Abstract:
Apparatus for eliciting a blood sample, the apparatus comprising; a testing member rotatably mounted on a shaft; and an aperture for positioning a body part of the user relative to the edge of the testing member, wherein an edge of the testing member is shaped such as repeatedly to exert pressure on the skin of a user when the testing member is rotated.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a U.S. National Phase Application pursuant to 35 U.S.C. §371 of International Application No. PCT/EP2012/068699 filed Sep. 21, 2012, which claims priority to European Patent Application No. 11182383.7 filed Sep. 22, 2011. The entire disclosure contents of these applications are herewith incorporated by reference into the present application. 
     
    
     FIELD OF INVENTION 
       [0002]    This invention relates to method and apparatus for eliciting a blood sample. 
       BACKGROUND 
       [0003]    Diabetes sufferers may be provided with quantities of insulin, for instance by injection, sometimes a number of times daily. The quantity of insulin that is appropriate depends on the person&#39;s blood glucose level, so blood glucose level measurement can also occur a number of times daily. 
         [0004]    Blood glucose level measurement typically is a multi stage process. The first is lancing, in which a lancet, or needle, is used to pierce the skin of a user, for example on the end or side of a finger. Once a suitable amount of blood has been produced, a sample is taken on a testing strip. A person may need to squeeze their finger in order to cause sufficient blood to be expelled. Sometimes lancing needs to be reperformed. The testing strip then is provided to a meter, typically an electronic meter, which analyses the sample, for example by determining a parameter (e.g. an electrochemical potential or voltage, resulting from a chemical reaction between the blood sample and an enzyme present in the testing strip, and provides a blood glucose measurement result. This measurement is then used to determine an amount of insulin to be consumed by the person. 
       SUMMARY 
       [0005]    A first aspect of the invention provides apparatus for eliciting a blood sample, the apparatus comprising;
       a testing member rotatably mounted on a shaft; and   an aperture for positioning a body part of the user relative to the edge of the testing member,   wherein an edge of the testing member is shaped such as repeatedly to exert pressure on the skin of a user when the testing member is rotated.       
 
         [0009]    The aperture for positioning the body part may be part of a housing having, the shaft being mounted inside the housing. 
         [0010]    The apparatus may further comprise a lancet protruding from one position at an edge of the testing member, the lancet being configured to piece the skin of the user&#39;s body part when in a first rotational position. 
         [0011]    The edge of the testing member may be shaped as a plurality of ridges. The edge of the testing member may be shaped as three ridges. The ridges may be curved, optionally sinusoidal. 
         [0012]    First ends of one or more capillaries may be disposed on each of the plurality of ridges on an edge of the testing member. A first end of a capillary may be disposed approximately at the crest of each ridge on an edge of the testing member. Each of the one or more capillaries may extend through the body of the testing member and may terminate at a blood collection part supported on or within the testing member. 
         [0013]    The testing member may further comprise at least two electrical contact points connected to the blood collection part for communication with a meter for determining a parameter of blood chemistry. 
         [0014]    The blood collection part may comprise an absorbent material which contains an enzyme for blood glucose determination. The blood collection part may have a higher capillary pull force than the capillaries. 
         [0015]    The apparatus may be configured to control the speed of rotation of the testing member such that, having regard to the spacing between adjacent ridges, the frequency of the periodic pressure applied to a user&#39;s body part is consistent with the common thickness and elasticity of human skin. 
         [0016]    The frequency may encourage venous blood to exit a puncture wound in the user&#39;s body part or alternatively the frequency may encourage plasma blood to exit a puncture wound in the user&#39;s body part. 
         [0017]    A second aspect of the invention provides a method for eliciting a blood sample, the method comprising;
       providing a testing member rotatably mounted on a shaft and an aperture for positioning a body part of a user relative to an edge of the testing member; and   rotating the testing member so that an edge of the testing exerts periodic pressure on the skin of the user.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
           [0021]      FIG. 1  is a perspective view of a blood glucose meter (BGM) according to aspects of the invention; 
           [0022]      FIG. 2  illustrates components of one embodiment the BGM of  FIG. 1 ; 
           [0023]      FIG. 3  is a perspective view of components of the BGM of  FIG. 2  but with a hollow cylindrical housing part shown as transparent; 
           [0024]      FIG. 4  is a perspective view of a test disc member forming part of the BGM of  FIGS. 1 and 2 ; 
           [0025]      FIG. 5  is an underneath perspective view of the test disc member of  FIG. 4 ; 
           [0026]      FIG. 6  illustrates a test disc member forming part of a second embodiment of the BGM of  FIG. 1  in a perspective view; 
           [0027]      FIG. 7  illustrates components of the second embodiment of the BGM of  FIG. 1  in a perspective view; 
           [0028]      FIG. 8  is a perspective view of components of the BGM of  FIG. 1 ; and 
           [0029]      FIG. 9  is a flowchart illustrating operation of the first embodiment of the BGM of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    A blood glucose meter (BGM)  100  is shown in  FIG. 1 . The BGM  100  is shown in a perspective view. The BGM  100  has a generally flat base, that is not visible in the figure. The BGM  100  is approximately as tall as it is long, and its width is approximately one-third of its height. 
         [0031]    On one side face of the BGM are provided first, second and third inputs  101 ,  102 ,  103 . These may take the form of push-switches or touch sensitive transducers, for instance. Also provided on the side of the BGM next to the input devices  101  to  103  is a display  104 . This may take any suitable form, for instance a liquid crystal display (LCD), e-ink etc. In use, a user may control the BGM  100  using the input devices  101  to  103  and may be provided with information by the BGM through the display  104 . 
         [0032]    Located at a front face of the BGM  100  is an aperture  105 . The aperture  105  is located at approximately half of the height of the BGM. The aperture  105  is configured such as to be able to receive a part of a user&#39;s body, for the purpose of extracting a blood sample therefrom. For instance, the aperture  105  may be dimensioned so as to receive an end or a side part of a finger or thumb, or may be dimensioned so as to receive a side of a user&#39;s hand or a pinch of skin from a user&#39;s arm. The aperture may be rectangular in shape. Its edges may be bevelled, so as to guide a user&#39;s digit into a specific location. 
         [0033]    The aperture  105  is provided in the side of a cartridge  106 . The cartridge  106  has a generally cylindrical form, and is arranged vertically in the BGM  100 . 
         [0034]    In particular, the BGM includes a first housing part  107 . The first housing part  107  forms the base, left and right side face and the rear face of the BGM  100 . On the front face of the BGM  100 , the first housing part  107  also comprises the lowermost part of the side face. A fixed lid part  108  is attached to the first housing part  107 . The fixed lid part  108  comprises most of the top surface of the BGM  100 . A removable lid part  109  comprises the remaining part of the top surface of the BGM  100 . The removable lid part is disposed above the cartridge  106  at the front face of the BGM  100 . The first housing part  107 , the fixed lid part  108  and the removable lid part  109  are configured such that when the removable lid part is in place on the BGM the cartridge  106  is retained by mechanical interaction between the three components but is removable by a user. The exact way in which the removable lid part  109  is released from the BGM  100  is not critical and is not described in detail here. 
         [0035]    The first housing part  107  is configured such as to provide an elongate aperture  110  at the front face of the BGM  100 . The elongate aperture  110  may extend for most of the height of the front face of the BGM  100 . The elongate aperture  110  is defined at the uppermost part by the removable lid part  109  and is defined by the first housing part  107  at the right, left and bottom. The BGM  100  is arranged such that the cartridge  106  occupies the whole of the area of the elongate aperture  110 . The diameter of the cartridge  106  is greater than the width of the aperture  110  by a factor for instance of between 5 and 50%. The cartridge  106  has a length that is between 3 or 4 times its diameter. 
         [0036]    A slidable or pivotable door in the housing part  107  of the BGM  100  may cover all or a part of the elongate aperture  110  when the BGM is not in use. The door may cover at least the aperture  105 , such as to prevent the ingress of dirt and other potential contaminants into the aperture  105 . 
         [0037]    The removable lid part  109  is configured such that when removed from the BGM  100  the cartridge  106  is able to be extracted from the BGM by moving it vertically along its axis. When the cartridge  106  is fully removed, the elongate aperture  110  reveals a cavity in the BGM  100 . A replacement cartridge can then be introduced into the BGM  100  in the opposite manner to which the old cartridge  106  was removed. The cartridge  106  and the cavity which receives the cartridge may have a keying feature, such as a protrusion and a groove, a non circular diameter, or the like. Thus, when the cartridge  106  is fully inserted, the aperture  105  is in a fixed position to the elongate aperture  110 , for example in a centred position. 
         [0038]      FIG. 2  shows a subsystem  200  of the blood glucose meter  100 . The subsystem  200  includes the cartridge  106 , a drive wheel  201  and a drive belt  202 . 
         [0039]    In  FIG. 2 , the cartridge shown as having a hollow cylindrical housing part  203 , which constitutes part of a housing. The aperture  105  is formed in the hollow cylindrical housing part  203 . Coaxial with the hollow cylindrical part  203  is an elongate shaft  204 , only the top part of which is illustrated in  FIG. 2 . The length of the shaft  204  is such that its uppermost end is slightly below the uppermost end of the hollow cylindrical housing part  203 . As will be described below, the shaft  204  is mechanically coupled with the drive belt  202  so as to be rotatable by rotation of the drive wheel  201 . 
         [0040]    Formed with the inner surface of the hollow cylindrical housing part  203  are first and second guide members  205 ,  206 . In  FIG. 2 , it can be seen that the first and second guide members  205 ,  206  have a generally triangular cross section. One side of the triangular cross section of the first and second guide members  205 ,  206  is integral with the inner surface of the hollow cylindrical housing part  203 , with a point of the triangular cross section extending towards the centre of the cartridge  106 . A part of the length of the first guide member  205  is visible in  FIG. 2 , but only the uppermost surface of the second guide member  206  is visible in that figure. 
         [0041]      FIG. 2  also shows some electronic components that form parts of the blood glucose meter  100 . These components are provided within the housing  107  but do not form part of the cartridge  106 . 
         [0042]    A bus  211  is arranged to connect a number of components including a microprocessor  212 , random access memory (RAM)  213 , read-only memory (ROM)  214 , a keys interface  215 , a display driver  216 , an analyte interface circuit  219  and a motor interface  217 . All of these components are powered by a battery  218 , which may take any suitable form. 
         [0043]    Stored in the ROM  214  is software and firmware that governs operation of the blood glucose meter  100 . The software/firmware is executed by the microprocessor  212  using the RAM  213 . The software/firmware stored in the ROM  214  is operable to operate the blood glucose meter  100  such as to allow control by a user through the keys or input devices  101  to  103 , as detected by the keys interface  215 . A blood glucose measurement and other information is provided on the display  104  at suitable times by operation of the software/firmware and the microprocessor  212  through the display driver  216 . 
         [0044]    The motor interface  217  allows the microprocessor  212 , according to the software/firmware stored in the ROM  214 , to control the motor that is coupled to the drive wheel  201 , and any other motors that are included in the blood glucose meter  100  (as will be described below). 
         [0045]    The analyte interface circuit  219  is operable to provide electrical signals with certain voltages to the electrical contact terminals  401  (described in more detail with respect to  FIG. 8 ), and thus the contact pads  318  and thus the blood collection part  315  (described in more detail with respect to  FIG. 3 ), and to measure parameters of signals such as to allow the microprocessor  212  to measure a blood glucose level of a blood sample. 
         [0046]      FIG. 3  is the same as  FIG. 2  except that the hollow cylindrical housing part  203  is shown in wire frame, so as to reveal components internal to it, and in that the electronic components are omitted. In  FIG. 3 , a third guide member  207  is visible. As can be seen from this figure, the first and second guide members  205 ,  206  are located only in the uppermost half of the length of the cartridge  106 , and the third guide member  207  is located only in the lowermost half of the cartridge  106 . The first, second and third guide members  205  to  207  are distributed around the circumference of the hollow cylindrical housing part  203 . In particular, the first and second guide members  205 ,  206  are located at approximately 100 to 160 degrees from one another. The third guide member  207  is located approximately 60 to 130 degrees from each of the first and second guide members  205 ,  206 . 
         [0047]    Mounted on the shaft  204  are a plurality of members, three of which are shown in  FIG. 3  as  208 ,  209  and  210  respectively. The members  208  to  210  will hereafter be referred to as test disc members. Each of the test disc members  208  to  210  is substantially the same. 
         [0048]    One test disc member  208  is shown in some detail in  FIG. 4 . The test disc member  208  has a generally circular shape, although on one side a notch  301  is formed and on another side a cutaway portion  302  is provided. The cutaway portion  302  comprises a number of ridges or protrusions  322  and constitutes a milking portion. 
         [0049]    The test disc member  208  includes an uppermost surface  303 , a lowermost surface  304 , which is shown in  FIG. 5 , and a disc edge  305 . The diameter of the test disc member  208  is between 15 and 25 millimetres, for instance 20 millimetres. The thickness of the disc, which is equal to the height of the disc edge  305 , is between 0.5 millimetres and 1 millimetre.  FIG. 5  shows the test disc member  208  from the underside. As such, the lower surface  304  is visible and the upper surface  303  is not visible. The test disc member  208  will now be described with reference to  FIGS. 4 and 5 . 
         [0050]    A hole  306  is formed at the centre of the test disc member  208 . The hole  306  comprises two main parts. A circular part is centred on the test disc member  208  and has a diameter equal to or slightly larger than the external diameter of the shaft  204 . A drive notch  307  abuts the circular part of the hole  306  and includes edges that are able to be engaged by a drive dog. 
         [0051]    A drive dog  320  is formed on the shaft  204 . The drive dog  320  is engaged with the drive notch  307  in the hole  306  of the test disc member  208 . This engagement allows rotation of the shaft  204  to result in rotation of the test disc member  208 . 
         [0052]    On the underside of the test disc member  208  is provided a spacer member  308 . The spacer member  308  comprises a slice of a hollow cylinder. The cylinder is centred on the centre of the test disc member  208 . The inner diameter of the spacer member  308  is selected such that the hole  306  does not overlap with the spacer member  308 . The outer diameter of the spacer member  308  is only slightly greater than the inner diameter, so the spacer member  308  has little thickness. The height of the spacer member  308  is between 0.5 and 1 millimetre. When plural test disc members are stacked together, the spacer member  308  provides separation between the upper surface  303  of one test disc member and the lower surface  304  of the test disc member that is directly above it. The separation is determined by the height of the spacer member  308 . 
         [0053]    Referring again to  FIG. 4 , a lancet  309  is shown protruding from the disc edge  305 . The lancet  309  is provided in the cutaway portion  302 . A first end of the lancet  309  is embedded within the material of the test disc member  208 , and a second end is provided with a sharp point and extends outwardly. The lancet  309  extends at an angle between 30 and 60 degrees from a radius line of the test disc member  208  at the position where the end of the lancet  309  is embedded in the test disc member. The second end of the lancet  309  is located at or just outside a circumference  311  of the test disc member  208 . The circumference  311  is shown as a dotted line in  FIG. 4  because it is virtual, instead of tangible. The lancet  309  extends from the disc edge  305  at a first position  312  on the disc edge. The first position  312  is close to a second position  313  at which the cutaway portion  302  starts. The cutaway portion  302  ends at a third position  314 . Between the second and third positions  313 ,  314  opposite to the cutaway portion  302 , the disc edge  305  generally takes the form of a circle, although the notch  301  interrupts that circle. 
         [0054]    The cutaway portion  302  comprises a number of ridges  322 . The ridges  322  may have a partly or completely curved profile. For instance, they may be sinusoidal in shape. 
         [0055]      FIGS. 4 and 5  show a test disc member  208  having three ridges  322 , however the test disc may have any number of ridges greater than two, for example between two and twelve ridges. The ridges  322  do not extend beyond the boundary of the test disc circumference  311 . 
         [0056]    Some or all of the ridges  322  may have one or more capillary openings  324 . The capillary openings  324  are provided in the edge  305  of the test disc member  208 . The capillary openings  324  may be provides at the crests of the ridges  322 , i.e. the parts at the maximum distance from the centre of the disc  208 . 
         [0057]    Alternatively, an area of the test disc edge  305  at and around the crest of each ridge may be composed of an absorbent material. In these embodiments, capillaries  326  extend through the body of the test disc member  208  away from the capillary openings  324 . 
         [0058]    A blood collection part  315  is located within the body of the test disc member  208 . A recess may be provided in the upper surface  303  of the test disc member  208  to receive the blood collection part  315 . Each of the capillaries  326  terminates at the blood collection part  315 . The blood collection part may be formed of an absorbent material containing an enzyme for blood glucose determination, or some other parameter measurement. Blood may be drawn into the blood collection part  315  through capillary action. The material of the blood collection part  315  may have a higher capillary “pull-force” than the capillaries  326 , such that the blood collects in the blood collection part  315  rather than in the capillaries  326 . 
         [0059]    The enzyme in the blood collection part  315  reacts chemically with blood in such a way that blood glucose level can be measured. The blood collection part  315  is connected to first to third contact pads  318  by first to third conductive tracks  317 . The contact pads  318  and the conductive tracks  317  are formed on the upper surface  303  of the test disc member  208 . 
         [0060]    The aperture  105  is configured such as to allow an amount of the flesh making up the end of the user&#39;s digit to be present within the internal volume of the cylindrical part  203  when the user presses the digit up against the aperture  105 . When the user applies force into the aperture  105  with the digit, the digit distorts and a bulbous part is provided within the internal diameter of the hollow cylindrical housing part  203 . The size of the bulbous part, and in particular the height of the bulbous part, depends on a number of factors, including the physical characteristics of the user&#39;s digit and the amount of force that the user applies, as well as the configuration of the aperture  105 . The aperture  105  is dimensioned such that in normal use (i.e. with a typical user applying a typical amount of force) a bulbous part of the user&#39;s digit extends into the internal volume of the hollow cylindrical housing part  203  to a depth of approximately 1 millimetre. 
         [0061]    In use a part of a user is firstly pierced by the lancet  309 , the part is then milked by the ridges  322 , and blood then is provided to the blood collection part  315  through the capillaries  326 . A measuring circuit connected to the blood collection part  315  by way of the conductive tracks  317  and the contact pads  318  then is able to determine a blood glucose level of the user. The level then is displayed on the display  104 . 
         [0062]    Operation will now be described with reference to the figures. 
         [0063]    As shown in  FIG. 3 , the test disc members  208  to  210  commence at the same orientation. Here, the first test disc member  208  is uppermost. The third guide member  207  is located in the notch  301  of the lowermost test disc members  209 ,  210 . The notch  301  of the first test disc member  208  is aligned with the third guide member  207 , but is not constrained thereby. The upper surface  303  of the uppermost test disc member  208  is in contact with a lowermost surface of the first guide member  205 . The lowermost surface of the second guide member  206  is at the same level as the lowermost end of the first guide member  205 . However, the second guide member  206  coincides with part of the cutaway portion  302  of the first test disc member  208  at the orientation of the test disc member  208  shown in  FIG. 3 . As such, there is no contact between the second guide member  206  and the first test disc member  208  when the first test disc member is in this position. The test disc members  208  to  210  are biased in an upwards direction by bias means (not shown), which may be a spring. However, the test disc members  200  to  210  are prevented from moving upwards within the cartridge  106  by virtue of the contact between the upper surface  303  of the first test member  208  and the lowermost end of the first guide member  205 . 
         [0064]    At the position shown in  FIG. 3 , the distal end of the lancet  309  is not co-located with the aperture  105 . As such, the lancet  309  is in this position not operational. Put another way, the lancet  309  at this position is shielded by the hollow cylindrical part  203 , which constitutes part of the housing. 
         [0065]    From the position shown in  FIG. 3 , the shaft  204  is caused to rotate in a clockwise direction by action of the drive wheel  201  and drive belt  202 . The drive dog  320  is engaged with the drive notch  307  in the hole  306  of the test disc member  308 , and so allows rotation of the shaft  204  to result in rotation of the test disc member  308 . Rotation brings the lancet  309  in front of the aperture  105 . As such, a skin-covered part of a user (hereafter the part will be referred to as a user&#39;s digit, for the sake of convenience) is lanced by the lancet  309 . This produces a puncture in the skin of the digit, through which blood can escape The shaft  204  is caused to rotate only by a predetermined amount, the maximum extent of travel of the lancet  309  is controlled. The penetration of the lancet  309  in the user&#39;s digit depends on a number of factors, as will be appreciated by the person skilled in the art. The amount of rotation, and thus the depth of penetration, may be definable by a user. 
         [0066]    Subsequently, the shaft  204  is controlled to rotate in an anticlockwise direction. This causes the lancet  309  to be removed from the user&#39;s digit, and for the disc edge  305  at the cutaway portion  302  to rub the user&#39;s digit as the test disc member  208  rotates. As the test disc member  208  rotates, pressure is applied periodically to the user&#39;s digit by the ridges  322 . The pressure on the user&#39;s digit increases as the first ridge “height” increases, provided that the user continues to press their digit against the aperture  105  with sufficient force. This gradual increase in pressure encourages blood to exit the puncture wound in the user&#39;s skin. At least some of this blood is absorbed into the capillary opening  324  on the crest of the first ridge  322  and is drawn through the capillary  326 . 
         [0067]    The capillary opening  324  may alternatively be located just after the crest of the ridge  322  i.e. offset clockwise of the ridge crest. This positioning may improve the efficiency of blood collection. Alternatively two or more capillary openings  324  may be provided at several locations at or near the crest of the ridge  322 . 
         [0068]    After the test disc member  208  has rotated past the crest of the first ridge, pressure on the user&#39;s digit reduces. For a period when the test disc member  208  is located between the crests of successive ridges  322 , no pressure is exerted on the digit of the user. Pressure is then exerted again as the second ridge “height” increases. Blood is then absorbed via the capillary opening  324  on the second ridge. 
         [0069]    During this part of the rotation, blood is drawn by the capillary action of the capillaries  326  to the blood collection part  315 . The blood and the enzyme present in the blood collection part  315  then react. 
         [0070]    This periodic application of pressure by successive ridges efficiently encourages blood to exit the wound. The periodicity of the pressure is determined by the spacing between successive ridges and by the speed of rotation of the test disc member  208 . The frequency of the pressure applied by the ridges  322  may be consistent with the common thickness and elasticity of skin. The frequency may be such as to encourage venous blood to exit the wound. Alternatively, the frequency of the pressure may encourage plasma blood to exit the wound. The device  100  may allow the speed of rotation to be changed such that the user can control the frequency of the pressure applied by the ridges  322 . For example, the device may have settings for “venous blood” and “plasma blood” and the user may select one of these settings via user inputs  101  to  103 . An advantage of being able to encourage a different type of blood to exit the wound is that certain types of blood may be more suitable for testing a specific property of blood, for example the blood glucose level, haemoglobin concentration or ketone concentration. 
         [0071]    After the blood collection stage of the rotation, the test disc member  208  is caused to continue to rotate in an anticlockwise direction. At a point in this rotation of the test disc member  208 , the lowermost part of the second guide member  206  ceases to coincide with the cutaway portion  302  and so is able to exert a reaction force on the upper surface  303  of the test disc member  208 . A short time thereafter, the lowermost part of the first guide member  205  becomes coincident with the cutaway portion  302 , and ceases to contact the upper surface  303  of the test disc member  208 . At this point, it is the second guide member  206  that prevents the first test disc member  208  moving upwards within the cartridge  206 . 
         [0072]    The shaft  204  is then caused to be rotated further in an anticlockwise direction until the notch  301  is aligned with the second guide member  206 . Because at this location the first guide member  205  is coincident with the cutaway portion  302  of the test disc member  208 , neither of the first or second guide members  205 ,  206  prevents upwards movement of the first test disc member  208 . At this rotational position, the first guide member and the ridges  322  may be arranged such that there is no overlap between the test disc member  208  in the cutaway portion  302  and the first guide member  205 . Alternatively, the guide members  205 ,  206  may prevent upward movement of the test disc member until the first guide member  205  is coincident with the first trough of the ridges  322  i.e. the area between the first and second ridges  322 . At this point, the first to third disc members  208  to  210  are moved upwards by virtue of the bias means (not shown). 
         [0073]    When the first test disc member  208  moves upwards, the drive dog  320  ceases to cooperate with the drive notch  307  of the hole  306  of the first test disc member  208 . A lower surface of the drive dog  320  therefore contacts the upper surface  303  of the second test disc member  209 . This prevents further upward movement of the second test disc member  209 , and thus prevents further movement of the test disc member  210 . At this position, the shaft  204  is caused to be rotated by the drive wheel  201  and the drive belt  202  such that the drive dog  320  is coincident with the drive notch  307  of the second test disc member  209 . At this location, the second disc member  209  is able to move upwards on the shaft  204 , thereby engaging the drive dog  320  with the drive notch  307  of the second test disc member  209 . After the second test disc member  209  has moved upward by a distance equal to the height of the spacer member  308 , further upwards movement of the second test disc member  209  is prevented by contact between the first guide member  205  and the upper surface  303  of the second test disc member  209 . At this point the second guide member  206  is located within the notch  301  of the first test disc member  208 . This prevents further rotation of the first test disc member  208  within the cartridge  106 . 
         [0074]    By virtue of movement up the cartridge  106  of the first to third test disc members  208  to  210 , the third guide member  207  ceases to be within the notch  301  of the second test disc member  209 . At this stage, the third guide member  207  does not prevent rotational movement of the second disc member  209 . 
         [0075]    At the end of the operation described above, the second test disc member  209  is in exactly the same position as was the first test disc member  208  at the position shown in  FIG. 3 . Furthermore, the shaft  204 , and thus the drive dog  320 , has the same orientation. As such, the second test disc member  209  is able to be used to elicit a blood sample from a user and test the glucose level thereof in the same way as was the first test disc member  208 . 
         [0076]    By providing a stack of test disc members  208  to  210  within the cartridge  106  and by providing a suitable physical arrangement, a cartridge  106  can be used for multiple tests. When the cartridge  106  is new, the test disc members  208  to  210  are located in the bottom half of the cartridge  106 , with the uppermost test disc member being aligned with the aperture  105 . As test disc members are used, the stack of test disc members moves upwards in the cartridge. When the last test disc member is used, the cartridge can be said to be spent. At this stage, all of the test disc members are located in the uppermost portion of the cartridge  106 . 
         [0077]    It will be appreciated that the number of test disc members  208  to  210  that can be accommodated within the cartridge  106 , and thus the number of tests that can be provided by a cartridge  106 , is a factor of the height of the cartridge  106 , and the separation between corresponding parts (e.g. the upper surfaces) of adjacent test disc members  208  to  210 . A taller cartridge and/or a reduced separation of test disc members increases the number of tests that can be performed using a single cartridge  106 . 
         [0078]    The lancet  309  shown in  FIGS. 4 and 5  is a substantially straight rod, sharpened to a point. However, in some embodiments, the lancet  309  may instead be curved. A first end of this curved lancet may be embedded within the material of the test disc member  208 , and a second end may be provided with a sharp point and extends outwardly. The curved lancet may protrudes from the disc edge  305  at the same position  312  as the straight lancet  309 . The curved lancet may extend at an angle between 30 and 60 degrees from a radius line of the test disc member  208  at the position  312  where the end of the curved lancet is embedded in the test disc member. The second end of the curved lancet may be located at or just outside a circumference  311  of the test disc member  208 . 
         [0079]    At the part of the curved lancet that is adjacent the disc edge  305 , the longitudinal axis of the curved lancet is at an angle X with respect to a straight line drawn between the junction between the curved lancet and the disc edge  305  and the centre of the shaft  204 . The curve of the curved lancet is such that the longitudinal axis of the curved lancet at the end distant from the disc edge  305  is at an angle greater than the angle X with respect to the line drawn between the junction between the curved lancet and the disc edge  305  and the centre of the shaft  204  (the axis is different at different points on a curve). The effect is that the curved lancet is more aligned with the circumference of the test disc member  208  at its distal end than it is at the end that adjoins the disc edge  305 . This has the positive effect that when the lancet penetrates a user&#39;s digit, or other body part, due to rotation of the test disc member  208 , the path taken by the lancet as it penetrates the user&#39;s digit more closely matches the shape and orientation of the lancet than is experienced in a corresponding arrangement with a straight lancet. 
         [0080]    This effect is enhanced with the curved lancet since the cylindrical form of the lancet is terminated at the distal end by an oblique cut. In particular, the distal end of the curved lancet resembles a cylinder that has been cut at an angle that is not perpendicular to the longitudinal axis of the cylinder. As such, the end face of the curved lancet has the shape of an ellipse. The ellipse has a semi-major axis and a semi-minor axis and the point that is at the end of the semi-major axis that is furthest from the disc edge  305  forms a point. The cut is made through the lancet such that the point is formed extending in a direction that is circumferential with respect to the test disc member  208 . In particular, at least  1  mm of the end portion of the curved lancet is coincident with a line that is concentric with respect to the shaft. 
         [0081]    In other embodiments, a lancet is provided that extends substantially radially from the disc edge. Operation of the device  100  comprising a radial lancet will now be described with reference to  FIGS. 6 and 7 . Here, the arrangement and operation is as described above with reference to  FIGS. 2 to 5  unless otherwise stated. Reference numerals are retained from earlier described figures for like elements. 
         [0082]    Referring to  FIG. 6 , a test disc member  505  comprising a radial lancet is shown. A lancet  506  is provided extending from the disc edge  305  in the cutaway portion  302 . In particular, the lancet  506  extends in a radial direction with respect to the centre of the test disc member  505 . The lancet  506  extends from a fourth position  507 , which is near to the second position  313 . The fourth position  507  is further from the second position  313  than is the corresponding first position  312  in the arrangement described above with reference to  FIGS. 2 to 5 . However, because the lancet  506  is radial with respect to test disc member  505 , a distal end  506 A of the lancet  506 , i.e. the end that is furthest from the centre of the test disc member  505 , is at approximately the same position as the corresponding end of the lancet  309 . 
         [0083]    The majority of the test disc member  505  is substantially rigid. However, an annular centre portion  508  is comprised of an elastically deformable material. In particular, the annular centre position  508  is deformable in the presence of an externally applied force. This means that the test disc member  505  can be displaced relative to the shaft  204 , as will be described in more detail below. The material used to form the annular centre portion  508  may take any suitable form, and for instance may be a rubberised plastic. The arrangement of the ridges  322 , capillaries  326  and blood collection part  315  may be the same as in previous embodiments. 
         [0084]    Referring now to  FIG. 7 , cartridge  106 , adapted to operate with test disc members  505 , is shown. The hollow cylindrical housing part  203  is provided with the aperture  105  and a slit aperture  400 . The shaft  204  is supported centrally within the hollow cylindrical housing part  203  of the cartridge  106 . However, the diameter of the shaft is less than in  FIGS. 2 to 5 . 
         [0085]    A plunger arrangement  500  comprising a plunging arm  501  and a plunging head  502  is provided adjacent a plunging aperture (not shown) in the hollow cylindrical housing part  203 . The plunging aperture (not shown) is located next to the slit aperture  400 . The plunging aperture (not shown) is located directly opposite to the aperture  105 . The plunger aperture and the slit aperture  400  may be combined to form a single aperture. The plunger aperture is configured to allow the plunging head  502  to be forced by the plunging arm  501  to a position internal to the hollow cylindrical housing part  203 . 
         [0086]    In operation, the test disc member  505  is rotated to a position at which the lancet  506  is coincident with the aperture  105 . The plunging head  502  is then aligned with the test disc member  505  such that movement of the plunger arrangement  500  along the longitudinal axis of the plunging arm  501  causes the plunging head to contact the test disc member  505  and apply force to it. Since the longitudinal axis of the plunging arm  501  is radial with respect to the shaft  204 , the force applied by the plunger arrangement is directed towards the shaft  204 . 
         [0087]    When the plunging head  502  has contacted the test disc member  505  on the opposite side of the test disc member to the lancet  506 , the annular centre portion  508  becomes compressed on the side closest to the plunger arrangement  500  such as to allow the whole of the test disc member  505  to be displaced in the direction of the force supplied by the plunger arrangement  500 . The test disc member  505  remains horizontal by virtue of the spacer members  308 . 
         [0088]    Displacement of the test disc member  505  in the direction of the force supplied by the plunger arrangement  500  results in displacement of the lancet  506  in a radial direction away from the shaft  204 . In this position, the lancet  506  penetrates the skin of the user&#39;s digit. Removal of the force by the plunger arrangement  500  allows the annular centre portion  508  to return to its original form, through elastic reformation. After the plunger arrangement  500  has been fully retracted, the test disc member  505  is in its original position and the lancet  506  is retracted from the user&#39;s digit. It will be appreciated that it is the elasticity of the annular centre portion  508  of the test disc member  505  that allows the test disc member  505  to return to this position once the force applied through the plunger arrangement  500  is removed. 
         [0089]    After removal of the force supplied by the plunger arrangement  500 , the test disc member  505  can be rotated by the drive wheel  201  and the drive belt  202  so as to provide milking of the user&#39;s digit and collection of blood by the ridges  322  and capillary openings  324 . After a measurement of blood glucose level is taken (described in more detail below), the test disc member  505  is rotated further anticlockwise so that the second guide member  206  is aligned with the notch  301 , and thus the test disc member  505  is allowed to move upwards within the cartridge  106 . As a result, the test disc member that is immediately below the first test disc member  505  also moves upwards within the cartridge  106  and is provided to be coincident with the aperture  105 , the slit aperture  400  and the plunger aperture (not shown). Subsequent application of a plunging force by the plunger arrangement  500  causes a lancet  506  of the second test disc member to be forced out of the aperture  105 . The process can be repeated for other test disc members included in the cartridge  106 . 
         [0090]    An advantage of the arrangement shown in  FIGS. 6 to 7  is that a rotational arrangement can be used whilst allowing the lancet  506  to penetrate a user&#39;s skin in a longitudinal direction with respect to the lancet  506 . Another advantage is that puncture can occur at any desired location, for instance on the end of the user&#39;s digit, instead of puncturing occurring slightly on the side of the end of the digit. 
         [0091]    Another advantage is that the arrangement can allow the penetration depth of the lancet  506  to be easily predictable. 
         [0092]    Furthermore, it allows the penetration or puncturing depth to be adjustable. In particular, the adjustment of the penetration depth can be achieved by a mechanical arrangement that limits movement of the plunger arrangement towards the shaft  204 . Alternatively, it can be achieved in an electro-mechanical manner by measuring the location or displacement of some part of the mechanism and ceasing applying an energising voltage to a solenoid or other transducer that is used to affect movement of the plunger arrangement  500 . The penetration depth may be specified by a user. The depth may be specified by a user may be achieved through software or firmware control of rotation of the shaft  204 . The penetration depth may be defined by the user for example using one or more of the first, second and third inputs  101  to  103 . For instance, the first and second inputs  101 ,  102  may be increase and decrease respectively, with the third input  103  being a select or confirm input. The value defining the depth may be stored in memory. Penetration depth control is important to many users since lancet penetration usually is painful and since penetration depth control allows users some control over their experience. 
         [0093]    Reference will now be made to  FIG. 8 , which illustrates a mechanism for connection of the contact pads  318  of the test disc members  208 ,  505  to measurement circuitry (not shown). 
         [0094]    In  FIG. 8  the hollow cylindrical housing part  203  is shown with the aperture  105  and the shaft  204  located as described above. A slit aperture  400  is provided in the hollow cylindrical housing part  203 . The slit aperture  400  is located at substantially the same height as the aperture  105 . However, the slit aperture  400  is located on a side of the hollow cylindrical housing part  203  that is substantially opposite the aperture  105 . 
         [0095]    The slit aperture  400  does not coincide with the elongate aperture  110  that is formed at the front side of the BGM  100 . As such, the slit aperture  400  is not visible when the cartridge  106  is in place within the BGM  100 . 
         [0096]    Adjacent to the slit aperture  400  is located a swing arm  401 . The swing arm  401  is rotatable about a spindle  402 . The spindle  402  has an axis that is parallel to the axis of the shaft  204 . The axis of the spindle  402  is located above the drive belt  202 . A connecting arm (not visible) connects the spindle  402  to the swing arm  401 . In this example, the connecting arm is connected to the swing arm  401  by a vertical connector  404 . The vertical connector  404  allows the spindle  402  on which the connecting arm is mounted to be located at a different vertical position to the swing arm  401 . The spindle  402 , the connecting arm and the vertical connector  404  are arranged such that when the connecting arm is rotated on the axis of the spindle  402  the swing arm  401  is moved towards the shaft. The movement of the swing arm  401  is substantially radial with respect to the shaft  204 . 
         [0097]    Mounted on the swing arm  401  are first to third electrical contact terminals  405 . Each includes a generally horizontal arm and a depending contact head. The electrical contact terminals  405  are made of a resilient conductive material, for instance metal. The depending contact heads are angled at their ends furthest from the swing arm  401 . 
         [0098]    In one position, shown in  FIG. 8 , the electrical contact terminals  405  are supported by the swing arm  401  such that the dependent contact heads are located within the slit aperture  400  or alternatively outside of the hollow cylindrical housing part  203 . After the test disc member  208 ,  505  has been rotated such that the ridges  322  have moved past the aperture  105 , the shaft  204  is configured to stop the rotation of the test discs  208 ,  505  such that the contact pads  318  are coincident/aligned with the slit aperture  400 . As the test disc member  208 ,  505  is held in this position, the connecting arm is caused to rotate around the axis of the spindle  402  such that the swing arm  401  moves towards the shaft  204 . The arrangement is such that the depending contact heads of the electrical contact terminals  405 , but not the horizontal arms, come into contact with the contact pads  318  as the electrical contact terminals  405  move into the volume above the upper surface  303  of the test disc member  208 ,  505 . The resilient properties of the electrical contact terminals  405  causes the electrical contact terminals to be forced against the contact pads  318 . As such, an electrical connection is provided between the horizontal arms of the electrical contact terminals  405  and the blood collection part  315 . Electronic measuring means (not shown) connected to the electrical contact terminals  405  operate to pass a voltage through the contact terminals  405  and the blood collection part  315  and to take measurements of electrical parameters, from which a measurement of an analyte concentration level, for example a blood glucose level, can be determined. 
         [0099]    The connecting arm is controlled to remain in this position for a predetermined time or alternatively until it is detected that a blood glucose level measurement has been made, after which the connecting arm is caused to rotate around the shaft  402  so as to remove the electrical contact terminals  405  from the position above the upper surface of the test disc member  208 ,  505 . Once the electrical contact terminals  405  have been retracted, the test disc member  208 ,  505  is rotated anticlockwise so as to allow the test disc members  208 ,  505  to move upwards on the shaft  204 . 
         [0100]    It will be appreciated that the maximum permissible height dimension of the electrical contact terminals  405  is determined by the height of the spacer member  308 . A thicker spacer member allows larger electrical contact terminals  405  to be used. However, this is at the expense of an increase in separation between adjacent test disc members  208 ,  505 , and thus a reduced capacity for the cartridge  106 . The use of electrical contact terminals  405  including a horizontal arm and a depending contact head allows the height dimension of the electrical contact terminals to be minimised whilst allowing good electrical contact between the electrical contact terminals and the contact pads  318  and also allowing the electrical contact terminals  405  to operate correctly over a sufficient number of cycles. 
         [0101]    Operation of the blood glucose meter  100  will now be described with reference to the flowchart of  FIG. 9 . Operation starts at step S 1 . At step S 2 , the user locates their digit in the aperture  105 . As mentioned above, the user forces their digit into the aperture  105  with a pressure or force that is suitable to allow lancing and blood collection. At step S 3 , the user initiates blood glucose measurement. This involves the user pressing one of the inputs  101  to  103 . This is detected by the microprocessor  212  by way of the keys interface  215 . The software/firmware stored in the ROM  214  uses the key input to call a function or to execute a software module. The software/firmware stored in the ROM  214  then causes the microprocessor  212  to issue a command to a motor attached to the drive wheel  201  through the motor interface  217  to rotate the shaft  204  in a clockwise direction. The software/firmware controls the extent of the rotation. At step S 4 , the amount of rotation is sufficient to lance the user&#39;s digit with the lancet  309 . The software/firmware stored in the ROM  214  then causes the microprocessor  212  to control the motor to rotate the shaft  204  in the opposite direction, at step S 5 . 
         [0102]    As the test disc member rotates anticlockwise, milking and blood collection occurs at step S 6 . Firstly, at step S 6 A, there is no pressure applied by the test disc member on the digit. This step relates to the period before the first ridge  322  has contacted the user&#39;s digit. At step S 6 B, pressure is exerted by the first ridge  322  on the user&#39;s digit. This step relates to the period in which the “height” of the ridge  322  is increasing. At step S 6 C, blood is absorbed into the capillaries  326  through the capillary openings  324  provided on the ridges  322 . This step may coincide with the time when the pressure on the user&#39;s digit is highest. At step S 6 D, there is low or no pressure on the user&#39;s digit. This step relates to the period in between ridges  322 . Thus, steps S 6 B to S 6 D may be repeated several times according to the number of ridges  322  present. In some embodiments, the ridges  322  may be sized such that a part of the user&#39;s digit is in contact with one or more of the ridges  322  at all times during this part of the rotation. In this case, the pressure may become “low”, but not disappear entirely. 
         [0103]    It will be appreciated that in the embodiments described using the test disc member  208 , the user&#39;s digit or other body part is lanced from the side in a clockwise direction by rotational action of the lancet  309 . In the subsequent rotation, the ridges  322  apply pressure to the user&#39;s digit in an anticlockwise direction i.e. on the other side of the user&#39;s digit from the puncture wound. This directional application of pressure by the ridges  322  results in an efficient expression of blood from the wound. Furthermore, the wound is not contacted by the ridges  322  while pressure is applied. This reduces the amount of pain experienced by the user while allowing a blood droplet to form on the surface of the user&#39;s digit. This blood droplet can then be absorbed by the capillaries  326  as the wound location passes the capillary openings  324 . 
         [0104]    At step S 7 , the software/firmware causes the microprocessor  212  to control the motor to cease rotation when the shaft  214  is such that the contact pads  318  are coincident with the slit aperture  400 . At step S 8 , the software/firmware controls a motor such as to cause the swing arm  401  to be rotated towards the shaft  204 . The software/firmware stored in the ROM  214  is such that the microprocessor  212  causes only the required amount of travel of the swing arm  401 . At this point, the analyte interface circuit  219  is coupled directly to the blood collection part  315 , which has been provided with blood from the user&#39;s digit. At step S 9 , analyte measurement is performed. This involves the analyte interface circuit  219  providing voltages to the electrical connection contacts  318 , and thus to the blood collection part  315 , and measuring parameters of resulting signals. The measured parameters, particularly voltage parameters, are used by the software/firmware stored in the ROM  214 , as executed by the processor  212 , to calculate a blood glucose measurement level of the user. The blood glucose measurement is then caused by the software/firmware to be displayed on the display  104  through action of the microprocessor  212  on the display drive  216 . At step S 10 , the swing arm is caused to be removed by action of the microprocessor  212 , under control of the software stored in the ROM  214 , the motor interface  217  and the motor (not shown). 
         [0105]    At step S 11 , the software/firmware results in the microprocessor  212  controlling the drive disc  201  to rotate anticlockwise. Rotation continues until the notch  301  on the test disc member is coincident with the guide  206 . At step S 12 , the test disc member rises up the cartridge  106 . In the case where biasing of the test discs up the cartridge  106  is provided by a bias means, for instance a spring, step S 12  requires no action on part of the software/firmware and microprocessor  212 , although there may be a pause before the next step. In embodiments where movement of the test disc members along the shaft  204  occurs through driving action, step S 12  involves the microprocessor  212 , under control of the software/firmware stored in the ROM  214 , controlling a motor through the motor interface  217 . Subsequently, at step S 13 , the microprocessor  212 , under control of the software/firmware stored in the ROM  214 , causes the shaft  204  to rotate again in a clockwise direction and to cease rotating when the drive dog  320  engages with the drive slot  307  of the next test disc member in the cartridge  106 . At this stage, the test disc members rise up the cartridge  106  slightly. 
         [0106]    The operation ends at step S 14 . 
         [0107]    Various modifications and alternative features can be used in connection with the above-described embodiments. Some alternatives now follow. 
         [0108]    Although in the above the shaft  204  is said to be driven by a drive wheel  201  that is coupled to the shaft  204  by a drive belt  202 , the drive may instead be direct (i.e. the drive mechanism is coupled directly to the shaft  204 ), or connection may be made by a notched belt, a vee belt, or by a direct gear mechanism. Instead of an electric motor, a clockwork drive could be used. A clockwork drive mechanism has a number of advantages, particularly where access to batteries or battery chargers or electricity supplies are limited. In the embodiments in which a clockwork mechanism is used, the user can be sure that the BGM  100  will not cease operating because of drained batteries. A clockwork mechanism may be particularly suited to developing countries and emerging markets. 
         [0109]    In embodiments in which an electrical motor is used to drive the shaft  204 , preferably control is exerted over the motor by software. In this way, the speed of rotation can easily be controlled. Additionally, the extent of rotation can more easily be controlled. The motor may be a stepper motor. 
         [0110]    Alternatively, a mechanical drive arrangement may be present, for instance using a lever or other device for manual actuation. A suitable mechanism may be one similar to those previously used in SLR cameras. 
         [0111]    The swing arm  401  may be actuated in any suitable way. For instance, it may be driven by the same motor or mechanism as the shaft  204 . Alternatively, it may be driven by a separate motor. In either case, the rotation of the swing arm  404  may be affected by a cam mechanism, or by a pin and slot (track path) mechanism. In the event of an electric motor being used, the motor preferably is software driven. The motor preferably is a stepper motor. 
         [0112]    The mechanical arrangement may include a mechanism by which a bias means, for instance a mechanical compression spring, is biased and then released in order to push the electrical contact terminals  405  into place. The terminals  405  can then be retracted by the swing arm  401  using a rotating motion. The overall mechanism can be termed a latch type trigger mechanism. 
         [0113]    Instead of a swing arm  401  being used to rotate the electrical contact terminals  405  into place, the contact pads  318  may instead be located on the disc edge  305 , allowing the use of fixed electrical contact terminals  405 . The electrical contact terminals may include a brush or other deformable feature such that the test disc members  208  to  210 ,  505  can move whilst in contact with the electrical contact terminals without damage occurring to any of the components. Similar arrangements are used in brushed DC motors. In this case the electrical contact terminals  405  could be flexible finger contacts that rest on the periphery of the test disc members  208  to  210 ,  505  in order to contact the contact pads  318 . 
         [0114]    Alternatively, instead of a swing arm  401 , a mechanism may be used to affect longitudinal movement of the electrical contact terminals  405  into place to contact the contact pads  318 . 
         [0115]    The conductive tracks  317  and the contact pads  318  may be formed by leadframe. Alternatively, overmoulding may be used. Alternatively, printed circuit board (PCB) printing may be used. 
         [0116]    Optionally, each of the test disc members  209 ,  210 ,  505  is separated from adjacent test disc members by a membrane (not shown in the drawings). In this case, the membrane preferably fits closely to the internal surface of the hollow cylindrical housing part  203 . An effect of the membrane is to reduce the possibility of disc cross-contamination. Use of a membrane may allow the test disc members  208  to  210 ,  505  to have a reduced separation than would be the case without the use of a membrane. 
         [0117]    In the above, the test disc members  505  are said to be biased upwards by a bias means, for instance a compression spring. Alternative mechanisms for moving the test disc members  505  up the cartridge may be used. For instance, a threaded lifting cam may be provided on the shaft  204  or alternatively on the interior surface of the hollow cylindrical housing part  203 . Alternatively, the test disc members  505  may remain stationary, with the aperture  105  and the drive dog  320  instead being moved along the axis of the cartridge  106 . Movement of the aperture  105  may be achieved by the use of a sliding door in an elongated slot. Movement of the door allows a different strip to be revealed at the aperture  105 . 
         [0118]    Additionally, the test disc members  505  may include a disinfecting or cleaning portion that contacts the digit before lancing. This can reduce risk of infection of the wound and also can increase accuracy in particular by removing any glucose from the skin (as may occur after eating fruit etc.). 
         [0119]    Although the test disc members  208  are illustrated as lancing in a clockwise direction, and applying pressure via the ridges  322  in an anticlockwise direction, the direction of lancing and milking may be reversed.