 5 c. After the lancet 28 is retracted from the skin S of the subject, blood B begins to fill the collection chamber 16. Some blood B, after entering collection chamber 16, begins to enter capillary passage 18. As blood B continues to fill the capillary passage 18, it can be seen from fig. 5d that blood B contacts the cap 14 and the cap 14 directs the blood B towards the opening of the capillary passage 18. The collection chamber 16 is defined by the containment ring 24 and the lid 14 and collects and contains the blood sample B. Thus, according to one embodiment of the present invention, the collection of a blood sample is not dependent on any particular drop formation.

Referring to fig. 5e, blood B continues to flow from collection chamber 16 to test element 20 along capillary channel 18 after further filling collection chamber 16. Blood B, once flowing into test zone 19, contacts the test element. In accordance with the illustrated embodiment of test strip 10, vent 22 facilitates the flow of blood B through capillary channel 18, which allows air in capillary channel 18 to vent from the channel as blood B fills channel 18.

After reaching the end of the capillary channel 18, the blood B enters the test zone 19 and comes into contact with the test element 20, where it is absorbed, as shown in fig. 5 f. The voids along the sides of the test element 20 increase the exposure of the test element 20 to blood in the reaction zone, thereby allowing blood B to be more quickly absorbed by the test element 20. Also, if desired, a gap may be left above and below the test element 20 to further facilitate rapid absorption of blood B, as discussed above. Once the blood B is absorbed by the test element, the blood mixes with the reagent applied to the test element 20, producing a response indicative of the concentration of the analyte (e.g., glucose) in the blood. If the nature of the test is a colorimetric reaction, a light sensor is positioned in the end cap 30 to measure the colorimetric reaction. If the nature of the test is an electrochemical reaction, an instrument is used to measure the amount of current generated by the electrochemical reaction. In one embodiment, the end cap 30 and test strip 10 can be removed from the lancing and collection device 26 and discarded after use.

Referring to fig. 6, a test strip 50 according to an alternative embodiment of the present invention is shown. Test strip 50 includes a partially enclosed collection chamber 56 formed at one end of the base 52 of test strip 50. According to alternative embodiments of the present invention, the partially enclosed collection chamber 56 may have varying degrees of enclosure. Test strip 50 includes a cover 54 having a lip 57 extending a distance from cover 54. When blood collection is performed in the partially enclosed collection chamber 56, the blood contacts the cap 54 and the rim 57, thereby directing the blood sample to the inlet of the capillary channel 19.

Although the test strip is described in this regard as having a two-part member (i.e., base 12 and cover 14) with a capillary channel 18 formed in base 12, test strip 10 can also have a three-part member. In such embodiments, a U-shaped separator layer is disposed between the base 12 and the cover 14 and may be adhered thereto with an adhesive. The interior of the U-shaped spacer layer forms the side walls of the capillary channel, while the lid and base form the top and bottom, respectively.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims (32)

1. A test strip for use in the determination of an analyte in a liquid sample, said test strip comprising:

a substrate having a top and a bottom;

a collection chamber extending between the top and bottom of the substrate;

a volume ring disposed at the bottom of the base, the volume ring surrounding the collection chamber;

a capillary channel formed on top of the substrate, the capillary channel having an inlet in fluid communication with the collection chamber;

a test element disposed within the capillary channel; and

a cover attached to the top of the base, the cover covering the collection chamber, test membrane, and at least a portion of the capillary channel.

2. The test strip of claim 1, wherein the cover is constructed of a substantially optically transparent material.

3. The test strip of claim 1, wherein the cover is comprised of a substantially non-porous material.

4. The test strip of claim 1, wherein the test element comprises a reagent for generating a reaction indicative of the concentration of an analyte in the liquid sample.

5. The test strip of claim 4, wherein the analyte is glucose.

6. The test strip of claim 4, wherein the sample is blood.

7. The test strip of claim 1, wherein the test strip is coupled to a lancing device.

8. The test strip of claim 1, comprising a hydrophilic coating disposed on at least a portion of the capillary channel.

9. The test strip of claim 1, wherein the test element is secured to the cover.

10. The strip of claim 9, wherein the test element is secured to the cover with a substantially optically clear adhesive.

11. The test strip of claim 1, wherein the capillary channel comprises a test zone for receiving the test element, the test zone having a lateral dimension greater than a lateral dimension of the test element.

12. The test strip of claim 1, wherein the capillary channel comprises a test zone for receiving the test element, the test zone having a depth greater than the thickness of the test element.

13. The test strip of claim 1, wherein the capacity ring extends outwardly from the base bottom.

14. A device for determining an analyte in a bodily fluid, the device comprising a lancet kit having a lancet for piercing the skin of a subject, the lancet adapted to move between a retracted position and an extended position to pierce the skin of the subject, the device comprising:

an end cap movably connected to the lancing device, the end cap having an edge for contacting the skin of a subject, the lancet extending from the edge of the end cap when in the extended position; and

a test strip disposed in said end cap, said test strip comprising a collection chamber and a capillary channel in fluid communication with said collection chamber, said test strip comprising a test element disposed in said capillary channel, said test element being in fluid communication with said collection chamber, said test strip comprising a cover disposed over said collection chamber and at least a portion of said capillary channel, said lancet piercing said cover and extending from said collection chamber when moved between said retracted position and said extended position.

15. The device of claim 14, wherein the test strip includes a containment ring extending outwardly from the bottom of the test strip, the containment cup for contacting the skin of a subject.

16. The device of claim 14, wherein the lancet kit is vacuum-assisted.

17. The device of claim 14, wherein the cover of the test strip is constructed of a substantially optically transparent material.

18. The device of claim 14, wherein the cover is comprised of a substantially non-porous material.

19. The device of claim 14, wherein said test element of said test strip comprises a reagent for generating a reaction indicative of the concentration of an analyte in said liquid sample.

20. The device of claim 19, wherein the analyte is glucose.

21. The device of claim 19, wherein the sample is blood.

22. The device of claim 19, wherein said reagents produce a colorimetric reaction, said device comprising optical means for reading said reaction.

23. The device of claim 19, wherein said reagent produces a photochemical reaction and said device comprises instrumentation for measuring said reaction.

24. The device of claim 14, wherein a hydrophilic coating is disposed on at least a portion of the capillary channel of the test strip.

25. The device of claim 14, wherein said test element is secured to said cover of said test strip.

26. The device of claim 14, wherein said test element is secured to said cover of said test strip with a substantially optically clear adhesive.

27. The device of claim 14, wherein said capillary channel of said test strip includes a test zone for receiving said test element, said test zone having a transverse dimension greater than a transverse dimension of said test element.

28. The device of claim 14, wherein said capillary channel of said test strip includes a test zone for receiving said test element, said test zone having a depth greater than the thickness of said test element.

29. The device of claim 14, wherein said test element of said test strip includes reagents for generating a reaction indicative of the concentration of an analyte in said liquid sample.

30. A method of lancing and collecting a sample of bodily fluid using a lancing and collecting device having a test strip including a collection chamber, a containment ring surrounding the collection region, a capillary channel in fluid communication with the collection region, and a cover disposed over the collection chamber and at least a portion of the capillary channel, the lancing and collecting device having a lancet adapted to pierce the cover and exit the collection chamber when moved between the retracted position and the extended position, the method comprising:

placing the capacity ring of the test strip on the skin of a subject:

piercing a skin site of the subject defined by the perimeter of the volume ring;

maintaining a body fluid sample produced at a puncture site within the circumference of the containment ring;

collecting said body fluid sample produced at said puncture site with said test strip; and

directing at least a portion of the bodily fluid sample from the collection chamber to the inlet of the capillary channel with the cover.

31. The method of claim 30, comprising determining the concentration of an analyte in the collected bodily fluid sample.

32. The method of claim 31, wherein measuring further comprises reacting an analyte in the collected bodily fluid sample with a reagent disposed on a test element held by a capillary of the test strip.