Abstract:
A method of dispensing gel for separation of the serum and coagulum portions of a blood sample in a blood collection tube is provided. The present disclosure of dispensing the gel comprises utilizing a gel dispensing apparatus with a nozzle head having a plurality of openings. The gel dispensing apparatus dispenses either a continuous band of gel around the central portion of the collection tube or a plurality of discrete stripes that form a circumferential pattern thereto. Once the gel is dispensed, the tube is ready for accepting a blood sample for eventual separation in a centrifuge where the dispensed gel will form a barrier that exhibits strong adhesive properties after separation of the blood sample has occurred.

Description:
FIELD OF THE INVENTION  
         [0001]    The present disclosure relates generally to a method and apparatus for separating blood components in a blood collection device. Specifically, the present disclosure relates to a method for the separation of a light serum portion of blood from a heavy cellular portion of blood, the blood collection device used to collect and separate blood, and manufacturing the blood collection device. More particularly, the present disclosure relates to a method of dispensing separator gel in a blood collection tube for improving gel barrier stability and adhesion of the gel to a tube wall during the separation process.  
         PRIOR ART  
         [0002]    Blood collection devices for separating the lighter serum portion of a blood sample from the heavier cellular portion thereof are well known. These devices usually comprise a collection tube containing a thixotropic gel and a contact activated clotting agent. The gel has a specific gravity intermediate the specific gravity of the serum and the cellular phases of the blood sample.  
           [0003]    After a sample of blood has been deposited into the collection tube, the contact-activated clotting agents begin to clot the blood sample by activating clotting factors within the blood. The agent facilitates the clotting process until the blood is completely coagulated. The agent coagulates substantially all of the blood sample in order for the subsequent serum separation process to be complete. Once the blood has coagulated, the collection tube is placed in a centrifuge to separate the lighter serum from the heavier coagulum portion. Coagulum is defined as the cellular portion and fibrin clot of the blood as opposed to the lighter serum portion of the blood. During centrifugation, the gel on the bottom of the collection tube is displaced upwardly through the blood sample until it reaches its equilibrium position at the interface between the serum and the coagulum. In this position, the gel forms a barrier between the serum and the coagulum which permits the lighter serum to be either decanted directly from the collection tube, or sampled using automated blood analyzing equipment, without interference from the coagulum.  
           [0004]    It has long been known in the art that human blood can be readily centrifuged to effect a separation of the blood into its lighter serum and heavier coagulum portions. The specific gravity of the serum portion of human blood is between approximately 1.026 and 1.031, while the specific gravity of the coagulum portion of human blood is between approximately 1.092 and 1.095. The specific gravity of the gel is therefore chosen to be approximately between 1.032 and 1.091, so that once a blood sample is centrifuged, the gel will form an effective barrier between the serum and the coagulum. A preferred gel to be used with the method of the present disclosure is a thixotropic composition described in U.S. Pat. No. 4,140,631 to Okuda et al., entitled “Sealant for Separation of Serum or Plasma, and It&#39;s Use,” the entire disclosure of which is hereby incorporated herein by reference. As described in Okuda et al., the preferred thixotropic gel is a polymer essentially consisting of at least one compound from the group of alkyl acrylates and alkyl methacrylates, which has a specific gravity of 1.03 to 1.08 and a viscosity of about 5,000 to 1,000,000 cps at a shear rate of 1 second when measured at 25° C. However, any suitable gel-like composition which can be used as a barrier between blood portions separated in a centrifuge is felt to fall within the spirit and scope of the present disclosure.  
           [0005]    This type of gel is adapted to migrate or flow from the bottom of the tube under the influence of centrifugation to the interface position between the serum and the coagulum portions of the blood and adhere to the inside surface of the collection tube wall to form a barrier between the blood portions to maintain a separation therebetween. However, this migration causes an attendant loss of gel along the tube wall, thereby requiring initial placements of larger amounts of gel in the tube in order to insure the formation of a strong enough mechanical barrier to properly separate the two portions of blood during centrifugation.  
           [0006]    Weak adhesion of the gel to the collection tube&#39;s inner surface during centrifugation of the blood sample is a problem with prior art blood collection devices. Such weak adhesion of the gel is due to the blood sample wetting the inner surface of the blood collection device prior to the migration of the gel. This wetted inner surface inhibits the natural adhesive properties of the gel, thereby preventing the gel from forming a strong adhesive bond thereto. U.S. Pat. No. 4,257,886 seeks to overcome this deficiency by disclosing a blood separation assembly that coats the bottom portion of the collection tube with a hydrophobic material that resists wetting of the collection tube&#39;s inner surface and allows the gel to form a strong adhesive bond to the inner surface during centrifugation.  
           [0007]    Another method of addressing the gel migration problem with its attendant loss of adhesion is found in U.S. Pat. No. 4,417,981 which attempts to overcome the problems associated with gel migration by dispensing the gel in a separator assembly located in the central portion of the collection tube near the eventual formation of the gel barrier. The pre-placement and dispensation of the gel in a separator assembly permits the gel to quickly adhere to the tube wall during centrifugation without migration and attendant loss of gel. However, the above method of dispensing gel using a device incurs further expense in manufacturing an additional element to attain proper separation of the blood sample.  
           [0008]    Referring to FIGS.  1 - 4 , the prior art method of dispensing separator gel  3  and separating a blood sample into two portions is shown. The method involves utilizing a commonly known gel dispensing apparatus (not shown) to dispense a predetermined amount of gel  3  into the bottom  5  of a collection tube  2 . Contact-activated clotting powder or particles  6  are then deposited inside collection tube  2  for eventual activation of clotting factors within blood  7  after blood  7  is added to collection tube  2 .  
           [0009]    As shown in FIG. 2, a predetermined amount  4  of blood  7  is added to collection tube  2  and contact clot-activating material  6  within collection tube  2  begins to coagulate blood  7  before collection tube  2  is placed in a centrifuge (not shown) for centrifugation of blood  7 . Contact clot-activating material  6  promotes clot formation and includes but is not limited to glass and silica. Referring now to FIG. 3, during centrifugation of blood  7  in collection tube  2 , gel  3  becomes less viscous and begins to migrate upward along an inner surface  8  of collection tube  2  until it reaches an interface point  9  where lighter serum portion  10  of blood  7  begins to separate from heavier coagulum portion  11 . Interface point  9  is a result of the two portions of blood, serum  10  and coagulum  11 , being physically separated due to the effect of their different specific gravities during centrifugation. As shown in FIG. 4, separation gel  3 , having a specific gravity intermediate that of serum  10  and coagulum  11 , has migrated to interface point  9  between the two blood portions. At interface point  9 , gel  3  forms a mechanical barrier  12  inside collection tube  2  that physically separates the two blood portions and prevents serum  10  from being contaminated by coagulum  11 .  
           [0010]    As of yet, nothing in the prior art has addressed the problem of developing an efficient means of dispensing gel that does not suffer from either attendant loss of gel caused by migration or weak adhesive properties when gel barrier  12  is formed.  
           [0011]    Therefore, there exists a need in the blood collection art for an improved means of dispensing gel into a collection tube in an inexpensive and efficient manner which promotes both quick formation of the barrier separating the two blood portions and a strong adhesion of the barrier to the collection tube&#39;s inner surface once the gel barrier is formed.  
         SUMMARY OF THE INVENTION  
         [0012]    In brief summary, the present disclosure relates to a means of dispensing gel for separation of the lighter serum portion and the heavier coagulum portion of a blood sample in a blood collection tube. The preferred method of dispensing the gel comprises utilizing a gel dispensing apparatus with a nozzle head or like portion having a plurality of openings. The gel dispensing apparatus dispenses either a continuous band of gel around the central portion of the collection tube or a plurality of discrete stripes that flow to form a continuous band pattern around the central portion of the collection tube. Once the gel is so dispensed around the central portion of the collection tube, the tube is ready for accepting a blood sample for eventual separation in a centrifuge where the dispensed gel will form a barrier between the serum portion and the coagulum portion of the blood sample while exhibiting strong adhesive properties, i.e., few to no points of fluid communication between blood portions.  
           [0013]    The present disclosure includes a method of dispensing gel into a tube having opposed open and closed ends, a central body portion between the opposed open and closed ends, and an interior surface formed by the central body portion and the closed end, comprising the steps of: providing the tube, providing a gel dispensing apparatus for dispensing a gel into the tube, placing a portion of the apparatus inside the tube, dispensing the gel from the portion of the apparatus onto an interior wall surface formed by the central body portion, and terminating the dispensation of the gel.  
           [0014]    The present disclosure further includes a blood collection device for use in separating blood into different portions comprising a tube having a central body portion, opposed closed and open ends, and an interior surface with gel dispensed on an interior wall surface thereof. Optionally, contact clot-activating particles may be placed within the device.  
           [0015]    The present disclosure still further includes a method of separating blood into different portions using the aforementioned blood collection device optionally containing contact clot-activating particles comprising the steps of: placing a blood sample inside the blood collection device, centrifuging the device containing the blood collection sample wherein centrifuging the device and the blood sample permits the gel to flow inwardly from the interior wall surface to form a barrier between the different portions of the blood sample after centrifugation is complete.  
           [0016]    Accordingly, a principal object of the present disclosure is to provide an efficient and inexpensive method for dispensing gel in a collection tube for use in separating a blood sample into portions.  
           [0017]    Another important object of the present disclosure is to provide an improved method of dispensing gel that requires minimal or no migration of the gel along the tube wall to form a barrier between portions of blood being separated during centrifugation.  
           [0018]    A further object of the present disclosure is to provide a method of dispensing gel that forms a continuous and stable barrier in a short period of time and exhibits strong adhesive properties, i.e., few to no points of fluid communication between the blood portions.  
           [0019]    Another important object of the present disclosure is to provide a means of dispensing gel in discrete stripes or a continuous band around the interior wall surface of a collection tube.  
           [0020]    A further object of the present disclosure is to provide a blood collection device that has gel dispensed on the interior wall portion of a tube.  
           [0021]    Another principal object of the present disclosure is to provide a method of using a tube with gel dispensed on the inner surface thereof for separation of blood into separate portions.  
           [0022]    Additional objects, advantages and novel features of the present disclosure will become apparent to those skilled in the art upon examination of the following more detailed description and drawings in which like elements of the present disclosure are similarly numbered throughout.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    [0023]FIG. 1 shows the prior art method of dispensing gel at the bottom of a blood collection tube;  
         [0024]    [0024]FIG. 2 shows the prior art blood collection tube of FIG. 1 after a blood sample has been added thereto;  
         [0025]    [0025]FIG. 3 shows the prior art migration of gel toward the serum/coagulum interface during centrifugation of the blood sample;  
         [0026]    [0026]FIG. 4 shows the prior art blood collection tube after centrifugation of the blood sample and the formation of the gel barrier at the interface between the two portions of the blood;  
         [0027]    [0027]FIG. 5 shows the present method of dispensing gel on the interior wall portion of a collection tube using a nozzle head for dispensing gel in a continuous band around the interior wall portion of the collection tube;  
         [0028]    [0028]FIG. 6 shows a top section view of the blood collection tube of FIG. 5 showing the gel on the inner surface of the tube with an opening therethrough;  
         [0029]    [0029]FIG. 7 shows the blood collection tube of the present disclosure demonstrating the method of determining the lower and upper limits for dispensing gel; and  
         [0030]    [0030]FIG. 8 is a perspective view of the gel dispensing apparatus showing the alternative embodiment of a continuous opening at the nozzle head.  
     
    
     DETAILED DESCRIPTION  
       [0031]    In one embodiment, in accordance with the present disclosure, a method of dispensing gel within a blood collection tube is shown in FIG. 5. A blood collection apparatus  20 , including a conventional collection tube  21  having an opposed open end  23  and closed end  34  is made of a material which is non-interactive with a blood sample  35 , such as but not limited to plastic, glass, plastic-lined glass or glass-lined plastic. Collection tube  21  has a separator gel  22  which is a thixotropic substance dispensing into the central portion of tube  21  between opposed open end  23  and closed end  34  prior to adding a blood sample  35 .  
         [0032]    Gel  22  is placed within tube  21  by using a positive displacement metering apparatus  24  that uses a nozzle head  25  for dispensing a gel or the like. Nozzle head  25  includes one or more openings but preferably a plurality of openings  26  located at its free distal end  31 . In an alternative embodiment, one opening  126  is provided at free distal end  31  of nozzle head  25 . Opening  126  is a continuous opening around the periphery of an exterior surface  128  of nozzle head  25 , as illustrated in FIG. 8. It is contemplated that opening  126  may be disposed about the entire circumference about only a portion thereof or intermittently disposed about nozzle head  25 . Although one or more openings  26  can be utilized for the present disclosure, a plurality of openings  26  will be exemplified throughout the remainder of this description for purposes of simplicity only.  
         [0033]    Plurality of openings  26  dispense gel  22  onto inner surface  29  of tube  21  in discrete stripes  30  that flow to form a circumferential band pattern around collection tube  21 . Preferably, gel  22  is dispensed in discrete stripes  30 , although any suitable configuration that ultimately flows to form one or more continuous circumferential bands around inner surface  29  of collection tube  21  is included, within the spirit and scope of the present disclosure.  
         [0034]    Prior to dispensing gel  22 , nozzle head  25  is placed inside collection tube  21  such that openings  26  are positioned at a predetermined first limit, such as, for example, a predetermined lower point  27  to begin dispensing gel  22  along inner wall surface  29  of collection tube  21 . As gel  22  is dispensed through openings  26 , collection tube  21  is slowly drawn downward so as to move closed end  34  away from nozzle head  25  until openings  26  reach a predetermined second limit, such as, for example, a predetermined upper limit  28  near open end  23 . As the dispensing procedure is about to terminate, nozzle head  25  is slightly ahead of gel  22  flow, thereby forming a discontinuous circumferential pattern  32  at predetermined upper limit  28 . It is contemplated that during dispensation from plurality of openings  26 , a discontinuous circumferential pattern  32  is formed at the end of dispensation in a crown shape design, but any suitable pattern may be made. Once the dispensation of gel  22  is terminated, gel  22  flows and adheres to inner surface  29  forming a circumferential band around the central portion of collection tube  21  between the predetermined upper and lower limits,  28  and  27 , respectively. As shown in FIG. 6, gel  22 , after flow thereof has ceased, forms the cirumferential band with discontinuous pattern  32  at the top of the circumferential band and an opening  33  through which blood sample  35  may initially pass before centrifugation and formation of the gel barrier. After gel  22  has set or flow has ceased, collection apparatus  20  is ready for blood sample  35  to be added for centrifugation and separation, as described above.  
         [0035]    The location of the upper and lower limits,  28  and  27 , respectively, in dispensing gel  22  forming the concentric band on inner surface  29  of collection tube  21  depends on the size of collection tube  21  being utilized and the volume of blood sample  35  to be added to collection tube  21 . Upper and lower limits,  28  and  27 , respectively, are measured from a location on collection tube  21  adjacent open end  23 . Referring to FIG. 7, a general formula for determining the upper and lower limits,  28  and  27 , respectively, for gel  22  dispensation will be discussed. X is a variable that represents a linear dimension, such as, for example, the length of collection tube  21  which holds a predetermined volume of blood sample  35  added to collection tube  21  prior to centrifugation. In determining the lower and upper limits for gel placement,  27  and  28 , respectively, variable X is multiplied by predetermined constants, C LL  for the lower limit  27  and C UL  for upper limit  28 .  
         [0036]    These constants are established by one skilled in the art based on factors including the configuration and dimension of collection tube  21 , the type of centrifuge (angled, horizontal, etc.), the particular gel configuration, the quantity of gel, the volume of blood, etc. Based on, for example, these factors, it has been established that C UL  is approximately 0.30 and that C LL  is approximately 0.70. It is envisioned that the constants C UL  and C LL , may vary within the numerical range of 0.30-0.70 to respectively facilitate determination of upper limit  27  and lower limit  28 .  
         [0037]    The general formulas used to determine upper limit  28  and lower limit  27  are shown below:  
         Lower limit  27 = X·C   LL    
         Upper limit  28 = X·C   UL    
         [0038]    For example, if C LL  and C UL  are established as being 0.70 and 0.31, respectively, as described above, for a particular tube to achieve a particular desired configuration, lower limit  27  and upper limit  28 , may be easily determined by knowing the length of collection tube  21  which holds the predetermined volume of the drawn blood sample  35  added to the collection tube  21  having a length of 100 mm. To illustrate, if the predetermined volume of blood sample  35  is added to collection tube  21 , lower limit  27  for dispensing gel  22  would be 70 mm and upper limit  28  would be 31 mm as set forth below.  
         Lower limit  27 =100 mm×0.7=70 mm  
         Upper limit  28 =100 mm×0.31=31 mm  
         [0039]    Thus, gel  22  would be dispensed between a range of 31 mm to 70 mm from the location on collection tube  21  adjacent open end  23  to form the circumferential band. It is contemplated that collection tube  21  may have variously dimensioned diameters, such as, for example, 13 mm, 16 mm, etc., according to the requirements of a particular application. It should be noted that the formula would be varied accordingly if more than one circumferential band would be desired for further separation techniques known in the art.  
         [0040]    The above example is used for the purpose of illustrating upper and lower limits,  28  and  27 , respectively, for dispensing gel  22  in collection tube  21  in accordance with the present disclosure. The above formula in accordance with the principals of the present disclosure advantageously provides that a firm mechanical gel barrier is formed after centrifugation regardless of the type of centrifuge used to separate blood sample  35 .  
         [0041]    The method of dispensing gel  22  of the present disclosure, as described, has the advantage of limited migration of gel  22  during centrifugation while promoting a stronger mechanical barrier after centrifugation. Moreover, dispensing gel  22  on the interior wall portion between upper and lower limits,  28  and  27 , respectively, of collection tube  21  has the further advantage of requiring less gel  22  than required in prior art methods in which gel  22  migration was utilized. For example, prior art methods for dispensing gel  22  dispense approximately 2.2 grams of gel  22  to form a sufficient barrier after centrifugation of blood sample  35  while the present disclosure requires approximately 1.4 grams of gel  22  to form the same strong barrier. Thus, the present disclosure requires approximately 36% less gel  22  which creates a significant cost savings.  
         [0042]    The method of separating blood sample  35  into different portions using blood collection apparatus  20 , similar to the present disclosure will be now illustrated. The method of separating a blood sample  35  using blood collection apparatus  20  having contact clot-activating particles  6  previously deposited inside apparatus  20  comprises the step of providing a blood sample  35  inside apparatus  20 . After blood sample  35  is deposited, blood sample  35  is then centrifuged, wherein centrifuging blood sample  35  permits gel  22  to flow inwardly as blood sample  35  travels through opening  33  until a barrier is formed between the different phases of blood sample  35  once centrifugation is complete.  
         [0043]    Blood collection apparatus  20  of the present disclosure may likewise optionally contain contact clot-activating particles such as but not limited to carbon, silica, fumed silica, glass and the like. Likewise, the entire interior surface or a portion of the interior surface of blood collection tube  21  of the present disclosure may optionally be sprayed with a water and/or silica mixture to prevent blood from sticking to the sides of collection tube  21 . This spray is preferably applied before dispensing of gel  22 , as described above.  
         [0044]    Optionally, the interior of blood collection apparatus  20  of the present disclosure may be sprayed with an ethylene copolymer such as but not limited to polyethylene oxide and/or polydimethyl siloxane to promote gel  22  binding to the wall.  
         [0045]    Although particular embodiments of the disclosure have been shown, it is not intended that the disclosure be limited thereby, instead the scope of the present disclosure is intended to be limited by the appended claims.