Patent Publication Number: US-2003224449-A1

Title: Accelerator for agglutination reactions, reagent for biochemical assays, and biochemical assay method

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to an accelerator for biochemical assays (e.g., immunoassays) based on a principle of an agglutination reaction, a reagent for biochemical assays comprising the accelerator, a kit for a biochemical assay comprising the reagent, a biochemical assay method in which the accelerator is used, and use of alginic acid and/or an alginate as the accelerator.  
       BACKGROUND ART  
       [0002] Immunoassays, in which a specific antigen or antibody is detected by using an immune agglutination reaction between an antigen and an antibody against it, have been widely conducted in various clinical diagnostic tests, biochemical research, and the like. In immunoassays, commonly, an antibody against an antigen that is a target to be detected or an antigen of an antibody that is a target to be detected is brought into contact with a specimen that may contain the target, and the amount of immune agglutinations is determined which have been formed in a reaction mixture as a result of an antigen-antibody reaction when the target is present in the specimen.  
       [0003] The antibody against an antigen or the antigen of an antibody may be supported on carriers. If the carriers are used, the immunoassay can give higher performance than the case where the carriers are not used. Thus, immunoassays in which carriers are used (for example, latex agglutination tests in which polystyrene beads are used as carriers) have been popularly conducted.  
       [0004] The amount of agglutinations is generally determined by nephelometry in which the intensity of scattered light is measured because the scattering of light occurs by the presence of agglutination or by turbidimetry in which the ratio of the intensity of transmitted light to that of incident light is measured because the transmission of light is obstructed by the agglutinations. Both of the nephelometry and turbidimetry have been commonly used although each has good and bad points.  
       [0005] While, in immunoassays, to improve the sensitivity and precision in determination, to facilitate an antigen-antibody reaction, and to stabilize agglutinations, various polymeric compounds such as polyethylene glycol pulluran, polyvinyl pyrrolidone, and carboxymethyl cellulose are commonly used as accelerators. For example, Japanese Patent Early-publication No. H.05-180838 discloses using pulluran or polyvinyl pyrrolidone. Japanese Patent Early-publication No. H.10-282100 discloses using a surfactant having a molecular weight of 500-2,000 and an HLB of 25-80 (erg., CHAPS, BIGCHAP, and digitonin). Japanese Patent Early-publication No. H.10-282101 discloses using a polymer having a molecular weight of 1,000-1,500,000 and being composed of a monomer having an HLB of 9-20 (e.g., polyvinyl pyrrolidone, polyethyleneimine, and polyethylene glycol). Japanese Patent Early-publication No. H.10-282100 discloses using a surfactant having a molecular weight of 500-2,000 and a steroid ring as its main skeleton or framing structure (e.g., CHAPS, BIGCHAP, and cycosaponin). Japanese Patent Early publication No. 2001-74742 discloses as accelerators for agglutination reactions polyvinyl pyrrolidone, polyethyleneimine, polyethylene glycol, CHAPS, BIGCHAP, digitonin, saponin, pulluran, and poly(glycosyl ethylmethacrylate).  
       [0006] However, they may increase the viscosity of a reagent or a reaction mixture. Some of them may also facilitate non-specific reactions. Thus, there are drawbacks in uses of the above polymeric compounds in determination systems based on the principle of immune agglutination.  
       SUMMARY  
       [0007] An object of the present invention is to provide an accelerator for agglutination reactions that is suitable to use in biochemical agglutination determination systems, shows a strong accelerative function to agglutination reactions, does not tend to increase viscosities of its aqueous solutions such as reagents and reaction mixtures, shows good reproducibility and precision in determination results, and can be readily handled, especially one that can contribute to realize in latex agglutination determination systems a high sensitivity and a determination or quantitative analysis in a wide range.  
       [0008] Another object of the present invention is to provide a reagent for biochemical assays that comprises the accelerator, a kit for a biochemical assay comprising the reagent, and a biochemical assay method that uses the accelerator or the reagent.  
       [0009] Another object of the present invention is to provide use of alginic acid and/or an alginate as the accelerator.  
       [0010] The present inventors have extremely studied to search an accelerator for agglutination reactions, by which the above objects can be attained. As a result they have found that alginic acid and alginates (e.g., sodium alginate and propylene glycol alginate) are excellent accelerators. Thus, they have accomplished the present invention.  
       [0011] Namely, the present invention provides an accelerator for agglutination reactions consisting essentially of at least one member selected from the group consisting of alginic acid and alginates.  
       [0012] Also, the present invention provides a reagent for biochemical assays comprising at least one member selected from the group consisting of alginic acid and alginates.  
       [0013] The reagent of the present invention includes the following embodiments alone or in combination of two or more of them:  
       [0014] a) the biochemical assays are immunoassays,  
       [0015] b) the reagent may be a diluent for specimens,  
       [0016] c) the reagent may further comprise a compound that can specifically bond to a target to be detected,  
       [0017] d) in the embodiment c), (1) the compound is an antibody and the target is an antigen of the antibody or (2) the compound is an antigen and the target is an antibody against the antigen,  
       [0018] e) in the embodiment c), (1) the compound is avidin and the target is biotin,  
       [0019] f) in the embodiment c), the reagent further comprises carriers on which the compound is supported, and  
       [0020] g) the reagent is one that is used in an immune agglutination reaction.  
       [0021] Further, the present invention provides a kit for a biochemical assay comprising the above reagent according to the present invention (Hereafter “reagent (x)”), and at least one member selected from the group consisting of a reagent (y) other than the reagent (x), a container, and an instruction for use.  
       [0022] The kit may be used for an immunoassay.  
       [0023] Furthermore, the present invention provides a biochemical assay method comprising a step of bringing a compound that can specifically bond to a target to be detected into contact with a specimen that may contain the target in the presence of at least one member selected from the group consisting of alginic acid and alginates and a step of determining the amount of agglutinations that have been made by the specific reaction between the compound and the target.  
       [0024] In the biochemical assay method, (1) the compound may be an antibody and the target may be an antigen of the antibody or (2) the compound may be an antigen and the target may be an antibody against the antigen, and the specific reaction may be an antigen-antibody reaction.  
       [0025] Moreover, the present invention provides use of at least one member selected from the group consisting of alginic acid and alginates as an accelerator for agglutination reactions. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0026]FIG. 1 is a graph where accelerative effects of an immune agglutination reaction by various accelerators are compared in a latex agglutination determination system.  
     [0027]FIG. 2 is a graph where accelerative effects of an immune agglutination reaction by diluents for specimens containing sodium alginate in various concentrations are compared in a latex agglutination determination system. 
    
    
     DETAILED DESCRIPTION  
     [0028] Hereafter, the present invention will be specifically explained  
     [0029] Examples of the agglutination reactions include immune agglutination reactions. Also, examples of the biochemical assays include immunoassays. Thus, hereafter we will explain the present invention with referring to immune agglutination reactions and immunoassays. However, the applications of the present invention are not limited to immune agglutination reactions and immunoassays. Agglutination reactions and biochemical assays in which a specific bonding or binding reaction between two compounds (e.g., avidin and biotin) is used are also included within the scope of the present invention.  
     [0030] 1. Accelerator for Agglutination Reactions  
     [0031] In the present invention, an accelerator means a compound that can facilitate or help to occur agglutination reactions. The accelerator of the present invention consists essentially of at least one member selected from the group consisting of alginic acid and alginates. In this specification, alginic acid and alginates may be comprehensively called as “alginic type polymers.” Alginates include alginic acid salts such as sodium alginate, calcium alginate, magnesium alginate, and ammonium alginate, and alginic esters such as propylene glycol alginate.  
     [0032] Alginic acid is a structural polysaccharide of Phaeophyta and has a high molecular structure of a straight chain in which D-mannuronic acid molecules are linked through β-1,4-linkage.  
     [0033] Among alginic type polymers, sodium alginate is desirable in view of storage stability and solubility. Sodium alginate is watersoluble, white or pale yellow powder. It is usually used as an emulsifier, an stabilizer, a water-absorbable polymer, or the like.  
     [0034] Among alginic type polymers, propylene glycol alginate is also desirable. This is because it readily dissolves in cold water, hot water, and acidic solutions, and does not precipitate in the presence of calcium, metal salts, etc.  
     [0035] In the present invention, alginic type polymers may be used alone or in combination of two or more of them.  
     [0036] The mechanism by which alginic type polymers facilitate agglutination reactions is thought as follows:  
     [0037] If in a colloidal solution colloidal particles such as latex particles come dose to each other, polymers that are dissolved in the colloidal solution and take each a finite space are cleared away from spaces between the particles. Namely, the so-called depletion effect occurs. In the area where the depletion effect occurs, the colloidal particles are concentrated. Therefore, the frequency of collision of those particles is increased. While, target compounds to be detected bond to compounds that can specifically bond to the target compounds and that have been bonded to the surfaces of the colloidal particles, and thus immune complexes each comprising a colloidal particle are formed. Because the frequency of collision of the colloidal particles is increased, the complexes also collide with each other in a high frequency. Therefore, the target compounds in the complexes can bond to the compounds in other complexes in a high frequency. As a result, large complexes, namely, agglutinations, are formed.  
     [0038] More specifically, there is an area where antibody-bonded colloidal particles are concentrated by the depletion effect. If antigen molecules are put into the area, they bond to the antibodies and thus immune complexes each comprising an antigen molecules and an antibody-bonded colloidal particle are formed These complexes collide with each other in a high frequency. Therefore, the antigen molecules in the complexes can bond to the antibodies in other complexes in a high frequency. As a result, large immune agglutinations are formed Thus, the immune agglutination may be facilitated.  
     [0039] The alginic type polymers have various molecular weights. Therefore, their aqueous solutions have various viscosities according to their molecular weights. The grades of commercial products of alginic type polymers are often specified by the viscosities (e.g., 100-150 cp, 300-400 cp, and 500-600 cp [1 w/v %, at 20° C.]) that their aqueous solutions have. In the present invention, commercial products of all grades can be used. However, from the view points of handling and reproducibility, alginic type polymers, of which aqueous solution shows lower viscosities, are excellent. Thus, those, of which 1 w/v % aqueous solution shows a viscosity of 300 cp or less at 20° C., are desirable (more desirably 200 cp or less and most desirably 100-150 cp).  
     [0040] The accelerator of the present invention may be a composition. The composition may contain, as additives that do not adversely affect the functions of the alginic type polymers, a pH buffer agent, a salt, bovine serum albumin (BSA), a surfactant, and the like.  
     [0041] The form of the accelerator of the present invention is not limited. One example of the form is a powdery one. If the accelerator has a powdery form, it is usually used by dissolving in an aqueous medium. The aqueous medium may be one that has been usually used in the biochemical field. Examples of it include deionized water and various pH buffers such as phosphate buffers, glycine buffers, Good&#39;s buffers, tris buffers, and ammonium salt buffers. Among them, phosphate buffers, glycine buffers, and Good&#39;s buffers are preferably used.  
     [0042] An accelerator composition of the present invention may have a form of an aqueous solution. The aqueous solution comprises, as essential components, an alginic type polymer and deionized water. It may comprise, in addition to the essential components, at least one member selected from the group consisting of a pH buffer agent, a salt, bovine serum albumin (BSA), and a surfactant. The accelerator composition may be the reagent for biochemical assays (e.g., immunoassays) according to the present invention.  
     [0043] The concentration of the alginic type polymer in the aqueous solution is preferably 0.001-1 w/v % from the view point of solubility and is more preferably 0.05-1w/v % from the view point of convenience in use.  
     [0044] The accelerator of the present invention shows a sufficient effect even if it is used in a small amount. In a liquid where an agglutination reaction would occur, i.e., in a reaction mixture comprising various reagents and a specimen, the final concentration of the alginic type polymer is preferably 0.001-1 w/v %, more preferably 0.01-0.5 w/v %, still more preferably 0.01-0.3 w/v %, and most preferably 0.03-0.1 w/v %. If the concentration is too low, it may be difficult to obtain a sufficient effect about the facilitation of the agglutination reaction. If the concentration is too high, the viscosity may come to be too high, and thus the precision of determination and easiness of handling may be decreased.  
     [0045] 2. Reagent for Biochemical Assays  
     [0046] The reagent for biochemical assays of the present invention comprises at least one member selected from the group consisting of alginic acid and alginates. The reagent may be a diluent for specimens. The reagent may further comprise a compound that can specifically bond to a target to be detected. The compound may be an antibody against an antigen that is a target to be detected or an antigen of an antibody that is a target to be detected. Thus, the reagent of the present invention may be a mixture of a reagent that has been used in, e.g., immunoassays and an alginic type polymer.  
     [0047] In biochemical assays such as immunoassays, various biological liquid sample such as serum and plasma is usually diluted with a liquid. The liquid for dilution is usually an aqueous solution that comprises at least one member selected from the group consisting of a pH buffer agent, a protein such as albumin or globulin, an amino acid, a surfactant and a salt. To prepare the reagent of the present invention, an alginic type polymer may be added to the liquid for dilution. The concentration of the alginic type polymer in the diluent for specimens, i.e., in the reagent of the present invention, is preferably 0.001-1 w/v % from the view point of solubility  
     [0048] Another example of reagents that have been used in immune agglutination methods is a reagent hereafter “agglutination reagent”) comprising a compound that reacts with a target to be detected by an antigen-antibody reaction. The agglutination reagent is usually a liquid comprising an antigen or antibody or a suspension comprising insoluble carriers on which an antigen or antibody is sensitized. To the agglutination reagent an alginic type polymer may be added. Thus, the reagent of the present invention may be prepared.  
     [0049] The target to be detected in immunoassays based on a principle of immune agglutination is an antigen or an antibody. Also, the compound that are contained in the agglutination reagent for immunoassays is an antibody or an antigen.  
     [0050] Examples of the antigen include receptors, enzymes, blood proteins such as carcinoembryonic proteins, and infectious disease-related antigens such as hepatitis B virus, hepatitis C virus, pathogen of syphilis (i.e.,  Treponema palladium ), human immunodeficiency virus, and pathogenic  Escherichia coli.  However, antigens in the present invention are not limited to those listed above. All compounds against which antibodies can be formed are antigens. Thus, in some cases antibodies may play as antigens. Further, as long as an antigenic determinant exists, a fragments, subunits, and compounds having the fragment or subunit may be antigens.  
     [0051] In this specification, the term “antibody” means compounds that bond to or bind with a specific antigen by an immunological reaction. Namely, as long as it can bind with a specific antigen, fragments of antibodies, for example, may also be called as “antibodies.” Examples of the antibodies in the present invention include antibodies against the above-listed antigens. The antibodies may be polyclonal ones or monoclonal ones.  
     [0052] Thus, one example of the agglutination reagents comprises, as an essential component, an antibody when the target to be detected is an antigen or an antigen when the target to be detected is an antibody. Specifically, if the target is an antibody against  Helicobacter pylori , the agglutination reagent comprises an antigen of  Helicobacter pylori.    
     [0053] Other example of the agglutination reagents comprises avidin as an essential component, and is used to detect biotin.  
     [0054] As mentioned above, the agglutination reagent and the reagent for biochemical assays of the present invention may comprise insoluble carriers on which a compound that can specifically bond to a target, e.g., an antigen or antibody, is supported. The insoluble carriers are, in other words, sensitized or coated with the compound. Namely, the compound is immobilized on the carriers. As the carrier, insoluble particles or particulates having a diameter of about 0.1-0.5 micrometer are usually used. Specifically, the insoluble particles or particulates may be erythrocyte, carbon powder, bentonite, kaolin, micelle of lecithin, gelatin particles, polystyrene particles, or the like. Among these insoluble particles or particulates, polystyrene particles, i.e., latex particles, are preferably used. Methods, by which an antigen or antibody is supported on the particulates, have been known by those skilled in the art. Of course, the reagent of the present invention may not comprise insoluble carriers.  
     [0055] The reagent for biochemical assays of the present invention may be one that comprises, as essential components, an alginic type polymer, components that should be contained in a liquid for dilution, and an antigen or antibody that should be contained in an agglutination reagent. This reagent for biochemical assays is one that plays as both a liquid for dilution and an agglutination reagent. When this reagent is used, it is unnecessary to preliminary dilute a specimen. By simply mixing the specimen with this reagent, an adequate agglutination reaction may occur.  
     [0056] 3. Kit for Biochemical Assay  
     [0057] A kit for a biochemical assay is also provided that comprises the reagent for biochemical assays according to the present invention (hereafter “reagent (x)”), and at least one member selected from the group consisting of a reagent (hereafter “reagent (y)”) other than the reagent (x), a container, and an instruction for use.  
     [0058] For example, if the kit comprises a diluent for specimens comprising an alginic type polymer, it may further comprise, as other constitutional elements, a target-positive control sample (for example, this comprises a standard compound for calibration), a target-negative control sample, an agglutination reagent comprising particulate carriers on which an antigen of antibody that is a target to be detected or an antibody against an antigen that is a target to be detected is supported, a reaction container, an instruction for use, etc. In the instruction for use, the amount of a specimen, the amount(s) of the reagent(s), reaction conditions, a method for determination, a method for judging the results, etc. are generally explained.  
     [0059] For example, if the kit comprises an agglutination reagent comprising an alginic type polymer and an antigen or antibody, it may further comprise a liquid for dilution which does not comprise an alginic type polymer. If the kit comprises an agglutination reagent comprising an alginic type polymer, components that should be contained in a liquid for dilution, and particulate carriers on which an antigen or antibody is supported, it may further comprise only an instruction for use.  
     [0060] 4. Biochemical Assay Method  
     [0061] The biochemical assay method of the present invention comprises a step of bringing a compound that can specifically bond to a target to be detected into contact with a specimen that may contain the target in the presence of at least one member selected from the group consisting of alginic acid and alginates and a step of determining the amount of agglutinations that have been made by the specific reaction between the compound and the target. When the specific reaction is an antigen-antibody reaction, (1) the compound may be an antibody and the target may be an antigen of the antibody or (2) the compound may be an antigen and the target may be an antibody against the antigen.  
     [0062] In the step for reaction, an agglutination reagent, an alginic type polymer, and a specimen should coexist in a liquid. However, the method by which the liquid is prepared, in other words, the order of the addition or mixing of them, is not limited. Thus, they may be mixed at one time. Or, before the reaction step, the agglutination reagent and the alginic type polymer, the agglutination reagent and the specimen, or the alginic type polymer and the specimen may be mixed. Specifically, for example, a specimen is diluted with a diluent for specimens comprising an alginic type polymer, and then to the diluted specimen thus prepared, an agglutination reagent is added. Or, a suspension comprising an alginic type polymer and an agglutination reagent is prepared, and then to the suspension, an specimen is added.  
     [0063] The reaction temperature is not limited. However, it is in the range of generally 4-50° C., preferably 15-40° C., and more preferably 30-40° C. If the temperature is extremely low, occasions to collide antigens with antibodies may decrease. Also, occasions to collide antigen- or antibody-sensitized particles may decrease. If the temperature is extremely high, the stability of the immune complex comprising an antigen and an antibody against it may decrease.  
     [0064] The reaction time is not limited. However, it is in the range of generally 0-60 minutes, and preferably 1-30 minutes. If the reaction time is extremely short, the immune complex may be insufficiently formed, especially in the case where the concentration of the target to be detected is low in the reaction mixture. If the reaction time is extremely long, the stability of the immune complex may decrease. The step for reaction and the step for determination may overlap.  
     [0065] It is preferable that the reaction is conducted in a buffer solution which is commonly used in the biochemical field. The pH of the reaction mixture is in the range of generally 5-10, and preferably 6-9 from the view point of the stability of the immune complex.  
     [0066] In the step for determination, whether agglutination has been formed may be judged with the naked eye. However, from the view point of the unity of the judgment and to treat a large number of specimens, it is preferable to determine the degree or amount of agglutinations by using an optical determination instrument. The instrument may be one that is based on the principle of nephelometry or one that is based on the principle of turbidimetry.  
     [0067] 5. Use of Alginic Type Polymer as Accelerator for Agglutination Reactions  
     [0068] The alginic type polymer is used to facilitate agglutination reactions. Specifically, in a reaction mixture for an immune agglutination reaction, the alginic type polymer is used. Because of the presence of it, the immune agglutination reaction is facilitated and the sensitivity of the reaction is enhanced. Methods for using the alginic type polymer in various agglutination reactions have been already explained in this specification.  
     [0069] According to the present invention, an accelerator for agglutination reactions can be provided that is suitable to use in various agglutination determination systems (e.g., immune agglutination determination systems), shows a strong accelerative function to agglutination reactions, does not tend to increase the viscosity of its aqueous solution, shows good reproducibility and precision in the determination results, and can be readily handled. By using the accelerator of the present invention, a high sensitivity and a determination or quantitative analysis in a wide range can be realized especially in latex agglutination determination systems.  
     [0070] Further, according to the method of the present invention, the viscosities of reaction mixtures do not tend to increase, and based on agglutination reactions, results of biochemical assays that show good reproducibility and precision can be readily obtained  
     EXAMPLES  
     Example 1  
     [0071] Test about Function to Facilitate Immune Agglutination  
     [0072] 1. Preparation of Diluents for Specimens  
     [0073] By dissolving sodium dihydrogenphosphate and disodium hydrogenphosphate in deionized water, a phosphate buffer (pH7.4) having a total concentration of phosphates of 0.1M was prepared. Then, by dissolving bovine serum albumin (BSA) in the phosphate buffer in an amount that the concentration of BSA comes to 1 w/v %, 1% BSA/phosphate buffer hereafter “1% BSA-PB”) was prepared. The 1% BSA-PB was also called as a diluent for specimens comprising no accelerator (hereafter “diluent No. 0 for specimens”). To diluent No. 0 for specimens, sodium alginate (grade: 300-400 cp; Wako Pure Chemical Industries, Ltd; viscosity: 300-400 cp [1 w/v %, at 20° C.]) was added in an amount that the concentration of sodium alginate comes to 0.080 w/v %. Thus, a diluent for specimens comprising an accelerator of the present invention Hereafter “diluent No. 1 for specimens”) was prepared. Further, diluent Nos. 2-10 for specimens, which respectively comprised accelerators listed in Table 1 in amounts listed in Table 1, were prepared in the same way.  
                               TABLE 1                                   Conc.   Final                   of   conc.                   accelerator   of                   in   accelerator                   diluent   in                   for   reaction               Manu-   specimens   mixture       No.   Accelerator   facturer   (w/v)   (w/v)                                                    1   sodium alginate   Wako Pure   0.080%   0.067%           300˜400 cp   Chemical               Industries,               Ltd.       2   polyvinylpyrrolidone K-90   Junsei   0.700%   0.583%           (M.W. = 1,200,000)   Chemical               Co., Ltd.       3   pectin   Wako Pure   0.250%   0.208%               Chemical               Industries,               Ltd.       4   hydroxyethyl cellulose   Wako Pure   0.230%   0.192%           1000˜4000 cp   Chemical               Industries,               Ltd.       5   propylene glycol   Wako Pure   0.150%   0.125%           alginate   Chemical               Industries,               Ltd.       6   FICOLL* (Approx. Mol.   SIGMA   5.000%   4.167%           Wt.: 400,000) Type 400       7   poly(vinylsulfuric acid   Nacalai   1.150%   0.958%           potassium salt)   Tesque, Inc.       8   polyacrylic acid 250,000   Wako Pure   0.220%   0.183%               Chemical               Industries,               Ltd.       9   carboxymethyl cellulose   Wako Pure   0.140%   0.117%           sodium salt   Chemical               Industries,               Ltd.       10   polyethylene glycol   Wako Pure   0.375%   0.313%           500,000   Chemical           (M.W. = 300,000˜500,000)   Industries,               Ltd.                          
 
     [0074] 2. Test Method  
     [0075] By using diluent Nos. 0-10 for specimens, accelerative functions for forming agglutinations of the accelerators listed in Table 1 were examined in a determination system for an antibody against a syphilis surface antigen.  
     [0076] Specifically, first, 20 microliter of one of specimens (syphilis-negative simulated serum having a concentration of 0 T.U.* and syphilis-positive standard serums having concentrations of 39, 121, 237, and 405 T.U.*; Sekisui Chemical Co., Ltd.) and 350 microliter of one of diluent Nos. 0-10 for specimens were mixed to each other. After 315.5 seconds, 50 microliter of an agglutination reagent in the form of a suspension comprising latex carrier particles on which a syphilis surface antigen had been sensitized (Mediace TPLA latex suspension; Sekisui Chemical Co., Ltd.) was added to prepare a reaction mixture 79.7 seconds after the agglutination reagent was added, the absorbance (1st absorbance) of the reaction mixture was determined at a wavelength of 700 nm by using a biochemical automatic analyzer (type 7080; Hitachi, Ltd.). Also, 274.5 seconds after the agglutination reagent was added, the absorbance (2nd absorbance) of the reaction mixture was determined in the same way. The difference between the 1st absorbance and the 2nd absorbance was calculated and identified as absorbance of a specimen.  
     [0077] From the results of the determinations, for each accelerator the relationship between the concentrations of antibody (X axis) and the determined values (Y axis) was analyzed. The results are shown in Table 2 and FIG. 1. In the column of “blank” in Table 2, the 2nd absorbance of the reaction mixtures containing syphilis-negative simulated serum (0 T.U) was listed.  
                           TABLE 2                                      ΔAbs. × 10000                             Conc. of antibody against syphilis surface antigen           in standard serum (Unit: T.U.)                                                 No.   Accelerator   n   Blank   0   39   121   237   405                                                         0   none   1   10874   −42   −34   13   85   198               2   10905   −59   −11   76   95   195               average   10890   −51   −23   45   90   197       1   sodium alginate   1   11619   −43   400   1730   2899   3484               2   11407   −52   419   1733   2935   3504               average   11513   −48   410   1732   2917   3494       2   polyvinylpyrrolidone   1   11427   −10   298   1195   2058   2697               2   11390   −20   318   1192   2081   2683               average   11409   −15   308   1194   2070   2690       3   pectin   1   11882   −36   379   1544   2612   3209               2   11760   −16   385   1549   2616   3228               average   11821   −26   382   1547   2614   3219       4   hydroxyethyl   1   11409   −32   319   1449   2532   3180           cellulose   2   11464   −21   333   1455   2562   3175               average   11437   −27   326   1452   2547   3178       5   propylene glycol   1   11433   4   430   1749   2866   3402           alginate   2   11456   −11   411   1757   2842   3398               average   11445   −4   421   1753   2854   3400       6   FICOLL*   1   10949   −43   112   473   908   1330               2   10933   −52   93   448   900   1331               average   10941   −48   103   461   904   1331       7   poly(vinylsulfuric   1   11433   −18   484   1655   2322   2462           acid potassium salt)   2   11362   −112   482   1646   2187   2388               average   11398   −65   483   1651   2255   2425       8   polyacrylic acid   1   10013   −25   295   1135   1810   2308           250,000   2   10254   −50   312   1166   1925   2438               average   10134   −38   304   1151   1868   2373       9   carboxymethyl   1   10351   −11   358   1499   2483   3064           cellulose sodium salt   2   10284   −26   377   1522   2521   3116               average   10318   −19   368   1511   2502   3090       10   polyethylene glycol   1   10608   −23   520   1696   2470   2914           500,000   2   10769   −31   511   1687   2452   2967               average   10689   −27   516   1691   2461   2941                          
 
     [0078] As is apparent from the results, as compared with the case where no accelerator was used (diluent No. 0 for specimens), accelerator Nos. 1-10 had functions to facilitate immune agglutination. However, FICOLL exhibited only a poor effect as compared with other accelerators. Poly(vinylsulfuric acid potassium salt) and polyacrylic acid exhibited low effects in a region where the concentration of the antibody against a syphilis surface antigen was high.  
     [0079] Sodium alginate and propylene glycol alginate, which were accelerators of the present invention, exhibited high effects in the accelerative function throughout the entire regions (i.e., from a low concentration region to a high concentration region). Further, although they were used in extremely low concentrations, they exhibited effects that were equivalent to or higher than those of other accelerators.  
     Example 2  
     [0080] Study of Concentrations of Sodium Alginate in Diluent for Specimens and in Reaction Mixture  
     [0081] In the same way as described in Example 1, 1% BSA-PB was prepared. By using this, diluent Nos. 1-6 for specimens listed in Table 3 were prepared. Table 3 also discloses the names of the accelerators and their concentrations.  
     [0082] By using diluent Nos. 1-6 for specimens, an antibody against a syphilis surface antigen was determined in the same way as described in Example 1.  
     [0083] From the results of the determinations, for each accelerator the relationship between the concentrations of antibody (X axis) and the determined values (Y axis) was analyzed. The results are shown in Table 4 and FIG. 2.  
                               TABLE 3                                   Conc.   Final                   of   conc.                   accelerator   of                   in   accelerator                   diluent   in                   for   reaction               Manu-   specimens   mixture       No.   Accelerator   facturer   (w/v)   (w/v)                                                    1˜4   sodium alginate   Wako Pure   0.05˜   0.042˜           300˜400 cp   Chemical   0.1%   0.083%               Industries,               Ltd.       5   polyvinylpyrrolidone K-90   Junsei   0.700%   0.583%           (M.W. = 1,200,000)   Chemical               Co., Ltd.       6   polyethylene glycol   Wako Pure   0.375%   0.313%           500,000   Chemical           (M.W. = 300,000˜500,000)   Industries,               Ltd.                  
 
     [0084]                           TABLE 4                                      ΔAbs. × 10000                                                 Conc. of accelerator           Conc. of antibody against syphilis               in diluent for           surface antigen in standard serum (Unit: T.U.)                                                     No.   Accelerator   specimens (w/v)   n   Blank   0   39   121   237   405                                                             1   sodium alginate   0.10%   1   11496   −56   1031   3246   3866   3902           300˜400 cp       2   11483   −54   1092   3207   3908   3837                   average   11490   −55   1062   3227   3887   3870       2       0.08%   1   11619   −43   400   1730   2899   3484                   2   11407   −52   419   1733   2935   3504                   average   11513   −48   410   1732   2917   3494       3       0.07%   1   11499   −46   341   1452   2622   3339                   2   11427   −46   334   1457   2607   3309                   average   11463   −46   338   1455   2615   3324       4       0.05%   1   11542   −44   101   491   1051   1748                   2   11383   −42   87   480   1017   1777                   average   11463   −43   94   486   1034   1763       5   polyvinylpyrrolidone   0.70%   1   11427   −10   298   1195   2058   2697                   2   11390   −20   318   1192   2081   2683                   average   11409   −15   308   1194   2070   2690       6   polyethylene glycol   0.375%   1   10608   −23   520   1696   2470   2914           500,000       2   10769   −31   511   1687   2452   2967                   average   10689   −27   516   1691   2461   2941                    
     [0085] As the concentration of sodium alginate increased, the reactivity of the immunoreaction, i.e., the accelerative function, was enhanced. However, when the concentration of sodium alginate in the diluent for specimens was 0.1 w/v %, in a region where the concentration of the antibody was high, the determined values were invariable Namely, a region where the relationship between the concentrations of antibody (X axis) and the determined values (Y axis) was linear was narrow.  
     Example 3  
     [0086] Test of Storage Stability  
     [0087] In the same way as described in Example 1, 1% BSA-PB was prepared. By using this, diluent Nos. 1-8 for specimens listed in Table 5 were prepared. Table 5 also discloses the names of the accelerators and their concentrations.  
     [0088] Diluent Nos. 1-8 for specimens were stored at 40° C. for one day or seven days. By using three kinds (i.e., the periods of storage were zero, one day, and seven days) of diluent Nos. 1-8 for specimens, an antibody against a syphilis surface antigen was determined in the same way as described in Example 1.  
     [0089] From the results of the determinations, for each accelerator the relationship between the concentrations of antibody and the determined values was analyzed Also, for each accelerator the influence of storage at 40° C. was analyzed. The results are shown in Table 6.  
     [0090] In Table 6, the differential rate (%) in the column of“Blank” was calculated as follows:  
     differential rate (%)=[(average of the values determined by using the diluent for specimens that was stored one or seven days)/(average of the values determined by using the diluent for specimens that was not stored)]×100  
     [0091] The differential rate (%) in the column of “Conc. of antibody against syphilis surface antigen in standard serum” was calculated as follows:  
     differential rate (%)={[(average of the values determined by using the diluent for specimens that was stored one or seven days)/(average of the values determined by using the diluent for specimens that was not stored)]×100}−100  
     [0092]                               TABLE 5                                   Conc.   Final                   of   conc.                   accelerator   of                   in   accelerator                   diluent   in                   for   reaction               Manu-   specimens   mixture       No.   Accelerator   facturer   (w/v)   (w/v)                  1   sodium alginate   Wako Pure   0.080%   0.067%           300˜400 cp   Chemical               Industries,               Ltd.       2   polyvinylpyrrolidone K-90   Junsei   0.700%   0.583%           (M.W. = 1,200,000)   Chemical               Co., Ltd.       3   pectin   Wako Pure   0.250%   0.208%               Chemical               Industries,               Ltd.       4   hydroxyethyl cellulose   Wako Pure   0.230%   0.192%           1000˜4000 cp   Chemical               Industries,               Ltd.       5   propylene glycol   Wako Pure   0.150%   0.125%           alginate   Chemical               Industries,               Ltd.       6   polyacrylic acid 250,000   Wako Pure   0.220%   0.183%               Chemical               Industries,               Ltd.       7   carboxymethyl cellulose   Wako Pure   0.140%   0.117%           sodium salt   Chemical               Industries,               Ltd.       8   polyethylene glycol   Wako Pure   0.375%   0.313%           500,000   Chemical           (M.W. = 300,000˜500,000)   Industries,               Ltd.                    
     [0093]                           TABLE 6                                      ΔAbs. × 10000                                                             Conc. of antibody against syphilis surface               Conc. of   Number of days       antigen in standard serum (Unit: T.U.)                                                     No.   Accelerator   accelerator   stored   Blank   0   39   121   237   405                                                             1   sodium   0.080%   0   11456   −22   262   1281   2347   3083           alginate           11421   −16   269   1264   2338   3085                   average   11439   −19   266   1273   2343   3084                   1   11528   −12   295   1234   2430   3117                       11535   −20   313   1344   2386   3118                   average   11532   −16   304   1289   2408   3118                   differential rate (%)   100.8   —   14.5   1.3   2.8   1.1                   7   11450   17   300   1327   2480   3116                       11533   23   288   1380   2361   3095                   average   11492   20   294   1354   2421   3106                   differential rate (%)   100.5   —   10.7   6.4   3.3   0.7       2   polyvinyl-   0.700%   0   11427   −10   298   1195   2058   2697           pyrrolidone           11390   −20   318   1192   2081   2683                   average   11409   −15   308   1194   2070   2690                   1   11508   −9   312   1218   2089   2720                       11529   −9   321   1213   2116   2726                   average   11519   −9   317   1216   2103   2723                   differential rate (%)   101.0   —   2.8   1.8   1.6   1.2                   7   11419   −10   328   1260   2165   2739                       11461   −2   331   1260   2157   2787                   average   11440   −6   330   1260   2161   2763                   differential rate (%)   100.3   —   7.0   5.6   4.4   2.7       3   pectin   0.250%   0   11777   −3   413   1629   2652   3225                       11766   −19   381   1581   2694   3207                   average   11772   −11   397   1605   2673   3216                   1   11786   −21   288   1137   2069   2825                       11776   −26   276   1112   2088   2813                   average   11781   −24   282   1125   2079   2819                   differential rate (%)   100.1   —   −29.0   −29.9   −22.2   −12.3                   7   11740   −17   82   376   821   1381                       11725   −32   87   395   831   1367                   average   11733   −25   85   386   826   1374                   differential rate (%)   99.7   —   −78.7   −76.0   −69.1   −57.3       4   hydroxyethyl   0.230%   0   11409   −32   319   1449   2532   3180           cellulose           11464   −21   333   1455   2562   3175                   average   11437   −27   326   1452   2547   3178                   1   11552   −7   358   1384   2465   3147                       11476   −5   344   1391   2476   3170                   average   11514   −6   351   1388   2471   3159                   differential rate (%)   100.7   —   7.7   −4.4   −3.0   −0.6                   7   11474   −29   253   1026   1911   2680                       11486   −12   242   1000   1929   2718                   average   11480   −21   248   1013   1920   2699                   differential rate %   100.4   —   −24.1   −30.2   −24.6   −15.1       5   propylene   0.150%   0   11562   −16   262   1163   2212   2996           glycol           11615   −6   231   1158   2177   3029           alginate       average   11589   −11   247   1161   2195   3013                   1   11594   −38   95   415   884   1447                       11423   −43   81   401   847   1440                   average   11509   −41   88   408   866   1444                   differential rate (%)   99.3   —   −64.3   −64.8   −60.6   −52.1       6   polyacrylic   0.22%   0   10013   −25   295   1135   1810   2308           acid 250,000           10254   −50   312   1166   1925   2438                   average   10134   −38   304   1151   1868   2373                   7   10110   10   299   1091   1861   2290                       9969   −6   306   1098   1862   2348                   average   10040   2   303   1095   1862   2319                   differential rate (%)   99.1   —   −0.3   −4.9   −0.3   −2.3       7   carboxy-   0.14%   0   11228   −35   483   1869   2965   3620           methyl           11186   −10   433   1900   3011   3536           cellulose       average   11207   −23   458   1885   2988   3578           sodium salt       1   11267   −22   420   1566   2781   3323                       11347   −4   423   1541   2646   3362                   average   11307   −13   422   1554   2714   3343                   differential rate (%)   100.9   —   −8.0   −17.6   −9.2   −6.6                   7   9564   −31   238   998   1916   2621                       10148   −43   246   978   1907   2509                   average   9856   −37   242   988   1912   2565                   differential rate (%)   87.9   —   −47.2   −47.6   −36.0   −28.3       8   polyethylene   0.375%   0   10344   3   399   1384   2153   2504           glycol           10304   −11   402   1382   2086   2687           50000       average   10324   −4   401   1383   2120   2596                   1   10340   −6   369   1262   1988   2616                       10425   −15   350   1251   2022   2568                   average   10383   −11   359   1257   2005   2592                   differential rate (%)   100.6   —   −10.3   −9.1   −5.4   −0.1                   7   10119   −40   245   975   1691   2181                       10247   −19   291   961   1765   2293                   average   10183   −30   268   968   1728   2237                   differential rate (%)   98.6   —   −33.2   −30.0   −18.5   −13.8                    
     [0094] The diluent for specimens comprising sodium alginate, polyacrylic acid, or polyvinylpyrrolidone was stable after it had been stored at 40° C. for seven days. Namely, its function for facilitating immune agglutination reactions was not decreased. About accelerators other than sodium alginate, polyacrylic acid, and polyvinylpyrrolidone, their functions for facilitating immune agglutination reactions were decreased by storing at 40° C.  
     Example 4  
     [0095] Comparison of Reproducibility  
     [0096] In the same way as described in Example 1, 1% BSA-PB was prepared. By using this, diluent Nos. 1-5 for specimens listed in Table 7 were prepared. Table 7 also discloses the names of the accelerators and their concentrations.  
     [0097] By using diluent Nos. 1-5 for specimens, syphilis-negative simulated serum, and syphilis-positive standard serums, an antibody against a syphilis surface antigen was determined in the same way as described in Example 1. From the results of the determinations, for each accelerator the relationship between the concentrations of antibody and the determined values was analyzed, namely, a calibration curve was made. Then, by using each of diluent Nos. 1-5 for specimens, the concentration of syphilis-antibody in a syphilis-positive serum having a concentration of about 18.6 T.U. as a specimen was determined for ten times. From the results of the determinations, average values, standard deviations, coefficients of variation (CV values), and the like were calculated.  
     [0098] The results are shown in Table 8.  
                               TABLE 7                                   Conc.   Final                   of   conc.                   accelerator   of                   in   accelerator                   diluent   in                   for   reaction               Manu-   specimens   mixture       No.   Accelerator   facturer   (w/v)   (w/v)                  1   sodium alginate   Wako Pure   0.080%   0.067%           300˜400 cp   Chemical               Industries,               Ltd.       2   polyvinylpyrrolidone K-90   Junsei   0.700%   0.583%           (M.W. = 1,200,000)   Chemical               Co., Ltd.       3   polyacrylic acid 250,000   Wako Pure   0.220%   0.183%               Chemical               Industries,               Ltd.       4   carboxymethyl cellulose   Wako Pure   0.140%   0.117%           sodium salt   Chemical               Industries,               Ltd.       5   polyethylene glycol   Wako Pure   0.375%   0.313%           500,000   Chemical           (M.W. = 300,000˜500,000)   Industries,               Ltd.                  
 
     [0099]                                   TABLE 8                                       carboxymethyl cellulose               sodium alginate   polyvinylpyrrolidone   polyacrylic acid   sodium salt   polyethylene glycol       n   0.080%   0.700%   0.220%   0.140%   0.375%                                                        1   20.0   19.8   24.9   14.5   16.9       2   19.0   18.0   18.8   14.0   16.8       3   20.1   18.0   17.4   15.4   18.5       4   21.6   19.2   16.4   13.1   17.8       5   19.9   21.1   17.1   14.2   15.5       6   20.3   21.2   20.0   15.3   18.6       7   20.3   19.2   18.2   16.0   17.1       8   20.2   17.6   17.7   15.8   19.2       9   19.3   20.2   18.3   15.9   19.7       10   19.4   19.8   20.6   16.2   18.6       average   20.0   19.4   18.9   15.0   17.9       standard deviation (S.D.)   0.7   1.3   2.5   1.0   1.3       coefficient of variation (CV(%))   3.6%   6.5%   12.9%   6.9%   7.2%       average + S.D.   20.7   20.7   21.4   16.1   19.2       average − S.D.   19.3   18.1   16.5   14.0   16.6       maximun value   21.6   21.2   24.9   16.2   19.7       minimun value   19.0   17.6   16.4   13.1   15.5       max. − min.   2.6   3.6   8.5   3.1   4.2                    
     [0100] From the results shown in Table 8, it was understood that sodium alginate showed a less CV value than those of other accelerators. Namely, sodium alginate showed good reproducibility.  
     Example 5  
     [0101] Measurement of Viscosity  
     [0102] In the same way as described in Example 1, 1% BSA-PB was prepared. By using this, diluent Nos. 1-5 for specimens listed in Table 9 were prepared. Table 9 also discloses the names of the accelerators and their concentrations.  
     [0103] The viscosities of diluent Nos. 1-5 for specimens were measured at a room temperature (about 24° C.) by using an Ostwald viscometer (relative viscometer; TOP-K-11212-18; Sogo Rikagaku Glass Seisakusho). Specifically, 5 milliter of a sample (a diluent for specimens) having a temperature of 24° C. was injected into an inside of the Ostwald viscometer by using a pipet. This sample was sucked up from one end of a tube of the Ostwald viscometer to a certain height and then flowed down by itself. The time (seconds) that was required to flow down in a definite interval of the tube was measured.  
     [0104] The results are shown in Table 10.  
                               TABLE 9                                   Conc.   Final                   of   conc.                   accelerator   of                   in   accelerator                   diluent   in                   for   reaction               Manu-   specimens   mixture       No.   Accelerator   facturer   (w/v)   (w/v)                  1   sodium alginate   Wako Pure   0.080%   0.067%           300˜400 cp   Chemical               Industries,               Ltd.       2   polyvinylpyrrolidone K-90   Junsei   0.700%   0.583%           (M.W. = 1,200,000)   Chemical               Co., Ltd.       3   polyacrylic acid 250,000   Wako Pure   0.220%   0.183%               Chemical               Industries,               Ltd.       4   carboxymethyl cellulose   Wako Pure   0.140%   0.117%           sodium salt   Chemical               Industries,               Ltd.       5   polyethylene glycol   Wako Pure   0.375%   0.313%           500,000   Chemical           (M.W. = 300,000˜500,000)   Industries,               Ltd.                  
 
     [0105]                               TABLE 10                           Conc. of                       accelerator           in diluent           for specimens       Time required for       Accelerator   (w/v)   n   dropping (sec.)   Average                                                    sodium alginate   0.080%   1   375.0   375               2   375.0       polyvinylpyrrolidone   0.700%   1   394.0   395               2   395.0       polyacrylic acid   0.220%   1   619   618               2   617       carboxymethyl   0.140%   1   374   376       cellulose       2   377       sodium salt       polyethylene glycol   0.375%   1   404   405               2   405                    
     [0106] The diluent for specimens comprising sodium alginate or carboxymethyl cellulose sodium salt in a concentration that can show accelerative function for forming agglutinations had a lower viscosity than other diluents for specimens comprising accelerators in concentrations that can show accelerative function for forming agglutinations. Thus, the diluent for specimens comprising sodium alginate and the diluent for specimens comprising carboxymethyl cellulose sodium salt were preferable.  
     Example 6  
     [0107] Comparison among Sodium Alginates of Different Grades  
     [0108] In the same way as described in Example 1, 1% BSA-PB was prepared. By using this, diluent Nos. 1-4 for specimens listed in Table 11 were prepared. Table 11 also discloses the names and the grades (i.e., types) of the accelerators, and their concentrations.  
     [0109] In the same way as described in Example 5, the viscosities of diluent Nos. 1-4 for specimens were measured.  
     [0110] In the same way as described in Example 4, for each accelerator the relationship between the concentrations of antibody and the determined values was analyzed, namely, a calibration curve was made. Then, the concentration of syphilis-antibody in a syphilis-positive serum having a concentration of about 18.6 T.U. as a specimen was determined for ten times. From the results of the determinations, average values, standard deviations, coefficients of variation (CV values), and the like were calculated.  
     [0111] The results are shown in Tables 12-14.  
                                   TABLE 11                                       Conc. of accelerator in diluent   Final conc. of accelerator in       No.   Accelerator   Type*   Manufacturer   for specimens (w/v)   reaction mixture (w/v)                  1   polyvinylpyrrolidone K-90       Junsei Chemical Co., Ltd.   0.700%   0.583%           (M.W. = 1,200,000)       2   sodium alginate   100˜150 cp   Wako Pure Chemical Industries, Ltd.   0.090%   0.075%       3   sodium alginate   300˜400 cp   Wako Pure Chemical Industries, Ltd.   0.080%   0.067%       4   sodium alginate   500˜600 cp   Wako Pure Chemical Industries, Ltd.   0.075%   0.063%                          
 
     [0112]                           TABLE 12                          Accelerator                   Type       sodium alginate                                     Conc. of accelerator in diluent   PVP   100˜150 cp   200˜400 cp   500˜600 cp           for specimens (w/v)   0.70%   0.09%   0.08%   0.075%                                                 n   1   394.0   345.0   375.0   406.0               2   395.0   347.0   375.0   407.0                                     average   394.5   346.0   375.0   406.5   Unit: sec.                    
     [0113]                           TABLE 13                                      ΔAbs. × 10000                                                             Conc. of antibody against syphilis surface               Conc. of accelerator in           antigen in standard serum (Unit: T.U.)                                                     Accelerator   Type   diluent for specimens (w/v)   n   Blank   0   39   121   237   405                                                             PVP       0.70%   1   10607   −7   384   1456   2402   2938                   2   10828   −12   361   1504   2449   2986                   average   10718   −10   373   1480   2426   2962       sodium   100˜150 cp   0.09%   1   10881   −21   352   1541   2631   3363       alginate           2   10879   −8   369   1521   2620   3356                   average   10880   −15   361   1531   2626   3360           300˜400 cp   0.08%   1   10730   −29   377   1574   2800   3444                   2   10702   −13   388   1570   2707   3459                   average   10716   −21   383   1572   2754   3452           500˜600 cp   0.075%   1   10798   −14   382   1613   2730   3431                   2   10658   −30   388   1533   2750   3506                   average   10728   −22   385   1573   2740   3469                    
     [0114]                           TABLE 14                                      Unit: T.U.                             Accelerator               Type       sodium alginate                                 Conc. of accelerator in diluent for   PVP   100˜150 cp   300˜400 cp   500˜600 cp       specimens(w/v)   0.70%   0.09%   0.08%   0.075%                                             n   1   18.9   15.2   17.2   19.4           2   18.4   17.0   16.4   17.3           3   16.9   17.2   14.0   17.6           4   15.5   16.4   18.0   15.2           5   17.5   16.7   18.0   16.4           6   19.9   16.8   18.0   19.0           7   18.5   17.0   15.7   17.3           8   17.8   17.4   16.5   15.0           9   16.9   16.6   16.0   14.8           10    17.8   16.6   17.1   17.2                                 average   17.8   16.7   16.7   16.9       standard deviation (S.D.)   1.2   0.6   1.3   1.6       coefficient of variation (CV(%))   6.9%   3.6%   7.6%   9.4%       average + S.D.   19.0   17.3   18.0   18.5       average − S.D.   16.6   16.1   15.4   15.3       maximun value   19.9   17.4   18.0   19.4       minimun value   15.5   15.2   14.0   14.8       max. − min.   4.4   2.2   4.0   4.6                    
     [0115] All grades of sodium alginate tested showed sufficient functions for facilitating immune agglutination reactions. Among them sodium alginate of type 100-150 cp had the lowest viscosity and the best reproducibility, and thus it was especially preferable.  
     Example 7  
     [0116] Effect in Determination System for HBs Antigen  
     [0117] In the same way as described in Example 1, 1% BSA-PB was prepared. By using this, diluent Nos. 1-8 for specimens listed in Table 15 were prepared. Table 15 also discloses the names of the accelerators and their concentrations.  
     [0118] Diluent Nos. 1-8 for specimens were examined about their accelerative functions in a determination system for an HBs antigen, i.e., a hepatitis B surface antigen.  
     [0119] Specifically, first, 20 microliter of one of specimens (i.e., a solution comprising no HBs antigen standard compound, and solutions comprising an HBs antigen standard compound at concentrations of 9.6, 48.2, 96.4, and 482.2 IU/ml; Kyokuto Pharmaceutical Industrial Co., Ltd) and 140 microliter of one of diluent Nos. 1-8 for specimens were mixed to each other. After 315.5 seconds, 140 microliter of an agglutination reagent in the form of a suspension comprising latex carrier particles on which an HBs antibody had been sensitized (Lanpia latex HBs antibody latex suspension; Kyokuto Pharmaceutical Industrial Co., Ltd.) was added to prepare reaction mixtures. 79.7 seconds after the agglutination reagent was added, the absorbance (1st absorbance) of the reaction mixture was determined at a wavelength of 800 nm by using a biochemical automatic analyzer (type 7080; Hitachi, Ltd). Also, 274.5 seconds after the agglutination reagent was added, the absorbance (2nd absorbance) of the reaction mixture was determined in the same way. The difference between the 1st absorbance and the 2nd absorbance was calculated and identified as absorbance of a specimen.  
     [0120] From the results of the determinations, for each accelerator the relationship between the concentrations of antigen and the determined values was analyzed. The results are shown in Table 16. In the column of “blank” in Table 16, the 2nd absorbance of the reaction mixtures containing the solution comprising no HBs antigen standard compound was listed.  
                               TABLE 15                                   Conc.   Final                   of   conc.                   accelerator   of                   in   accelerator                   diluent   in                   for   reaction               Manu-   specimens   mixture       No.   Accelerator   facturer   (w/v)   (w/v)                                                    1˜6   sodium alginate   Wako Pure   0.1˜   0.047˜           300˜400 cp   Chemical   0.2%   0.093%               Industries,               Ltd.       7   polyvinylpyrrolidone K-90   Junsei   1.200%   0.560%           (M.W. = 1,200,000)   Chemical               Co., Ltd.       8   polyethylene glycol   Wako Pure   2.000%   0.93%           6000   Chemical               Industries,               Ltd.                  
 
     [0121]                           TABLE 16                                      ΔAbs. × 10000                                                             Conc. of HBs antigen in               Conc. of accelerator in           standard solution (Unit: IU/ml)                                                     No.   Accelerator   diluent for specimens (w/v)   n   Blank   0.0   9.6   48.2   96.4   482.2                                                             1   sodium alginate   0.20%   1   18540   151   302   932   1769   5514           300˜400 cp       2   18574   175   294   934   1748   5504                   average   18557   163   298   933   1759   5509       2       0.18%   1   18266   20   88   527   1119   4830                   2   18273   6   110   499   1118   4838                   average   18270   13   99   513   1119   4834       3       0.16%   1   18138   −47   15   362   772   3996                   2   18148   −48   57   320   785   4011                   average   18143   −48   36   341   779   4004       4       0.14%   1   18089   −28   49   289   606   3146                   2   18084   −12   26   286   594   3154                   average   18087   −20   38   288   600   3150       5       0.12%   1   18096   −6   47   228   470   2379                   2   18133   −13   37   214   471   2407                   average   18115   −10   42   221   471   2393       6       0.10%   1   18019   −14   28   179   356   1760                   2   18094   −4   46   175   339   1748                   average   18057   −9   37   177   348   1754       7   polyvinylpyrrolidone K-90   1.20%   1   18778   57   102   512   1042   4534           (M.W. = 1,200,000)       2   18637   42   120   483   1055   4555                   average   18708   50   111   498   1049   4545       8   polyethylene glycol 6000   2.00%   1   17550   −9   19   125   312   665                   2   17268   −9   25   170   309   686                   average   17409   −9   23   153   323   701                    
     [0122] Also in this determination system, sodium alginate showed an excellent function for facilitating immune agglutination reactions. The sensitivity of the immune agglutination reaction was enhanced as the concentration of sodium alginate became higher.  
     [0123] This specification involves the above explanations and the entire description of Japanese Patent Application No. 2002-98989 by reference. However, the present invention is defined or limited only by the following claims.