U.S. patent application number 09/803570 was filed with the patent office on 2001-07-12 for method and apparatus for dispensing separator gel in a blood collection tube.
Invention is credited to Fiehler, William R..
Application Number | 20010007315 09/803570 |
Document ID | / |
Family ID | 25064811 |
Filed Date | 2001-07-12 |
United States Patent
Application |
20010007315 |
Kind Code |
A1 |
Fiehler, William R. |
July 12, 2001 |
Method and apparatus for dispensing separator gel in a blood
collection tube
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.
Inventors: |
Fiehler, William R.; (St.
Louis, MO) |
Correspondence
Address: |
BROWN RUDNCIK FREED & GESMER
One Financial Center
18th Floor, BOX IP
BOSTON
MA
02111
US
|
Family ID: |
25064811 |
Appl. No.: |
09/803570 |
Filed: |
March 9, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09803570 |
Mar 9, 2001 |
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08762358 |
Dec 9, 1996 |
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6238578 |
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60008524 |
Dec 12, 1995 |
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Current U.S.
Class: |
210/787 ;
422/400 |
Current CPC
Class: |
B01D 21/262 20130101;
B01D 2221/10 20130101; B01L 3/5021 20130101; G01N 33/491
20130101 |
Class at
Publication: |
210/787 ;
422/101 |
International
Class: |
B04B 005/00; B01L
003/14 |
Claims
What is claimed is:
1. A blood collection apparatus comprising: a blood collection tube
defining an inner surface; and a gel being selectively disposed
along the inner surface.
2. A blood collection apparatus as recited in claim 1, wherein the
gel is configured as a barrier.
3. A blood collection apparatus as recited in claim 1, wherein the
gel is selectively disposed along a central portion of the inner
surface.
4. A blood collection apparatus comprising: a blood collection tube
defining a central inner surface; and a gel disposed along a
portion of the central inner surface, the portion of the central
inner surface defining a predetermined first limit and a
predetermined second limit.
5. A blood collection apparatus as recited in claim 4, further
comprising a dispensing apparatus configured to dispense the gel
along the portion of the central inner surface.
6. A blood collection apparatus as recited in claim 5, wherein the
dispensing apparatus includes a positive displacement meter
configured for dispensing the gel.
7. A blood collection apparatus as recited in claim 5, wherein the
dispensing apparatus includes a nozzle configured for dispensing
the gel.
8. A blood collection apparatus as recited in claim 7, wherein the
nozzle defines at least one opening configured to dispense the
gel.
9. A blood collection apparatus as recited in claim 8, wherein the
at least one opening is disposed about at least a portion of a
circumference defined by the nozzle.
10. A blood collection apparatus as recited in claim 8, wherein the
nozzle defines a plurality of openings.
11. A blood collection apparatus as recited in claim 4, wherein the
blood collection tube includes a non-stick coating selectively
disposed on the central inner surface.
12. A blood collection apparatus as recited in claim 4, wherein the
predetermined first limit is based on at least one dimension of the
blood collection tube.
13. A blood collection apparatus as recited in claim 4, wherein the
predetermined second limit is based on at least one dimension of
the blood collection tube.
14. A blood collection apparatus as recited in claim 4, wherein the
predetermined first limit is based on the following formula:
predetermined first limit=X.multidot.C.sub.LL, where X is a linear
dimension of the blood collection tube and C.sub.LL is a constant
based on at least one factor of the blood collection apparatus.
15. A blood collection apparatus as recited in claim 14, wherein
the constant C.sub.LL is equal to a numerical value in a range of
numerical values between 0.30 and 0.70.
16. A blood collection apparatus as recited in claim 4, wherein the
predetermined second limit is based on the following formula:
predetermined second limit=X.multidot.C.sub.UL, where X is a linear
dimension of the blood collection tube and C.sub.UL is a constant
based on at least one factor of the blood collection apparatus.
17. A blood collection apparatus as recited in claim 16, wherein
the constant C.sub.UL is equal to a numerical value in a range of
numerical values between 0.30 and 0.70.
18. A blood collection apparatus as recited in claim 4, wherein the
gel is disposed along the portion of the central inner surface to
prevent migration of the gel relative thereto during centrifuging
of the blood collection tube.
19. A blood collection apparatus comprising: means for collecting a
sample of blood defining a central inner surface; and a gel
disposed along a predetermined portion of the central inner
surface.
20. A blood collection apparatus as recited in claim 19, further
comprising dispensing means configured to dispense the gel along
the predetermined portion of the central inner surface.
21. A method for separating a sample of blood into portions
including a light serum portion and a heavy cellular portion, the
method comprising the steps of: providing a blood collection tube
defining a central inner surface; providing a dispensing apparatus
configured to dispense gel along a portion of the central inner
surface, the portion of the central inner surface defining a
predetermined first limit and a predetermined second limit;
dispensing the gel via the dispensing apparatus along the portion
of the central inner surface; providing a sample of blood within
the blood collection tube; and manipulating the blood collection
tube to separate the light serum portion of the blood sample from
the heavy cellular portion of the blood sample.
22. A method for separating a sample of blood as recited in claim
21, wherein the step of manipulating includes centrifuging the
blood collection tube.
23. A method for separating a sample of blood as recited in claim
22, wherein the step of dispensing includes the gel being dispensed
along the portion of the central inner surface to prevent migration
of the gel relative thereto.
24. A method for separating a sample of blood as recited in claim
21, wherein prior to the step of dispensing, the method further
comprises the step of determining the predetermined first
limit.
25. A method for separating a sample of blood as recited in claim
21, wherein the step of providing the dispensing apparatus includes
the predetermined first limit being determined based on the
following formula: predetermined first limit=X.multidot.C.sub.LL,
where X is a linear dimension of the blood collection tube and
C.sub.LL is a constant based on at least one factor of the
method.
26. A method for separating a sample of blood as recited in claim
25, wherein the step of providing the dispensing apparatus includes
the constant C.sub.LL being equal to a numerical value in a range
of numerical values between 0.30 and 0.70.
27. A method for separating a sample of blood as recited in claim
21, wherein prior to the step of dispensing, the method further
comprises the step of determining the predetermined second
limit.
28. A method for separating a sample of blood as recited in claim
21, wherein the step of providing the dispensing apparatus includes
the predetermined second limit being determined based on the
following formula: predetermined second limit=X.multidot.C.sub.UL,
where X is a linear dimension of the blood collection tube and
C.sub.UL is a constant based on at least one factor of the
method.
29. A method for separating a sample of blood as recited in claim
28, wherein the step of providing the dispensing apparatus includes
the constant C.sub.UL being equal to a numerical value in a range
of numerical values between 0.30 and 0.70.
30. A blood collection apparatus for separating a sample of blood
into portions including a light serum portion and a heavy cellular
portion, the blood collection apparatus comprising: a blood
collection tube having an open end, a closed end and defining a
central inner surface therebetween, at least a portion of the
central inner surface having a non-stick coating, the blood
collection tube being configured for receipt of a volume of a blood
sample; and a dispensing apparatus having a nozzle disposed at a
distal end thereof, the nozzle including a plurality of openings
disposed about a circumference defined by the nozzle, said
plurality of openings configured to dispense gel along a portion of
the central inner surface, the portion of the central inner surface
defining a predetermined first limit and a predetermined second
limit; wherein the predetermined first limit is based on the
following formula: predetermined first limit=X.multidot.C.sub.LL,
where X is a linear dimension of the blood collection tube and
C.sub.LL is a constant based on at least one factor of the blood
collection apparatus, and the predetermined second limit is based
on the following formula: predetermined second
limit=X.multidot.C.sub.UL, where C.sub.LL is a constant based on at
least one factor of the blood collection apparatus.
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'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.degree. 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'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'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'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] FIG. 1 shows the prior art method of dispensing gel at the
bottom of a blood collection tube;
[0024] FIG. 2 shows the prior art blood collection tube of FIG. 1
after a blood sample has been added thereto;
[0025] FIG. 3 shows the prior art migration of gel toward the
serum/coagulum interface during centrifugation of the blood
sample;
[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] 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] 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] 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] 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.sub.LL for the lower limit 27 and C.sub.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.sub.UL is approximately 0.30 and that
C.sub.LL is approximately 0.70. It is envisioned that the constants
C.sub.UL and C.sub.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.multidot.C.sub.LL
Upper limit 28=X.multidot.C.sub.UL
[0038] For example, if C.sub.LL and C.sub.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.times.0.7=70 mm
Upper limit 28=100 mm.times.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.
* * * * *