Patent Application
20080300508
1. Field of the Invention
The present invention generally relates to medical diagnostics devices and more specifically to a diagnostic patch attachable to a subject's skin for performing a rapid blood test.
2. Discussion of the Related Art
Diagnostics test kits for rapid detection of specific medical conditions and diseases are becoming increasingly widespread in the field of medical diagnosis. Such kits allow for immediate point-of-care diagnosis in the most basic of healthcare settings with no need for expensive instrumentation and with minimal specialized training.
A well-known format for performing rapid assays is the lateral flow platform where a sample is applied to a test strip impregnated with assay specific reagents, typically a binding assay such as immunoassay. The sample is applied to one end the test strip and is drawn through the strip by capillary action to pass through a reaction zone where the analyte, when present, reacts with the pre-impregnated reagents and further into a detection zone where the appearance of a visible or otherwise detectable signal indicates presence of the analyte in the sample. There exist many variations of this basic structure, regarding the number and nature of the immobilized, labeling and other reagents located along the strip and their interaction with the analyte, as well as to the nature and formation of the signal. A great variety of analytes may be detected in this manner. In particular relevant to the present invention are rapid diagnostic blood tests where the presence of a specific substance in the blood is indicative of the presence or absence of a disease or a physiological condition, such as for example, the Determine® series from Inverness Medical for the detection of sexually transmitted diseases, including HIV, Hepatitis B and Syphilis.
Although available rapid blood testing kits, such as the Determine® series, significantly shorten and simplify blood test procedures, they still require separate actions for collecting a blood sample from a tested subject and transferring the sample to the test device for analysis. Collection of blood sample usually involved withdrawing blood by means of a syringe or the use of a lancet to injure a body area such as a fingertip and collecting blood from the injury by means of a capillary tube. Such procedures are typically performed by a trained person and may expose the person to infectious blood samples. Moreover, blood sample collection and sample testing are not necessarily performed by the same person. Often blood specimens are collected in one location while tests are performed in another location. This requires transporting the collected specimens and a double identification recordation first for labeling the collected blood samples, then for labeling the test devices, e.g., test strips. In particular, where large groups of people are to be screened for an infectious agent, such as for example HIV, and where it is possible that tested individuals will not come for follow-up, it is particularly desirable to have means for obtaining rapid results while providing easy identification means that prevents possible mismatch between test subjects and test results.
It will be therefore desirable to have an all-in-one self-contained diagnostic device, which allows performing both collection and subsequent analysis of a blood sample in the same device with no need to transfer the collected sample to a separate test device. Such a device will simplify test procedure, will reduce the time required for the test and will minimize exposure of personnel to collected blood samples. It will be also desirable to have such an all-in-one blood test device which is attachable to the subject being tested, so that it can be attached to the subject just before the test is started and remains thereon until the test is complete. Such a device will ensure that test results are made known to the tested subject. It further eliminates the need to manage separate identification labels for blood samples and for test devices and prevents possible mismatch between tested subjects and test results.
Accordingly it is a general object of the present invention to provide an all-in-one self-contained rapid diagnostic device for collecting and analyzing a blood sample of a test subject by a one-step operation with no need to manipulate blood samples.
It is a further object of the invention to provide such a diagnostic device as defined above which is configured as a flexible patch that can be easily attached to the skin of the test subject to be left thereon until the test is complete and test results are visibly displayed.
Such a device has the advantages of simplifying test procedure and minimizing exposure of health care practitioners to blood samples and lancing devices. It has the further advantage of eliminating the need to manage separate identification records of blood samples and test devices.
Accordingly the present invention provides diagnostic device attachable to a skin segment of a test subject for a rapid detection of a pre-selected analyte in the subject's blood. The analyte may be a blood borne pathogen or any other substance the presence of which is indicative of a disease or a physiological condition.
The diagnostic device of the invention comprises a flexible patch attachable to the subject's skin, a puncturing unit for producing a blood sample of the subject, and an at least one test element embedded in said patch in a flow communication with the blood sample. The diagnostic device further comprises a display window through which test results can be visibly read. The puncturing unit may comprise a lancing element mounted within a flexible housing but may be any other lancet unit with an automatic retraction mechanism.
According to a preferred embodiment the invention, the flexible patch comprises a first flexible sheet comprising an aperture located opposite the puncturing unit and a second flexible sheet overlaying said first flexible sheet wherein said test element is sandwiched between the first and the second flexible sheets in a fluid communication with the aperture.
The test element is preferably a diagnostic strip adapted for a lateral flow assay of a whole blood sample wherein the assay may be an immunoassay, an enzymatic assay, a biochemical assay or a chemical assay. Preferably said assay is a positive/negative assay for detecting the presence of an analyte in the blood sample. Yet, according to other embodiments, the assay may be a quantitative or a semi-quantitative assay for detecting the concentration of the analyte. In accordance with a certain embodiment of the invention the analyte is a blood born pathogen. Preferably the diagnostic strip comprises a sample receiving zone, a whole blood separation zone for entrapping and retaining red blood cells, a reaction zone and a detection zone.
Optionally the device further include a reservoir of a releasable reagent solution adapted to release the reagent solution to facilitate running the diagnostic test. The reservoir may comprise a blister made of liquid impermeable film for encapsulating the reagent solution. The blister may be accommodated within the same puncturing unit that produces the blood sample or within a second puncturing unit located upstream to the blood sample producing unit. Optionally the device may further comprise a safety means for preventing premature activation of the puncturing units.
The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:
The present invention provides an all-in-one self-contained blood-test diagnostic device attachable to the skin of a tested subject. The device allows for performing a blood test by one operation step with no need to handle or manipulate blood samples, thus preventing exposure of health care providers to blood samples. The device has the further advantage of reducing to zero the time lag between initial sample collection and test performing. The device is configured as an adhesive skin patch that is easily adhered to a skin segment of the tested subject such as in an arm as depicted in
The device of the invention allows for screening a large number of subjects in a simple straightforward manner with no need to manage separate labeling for samples and for test devices. The patch may be used in developing areas where it is necessary to screen population for infectious diseases or for screening admitted patients in emergency rooms. The patch may also be used at blood donation sites for diagnosing potential donors.
The term analyte as used throughout the application is meant to denote any substance, compound or composition to be detected in a blood sample, including antigens, antibodies, hormones, proteins, enzymes, nucleic acids, drugs, or any other natural or synthetic substance whose presence and/or concentration in the blood may be of interest.
Referring to
As best seen in
In the embodiments shown here, patch 10 is essentially of a rectangular or oval shape, however it will be easily realized that patch 10 may assume other shapes without departing from the scope of the invention, as long as it is dimensioned to accommodate all essential components. It will be also realized that the layers of material used in the construction of patch 10 are quite thin and that the thickness of the different layers in
Flexible sheets 12 and 14 may be made from a large variety of nonirritating, hypoallergenic, cloth or plastic materials known in the art for use in the fabrication of skin adhesive tapes and bandages. The sheets may be selected from ready-made available tapes or may be especially designed and fabricated for the present purpose. Sheets 12 and 14 may also include multiple perforations as known in the art for preventing building up of sweat underneath the patch. Preferably, flexible sheet 12 is a double-sided adhesive tape having both faces coated by layers 12a, 12b of pressure sensitive adhesive. Top sheet 14 is preferably a one-sided adhesive tape coated with pressure sensitive adhesive layer 14a. However, it will be easily realized that other arrangements are possible that allow for overlaying the various layers of patch 10. A release liner 18 made from any of a variety of materials known in the art protects the adhesive coating 12a of patch 10 until the patch is to be used. Release liner 18 may have a similar size and shape as patch 10 or may be slightly larger for creating a rim or a tab to facilitate its removal. Similarly, release liner 18 may be divided into two or more abutting or partially overlapping parts for facilitating the attachment of patch 10 to skin.
Puncturing unit 30, comprising a housing 32 and a sterile lancing element 35, is configured for penetrating the skin for drawing blood. Lancing element 35 may be a hollow or a solid needle or any other sharp sterile element suitable for lancing dermal tissue for producing at least one drop of blood. The size and shape of lancing element 35 as well as the depth to which it penetrates the skin tissue may vary and designed in accordance with the amount of blood required for performing the test and the density of blood vessels in the skin tissue in the body area to which the diagnostic patch is applied. In its default position lancet 35 is having its pricking tip suspended above the upper surface of patch, substantially pointing at the center opening 15. Upon pressing, lancing element 35 penetrates through layers of patch 10, if present, and further into the underlying dermal tissue 60 to create an opening therein. Puncturing unit 30 is provided with a return/retract mechanism for withdrawing lancet 35 back to its default position once the puncturing unit is released. Various mechanisms may be employed for the firing of unit 30. In accordance with some embodiments, lancing element 35 may be fixedly mounted within an elastic or spring-loaded capsule-like housing 32 such that upon pressing, lancet 35 is pushed down to puncture skin while upon release, housing 32 as well as the lancet bounce back to their default position. Alternatively, lancet 35 may be movably mounted within a rigid housing to enable movement of element 35 relative the housing. For example, element 35 may be mounted to housing 32 by a spring loaded mechanism, or by another biasing mechanism, that biases element 35 to its default position above the upper surface of patch 10 and provided with a trigger element accessible from outside the housing that allow for firing the unit. Unit 30 may be further provided with a safely locking means for preventing unintentional premature actuation of the unit.
Upon being punctured, an opening is formed in dermal tissue 60 through which at least one drop of blood is generated in cavity 16 on the surface of the skin. Film 17, made of a liquid repellent, non-absorbent material, such as polyethylene, serves as a liquid barrier that prevents blood generated in cavity 16 from flowing or diffusing out of the cavity except via test strip 50. For the same reason, the edges of aperture 15 may be impregnated with a liquid repellent material. It will be appreciated that the shape of aperture 15 shape is not limited to a circle and that the aperture may be assume other forms to facilitate the guidance of blood into the receiving zone 52 of strip 50. Further in order to facilitate blood migration from aperture 50 to strip 50, patch 10 is preferably adhered to the skin in a vertical orientation with puncturing unit 30 at the upper end so that blood transport in the desired direction is enhanced by gravitation force.
In accordance with the embodiment demonstrated in
As mentioned above, the size and shape of lancing element 35 as well as the depth to which it penetrates the skin tissue may is designed in accordance with the amount of blood required for the specific diagnostic test strip embedded within the patch. Typically, the amount of blood required for lateral flow assays is in the range of 5 to 100 μL. Such amounts can be easily obtained by means of piercing the top layers of the skin. However it is sometimes necessary to add a small amount of an additional reagent, usually a diluent fluid, such as a buffer solution, in order to perform the test. The buffer could be for example a phosphate buffered saline or Tris buffered saline. For this purpose, the patch of the invention may further include a small reservoir of medically approved buffer or other appropriate reagent solution, adapted to release its content at the same time, or at a predetermined time before or after, the puncturing unit 30 is fired.
Diagnostic strip 50 may be any diagnostic test strip known in the art for detecting an analyte in a whole blood sample by a lateral flow assay, including immunoassays, enzymatic assays, biochemical assays and chemical assays.
It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims which follow.
