Patent Publication Number: US-2020275868-A1

Title: Glucose test arrangement and method

Description:
CLAIM OF PRIORITY 
     The present application is based on and claims priority to PCT/EP2018/070782, filed Jul. 31, 2018, which claims the priority filing benefit of European Application No. 17184572.0, filed Aug. 2, 2017, each of which are hereby incorporated herein by reference in their respective entireties. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The present application relates to a handheld device for measurement of an analyte, particularly to a glucose test arrangement for use in a handheld meter, and more particularly to a disposable test pad for a glucose test in a body fluid, and to a supporting member adapted to support the test pad at an application site for applying body fluid, particularly as a drop of blood, from a user&#39;s skin and in particular from a user&#39;s finger onto a receiving area of the test pad, wherein the receiving area faces away from the supporting member, such that the sample fluid is applied from the top and the opposite side is flatly supported. The invention specifically concerns a test tape cassette and is further directed to a handheld meter as a glucose concentration measurement device. 
     BACKGROUND 
     In the field of blood glucose testing, it is known to use disposable test elements in a handheld glucose meter for measurements on the spot. The user provides a fresh blood sample by pricking a finger and transferring a drop of blood onto the test element. Specifically, a plurality of test elements can be provided for successive use on a test tape, which is loadable into the meter in the form of a replaceable tape cassette. Thus, the user has no need to take care of the disposal of each single test element. However, the instrument is generally used by patients outside a laboratory environment, and therefore the measurement may be susceptible to unintended mishaps due to user handling. For example, contamination on a user&#39;s finger, e.g. from food, may lead to additional glucose content in a drop of blood produced on the finger. Thus, false high glucose values may occur if the user does not wash his finger properly before performing a test. Furthermore, some users may tend to press their finger relatively hard onto a test field or test pad, or a user may rub his finger during measurement across the test pad. In extreme cases of user handling scenarios, significant measurement deviations may occur. 
     On this basis an object of the invention is to further improve the known test arrangements and devices and methods to ensure improved accuracy of the blood glucose measurement during the data acquisition phase or detection phase of a measurement. 
     The combination of features stated in the independent claims is proposed to achieve this object. Advantageous embodiments and further developments of the invention are derived from the dependent claims. 
     SUMMARY 
     The invention is based on the idea of preventing measurements from being distorted due to user handling errors, by aiding a user with regard to sample application to a test field. Thus, a glucose test arrangement is proposed in which one or more spacer elements are arranged on the supporting member adjacent to the test pad, wherein the one or more spacer elements have a skin-contacting end section, particularly a finger-contacting end section, which protrudes above the receiving area of the test pad. In this way, the user receives a tactile feedback already before the test pad is contacted. The skin or finger is prevented from directly pressing onto the test pad, and/or even from contacting the test pad. Only the drop of blood reaches the receiving area of the test pad. Moreover, the spacer elements diminish the risk that the user wipes off contaminated blood from the finger surface. Instead, mostly non-contaminated blood from parts of the blood drop which are farther away from the skin or finger surface is applied to the test pad. 
     In order to provide the test pad at the application site, the test pad can be moved relative to the supporting member and relative to the spacer elements thereon. 
     For a test pad having a large-area to be wetted with body fluid, in one embodiment of the present invention a bottom side of the test pad flatly and/or full-facedly abuts against the supporting member, while the receiving area is arranged on a top side of the test pad opposite to the bottom side of the test pad. 
     In other embodiments, the spacer elements are arranged adjacent to a boundary of the receiving area such that they are bodily separate from the test pad at the application site and without solid connection to the test pad at the application site. 
     In yet other embodiments, the spacer elements are selected from the group comprising ridges, bars, pins, spikes, edges, rectangles, triangles, and saw-tooth structures. 
     In order to account for the specific sample application procedure, the spacer elements may have a beveled, chamfered and/or rounded contour. 
     To achieve the user-aiding effects, in one embodiment the spacer elements are made of a non-elastic material as a rigid formed part. 
     According to certain embodiments wherein the test pads are rectangularly contoured, the spacer elements are arranged on opposite sides of the test tape carrying the test pads. 
     In one embodiment, the spacer elements are adapted to provide a haptic feedback to the user during sample application. In one aspect, the end section of the spacer elements has a linear or pointed contact surface for contacting the user&#39;s skin. 
     In other embodiments, the spacer elements are adapted to essentially prevent direct finger contact with the test pad during sample application. Such an arrangement is useful when, for example, the test pad is at least partly compressible or becomes at least partly compressible after wetting. 
     For an optimized functional value, in certain embodiments the spacer elements have a height in the range from about 0.5 mm to about 5 mm, for example from about 1 mm to about 3 mm. 
     For a direct measurement at the application site, the supporting member may comprise a window for optically scanning a bottom side of the test pad opposite to the receiving area. In this connection, the window may also contain an optical element or delimit an opening free from an optical element. 
     In yet other embodiments useful in connection with a tape cassette, the supporting member may be formed as a tip for guiding a transport tape which carries a plurality of test pads spaced apart from each other. 
     Alternatively, for use of single disposables, the supporting member may be adapted to position a test strip carrying a test pad. 
     Another aspect of the invention concerns a tape cassette for glucose tests comprising the test arrangement according to the invention, wherein the supporting member is formed as a deflection tip for a transport tape which carries a plurality of test pads spaced apart from each other, and wherein the spacer elements are arranged on both longitudinal sides of the transport tape. In some embodiments, the spacer elements may comprise injection-molded parts. 
     The invention also concerns a handheld meter for glucose tests comprising the above described tape cassette or test arrangement and a detection unit operable for detecting measuring values on the test pad, using, for example, optical or photometric measurement techniques. 
     A still further aspect of the invention concerns a glucose test method for use in a handheld meter, comprising the steps of
         providing a disposable test pad which is responsive to glucose in a body fluid,   placing and positioning the test pad on a supporting member at an application site for body fluid, where one or more spacer elements are arranged on the supporting member adjacent to the test pad,   applying body fluid, particularly as a drop of blood, from a user&#39;s skin onto a receiving area of the test pad, where the receiving area faces away from the supporting member, and   contacting the user&#39;s skin by means of a skin-contacting end section of the one or more spacer elements which protrudes above the receiving area, thereby preventing direct finger contact with the test pad during sample application for enhanced accuracy of the glucose test.       

     In this way, similar effects and advantages are achieved as already mentioned above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, the invention is further elucidated on the basis of an embodiment example shown schematically in the drawings, where: 
         FIG. 1  shows a test tape cassette for glucose tests having a deflection tip and finger-contacting spacer elements projecting from the tip; testing system including; 
         FIG. 2  is a perspective view of a handheld glucose meter configured for using the test tape cassette; 
         FIG. 3  is an expanded cut-out from  FIG. 1 ; and 
         FIG. 4  illustrates various alternative forms of spacer elements on the tip, denoted as a.), b.), c.) and d.). 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION 
     As depicted in  FIG. 1 , an exemplary embodiment of a disposable tape cassette  10  for blood glucose tests comprises a housing  12 , a spoolable transport tape  14  which carries a plurality of test pads  16  spaced apart from each other and a deflection tip  18  for successive provision of the test pads  16  on the tip  18  for sample application in contact with a user&#39;s finger, wherein protruding spacer elements  20  on the tip  18  provide a haptic feedback to the user during sample application and prevent direct skin or finger contact with the test pad. Forwarding of the transport tape  14  is accomplished by two spools as in a conventional audio or video cassette (not shown). 
     As further shown in  FIG. 2 , a portable glucose meter  22  is adapted to receive the disposable test tape cassette  10  which can be inserted into a compartment of the meter housing  24 . The tip  18  of the inserted tape cassette  10  is accessible upon opening a tip cover  26 . Then, the user applies a drop of blood by pricking a finger with a lancing aid and contacting the top side of the test pad  16 . During this handling step, the tip  18  serves as a supporting member  30  underneath the test pad  16 . 
     The handheld meter  22  may be provided with a photometric-type measuring unit  28  for determining a glucose concentration from the measured values. For this purpose, the test pads  16  on the transport tape  14  are formed by a layered chemistry field which is responsive to the analyte, such as glucose, by a color change. Then, the measuring unit  28  allows a measurement of the analyte concentration by optical scanning of the rear side of transport tape  14  at the location of a dosed test pad  16 , through an optical window in the support member  30  and the transparent transport tape  14 . The measuring result and other information can be displayed to the user on a display  32 . 
     As apparent from  FIG. 3 , the spacer elements  20  are arranged laterally to the tape  14  as a rigid unitary structure of the tip  18 , made, for example, as injection-molded parts. These are formed as ribs or ridges protruding from the flat or curved supporting surface  34  of the supporting member  30 . The linear skin-contacting end section  36  of the spacer elements  20  protrudes above the upper fluid (blood) receiving area  38  of the active test pad  16  on the tip  18 . As the test pad  16  may be at least partly compressible or may become at least partly compressible after sample application, the spacer elements  20  should have a sufficient height in the range of about 0.5 mm to about 5.0 mm, such as from about 1 mm to about 3 mm, measured from the surface of the supporting member  30 , in order to avoid direct finger pressure. Pressure from a finger after wetting may lead to an unwanted modification of the layered test structure, for example if a covering net or mesh is provided for sample spreading it may become impressed into the chemistry field, thus impairing or impacting an optical measurement. 
     The spacer elements  20  may be arranged on opposite sides of the test pad  16 . As shown, the test pad  16  has a rectangular contour. Thereby, the user receives tactile feedback information before his finger reaches the test pad  16 . In this way, excessive exertion of pressure can be avoided. Furthermore, the spacer elements  20  may provide a certain stability for the applying finger, for example by reducing unwanted finger movement during sample application, such as due to tremor. 
       FIG. 4  schematically shows various alternative embodiments of spacer elements  20  on a cassette tip  18 . In  FIG. 4 a   , the spacer elements  20  have a chamfered, triangular shape ending in a pointed contact surface  36 . Also apparent is an optical window  40  in the center of the supporting surface  34  for reflectometric measurement.  FIG. 4 b    shows saw-toothed structures of spacer elements  20 , whereas  FIG. 4 c    and  FIG. 4 d    illustrate spikes and rounded pins as spacer elements  20 . 
     EXAMPLE 
     The improvement with the design according to an embodiment of the present invention was demonstrated in a comparative study, the results of which are given in Table 1 below. In the study, tape cassettes  10  with and without spacer elements  20  on the supporting member  30  have been used. In the glucose concentration range below 100 mg/dL, results in a commonly used benchmark interval of +/−10 mg/dL (+/−0.56 mmol/L) from reference values have been approved, whereas in the higher range of 100 mg/dL and above results in a relative interval of +/−10% from reference values have been counted as acceptable. The reference glucose values for the samples were determined using a hexokinase methodology (hexokinase/glucose-6-phosphate-dehyrogenase) and a commercially available Cobas 6000 c501 analyzer system. The obtained results clearly demonstrate the enhanced precision of the analyte measurements employing the spacer elements  20  on the tape cassette tip. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Comparative study of tape cassette design 
               
            
           
           
               
               
               
            
               
                   
                 Cassette without 
                 Cassette with 
               
               
                   
                 spacer elements 
                 spacer elements 
               
               
                   
                 (conventional) 
                 (inventive design) 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                 Glucose 
                 Result within 
                 98.7% 
                 99.5% 
               
               
                 concentration 
                 +/−10 mg/dL 
                 (154/156) 
                 (185/186) 
               
               
                 &lt;100 mg/dL 
                 from reference 
               
               
                   
                 value 
               
               
                 Glucose 
                 Result within 
                 92.3% 
                 99.3% 
               
               
                 concentration 
                 +/−10% from 
                 (410/444) 
                 (411/414) 
               
               
                 ≥100 mg/dL 
                 reference value