Abstract:
An instrument for reading test strips to determine concentrations of analytes from body fluid samples that are deposited onto the test strips. The instrument includes a novel modular optical block that can be replaced without requiring replacement of the entire instrument. Another feature of the invention is a novel encryption code that allows a technician during service calls to quickly identify all relevant manufacturing information for the test strips being used by the person placing the service call. Another feature of the instrument of the present invention is that it can be used in combination with a novel test strip capable of testing multiple analytes from a single sample.

Description:
RELATED APPLICATIONS  
       [0001]    This application claims priority from U.S. provisional application serial No. 60/355,165, filed Feb. 8, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates generally to testing of body fluids for concentration of analytes and more particularly to an instrument that receives test strips and measures the concentration of analytes from fluids deposited on the test strips.  
         BACKGROUND  
         [0003]    The level of certain analytes in blood and other body fluids can predict disease or risk thereof. For example, cholesterol in blood is a significant indicator of risk of coronary heart disease. “Total cholesterol” includes low density lipoproteins (LDL), very low density lipoproteins (VLDL) and high density lipoproteins (HDL). It is well established from epidemiological and clinical studies that there is a positive correlation between levels of LDL and VLDL cholesterol (“bad” cholesterol) and coronary heart disease and a negative correlation between levels of HDL cholesterol (“good” cholesterol) and coronary heart disease. The level of total cholesterol in blood, which is a measure of the sum total of HDL, LDL, VLDL and chylomicrons, is not generally regarded as an adequate indicator of the risk of coronary heart disease because the overall level of total cholesterol does not reveal the relative proportions of HDL, LDL and VLDL. To better assess the risk of heart disease, it is desirable to determine the amount of HDL, LDL and triglycerides in addition to total cholesterol.  
           [0004]    U.S. Pat. No. 5,597,532 discloses an apparatus for optoelectronic evaluation of test strips for use in the detection of certain analytes in blood or other body fluids. The test strip used with such instrument comprises an elongated plastic part including a hinged portion to allow a first portion to be folded over a second portion. A series of test strip layers are disposed between the folded over portions of the test strip. The method involves providing a separately colored strip and corresponding memory module for each test. For example, total cholesterol strips and modules may be colored red, whereas glucose strips and modules may be colored yellow, and so forth. However, a separate sample must be used and a separate test conducted for each analyte for which concentration is to be determined.  
           [0005]    Devices known to applicants for measuring multiple analytes in a single sample are complex. For example, one known device to measure the concentration of HDL cholesterol and other analytes from a whole blood sample is disclosed in U.S. Pat. No. 5,213,965 (Jones) and other related and commonly assigned patents. The device includes a well in which the whole blood sample is deposited and then drawn through a capillary to a sieving pad made of fibrous material. The sieving pad achieves initial separation of blood cells from plasma on the basis of the blood cell&#39;s slower migration rate therethrough. The sieving pad is covered with a microporous membrane which further filters blood cells. Covering the microporous membrane is a reagent reservoir membrane containing precipitating agents for LDL and VLDL on one side thereof. On the other side of the reagent reservoir, there are no precipitating agents.  
           [0006]    On top of and extending laterally beyond the reagent reservoir is an elongate matrix which distributes the sample laterally after it leaves the reservoir. Finally, one or more test pads are positioned above and biased apart from the elongate matrix. Plasma exits the filtering membrane and enters the reagent reservoir where LDL and VLDL cholesterol are precipitated on one side thereof and then flow from the reservoir and migrate laterally through one side of the elongate matrix. Similarly, plasma that enters the other side of the reagent reservoir encounters no precipitating agents, and this plasma exits the side of the elongate matrix opposite the side the plasma containing precipitated LDL and VLDL cholesterol exits. At a desired time, the test pads can be depressed so they are in fluid communication with the elongate matrix. The test pads that contact one side of the elongate matrix measure concentration of HDL, whereas the test pads that contact the opposite side of the elongate matrix measure total cholesterol.  
           [0007]    Undesirably, the test pads must be kept spaced apart from the elongate matrix until the entire operation is properly timed, whereupon the test plate having the test pads thereon can be depressed against the elongate matrix. Of course, manually depressing the test pad creates a process step that must be accomplished by hand or by mechanical means within the instrument.  
           [0008]    An undesirable drawback of presently known instruments that read test strips is that the area or port in which the test strip is received becomes contaminated by residual blood or fluid sample which escapes the confines of the test strip. The port must be cleaned frequently and often becomes contaminated to the extent that test results can be compromised. Similarly, the port typically contains a glass window which is susceptible to breakage. Thus, an otherwise functioning test strip instrument may need to be replaced merely because the port has been irreversibly contaminated or broken.  
           [0009]    Another undesirable drawback of presently known instruments that read test strips is that technicians responding to service calls often cannot readily identify all of the pertinent manufacturing information regarding the test strips that the caller is using.  
           [0010]    It would be desirable to overcome the drawbacks of the prior art noted above and provide a test strip diagnostic instrument that is generally easier to use and provides enhanced functionality.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention provides an instrument for determining concentrations of analytes from body fluid samples that are deposited onto test strips. The instrument includes a novel modular optical block that can be replaced without requiring replacement of the entire instrument. Another feature of the invention is a novel encryption code that allows a technician during service calls to quickly identify all relevant manufacturing information for the test strips being used by the person placing the service call. Another feature of the instrument of the present invention is that it can be used in combination with a novel test strip capable of testing multiple analytes from a single sample. The instrument reads the color density of multiple analytes and displays the same on an easy-to-read display. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]    The above-mentioned and other advantages of the present invention, and the manner of obtaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0013]    [0013]FIG. 1 is an exploded perspective view showing the instrument, optical block and test strip in accordance with the present invention;  
         [0014]    [0014]FIG. 2 is an exploded perspective view of a test strip holder in accordance with the present invention illustrating a test matrix and its relationship with the top and bottom portions of the test strip holder;  
         [0015]    [0015]FIG. 3 is a side sectional view of an exemplary test matrix in accordance with one embodiment of the present invention;  
         [0016]    [0016]FIG. 4 is a side sectional view of an exemplary test matrix in accordance with another embodiment of the present invention;  
         [0017]    [0017]FIG. 5 is a block diagram schematic view illustrating the parts and operation of the test instrument in accordance with the present invention; and  
         [0018]    [0018]FIG. 6 is a diagrammatic illustration of a display for the instrument of the present invention that illustrates a novel encryption scheme.  
         [0019]    Corresponding reference characters indicate corresponding parts throughout the several views. 
     
    
     DETAILED DESCRIPTION  
       [0020]    The embodiments of the present invention described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present invention.  
         [0021]    Referring now to FIG. 1, instrument  20  includes instrument body  21 , display  22 , keys  24  and  26 , port  28 , which receives a Memo chip (not shown), port  30  for an amperometric test strip (not shown), and opening  32 . In the inside of instrument  20  is the main circuit board  34  and compression spacer  35 , part of which can be seen in opening  32 . Optical block  36  includes optical hybrid chip  38 , light shield  40 , strip holder  42 , die cut adhesive  44 , and glass  46 . Finally, a test strip  48  is inserted into holder  42 .  
         [0022]    Still referring to FIG. 1, chip  38  has pins  50  that are received into holes  52  in circuit board  34  by soldering or other fastening means known in the art. Optical Hybrid chip  38  includes photodiodes  54  and LED arrays  56 . Photodiodes  54  align with openings or pores  58  in light shield  40  while LED arrays  56  align with rectangular openings  60  in light shield  40 . In turn, pores  58  align with the direct center of respective holes  62  and  64  in strip holder  42  and adhesive  44 , respectively. Rectangular openings  60  align with the sides of holes  62  and  64  so that the incident beam is directed to the relevant portions of test strip  48  at an angle, as explained below.  
         [0023]    Conveniently, optical hybrid chip  38  is first positioned and inserted into main circuit board  34  on top of compression spacer  3 . In turn, light shield  40  snaps into strip holder  42  by means of tabs  66  that are received in corresponding openings  68  as shown. Glass  46  is secured to strip holder  42  by adhesive  44  or other suitable means known in the art. The entire optical block assembly  36 , once fastened together, snaps into the main circuit board  34  by means of legs  70  that bias outwardly and engage the side of an oblong opening in the main circuit board  34 . Compression spacer  35  serves the purpose of compressing the optical hybrid chip  38  into light shield  40  to maintain minimal deviation of mechanical stack-up in the optical block assembly. After the optical block subassembly is firmly affixed into main circuit board  34 , optical hybrid chip  38  is soldered into place on the opposite side (not shown). The optical block of the present invention is advantageous because the optical hybrid chip  38  can be assembled separately and by a different facility that circuit board  34 , thereby saving time and manufacturing costs. Another advantage of the optical block is that it can be replaced as a single unit without requiring replacement of the entire instrument. Still another advantage of the optical block is that its modular design allows interchangeable optical blocks with different capabilities.  
         [0024]    When installed in instrument  20 , holder  42  of optical block  36  receives test strip  48 . More specifically, sides  72  of test strip  48  are fittingly received into grooves  74  of holder  42 . A handle portion  76  aids the user in inserting the strips  48  into the instrument.  
         [0025]    Turning now to FIG. 2, test strip  48  is preferably formed by injection molding. Test strip  48  includes handle  76  and top portion  80 , which is preferably hingedly attached to bottom portion  82 . Top portion  80  includes a leg member  84  that is inserted into a corresponding opening (not shown) in portion  82  and thereby secures top portion  80  to bottom portion  82 . The other side of top portion  80 , as mentioned, is preferably hingedly attached to bottom portion  82 . Bosses  86  receive complementary pegs (not shown) that extend downwardly from top portion  80  and produce a snap-fit engagement of top portion  80  to bottom portion  82 . Test matrix  88  is described with reference to FIGS. 3 and 4, except to note with reference to FIG. 2 that adhesive layer  90  having openings  92  is used to hold the matrix together during assembly.  
         [0026]    Turning now to FIGS. 3 and 4, two different test matrices  94  and  96  are illustrated. Both matrices  94  and  96  include top disbursement layer  98 . Layer  98  is an open cell layer capable of rapidly and effectively spreading the fluid sample. One suitable material for layer  98  is available under the name “Accuflow Plus-P,” Schleicher &amp; Schuell, Inc. Another suitable material for layer  98  is available under the name “Accuwik,” Pall Biochemicals. Both of these layers are made of polyester and provide excellent movement of blood therethrough as shown by the arrows in FIG. 3.  
         [0027]    Layer  100  is a blood separation layer that is adjacent to and in fluid communication with layer  98 . Blood separation layer  100  separates a portion of blood cells from plasma and passes blood filtrate therethrough. A suitable commercial membrane for layer  40  is Ahlstrom Grade 144, thickness 0.378 mm, available from Ahlstrom Filtration, Inc., Mt. Holly Springs, Pa.  
         [0028]    Below and in fluid communication with layer  100  are three “stacks.” For example, stack  102  can be an HDL Measurement Stack that includes layers  104  and  106 . Stack  104  can be a total cholesterol stack including layers  108  and  110 . Finally, stack  106  can be a triglyceride stack including layers  112  and  114 . Importantly, it should be understood that the “stacks” can be other than the examples just noted. For example, the stacks can measure, e.g., ketones, glucose, creatinine, and other body fluids. Further, more or less than the two layers shown for the stacks  102 ,  104  and  106  can be used, depending upon the particular analyte to be measured. With reference to FIG. 4, matrix  96  includes disbursement layer  98 , as does matrix  94 . However, blood separation layer  100  has been replaced with individual blood separation layers  116 .  
         [0029]    Turning now to FIG. 5, the operation of the instrument can be better understood. Once test strip  48  is inserted into test strip holder  42 , photodiodes  54  and LED arrays (or light sources)  56  align as shown so that the incident light  118  is directed towards the bottom reaction layer of the various stacks  102 ,  104  or  106  at an angle as depicted in FIG. 5. The reflected light  120  reflects directly back through pores  58  (see FIG. 1) and is measured by light detectors or photodiodes  54 . Digital to Analog Voltage Converters  122  drive the light sources based upon a predetermined calibration value. To more fully explain, the optical loop of the instrument is calibrated such that white corresponds to 100% reflectance and black corresponds to 0% reflectance. The light sources or LED arrays can be configured to emit green, red, blue or other colored lights depending upon the color of the reaction membrane to be measured. For example, cholesterol reaction membranes produce a blue color, such that a red LED has been found to work best to measure reflectance.  
         [0030]    The light detectors produce a very small current that is amplified and converted into a voltage which is then multiplexed by analog switch  124  into one of two amplifier stages  126  depending upon which LED is used. The output signal from amplifier stage  126  is then input into analog to digital converter  128  and converted into a digital signal for acquisition by microcontroller  130 .  
         [0031]    The instrument is essentially a closed loop control system, in that micro-controller  130  drives DAC&#39;s  122  and then reads the signal that is returned from converter  128 . Memo chip  132  is an interchangeable part that fits into port  28  (FIG. 1). The Memo chip contains information concerning the particular container of test strips that is to be used with the instrument, such as lot code, expiration date, which of the LEDs  56  to light (e.g., blue or red), the chemistry curve which correlates the reflectance to analyte concentration, etc. As shown in the upper left hand corner of FIG. 5, the lot code can be correlated to the color of the test strip, or shade of color. For example, if a green test strip is inserted into the instrument, and the Memo chip requires a yellow test strip, an error code would be displayed on display  22  (FIG. 1). Such a system is described, for example, in U.S. Pat. No. 5,597,532.  
         [0032]    Real time clock  134  maintains the time and date information for controller  130 . Micro-controller  130  sends a signal to buzzer  136  which in turn produces an audible sound when there is an error or warning signal. Keys  24  and  26  (also see FIG. 1) allow the user to operate the instrument  20 . Temperature sensor  138  inputs ambient temperature information to micro-controller  130 , whereby the micro-controller will not allow the instrument to perform chemistry tests if the sensed temperature is outside of a pre-determined range. Finally, data EEPROM  140  is a general storage device that stores information such as chemistry results and other parameters that are generated, for example, during calibration.  
         [0033]    With reference to the upper right-hand corner of FIG. 5, the amperometric testing functions when the DAC  139  applys a voltage across the strip  141  (resistive sensor) which in turn generates a current when dosed with whole blood. The current is proportional to the concentration of glucose, if that happens to be the analyte being tested. The current is amplified by amp  143  and converted into a voltage and input into the Analog-to-Digital Converter  128 , which in turn converts the signal into a binary value which can be read by micro-controller  130 . Micro-controller  130  processes the information and sends the result to display  22 , which then displays the concentration of analyte.  
         [0034]    Another aspect of the present invention relates to a code which flashes on display  22  after Memo chip  132  (FIG. 5) is installed into port  28  (FIG. 1) and the “Run Test” mode is selected. As shown in FIG. 6, display  22  has a four-digit code  134  consisting of first digit  236 , second digit  238 , third digit  240  and fourth digit  242 . In the exemplary embodiment, digit  236  is an alphanumeric character that corresponds to the chemistry, in this case “H” for HDL. The second digit  238  is an alphanumeric character that corresponds to the year in which the test strip was made, in this case “2” for  2002 . The third digit  240  is an alphanumeric character that corresponds to the month, in this case “1” for January. Finally, the fourth digit  242  is an alphanumeric character that corresponds to the sequential lot or batch from that particular month in which the test strip was made. Such a code presents a convenient way for a technician at the company which produces the instruments and strips to quickly identify all relevant manufacturing information regarding a particular test strip with only four alphanumeric characters. Such an encryption scheme saves time and helps the technician more quickly identify the source of a malfunction of the system during service calls.  
         [0035]    While a preferred embodiment incorporating the principles of the present invention has been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.