Abstract:
This invention relates to bio sensing meters for determining the presence of an analyte in a biological sample, and, more particularly, to a bio sensing meter whose operation is controlled by a code provided by a removably pluggable coding module. The invention further relates to a coding module pluggable into a bio sensing meter for receiving a sample strip. The coding module defines at least one code, said code ciphering at least one parameter value that is employed in controlling the operation of said meter, for example by controlling the execution of an algorithm performed by the meter that enables determination of an analyte concentration value. The at least one code is represented by at least one electrical component having a determined characteristic, preferably a resistance.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to bio sensing meters for determining the presence of an analyte in a biological sample, and, more particularly, to a bio sensing meter whose operation is controlled by a code provided by a removably pluggable coding module. The invention further relates to a coding module pluggable into a bio sensing meter for receiving a sample strip. The coding module defines at least one code, said code ciphering at least one parameter value that is employed in controlling the operation of said meter, for example by controlling the operation of the meter.  
       BACKGROUND OF THE INVENTION  
       [0002]     Bio sensing meters applied for detecting substances contained in the blood to be analyzed, such as glucose or cholesterol normally employ a disposable sample strip. The sample strip has a reaction zone to allow blood placed thereon. The operation is controlled by a microprocessor. By execution of various methods, analysis results of the measurement are obtained.  
         [0003]     It is normally necessary to calibrate instrumentation used in connection with test devices in order to compensate for variations from lot to lot on the sample strip manufactured. Various techniques have been suggested for encoding information into the sample strip, as disclosed by U.S. Pat. No. 5,053,199 and references cited therein, comprising electronically encoded information on a carrier having an optical bar code, a magnetizable film, a perforated strip, a fluorogens or an electrically conductive medium on a foil.  
         [0004]     Each of such known sample strips has to be furnished with an information code, which is an additional and thus expensive effort for a disposable device.  
         [0005]     Another conventional sensing meter uses an additional coding module or code key designed and inserted into a receptacle similar to the slot for the sample strip. While performing a measurement, the memory key has to be inserted in the sensing meter all the time for the same batch of sample strips. According to the data or the code provided by the coding module the operation method and parameter are chosen and a correct measurement result is obtained.  
         [0006]     U.S. Pat. No. 5,366,609 and documents cited therein disclose bio sensing meters which have pluggable coding modules that enable reconfiguration of test methods and parameters employed by the meter. Threshold potentials, test times, delay periods and other pertinent test methods and constants may be entered and/or altered.  
         [0007]     The main purpose of the coding module still is to provide information about the type of sample strip. So for each new batch of sensor strips new related information is needed.  
         [0008]     For processing the sample measurement and the analysing routines the bio sensing meter needs certain parameter values which determine thresholds, time intervals, control numbers and calibration curve attributes.  
         [0009]     As sample strips are disposable, preferably coding modules are disposable too. Costs for the module are therefore an important factor.  
       SUMMARY OF THE INVENTION  
       [0010]     It is therefore an object of the invention to overcome the drawbacks of the prior art, especially to avoid the usage of memory IC chip technology for storing codes on coding modules, and to provide a coding module and a bio sensing meter with a pluggable coding module, which has a simple design, and which can be produced cost effectively.  
         [0011]     In accordance with the present invention a coding module is presented, which includes at least one code, wherein the at least one code is represented by a parameter value of at least one electrical component having a determined characteristic, preferably a resistor, a switch or a capacitor.  
         [0012]     Electrical components can have various measurable characteristics, such as electrical characteristics, e.g. resistance, capacitance or impedance.  
         [0013]     The advantage of using electrical characteristics of a component for encoding information is that no additional measurement device, for example an optical or magnetic detector, is necessary in the bio sensing meter. Usually the bio sensing meter provides means for performing a voltage and/or current measurement for analysing the analyte concentration, the same measurement tools can be used for reading the code. Electrical components such as resistances are not expensive.  
         [0014]     Measuring resistances is a simple technique which is suitable for coding information, like in the present case, where e.g. only one code number or a few parameter values have to be identified.  
         [0015]     Contrary to the state of the art IC chip technology, no integrated circuits are needed. Macroscopic electrical components can be used.  
         [0016]     Preferably the coding module comprises at least one resistor, which is inexpensive and can be measured easily.  
         [0017]     Resistors are a simple implementation of non volatile information carriers.  
         [0018]     Since a broad variety of standard resistors is available, a big number of codes can be represented only by the value of the resistances.  
         [0019]     An even greater number of possibilities for encoding is achieved, when the at least one code is represented by a plurality of resistances, e.g. one to six, preferably four resistances.  
         [0020]     It turned out that 2 different resistance values on four to seven places, resulting in 16 to 24 different codes, provide enough information to control the analysing method.  
         [0021]     Preferably the code contains information regarding the sample strip batch. Samples strips should always be used with a related coding module. To reduce the error rate and to protect the slot of the bio sensing meter from pollution by the analyte or a biologic sample, in a preferred embodiment the coding module has a receptacle able to accept a sample strip.  
         [0022]     Usually, the sample strip includes a plurality of electrodes, for applying and/or measuring a voltage and/or a current.  
         [0023]     In a preferred embodiment said coding module comprises means for establishing an electrical contact between the bio sensing meter and the sample strip.  
         [0024]     The coding module allows for a direct connection of the sample strip electrodes and the contacts of the bio sensing meter, for example by providing a recess or a hole in the area of the connection zone.  
         [0025]     Alternatively the coding module may have contacts connecting the sample strip electrodes with the bio sensing meter contacts.  
         [0026]     According to another aspect of the invention a bio sensing meter is provided in connection with a pluggable coding module with at least one code. The bio sensing meter has an electrical receptacle able to accept a pluggable coding module and comprises means for receiving information from said coding module defining at least one code. The code is represented by at least one electrical component having a determined characteristic, preferably a resistance.  
         [0027]     The coding module is preferably of the above described type, wherein the code is represented by at least one, typically one to six, in particular four resistances and/or chosen from a variety of different resistances. The least one resistance can also be formed by at least one resistor.  
         [0028]     The bio sensing meter is provided with information about the sample batch by the code on the coding module.  
         [0029]     The code can be a simple binary code, represented by one or more resistance which is low or high, being interpreted as one of two sets of parameter values stored in the bio sensing meter or defining a binary code. Each resistance forms a bit.  
         [0030]     The encoding can be made more complex by using a wider range of resistance values or a bigger number of resistances.  
         [0031]     In a preferred embodiment the parameter values are correlated to the value of the at least one resistance. The parameters may also be encoded by the value and the order of at least two resistances, in particular by the order of four resistance values.  
         [0032]     In a preferred embodiment the coding module only hosts the code represented by the resistances. The value of the at least one resistance and/or the order of at least two resistances is detected by a microprocessor routine performed by said bio sensing meter.  
         [0033]     The generation of the code based on the resistance measurements and the translation of the code into parameter values is performed by the bio sensing meter. The coding module is only a carrier of the code. The bio sensing meter has the capability of reading the code, decoding and using the information.  
         [0034]     The code can be derived from the resistance measurement by correlating measured values, such as resistance, current or voltage, with code numbers. The code can also be formed by the resistance values.  
         [0035]     The parameter values can be derived from the code by a microprocessor routine.  
         [0036]     In a preferred embodiment the at least one code is decoded by extracting parameter values using a look-up table stored in a memory of the bio sensing meter.  
         [0037]     This memory can be a read only memory. It can also be exchangeable or it can be rewritable, so that the look-up table can be exchanged or updated.  
         [0038]     The bio sensing meter may have different receptacles for the sample strips, the coding module and a calibration module.  
         [0039]     In a preferred embodiment of the invention the electrical receptacle is able to accept the coding module and is also able to accept the calibration module.  
         [0040]     One single electrical receptacle is user friendly because less error prone, and electrical circuits can be framed more effectively.  
         [0041]     A further improvement of this concept is achieved by providing a coding module having a receptacle able to accept sample strip. The receptacle able to accept the coding module thus is at the same time a receptacle for the sample strip, without the necessity of coming into direct contact with the sample strip.  
         [0042]     For sample strips including electrodes the coding module enables electrical coupling between bio sensing meter and sample strip.  
         [0043]     According to a further aspect of the invention there is provided a bio sensing system for analysing an analyte, comprising a coding module with at least one code, preferably of the above described type and comprising a bio sensing meter, preferably of the above described type, with means for receiving the at least one code from said coding module. The code ciphers at least one parameter value that is used in controlling the operation of the bio sensing meter, for example in controlling the execution of an algorithm performed by said meter that enables determination of an analyte concentration value. The at least one code is represented by at least one electrical component having a determined characteristic, e.g. a resistance.  
         [0044]     According to a further aspect of the invention there is provided a bio sensing test set, comprising at least one test strip, and comprising a coding module with at least one code, preferably of the above described type, pluggable into a bio sensing meter. The code ciphers at least one parameter value that is used in controlling the operation of the bio sensing meter, for example in controlling the execution of an algorithm performed by said meter that enables determination of an analyte concentration value. The at least one code is represented by at least one electrical component having a determined characteristic, e.g. a resistance.  
         [0045]     Usually a bio sensing test set comprising one coding module and a plurality of samples strips form a commercial unit which is sold together in one package.  
         [0046]     According to a further aspect of the invention there is provided a method for operating a bio sensing meter, preferably of the above described type, comprising the steps of 
    (i) inserting a coding module with at least one code into the bio sensing meter;     (ii) detecting the at least one code;     (iii) determining at least one parameter value used for controlling operation of said meter;     (iv) inserting a sample strip and adding a biologic sample;     (v) analysing the sample on the basis of the at least one parameter value;     whereby the at least one code is represented by at least one electrical component having a determined characteristic, e.g. a resistance.    
 
         [0053]     Although the invention is presented in the context of a clinical or diagnostic instrument, the invention has utility in other fields as well.  
         [0054]     The invention may be more fully understood by referring to the following detailed description of illustrative embodiments of the invention and the accompanying drawings of them.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0055]      FIG. 1  is a perspective view of an example of a bio sensing meter incorporating the invention;  
         [0056]      FIG. 2   a  is a perspective bottom view of a coding module according to the invention;  
         [0057]      FIG. 2   b  is a perspective top view of a coding module according to the invention;  
         [0058]      FIG. 3   a  is an exploded top view of a coding module according to the invention;  
         [0059]      FIG. 3   b  is an exploded bottom view of a coding module according to the invention;  
         [0060]      FIG. 4  shows the relation between analyte concentration and a measuring current;  
         [0061]      FIG. 5   a  is a schematic representation of a first embodiment of the present invention;  
         [0062]      FIG. 5   b  to  5   c  are different tables showing coding information;  
         [0063]      FIG. 6   a  is a schematic representation of a second embodiment of the present invention;  
         [0064]      FIG. 6   b  and  6   c  show tables with coding information;  
         [0065]      FIG. 7  is a schematic representation of a third embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0066]     Referring to  FIG. 1 , a bio sensing meter  10  has a display  12 , and a receptacle able to get in contact with a disposable sample strip  18 . The sample strip  18  has a reaction zone which contains conductive electrodes. An enzymatic reactant layer (not shown) is formed in the reaction zone to cover the electrodes. An analyte-containing fluid, for example, a drop of blood, can be dripped on a substance entrance  20 .  
         [0067]     The bio sensing meter  10  further has a plug-in coding module  30 , which is inserted into a slot  14  of the bio sensing meter  10  to be electrically connected thereto and to establish a mutual communication there between.  
         [0068]     The coding module  30  has a receptacle  46  able to accept the sample strip  18 .  
         [0069]     The coding module  30  enables establishing an electrical connection between the bio sensing meter  10  and the sample strip  18 . When the coding module  30  is plugged into the slot  14  of the bio sensing meter  10 , contacts  52  of the bio sensing meter  10  get into electrical contact with the electrodes of the sample strip  18  inserted in the module  30 .  
         [0070]     The coding module  30  contains electrical components not explicitly shown in  FIG. 1 , which are connectable to contacts  56  of the bio sensing meter  10 .  
         [0071]     Alternatively the bio sensing meter  10  may have two slots, one for accepting the sample strip  18  and a further one for accepting the coding module  30 .  
         [0072]     A coding module  30  is shown in  FIGS. 2   a  and  2   b.    
         [0073]     After inserting the coding module  30  into the bio sensing meter  10 , the contacts  56  of the bio sensing meter  10  are in connection with contacts  36 , such that the resistance values of the resistors  32 ,  32   a,    32   b,    32   c,    32   d  (see  FIG. 3   a ) can be detected. That is, when the bio sensing meter  10  is performing the measurement, the coding module  30  has at least to be inserted in the bio sensing meter  10  once before the measurement or permanently.  
         [0074]     The contacts  34  of the module  30  get in contact with the contacts  52  of the meter  10  so that characteristics of the sample on the strip  30  can be measured.  
         [0075]     The chemistries used for sample strips and analyte determination algorithms are known in the art. They will not be described in detail.  
         [0076]     As an example, the analyte-containing sample may be a drop of blood that is subjected to a glucose determination. A disposable sample strip for a glucose determination will include, in a reaction zone, chemical reagents, basically an enzyme, for example glucose oxidase and a redox mediator, such as a potassium ferricyanide.  
         [0077]      FIG. 2   b  shows another perspective view of the code key  30 . Within the receptacle  46  for a sample strip, there are contacts  44  in the receptacle  46  which are electrically connected to the contacts  34 . Upon insertion of the sample strip  18  in the receptacle  46 , the electrodes of the sample strip  18  get in contact with the contracts  44 .  
         [0078]      FIGS. 3   a  and  3   b  show an upper and lower exploded view of the coding module  30 . The coding module  30  is formed by a upper part  30   a  and a lower part  30   b.  A printed circuit board  31  is arranged between these two parts. Resistors  32   a,    32   b,    32   c,    32   d  are arranged on the printed circuit board  31 . Resistors  32   a  to  32   d  are ciphering a code as will be described hereinafter. Contacts  44  are arranged between the printed circuit board and the upper part  30   a.  Springs  45  are arranged on spring contact pads  43 . The springs  45  are used to hold the contacts  44  in good contact against the electrodes of the strip  18 .  
         [0079]      FIG. 3   b  shows an exploded bottom view of the coding module  30 . The bottom part  30   b  is provided with a lock  33  for positioning and holding the coding module  30  in the meter  10 . The bottom part  30   b  comprises holes  35  through which the contact  34 ,  36  of the printed circuit board  31  may contact the contacts  52 ,  56  of the meter  10 . The upper part  30   a  and the lower part  30   b  are formed of plastic material, typically in injection moulding.  
         [0080]      FIG. 4  shows a diagram of a curve putting the concentration of the analyte in the sample, in particular glucose in the blood in relation to the measuring current determined by the meter. The concentration linearly depends on the measuring current. The concentration may be given by the formula Y=AX−B. The parameters A and B, however, depend on several conditions, in particular on the reactant composition which is used. Depending on the manufacturing process and depending on specific reactant compositions, different slopes (factor A) and different off-sets (factor B) may be applicable. The different relations are characterised by several codes C 1 , C 2 , . . . Cn which are associated to specific manufacturing batches. The coding module according to the present invention in particular may be used for coding the codes C 1  to Cn. It may, however, also be used for coding different analyte types or different measurement methods.  
         [0081]      FIG. 5   a  shows a schematic view of a meter  10  with a coding module  30  according to the present invention and with a test strip  18 . The meter  10  comprises standard components such as a microprocessor with a central processing unit, a read-only memory and a random accessible memory, a display, a current measuring unit, an electrode working voltage supply unit and a temperature measuring unit. Those elements are standard in state of the art devices. In addition, the meter comprises a resistance measuring unit  60  which on the one hand is in operative connection with the microprocessor and on the other hand is connected to the contacts  56  for contacting resistors  32   a,    32   b , . . .  32   n  in the coding module  30 . The resistors  32   a  to  32   n  have specific resistance values R 1 , R 2 , . . . Rn which cipher certain codes as will be shown hereinafter. Determination of the resistances is made in a manner known to those skilled in the art, in particular by measuring a current flowing through the resistances if a pre-defined potential is applied to the resistances. Analog/digital converters are used to transmit the resistance values to the microprocessor.  
         [0082]     The contacts  36  on the coding module  30  get in electrical contact with the contacts  56  on the meter  10 . In a similar manner, contacts  52  of the meter  10  are brought into electrical contact with the contacts  34  of the coding element  30  and consequently with the pins  40  and the electrodes of the sensor strip  18 .  
         [0083]      FIG. 5   b  shows a resistor table. If only one single resistor is used, different values of this resistance may be used for defining several codes, in particular codes for different linear relationships as shown in  FIG. 4 . Typically, one hundred different code values may be encoded with resistances in the range between 0 KΩ (short circuit) and 910 KΩ. In addition, one further code may be defined by an open circuit.  
         [0084]     Instead of directly coding certain codes, it is also possible to code the parameter values A, B of the linear relationship as shown in  FIG. 4 .  FIG. 5   c  shows a table where four different resistances are used for defining four codes. A quadruplet of resistance values is used to define specific values for the parameters A, B. E.g. the resistance sequence 150 KΩ/68 KΩ/51 KΩ/68 KΩ is used to define a slope A of 0.75 and an off set B of −45.  
         [0085]     Furthermore, it is also possible to code different calculation or measurement methods. Typically, incubation times or other method parameters may vary e.g. depending on a batch of strips. For this purpose, several, e.g. ten standard measurement methods may be used.  FIG. 5   d  shows a table where different resistance values lying between 10 KΩ and 390 KΩ are used to code for one of ten several measurement methods.  
         [0086]     The first resistor  32   a  shown in  FIG. 5   a  can e.g. be used for coding the values shown in  FIG. 5   b  and a second resistor  32   b  can be used for coding the method shown in  FIG. 5   d.    
         [0087]     In an alternative embodiment, it is also possible to code different analyte types with a coding module  30 . In the table in  FIG. 5   e,  three different analyte types are coded in context with a plurality of measurement methods by the use of eight different resistance values.  
         [0088]      FIG. 6   a  shows an alternative embodiment for a coding module  30 . The strip  18  and the meter  10  are built identically to the one shown in  FIG. 5   a.  For coding, instead of resistances having different values, a plurality of open or short circuits are used. These open or short circuited connections L 1 , L 2 , . . . Ln or switches code values such as “1” or “0” and thus form a binary code. Such open or short circuited connections my be easily arranged on the PCB layout. Determination of these resistances is made in a similar way as explained with reference to  FIG. 5   a.    
         [0089]      FIG. 6   b  shows a table where different calibration formula according to 16 different codes are coded with a 4 bit arrangement of open or short circuited connections defining code  1 , code  2 , code  3  and code  4 . Four binary codes allow for definition of 16 different calibration formula.  
         [0090]     In  FIG. 6   c,  there is shown a 3 bit coding for coding different analyte types or methods. Three additional open or short circuited connections L 5 , L 6  and L 7  define six further codes which may describe eight combinations of analyte and measurement methods.  
         [0091]      FIG. 7  shows another embodiment of an encoding module  30  according to the present invention. Instead of resistors as shown in  FIG. 5   a,  capacitors  62   a,    62   b,    62   n  having different capacitances C 1 , C 2 , . . . Cn are used for defining a code. Instead of a resistance measurement unit as shown in  FIG. 5   a,  a capacitance measuring unit  64  is used in the embodiment as shown in  FIG. 7 . Capacitance to frequency converters are used for providing a coding signal to the microprocessor.  
         [0092]     Coding module  30  thus may include a variety of data that are used in operation of meter  10 . Those data, e.g. encompass measurement delay times, incubation time, the number of measurements to be taken during a measurement period, thresholds against which voltage levels are to be compared, values of excitation voltage levels to be applied to sample strip  18  during a test method, glucose value conversion factors.