Patent Publication Number: US-2006008920-A1

Title: Combination assay for alcohol and drugs of abuse

Description:
FIELD OF THE INVENTION  
      The present invention relates to an apparatus and method to collect bodily fluids and provide an assay of one or more analytes present in those bodily fluids.  
     BACKGROUND OF THE INVENTION  
      Drugs of abuse and alcohol are the most frequent causes of driving under the influence, in addition to a host of other problems related to their use. For example, illegal drug use and excessive use of alcohol contribute to many accidents, injuries and medical conditions. Screening individuals for drugs of abuse and alcohol is an important method in identifying those who may cause harm to themselves and others. Screening may also provide an additional benefit as a deterrent against inappropriate and/or illegal use of drugs or alcohol. To that end, many tests have been developed in order to screen individuals for the presence of drugs of abuse and alcohol, or metabolites or other residue thereof. For example, some such test apparatus and methods involve the determination of the presence and/or amount of drugs of abuse or alcohol in biological fluids, such as blood, urine, and oral fluid. These have proven to be useful analytical methods.  
      However, the chemical methods of choice for such tests have often included complex laboratory procedures, such as gas chromatography for analyzing blood or urine, and a range of laboratory or field tests. These tests involve time-consuming procedures, and thus are not useful for a rapid determination of the intoxication of an individual, such as might be needed during a roadside traffic stop.  
      Thus, there is an increasing demand for a simple, accurate, and reproducible method for determining the presence of drugs of abuse or alcohol in bodily fluids. Not only would such a test lead to more rapid determinations of intoxication or sobriety during traffic stops, but also could be used in other fields, such as to assure that operators of dangerous equipment, such as heavy construction equipment or military equipment, are not intoxicated. Additionally, there is an added benefit that the rapid identification of such individuals aids in removing those individuals from the operation of automobiles and other equipment, thereby reducing costs, both in human terms (i.e., injuries, lives lost, etc.) and financial terms.  
      In order to provide a more rapid analysis, a number of testing devices, using rapidly reacting test strips, have been developed. In general, a sample of bodily fluids such as urine, blood, or oral fluid, is applied to the test strip in order to effect a reaction, such as an immunological or enzymatic reaction, to determine the presence of the analytes being tested. For example, one such test strip for drugs of abuse present in substances such as blood, urine, serum, and tissue, uses immunological principles. In particular, drug-specific antibodies and antigens have been used in a variety of immunological assay procedures for detecting antibodies or antigens in bodily fluids of humans and animals. Test devices are known which can identify the presence or absence of drugs of abuse, such as cocaine, opiates, and marijuana, using the protein conjugates of these drug derivatives and their accompanying antibodies.  
      In addition to the immunoassay test strips described above, other test strips use enzymatic reactions in order to determine the presence of alcohol in bodily fluids. Such devices are useful due to the prevalent use of alcohol tests in society today. For example, approximately one-third of all patients currently admitted to hospital emergency rooms are tested for blood alcohol levels for the purpose of making a correct judgment as to the nature of the patient&#39;s clinical condition. Before the advent of such test strips, measurements were determined by taking blood samples by venipuncture and hand carrying the sample to a laboratory for a blood alcohol determination. The previous procedure had taken from thirty minutes to as long as a few hours.  
      Newer tests, however, have included test strips employing the enzyme alcohol oxidase. Alcohol oxidase is a particularly unstable enzyme that undergoes rapid deterioration and loss of activity. Particularly, alcohol oxidase reacts with alcohol to form a hydrogen peroxide. The hydrogen peroxide can then be reacted with a chromagen, or other detectable marker, in order to produce the appearance of a particular color on a test strip, signifying the presence of alcohol in the body.  
      Most on-site drugs of abuse tests are based on lateral flow immunoassay, which is a dynamic assay with an undefined sample size. The enzymatic assay of alcohol is an end point assay with defined sample volume. By nature, these two types of tests require different sample applications and different result interpretations. Examples of commercially available drugs of abuse tests and alcohol tests are: Oratect™ Multiple Drug Screen COC/MET/THC/AMP/OPI/PCP Oral Fluid Test (Branan Medical Corporation, Irvine, Calif.), and Alco-Screen (Chematics, North Webster, Ind.), respectively. Further, U.S. Pat. No. 6,248,598, which is incorporated herein by reference, discloses an immunoassay that provides for both collection of oral fluid and an assay of oral fluid for one or more analytes with a visual readout. The &#39;598 patent discloses a device which collects oral fluid and initiates an assay or assays on the oral fluid, but does not disclose a device which may assay for both drugs of abuse and alcohol.  
      Thus, some drawbacks remain with current test apparatus. For example, while various tests have been developed, both for drugs of abuse and for alcohol, the drugs of abuse tests operate on immunological principles, while the alcohol tests operate via enzymatic reactions. In general, it is difficult to combine these two types of tests into one device. For example, devices which use various test strips (or other membranes) to house components of both drugs of abuse and alcohol tests, experience the disadvantage of reagents for the different tests cross-reacting with one another. For example, the reagents of the alcohol test used to effect color change can migrate to the immunoassay strip to interfere with the test for drugs of abuse. As a result of difficulties such as those described above, separate devices must presently be used when testing for both drugs of abuse and alcohol. This need for separate test strips increases the amount of equipment that must be kept on-hand in order to perform such tests, as well as increasing the time it takes to administer multiple different tests. The costs of keeping several different test devices on hand are increased, as well. Further, any test method that uses samples of blood and/or urine may also be invasive to the individual being tested.  
      In view of the above, additional assays and methods are desirable.  
     SUMMARY OF THE INVENTION  
      The present invention overcomes the above-described drawbacks of testing apparatus and methods by providing a test apparatus that allows testing for the presence of both drugs of abuse and alcohol within a single device. In general, the apparatus of the present invention includes an immunoassay for qualitative screening for various drugs of abuse and a reactive pad including an enzyme as a test for alcohol. The two types of tests are contained within the same housing and these tests are performed using the same sample source from a subject being tested.  
      In particular, the present invention provides an apparatus for testing for multiple analytes, which includes a housing contacting a sample collection pad that partially extends from the housing. The collection pad is in wicking contact with a single backing material supporting (either directly or indirectly): (1) a first test strip having components in wicking communication for a lateral flow immunological assay, and (2) a second test strip having components for an enzymatic reaction. In use, sample in the collection pad contacts both first and second test strips for both immunological and enzymatic detection of an analyte or analytes contained in the sample. Thus, once a sample is deposited on the collection pad, it flows to both the first and second test strips to trigger both the immunological and enzymatic tests.  
      The present invention also provides a method for testing for both drugs of abuse and alcohol by providing an apparatus as described above, initiating an immunological assay and an enzymatic reaction, and detecting the results of the immunological assay and the enzymatic reaction. In general, initiating the immunological assay and the enzymatic reaction includes delivering a sample to the collection pad. One then waits a predetermined amount of time for the sample to travel by wicking action to the first and second test strips, and then obtains control and test results on the test strips visually, by an automatic readout device, etc.  
      The test apparatus and method of the present invention may use oral fluid as the sample. Because oral fluid is used instead of blood, urine, or another bodily fluid as the test sample, the apparatus avoids the problems described above of intruding on privacy, invasiveness to the person, and can also avoid the problem of sample alteration. That is, because the subject may be observed while taking the test, the opportunity for the subject to use a phantom sample not his/her own, or to alter his/her own sample, is eliminated. Further, due to their size, simple and rapid nature, etc., the test strips can be used on job sites, in schools, and can be customized for rapid screening of illegal use of controlled materials or other substances.  
      The physical and chemical character of the device of the present invention assays both types of analytes within a single test housing. While the assays are run at the same time using the same sample, the readouts may not necessarily appear at the same time, although it will be beneficial for the readouts to appear close in time to one another.  
      More specifically, the apparatus of the present invention includes a housing having a collection pad for collection of oral fluid. This collection pad further includes an absorbent material that, when placed in the mouth of a subject, provides for absorption of oral fluid to the collection pad. The oral fluid flows along the collection pad via a wicking action (i.e., capillary action) to a first test strip and a second test strip. The use of separate test strips prevents the reagents of the alcohol test from cross-reacting with the drugs of abuse test, and vice-versa. This is because the reagents for each of the tests are not housed on the same strip or membrane. While the first and second test strips are each associated with the collection pad, it is not necessary that they be associated with one another. One test strip is used to test for drugs of abuse and the other test strip is used to test for the presence of alcohol. The designations of “first” and “second” are used for convenience only and need not indicate any reaction order. Either test strip may be designated as “first” or “second.” 
      The apparatus further includes test reagents on each of the first and second test strips, which are used to detect the presence of any sought-after drug or alcohol analytes. More specifically, the first test strip has components or reagents including a detectable marker specifically adapted to bind a drug analyte to be detected. The marker is adapted to bind analyte by being conjugated to an antibody to the drug analyte being tested. The marker is not immobilized or otherwise bound to the first test strip, and moves along the first test strip with the flow of the sample oral fluid. The first test strip further includes a drug analyte immobilized at a test region on the test strip. This drug analyte corresponds to the drug being tested for in the sample. The marker is located on the first test strip between the point where the collection pad receives the sample and the immobilized drug analyte. If the sample of oral fluid includes any one of the drugs to which antibody and analyte are present, the drug(s) are bound by antibody present in the conjugate pad. Thus, the corresponding antibody will not be available to bind analyte in the test region [detectable by the assay as it flows past the test region]. This is a positive result. If there is no drug analyte in sample, then the antibody present in the conjugate pad will be free to bind drug analyte in the test region. The antibody analyte conjugate in the test region will create a detectable signal, due to the detectable marker, indicating a test that is negative for the presence of drug analyte.  
      The second test strip includes enzyme reagents specifically adapted to effect a color change of a particular portion of the test strip, the reactive pad, when alcohol is present in the oral fluid sample. In general, the enzymatic test for alcohol includes an enzymatic pad, including alcohol oxidase and peroxidase. This enzymatic pad is in communication with a wicking membrane that is, in turn, operatively connected to the collection pad. The reactive pad, on contact with solutions of alcohol, will rapidly turn different colors, in one embodiment from shades of green to blue, depending on the amount of alcohol present.  
      In another embodiment, the present invention also provides a method for detecting analytes in the oral fluid of a subject. The method includes providing an apparatus generally as described above, collecting oral fluid on the first portion of the apparatus, and detecting any analyte present in the oral fluid by observing any detectable marker on the first test strip, and any color change on the second test strip.  
      These and other advantages of the present invention will be apparent in light of the following figures and detailed description 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of the apparatus of the present invention, showing a top surface of the apparatus adapted to test for drugs of abuse;  
       FIG. 2  is a perspective view of the apparatus of the present invention, showing a bottom surface of the same apparatus adapted to test for alcohol;  
       FIG. 3A  is a side view of components of the interior of the apparatus of the present invention showing components of first and second test strips for drugs of abuse and for alcohol;  
       FIG. 3B  is a side view of components of the interior of an alternate embodiment of the apparatus of the present invention showing components of first and second test strips for drugs of abuse and for alcohol;  
       FIG. 4  is a schematic of a test of one embodiment of the present invention depicting sample added to the collection pad, marker-antibody conjugates at the conjugate pad, drug analytes bound at a test region, control analyte bound at a control region, and an absorbent pad;  
       FIG. 5  is a schematic of the test of  FIG. 4  depicting drug analytes in the sample flowing to the conjugate pad and binding with marker-antibody conjugates; and  
       FIG. 6  is a schematic of the test of  FIG. 4  after flow of sample has proceeded to the absorbent pad, depicting binding of some marker-antibody conjugates in the test region, and binding of control conjugate in the control region.  
       FIGS. 4-6  are not drawn to scale to correspond to  FIGS. 1-3 . 
    
    
      The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
     DETAILED DESCRIPTION  
      A test apparatus and method whereby test strips for drugs of abuse and alcohol are provided in a single test apparatus. Such an apparatus and method reduces equipment, cost, and length of time of testing. It also provides a test that minimizes the invasiveness experienced by the test subject.  
      Referring now to the Figures, the invention is directed to an apparatus  10  that allows testing for the presence of both alcohol and non-alcohol drugs conventionally termed drugs of abuse, as will be further described, within a single apparatus. In general, the apparatus  10  of the present invention includes one or more first test strip  12 , collectively called a “first test strip,” although the apparatus is not limited to a single strip. The apparatus  10  further includes a second test strip  14  for alcohol. More particularly, the first test strip  12  may include an immunoassay to screen for various drugs of abuse and the second test strip  14  may include a reactive pad including at least one enzyme reactive with alcohol. The present invention modifies both the physical and chemical character of these tests to achieve the goal of assaying both types of analytes within a single test device.  
      Although a combined test apparatus  10  as described herein can be used with many different types of samples  16 , such as blood, urine, etc., in a particular embodiment, oral fluid is used as a sample  16 . Since oral fluid is used instead of blood, urine, or another bodily fluid as the test sample  16 , the apparatus  10  avoids the problems described above of intruding on privacy, invasiveness to the person, and can also avoid the problem of sample alteration. Further, due to their simple and rapid nature, the test strips  12 ,  14  can be used on job sites, in schools, and customized for quick screening of illegal use of controlled materials.  
      More specifically, and referring to  FIGS. 1-3 , the apparatus  10  of the present invention includes a housing  18  for containing components of the testing device, including reagents and material for an assay for drugs of abuse, reagents and material for an assay for alcohol, and including a collection pad  20  for collection of oral fluid. As used herein, the term “drugs of abuse” excludes alcohol but includes all drugs of abuse, since a separate test for alcohol is provided with the same device. In the illustrated embodiment, the collection pad  20  extends from the housing  18  such that this portion can be readily inserted into the mouth. The collection pad  20  includes an absorbent material that, when placed in the mouth of a subject, absorbs oral fluid. The oral fluid flows along the collection pad  20  via a wicking action to contact the sample pad of the drug of abuse first test strip  12  and the wicking pad of the alcohol second test strip  14 . In the illustrated embodiment, a backing  15  is associated with the first test strip  12 . This backing  15  thus supports the first test strip  12 . It also provides indirect support (in the illustrated embodiment) to the second test strip  14 . While the first and second test strips  12 ,  14  are each associated with the collection pad  20 , they are not associated with one another in the illustrated embodiment. The first test strip  12  is used to test for drugs of abuse and the second test strip  14  is used to test for the presence of alcohol. As can be seen from the Figures, both the first test strip  12  and the second test strip  14  are disposed within the housing  18 , in the illustrated embodiment.  
      Referring more particularly to  FIG. 3A , the first test strip  12  (for drugs of abuse) of the apparatus  10  of the present invention includes at least a conjugate pad  22  associated with a test membrane  24 . This first test strip  12  initiates at least one immunoassay that provides a visual qualitative result indicating the presence of one or more drugs and/or drug metabolites (referred to as “analytes”) in the sample. In one embodiment, the test membrane  24  includes a test region  26 , including one or more reaction zones  54 , and a control region  28 . The test region  26  includes drug analytes and protein conjugates (both represented by reference number  30 ) for particular drugs of abuse being tested. These drug analytes and protein conjugates  30  are immobilized on the membrane  24  in the test region  26 . The control region  28  includes a control analyte  32  immobilized to the membrane  24 . In a particular embodiment, this control analyte  32  is goat anti-rabbit antibody coated on or otherwise bound to the membrane  24  at the control region  28 . The conjugate pad  22  includes marker-antibody conjugates  34  disposed thereon in such manner that they are freely movable therefrom. The term “marker-antibody conjugate” as used herein refers to a mobile labeled anti-analyte antibody. The apparatus  10  of the present invention may further include a sample pad  40  and an absorption pad  42  associated with the first test strip  12 . In the illustrated embodiment, it can be seen that the sample pad  40  is in contact with both the collection pad  20  and the conjugate pad  22 . The absorption pad  42  is located at the end of the apparatus  10  in the direction of sample flow and associated with the membrane  24  of the first test strip  12 .  
      The second test strip  14  of the apparatus  10  of the present invention, in the illustrated embodiment, includes a wicking strip  44  in wicking association with a reaction pad  46 . The wicking strip  44  in the illustrated embodiment, is associated with the collection pad  20 . As a result, the test apparatus  10  of the present invention includes first and second sides  48 ,  50 , each of the first and second sides  48 ,  50  including at least one window  52  for obtaining results of the tests of the apparatus  10 . As can be seen in  FIG. 1 , the illustrated embodiment includes two windows  52  disposed over the test and control regions  26 ,  28  of the membrane  24  of the first test strip  12 , and referring to  FIG. 2 , the second side  50  of the apparatus  10  includes one window  52  disposed over the reaction pad  46  of the second test strip  14 .  
      As described above, the apparatus  10  further includes test reagents on each of the first and second test strips  12 ,  14 , which are used to detect the presence of any sought-after drug or alcohol analytes. More specifically, the conjugate pad  2  includes marker-antibody conjugates adapted to bind analyte through an analyte-specific antibody  38 . The first test strip  12  further includes at least a first drug analyte and protein conjugate  30  bound at a test region  26  on the first test strip  12 . If the sample  16  includes drug analytes, the analytes will be bound by the marker-antibody conjugate  34  and thus the marker-antibody conjugate  34  will not bind drug analyte and protein conjugate  30  immobilized at the test region  26 . If there is no drug analyte in sample  16 , then the marker-antibody conjugate will bind drug analyte and protein conjugate  30  immobilized in the test region  26 . The marker-antibody conjugate  34  bound to drug analyte and protein conjugate at the test region  26  will create a detectable signal, indicating a negative test. This test will be described in greater detail later. Although a competitive immunoassay including marker that signals a negative test, as used in the apparatus  10  of the present invention, it will be recognized by those of skill in the art that the invention is not limited to this type of test, as other types of tests may be used. The invention is also not limited to the particular alcohol test described herein, as will be recognized by those of skill in the art.  
      The membrane  24  may be made of nitrocellulose or activated nylon. Immunoassay reagents are dried and immobilized on the membrane  24 . In the illustrated embodiment, the first test strip  12  contains components for the immunoassay, being preformulated reagents deposited at multiple separate reaction zones  54  within the test region  26  of the membrane  24 , one reaction zone  54  for each drug of abuse being tested. For example, the apparatus  10  of the present invention may include reaction zones  54 , with each reaction zone  54  including one type of immobilized drug analyte and protein conjugate  30 . Those drug analytes and protein conjugates  30  may be chosen from cocaine, d-methamphetamine, 11-nor-Δ9-tetrahydrocannabinol, d-amphetamine, opiates, and phencyclidine, etc. It will be recognized by those skilled in the art that these drug analytes and protein conjugates  30  are merely exemplary, and that one may immobilize an analyte of any substance one wishes to test in a particular reaction zone  54 .  
      Regarding the drugs of abuse assay, pharmacokinetics of cocaine, opiates, amphetamine, methamphetamine, phencyclidine, and cannabinoids, show that these drugs are detectable in bodily fluids, such as oral fluid. Alcohol is also detectable in oral fluid. The apparatus  10  of the present invention integrates oral fluid collection and a lateral flow immunoassay screening test for drugs of abuse and an enzymatic assay for ethanol in a single integrated device.  
      The drugs of abuse test may be based on a competitive immunoassay procedure in which drug analytes and protein conjugates  30  immobilized on the membrane  24  of the first test strip  12  compete with drug or analytes, which may be present in oral fluid, for limited antibody binding sites  38  on the marker-antibody conjugate  34 . In a particular embodiment, the detectable marker  36  is colloidal gold. However, those skilled in the art will recognize that any other detectable marker  36  may be used, including those detectable visually by the naked eye, those which fluoresce, or other non-visual methods of detection. During testing, oral fluid is collected at the collection pad  20  and migrates along the flow path of membrane  24 . If no drug is present in the oral fluid, the marker-antibody conjugate  34  will bind to the drug analytes and protein conjugates  30  on the membrane  24  to form bands at specific reaction zones  54  in the test region  26 . When colloidal gold is used as the marker, those bands are visible. Therefore, the presence of a colored band at a specific reaction zone  54  indicates a negative result for that specific drug. If any drug or drugs are present in the oral fluid, it competes with the immobilized drug analytes and protein conjugates  30  for limited antibody binding sites of the marker-antibody conjugate  34 . When a sufficient amount of drug is present, the drug will saturate the antibodies, and the detectable marker-antibody conjugate  34  cannot bind to the drug analytes and protein conjugates  30  on the membrane  24 . Therefore, the absence of a color band at the visually observable test region  26  indicates a positive result for that particular test.  
      A control is also provided for the first test strip  12  of the apparatus  10  of the present invention, to ensure that the test procedure has been performed properly. A band should always appear at the control region  28  on the membrane  24  regardless of the presence of drug or drug metabolite to indicate the device and components are operable.  
      More specifically, and referring to  FIGS. 4-6 , the marker  36 , being colloidal gold or other microparticles, such as colored latex particles, are sensitized with specific purified antibodies to the drugs of the test and a control, and are deposited on the conjugate pad  22  along the flow path of the sample  16 . Colloidal gold may range in size from 10 nm to 60 nm. Microparticles, such as colored latex particles, may be about 400 nm. These marker-antibody conjugates are not immobilized on the conjugate pad  22 , but rather, are freely movable therefrom. The particles of the detectable marker  36  may be any color. The detectable marker  36  is blocked with a protein buffer solution to prevent nonspecific aggregation.  
      The test is performed as follows. The sample  16  is applied onto the collection pad  20  and is wicked to the conjugate pad  22 . In the illustrated embodiment, a sample pad  40  is disposed between collection pad  20  and conjugate pad  22  ( FIG. 3 ). As the sample  16  is wicked through the conjugate pad  22 , it mobilizes the marker-antibody conjugates  34  on the conjugate pad  22 . The marker-antibody conjugates  34  then are wicked from the conjugate pad  22  to the membrane  24  by a wicking action (such as capillary action) and to and past the reaction zones  54  of the test region  26 . In the absence of drug analyte(s) in the sample  16  that are specific for the drug analytes and protein conjugates  30  in the first test strip  12 , the marker-antibody conjugates  34  bind to the specific drug analytes and protein conjugates  30  that are immobilized in the reaction zones  54  through immunocomplexation, forming definite, visible lines. This is a negative test; if a line appears in a reaction zone  54  specific for a particular drug of abuse, the test is negative for that particular drug of abuse.  
      In the presence of specific analytes in the sample  16 , the marker-antibody conjugate  34  in the conjugate pad  22  will bind to those analytes in the sample, and thus so not bind to the drug analytes and protein conjugates  30  that are immobilized in the reaction zones  54 . Thus, the immune complex formation between the drug analytes and protein conjugates  30  in the reaction zones  54  and the marker-antibody conjugate  34  is prevented. In a positive test, therefore, lines will not form in the reaction zones  54 .  
      At one end of the membrane  24  is the reference control region  28  with a different antigen antibody reaction. In particular, goat anti-rabbit antibody is immobilized on the membrane  24 . Conjugate  34  form the conjugate pad including a detectable marker  36 , always binds at the control region  28  during a viable test. The line created in the control region  28  indicates that the test is viable and serves as a reference control. If the test device has been properly stored, is correctly used, and is within the expiration time limit, the control line should always be present. Therefore, in the illustrated embodiment, for all negative tests, there will be visible lines. Thus, with multiple analytes being tested for, if all tests are negative, there will be lines visible in each of the reaction zones  54 . If only certain tests are negative, there will be lines visible in some reaction zones  54  and absent in others. For positive tests for each analyte, there will be only one visible line, i.e., the reference control line. It will be further recognized by those skilled in the art that lines need not be used to indicate test and/or control results. Other symbols may be used, including but not limited to “+,” “−,” “POS,” and “NEG.” 
      Although the test device above is described as having a first test strip  12 , such an embodiment is merely exemplary and it will be recognized that multiple immunochromatographic test strips may be present in the housing of the device of the present invention. As one example, the device may include two immunoassay test strips, with reaction and control zones, one strip being visible through a first window and the other strip being visible through a second window. As another example, the device may include two immunoassay test strips with both being visible through the same window. As another example, the device may include more than two test strips, with test and control zones visible through the same or separate windows.  
      The housing  18  of the apparatus  10  of the present invention not only includes the drugs of abuse test as described above, but also includes a test for the presence of alcohol. It is well established that the concentration of alcohol in oral fluid is comparable to that of alcohol in blood. The test for alcohol, in a particular embodiment of the present invention, is an enzymatic test. The enzymatic test for alcohol includes an enzymatic reaction pad  46 , including alcohol oxidase and peroxidase. This reaction pad  46  is in wicking communication to a wicking membrane which is, in turn, in wicking communication to the collection pad  20 . The reaction pad  46 , on contact with solutions of alcohol, such as alcohol present in oral fluid, will rapidly turn different colors, in one embodiment from shades of green to blue, depending on the amount of alcohol present. The test is used by applying a sample, such as oral fluid, to the wicking membrane. The sample then moves via wicking action to the enzymatic reaction pad  46 .  
      The reaction pad  46  contains a reagent system. The reagent system, as described briefly above and in more detail here, is made up of stabilized alcohol oxidase, a peroxidase, and a chromogen including color-changing oxygen acceptor. It may contain other materials as well. “Stabilized alcohol oxidase” can mean alcohol oxidase that retains at least 50% of its activity, in one embodiment, and at least 70% of its activity, in another embodiment, when stored in dried form at 56° C. for fifteen days. The stabilized alcohol oxidase in its simplest form comprises alcohol oxidase in intimate admixture with an effective stabilizing concentration of stabilizing proteins.  
      The reagent system further includes a peroxidase (any material having peroxidative activity). This material promotes the reaction of the hydrogen peroxide, generated by the reaction of ethanol with oxygen, with the color-changing oxygen acceptor. While enzymatic plant peroxidases such as horseradish peroxidase or potato peroxidase may be employed, various other organic or inorganic peroxidases may be employed as well. These include organics such as some of the porphyrins, as well as inorganics such as ammonium or alkali metal iodides, alkali metal chromic sulfates, iron to ferrocyanide, ferrous chloride, and iron sulfacyanate, and the like, as known to one skilled in the art. Yeast peroxidase may also be used. The peroxidase promotes reaction of hydrogen peroxide with the color-changing oxygen acceptor.  
      In one embodiment, the reagent system includes tetramethylbenzidine (0.176 mg), alcohol oxidase (EC 1.1.3.1.3) (0.5 IU), peroxidase (EC 1.11.1.7) (30 IU), a buffer (0.747 mg), and stabilizing proteins (0.19 mg).  
      In one embodiment, the reaction pad  46  employs a solid phase chemistry which uses the following highly specific enzyme reaction:  
                 
 
      The alcohol test also includes a reaction inhibitor. This reaction inhibitor is used to control the timing of the result of the alcohol test by controlling the rate of the enzymatic reaction. The reaction inhibitor may be a quenching agent that consumes the hydrogen peroxide of the reagent system. In one embodiment, the quenching agent used as a reaction inhibitor is vitamin C.  
      The alcohol reaction pad  46  of the apparatus  10  of the present invention will react with methyl, ethyl, and allyl alcohols. The apparatus  10  may be formed such that the reaction of the alcohol test will not proceed in the presence of alcohols having 5 or more carbons, or with glycine, glycerol, or serine. The reaction will proceed in the presence of methyl, ethyl, and allyl alcohols. This property is a result of the specificity of the alcohol oxidase enzyme extracted from yeast.  
      One an alcohol test has been performed using the apparatus  10 , the color of the reaction pad  46  may be compared to a color chart (such as may be located on the test package) in order to estimate the approximate blood alcohol concentration of the subject.  
      The integrity of the reaction pad  46  may be qualitatively verified using a test solution prepared by adding four drops of 80 proof distilled spirits to 8 oz. water. This solution may then be applied to the reaction pad. The solution should provide a color reaction equal to or higher (darker) than a color that would appear for 0.04% blood alcohol.  
      While the present invention has been disclosed by reference to the details of preferred embodiments of the invention, it is to be understood that the disclosure is intended as an illustrative rather than in a limiting sense, as it is contemplated that modifications will readily occur to those skilled in the art, within the spirit of the invention and the scope of the amended claims.