Abstract:
A method of making a fluid sample collection card includes providing a support layer, forming an upper layer with a card stock, the upper layer including a sample window and a viewing window, supporting an absorbent layer with the support layer, and positioning the upper layer on the absorbent layer, wherein the upper layer is configured such that as a fluid is being absorbed by the first absorbent layer portion, presence of a portion of the fluid within the second absorbent layer portion indicates that a first volume of the fluid absorbed by the absorbent layer is a minimum necessary volume of the fluid sufficient to perform at least one test on at least one component in the fluid.

Description:
[0001]    This application is a divisional of co-pending prior application Ser. No. 12/120,972, filed on May 15, 2008, which claims the benefit of U.S. Provisional Application No. 60/930,526, filed May 17, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to collection and separation of biological fluids. More particularly the invention relates to fluid sample collection devices used for collection and separation of fluids such as blood. 
       BACKGROUND 
       [0003]    Biological samples are frequently used in laboratory and clinical settings to analyze various components in the samples. The biological samples include blood samples, sputum samples, and urine samples. Such samples, for example, are used to determine the levels or concentrations of various components such as HDL, LDL, Cholesterol, hemoglobin, detection of genes using DNA or RNA along with detection of HIV antibodies, or concentrations of drugs. 
         [0004]    The biological sample is frequently processed in a liquid form. Accordingly, the liquid sample is collected, handled by the collection facility, transported to a laboratory, and stored pending processing. Activities surrounding a liquid blood sample present various problems including the risk of container breakage or leakage which causes loss of sample and the danger of infection, sample instability during shipment and storage, transport carrier restrictions related to transport of liquid biohazard materials, and collection of significantly more sample than is necessary for testing so as to ensure sufficient sample quantity is available for common methods of serum or plasma preparation and subsequent analysis. Thus, collection of several vials of fluid such as blood from a patient is not uncommon. 
         [0005]    In response to the shortcomings of liquid sample collection, transport, and processing, various dried sample devices and methods have emerged. In dried sample devices, a biological sample is collected in the form of a drop or two of fluid such as whole blood. The blood is collected on filter paper and allowed to dry prior to leaving the collection facility. One benefit of using dried blood samples is that dried blood samples are not classified as a special shipping required biohazard material and may be transported through the mail system or other common delivery service just as any other package. 
         [0006]    Additionally, even when a blood or other fluid sample is removed from the body, the concentration of various components within the sample can change over time due to various ongoing reactions. For example, biochemical and cellular changes, such as red blood cells metabolizing plasma glucose for continued cellular respiration, continue in liquid samples. Additionally, when using dried whole blood collection methods, such as collection on Whatman 903 filter paper, as the blood dries, the red cells hemolyze which then becomes mixed with red blood cell membrane cholesterol. The red blood cell membrane cholesterol, which is not normally in the serum portion of the blood, then becomes mixed in with serum cholesterol. Such a mixing may yield a clinically significant increase in a patient cholesterol result. Dried fluid samples have the advantage of reducing various reactions, thereby preserving certain components for later analysis. 
         [0007]    The transportation and handling of dried fluid samples is thus a significant improvement over transportation and handling of liquid samples. Merely drying a fluid sample does not always ensure the usefulness of the sample. By way of example, in order to perform analysis of certain dissolved blood components a whole blood sample cannot be used. For example, hemoglobin can interfere with serum analytes at the light absorbance in the instrumental step of clinical analyte testing. Accordingly, the red blood cells must first be separated from the blood plasma or serum prior to drying. The most conventional manner of separating serum or plasma from blood cells is by centrifugation. Centrifugation, of course, requires more than a few drops of blood. Additionally, expensive and space consuming equipment must be maintained at the collection site to perform centrifugation. 
         [0008]    Various approaches have been developed to provide for separation of blood samples prior to drying of the samples. For example, U.S. Pat. No. 5,064,541, issued to Jeng et al. on Nov. 12, 1991, describes a device which separates plasma from red blood cells that uses an agglutination agent in a filter to clump red blood cells together. The incorporation of an additional biochemical filter in the device adds to the complexity and cost of the device. Additionally, the amount of blood collected may overwhelm the ability of the red blood cell agglutinating agent to work on all of the red blood cells applied in the whole blood sample. 
         [0009]    U.S. Pat. No. 4,816,224, issued to Vogel, et al. on Mar. 28, 1989, describes a series of wicking papers and a relative large sample holder with different embodiments that contain many different components. The device is complex and requires significant foot print space when shipping or undergoing sample extraction at a remote laboratory. 
         [0010]    U.S. Pat. No. 6,258,045, issued to Ray et al. on Jul. 10, 2001, describes a device which requires tubing for capillary collection of whole blood along with filtration and multiple layers of reactive or non-reactive materials for plasma separation and testing. Capillary collection tubes require a certain level of operator experience and inflict additional pain on the patient when compared to a simple lancet stick. Additionally, the glass tube can be broken or become detached. 
         [0011]    Traditional devices for obtaining dried fluid samples further incorporate indirect methods for ensuring that the proper amount of fluid has been collected to allow the desired separation. Some devices incorporate an indicator which changes color or a portion of the strip which provides a chemical reaction. Such devices do not provide an indication of whether or not too large a sample of fluid has been collected. 
         [0012]    Therefore, a collecting device that is self-contained and can be used to provide stable dried biological components to a laboratory would be beneficial. Further benefits would be realized if the device is simple to manufacture and provides accurate results. Further benefits would be provided by a device which enables both the sample collector and laboratory personal to visually directly observe the amount of fluids, such as serum or plasma or red blood cells, which have been collected. A device that can be used to separate fluids such as blood into separate components and which is easy to mail without additional charges would also be beneficial. 
       SUMMARY 
       [0013]    The present invention is directed to a method of making a fluid sample collection card including providing a support layer with a substantially planar upper surface, providing a card stock, forming an upper layer with the card stock, the upper layer including a sample window and a viewing window formed through the upper layer, supporting an absorbent layer with the substantially planar upper surface, and positioning the upper layer on an upper surface of the absorbent layer such that a first absorbent layer portion of the absorbent layer is directly accessible and viewable though the sample window and a second absorbent layer portion of the absorbent layer is visible through the viewing window, wherein the upper layer is configured such that as a fluid is being absorbed by the first absorbent layer portion, presence of a portion of the fluid within the second absorbent layer portion indicates that a first volume of the fluid absorbed by the absorbent layer is a minimum necessary volume of the fluid sufficient to perform at least one test on at least one component in the fluid. 
         [0014]    In another embodiment, a method of making a fluid sample collection device includes providing an upper layer, compressing a first portion of the upper layer to form a first compressed portion of the upper layer defining a first window with a length and a width through the upper layer, compressing a second portion of the upper layer to form a second compressed portion of the upper layer defining a second window with a length and a width through the upper layer, the first window and the second window spaced apart by a bridge member with a length and a width, providing a non-absorbent layer with a length that is longer than the combined lengths of the first window, the second window and the bridge member, and positioning an absorbent layer between the upper layer and the non-absorbent layer such that a first absorbent layer portion of the absorbent layer is directly beneath the first window and a second absorbent layer portion of the absorbent layer is directly beneath the second window, wherein the upper layer is configured such that when the fluid sample collection device is formed and a fluid is being absorbed by the first absorbent layer portion, presence of a portion of the fluid within the second absorbent layer portion indicates that a volume of the fluid absorbed by the absorbent layer is a minimum necessary volume of the fluid sufficient to perform at least one test on at least one component in the fluid. 
         [0015]    In a further embodiment, a method of assembling a fluid sample collection device includes providing an upper layer, forming a first window in the upper layer, forming a second window in the upper layer, positioning an absorbent layer on an upper surface of a non-absorbent layer, positioning the first window directly above a sample receiving portion of the absorbent layer so that the sample receiving portion is touchable through the first window, positioning the second window directly above a sample indicating portion of the absorbent layer so that the sample indicating portion is viewable through the second window, and configuring the upper layer such that when the fluid sample collection device is assembled and as a fluid is being absorbed by the first absorbent layer portion, presence of a portion of the fluid within the second absorbent layer portion indicates that a first volume of the fluid absorbed by the absorbent layer is a minimum necessary volume of the fluid sufficient to perform at least one test on at least one component in the fluid. 
         [0016]    These and other advantages and features of the present invention may be discerned from reviewing the accompanying drawings and the detailed description of the preferred embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present invention may take form in various system and method components and arrangement of system and method components. The drawings are only for purposes of illustrating exemplary embodiments and are not to be construed as limiting the invention. 
           [0018]      FIG. 1  depicts a top plan view of a separator card including a sample receiving portion of an absorbent layer accessible through an upper layer of the card and a sample indicating portion of the absorbent layer viewable through the upper layer of the card in accordance with principles of the invention; 
           [0019]      FIG. 2  depicts an exploded perspective view of the card of  FIG. 1 ; 
           [0020]      FIG. 3  depicts a side cross-sectional view of the layers of the separator card of  FIG. 1  before the upper layer is attached to the support layer by an adhesive layer; 
           [0021]      FIG. 4  depicts a side cross-sectional view of the layers of the separator card of  FIG. 1  after the upper layer is attached to the support layer by an adhesive layer; 
           [0022]      FIG. 5  depicts a perspective view of a patient providing a blood sample onto the absorbent layer of the separator card of  FIG. 1  through a sample window; 
           [0023]      FIG. 6  depicts a top plan view of the separator card of  FIG. 1  after sufficient fluid has been provided to the absorbent layer through the sample window to perform one test on a component of the fluid that will be separated by the absorbent layer in accordance with principles of the invention; 
           [0024]      FIG. 7  depicts a perspective view of a resealable packet that may be used to transfer the separator card of  FIG. 1  through a carrier service to a laboratory or other facility; and 
           [0025]      FIG. 8  depicts a perspective view of a removal tool that may be used to separate the absorbent strip of the separator card of  FIG. 1 . 
       
    
    
     DESCRIPTION 
       [0026]    Referring to  FIGS. 1 and 2 , a separator card  100  is shown which in this embodiment is configured to separate serum and plasma in a blood sample. The separator card  100  includes an upper layer  102 , an absorbent layer  104 , a non-absorbent layer  106  and a support layer  108 . The upper layer  102  includes a sample window  110  and a viewing window  112 . A bridge  114  is located between the sample window  110  and the viewing window  112 . 
         [0027]    The upper layer  102  is fabricated from card stock. Accordingly, a user or manufacturer can easily print data on the upper layer  102 . By way of example, a series of reference marks  116 ,  118 , and  120 , which extend outwardly from the sides of the viewing window  112 , along with an identification block  122  are shown on the upper layer  102 . Instructions for using the separator card  100  may be printed in the identification block  122  and space for insertion of patient identification data may also be provided therein. 
         [0028]    The absorbent layer  104  is sized to be slightly longer than the length of the upper layer  102  between the outer ends of the sample window  110  and the viewing window  112  and slightly wider than the sample window  110  and the viewing window  112 . The absorbent layer  104  in this embodiment is made from Whatman LF-1 material, commercially available from Whatman Inc. of Florham Park, N.J. Other suitable material may be used, such as, but not limited to, porous materials that allow liquid and suspended solids to differentially flow and separate based on the molecular size of the molecules. 
         [0029]    Additionally, the characteristics of the absorbent layer  104  may be modified by incorporating designs that utilize other physical forces that affect the flow of substances through the absorbent layer  104 . Such physical forces include hydrophobic or hydrophilic interactions as well as ionic interactions. Additionally, temporary hydrogen bonding interactions and gravitational effects may be used to augment or retard flow to provide the desired separation or alteration of a separation of the flowing liquids and suspended cells or other solid materials. 
         [0030]    The non-absorbent layer  106  is sized to be at least slightly longer and wider than the absorbent layer  104 . The non-absorbent layer  106  in this embodiment is Mylar, which is used for its imperviousness to liquid penetration. Other materials which may be used to form an acceptable liquid barrier include thin sheets of Polyethylene, porous UHMWPE film, FEP film, polyester treated sheeting and polypropylene. 
         [0031]    Another material which provides an acceptable liquid barrier is porous ePTF film, commercially available from DeWal Industries, Inc. of Saunderstown, R.I. as product number D/W 233MS. The ePTF material is a fluoropolymer material which contains a fluorocarbon material at its surface. The fluorine molecule is the most electronegative element, thereby providing a desired hydrophobic quality. Specifically, it is believed that the fluorocarbon additive to the base plastic polymer in this material and other fluoropolymers enhances the separation of plasma from the red blood cells in the touching absorbent layer  104 . 
         [0032]    Assembly of the separator card  100  includes cutting of card stock into the shape of the upper layer  102  and the support layer  108  and forming the sample window  110  and the viewing window  112  by press stamping the upper layer  102 . The upper layer  102  and the support layer  108  in this embodiment are about 10 centimeters long and about 4.5 centimeters wide. 
         [0033]    The layers of the separator card  100  may be joined by initially applying a layer of adhesive  124  (see  FIG. 3 ) on the support layer  108 . Subsequently, the non-absorbent layer  106 , the absorbent layer  104  and the upper layer  102  are placed onto the support layer  108  resulting in the configuration of  FIG. 3 . The separator card  100  is then pressed together as indicated by the arrows  130  and  132  resulting in the configuration of  FIG. 4 . If desired, heat may also be applied to assist in attaching the upper layer  102  and the non-absorbent layer  106  to the support layer  108 . 
         [0034]    As shown most clearly in  FIG. 4 , the non-absorbent layer  106  is at least slightly wider and slightly longer than the absorbent layer  104 . Accordingly, while the non-absorbent layer  106  is adhered to the support layer  108 , the adhesive  124  does not contact the absorbent layer  104 . Rather, the absorbent layer  104  is maintained in position by the upper layer  102 . 
         [0035]    Specifically, the upper layer  102  contacts the adhesive layer  124  completely around the periphery of the non-absorbent layer  106 . The absorbent layer  104  is thus entrapped by a lip  134  about the sample window  110  and a lip  136  about the viewing window  112 . The bridge  114  also entraps the absorbent layer  104  within the separator card  100 . 
         [0036]    Additionally, pressing of the upper layer  102  against the sandwiched layers (the absorbent layer  104  and the non-absorbent layer  106 ) causes deformation of the upper layer  102 . The deformation includes some amount of compression of the upper layer  102  in an area of the upper layer  102  beginning with the portions of the upper layer  102  which are in contact with the absorbent layer  104  and the non-absorbent layer  106  and extending upwardly from those portions. Accordingly, the portions of the upper layer  102  which define the sample window  110  and the viewing window  112  are more impervious to fluids. The compacted areas of the upper layer  102  along with the non-absorbent layer  106  thus form a channel tending to maintain fluids within the absorbent layer  104 . 
         [0037]    The assembled separator card may be packaged for storage until a fluid sample is needed. A fluid sample may be obtained in a clinical or laboratory setting. Alternatively, the separator card  100  may be used by lay persons at virtually any location. A sample is obtained by producing the fluid, such as by pricking a finger to obtain blood. By way of example, a finger  140  has been lanced to obtain a blood sample  142  in  FIG. 5 . Drops of blood from the finger  140  are then dripped onto the absorbent layer  104  through the sample window  110  such that the blood sample  142  contacts the absorbent layer  104 . 
         [0038]    When the fluid sample contacts the absorbent layer  104 , the sample is wicked by the absorbent layer  104 , and preferentially aided in movement and separation by the chemical or physical nature of the non-absorbent layer  106 , into the portion of the absorbent layer  104  viewable through the viewing window  112  along the channel formed by the compacted areas of the upper layer  102  along with the non-absorbent layer  106 . As additional blood is placed into the portion of the absorbent layer  104  accessible through the sample window  110 , the wicked fluid will become visible through the viewing window  112 . 
         [0039]    Once the fluid reaches the reference line  116  as shown in  FIG. 6 , sufficient blood has been absorbed to separate a quantity of plasma to perform a single test. The reference lines  118  and  120  may be provided to indicate when sufficient blood has been absorbed to separate a quantity of plasma necessary for performance of two tests and three tests, respectively. 
         [0040]    The bridge  114  ensures a minimum spacing between the location at which the sample is deposited on the absorbent layer  104  and the reference lines  116 ,  118 , and  120 , thereby ensuring that a minimum volume of fluid has been placed into the absorbent layer  104 . Thus, not only does the bridge  114  assist in maintaining the absorbent layer  104  within the separator card  100 , the bridge  114  also assists in providing an accurate indication of the amount of fluid collected. 
         [0041]    The amount of blood that is necessary to obtain the desired amount of plasma will vary based not only on the materials used, but also based upon the geometry of the channel formed. By way of example, using materials identified above absorbent layers may be formed with a width of from about 0.6 centimeters to about 4 centimeters. Optimum separation of plasma, however, is obtained with a width of about 1 centimeter. By optimizing the separation of the plasma, less blood is needed to obtain a particular amount of plasma. 
         [0042]    The length of the absorbent layer  104  is also a consideration in ensuring sufficient separation of a sample fluid. By way of example, as the volume of sample fluid deposited in the absorbent layer  104  increases, the red blood cells, in the case of blood, will travel further along the absorbent layer  104 . Thus, to ensure that a sufficient separation of a sample fluid occurs in the event too much sample is provided, the length of the absorbent layer  104  may be increased. 
         [0043]    Once the desired sample has been collected, the separator card  100  is left to dry. The separator card may then be shipped via any desired mode of transportation to a processing facility. The dried fluid sample contained in the absorbent layer  104  may be stored for a relatively long time without undue degradation of the sample. Nonetheless, the shelf life of the sample may be extended by placement of the separator card  100  in a storage container such as the package  150  shown in  FIG. 7 . 
         [0044]    The package  150  is a gas impermeable package such as a plastic or foil package. The package  150  includes a resealable opening  152 . The resealable opening  152  may include a tamper proof mechanism to provide an indication that the package  150  has been opened after a sample has been sealed therein. The package  150  is sized to accept the separator card  100  therein, and may be further dimensioned to allow for insertion into a flat envelope of standard size for automated processing by a postal facility. 
         [0045]    In one embodiment, an oxygen scrubber (not shown) is provided with the package  150 . An oxygen scrubber typically includes thin shavings including pieces of metal and a carrier desiccant that loosely holds some amount of water. When the package  150  is sealed with an oxygen scrubber therein, oxygen present within the package  150  reacts with the metal in the presence of water to form rust, thereby binding the oxygen. Elimination of oxygen from the atmosphere of the package  150  provides increased stability for various components within the dried fluid sample. For example, lipid analytes such as HDL, cholesterol, and triglycerides may be further stabilized by removal of oxygen from the atmosphere in which the sample is stored. 
         [0046]    If desired, the separator card  100  may be placed within the package  150  and the package  150  sealed before a fluid sample within the absorbent layer  104  has been dried. Sealing the package  150  with a wet fluid sample held in the separator card  100  inhibits drying of the sample. 
         [0047]    Removal of the absorbent layer  104  from the separator card  100  for further processing is facilitated by the absence of an adherent between the absorbent layer  104  and any of the other components of the separator card  100 . One device that may be used to remove the absorbent layer  104  is the removal tool  160  shown in  FIG. 8 . The removal tool  160  includes a lever arm  162 , a guide stop  164 , an upper mandrel  166  and a lower mandrel  168 . The lower mandrel  168  includes a shaped cutting edge  170  which is sized to mate with the viewing window  112 . The upper mandrel  166  includes a protuberance (not shown) that is slightly smaller than the viewing window  112  and positioned to fit within the shaped cutting edge  170 . 
         [0048]    Accordingly, removal of the portion of the absorbent layer  104  including the separated sample is accomplished by placement of the separator card  100  on the removal tool  160 . Correct placement of the separator card  100  on the removal tool  160  may be guided by the guide stop  164 . Alternatively, the viewing window  112  is simply positioned over the shaped cutting edge  170 . Thereafter, movement of the lever arm  162  in the direction of the arrow  172  forces the protuberance (not shown) on the upper mandrel  166  against the support layer  108  at a location aligned with the viewing window  112 . The absorbent layer viewable through the viewing window  112  is thus forced against the shaped cutting edge  170  which separates the portion of the absorbent layer  104  including the separated sample from the separator card  100 . 
         [0049]    If desired, the entire absorbent layer  104  may be removed from the separator card  100  by separating at least one end of the bridge  114  and applying sufficient force against the support layer  108  to deform the upper layer  102  sufficiently to allow the absorbent layer  104  to move past the rims or lips  134  and  136 . A punch type device similar to the removal tool  160  may be used for this purpose. 
         [0050]    Various other modifications of the separator card  100  may be incorporated to optimize the separator card for particular tests. In one embodiment, polyhexamethylene biguanide hydrochloride (PHMB) is incorporated into the absorbent layer  104 . PHMB is an additive used in bandages for inhibiting the growth of microbial organisms such as bacteria and fungi. 
         [0051]    In a further embodiment, prior to blood or other biological fluid application, a polypeptide fraction of highly purified dermal collagen of porcine origin (Prionex from Pentapharm) is applied and dried to the separator card absorbent layer  104 . A separator card  100  treated with Prionex applied to the absorbent layer  104  at a 0.1 percent concentration can yield close to double the separation area of serum or plasma for a given volume of blood applied to the absorbent layer  104 . Other substances such as various proteins, detergents, salts or solvents, or other chemicals may also be used to enhance separation of a sample fluid. 
         [0052]    Another additive that is useful when obtaining fluid samples in the form of blood is sucrose. In particular, cholesterol containing molecules and cholesterol itself are hydrophobic molecules which in pure form do not mix with an aqueous solution. The complex arrangement of proteins, salts and carbohydrate and complex carbohydrate in blood, however, holds these hydrophobic molecules in suspension. Disruption of these serum components during drying could result in clumping or aggregation of the hydrophobic molecules rendering successful hydration of the hydrophobic molecules problematic. 
         [0053]    Application of sucrose in 1 to 10% wt./vol. concentration followed by drying to the absorbent layer  104 , however, provides a more reproducible drying and rehydration of cholesterol containing molecules such as HDL, LDL and the cholesterol molecule itself. It is believed that the carbohydrate sucrose molecules are surrounded by water molecules when a fluid sample is added. Thus, the sucrose layers surround the hydrophobic cholesterol or triglyceride molecules during the drying and inhibit aggregation via hydrophobic binding of the sucrose shielded hydrophobic molecules. 
         [0054]    While the present invention has been illustrated by the description of exemplary processes and system components, and while the various processes and components have been described in considerable detail, applicant does not intend to restrict or in any limit the scope of the appended claims to such detail. Additional advantages and modifications will also readily appear to those skilled in the art. The invention in its broadest aspects is therefore not limited to the specific details, implementations, or illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.