U.S. patent application number 12/421372 was filed with the patent office on 2009-08-13 for method and device for monitoring platelet function.
This patent application is currently assigned to PLACOR INC.. Invention is credited to Daniel G. Ericson.
Application Number | 20090203064 12/421372 |
Document ID | / |
Family ID | 31993962 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090203064 |
Kind Code |
A1 |
Ericson; Daniel G. |
August 13, 2009 |
METHOD AND DEVICE FOR MONITORING PLATELET FUNCTION
Abstract
The invention provides a method of monitoring platelet function
in a mammal by passing blood removed from the body of the mammal
through a passageway to contact an obstruction or irregularity in
the passageway to generate a platelet mass in the passageway, and
monitoring the flow or composition of the blood in the passageway
to detect the platelet mass. The flow and composition change in
response to the formation of a platelet mass in the passageway.
Devices, articles, and kits for performing the methods are also
disclosed.
Inventors: |
Ericson; Daniel G.;
(Rochester, MN) |
Correspondence
Address: |
POPOVICH, WILES & O'CONNELL, PA;650 THIRD AVENUE SOUTH
SUITE 600
MINNEAPOLIS
MN
55402
US
|
Assignee: |
PLACOR INC.
Plymouth
MN
|
Family ID: |
31993962 |
Appl. No.: |
12/421372 |
Filed: |
April 9, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11952328 |
Dec 7, 2007 |
7534620 |
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12421372 |
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11077191 |
Mar 10, 2005 |
7309607 |
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11952328 |
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PCT/US03/28596 |
Sep 10, 2003 |
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11077191 |
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60409377 |
Sep 10, 2002 |
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Current U.S.
Class: |
435/29 |
Current CPC
Class: |
G01N 33/4905
20130101 |
Class at
Publication: |
435/29 |
International
Class: |
C12Q 1/02 20060101
C12Q001/02 |
Claims
1. A method of monitoring platelet function comprising: passing
blood removed from a mammal through a passageway comprising an
obstruction or an irregularity, to contact the obstruction or the
wall of the passageway at the irregularity, to generate a platelet
mass in the passageway; and monitoring the flow or composition of
the blood in the passageway to detect formation of the platelet
mass; wherein the passageway does not comprise an added biological
agent that activates platelets.
2. The method of claim 1 wherein the blood passes the obstruction
or irregularity.
3. The method of claim 1 wherein the blood does not comprise an
added biological agent that activates platelets.
4. The method of claim 1 wherein the passageway and blood do not
comprise an added chemical agent that activates platelets.
5. The method of claim 1 wherein no biological or chemical agents
are added to the removed blood.
6. A method of monitoring platelet function in a mammal comprising:
passing blood removed from a mammal through a passageway comprising
an obstruction or an irregularity, to contact the obstruction or
the wall of the passageway at the irregularity, to generate a
platelet mass in the passageway, and monitoring the flow or
composition of the blood in the passageway to detect formation of
the platelet mass; wherein the platelet mass is substantially
depleted in fibrin in comparison to a natural clot.
7. The method of claim 6 wherein the blood passes the obstruction
or irregularity.
8. The method of claim 1 wherein the flow of the blood in the
passageway is monitored.
9. The method of claim 8 wherein the flow is monitored by
monitoring the pressure of the blood in the passageway.
10. The method of claim 9 wherein the pressure is monitored with a
pressure transducer.
11. The method of claim 8 wherein the flow is monitored
optically.
12. The method of claim 11 wherein the flow is monitored with a
light-emitting diode and a light detector.
13. The method of claim 1 wherein the composition of the blood in
the passageway is monitored.
14. The method of claim 13 wherein the size of the platelet mass is
directly monitored.
15. The method of claim 13 wherein the chemical composition of the
blood is monitored.
16. The method of claim 15 wherein the pH, concentration of
O.sub.2, concentration of CO.sub.2, concentration of Mg.sup.++, or
concentration of K.sup.+ is monitored.
17. The method of claim 1 wherein the passageway comprises an
obstruction.
18. The method of claim 17 wherein the obstruction is a plug.
19. The method of claim 18 wherein the plug partially obstructs the
passageway.
20. The method of claim 18 wherein the plug fully obstructs the
passageway.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 11/952,328, filed Dec. 7, 2007, which is a
continuation of U.S. patent application Ser. No. 11/077,191, filed
Mar. 10, 2005, now U.S. Pat. No. 7,309,607 B2, issued Dec. 18,
2007, which is a continuation of International Application No.
PCT/US03/28596, filed Sep. 10, 2003, the contents of each of which
are hereby incorporated herein by reference. This application
claims the benefit of U.S. Provisional Application No. 60/409,377,
filed Sep. 10, 2002.
BACKGROUND
[0002] Platelets are anucleated cells that are the primary cells
responsible for stopping bleeding. Blood platelets are
approximately 3 microns in size and circulate in the blood stream
as disc shaped cells that upon activation by either tissue injury
or exposure to a foreign material undergo physiological changes
that lead to aggregate formation at the site of injury or foreign
material. Blood platelets circulate at approximately 250,000 to
350,000 platelets per microliter of whole blood. Upon activation,
platelets change shape from a disc to a sphere and form pseudopodia
elongations.
[0003] The normal platelet response to initiate cessation of
bleeding is to undergo a shape change, attach to the surface, and
release intraplatelet components that act to provide an
autocatalytic recruitment of more platelets. With the recruitment
of additional platelets, a platelet plug or aggregate mass forms.
The aggregate mass evolves from a single platelet of only 3 microns
in size to a mass on the order of millimeters in size. The platelet
mass additionally recruits and participates with the plasma
coagulation proteins. The plasma coagulation proteins undergo a
cascade of events involving 13 enzymes and cofactors, which leads
to the activation of plasma fibrin to form a fibrin clot.
[0004] It is useful here to briefly summarize the biochemical
events of hemostasis (the cessation of bleeding). Normal intact
endothelium does not initiate or support platelet adhesion
(although in certain vascular diseases platelets may adhere to
intact endothelium). Vascular injury, however, exposes the
endothelial surface and underlying collagen. Following vascular
injury, platelets attach to adhesive proteins such as collagen via
specific glycoproteins on the platelet surface. This adhesion is
followed or accompanied by platelet activation, where platelets
undergo a shape change from a disc shape to a spherical shape with
extended pseudopodia. At this time, the platelet release reaction
also occurs. The platelets release biologically active compounds
stored in the cytoplasmic bodies that stimulate platelet activation
or are otherwise involved in clotting reactions. These include ADP,
serotonin, thromboxane A.sub.2, and von Willebrand factor.
Thromboxane A.sub.2 is a potent inducer of platelet secretion and
aggregation. It is formed by the enzyme cyclooxygenase, which is
inhibited by aspirin, among other drugs.
[0005] Following activation, glycoprotein IIb and IIIa (GPIIbIIIa)
receptors on the surface of the platelets undergo a conformational
change from a relatively inactive conformation to an activated
form. GPIIbIIIa receptors mediate the adhesion of more platelets by
adhering to the circulating plasma protein fibrinogen, which serves
as a bridging ligand between platelets. The adhesion and
aggregation of platelets constitutes primary hemostasis.
[0006] Secondary hemostasis stabilizes the platelet mass by forming
a fibrin clot. The fibrin clot is the end product of a series of
reactions involving plasma proteins. The process is known as blood
coagulation. Among the plasma proteins involved are the activated
forms of the clotting factors II, VII, IX, X, XI, and XII (the
activated forms have an "a" following the Roman numeral, e.g.,
factor IIa). The activated forms of these proteins are serine
proteases.
[0007] Fibrin is formed from fibrinogen, a large circulating plasma
protein, by specific proteolysis. In the process, the protein
thrombin (factor IIa) is consumed. Fibrin monomers next
spontaneously associate to form polymers and form a loose
reinforcement of the platelet plug. Fibrin polymers are then
cross-linked by certain enzymes. The fibrin polymer also traps red
cells and white cells to form a finished clot.
[0008] Under normal conditions of hemostasis, the individual
experiencing bleeding benefits from the ability of platelets to
change shape, adhere, spread, release chemical messengers and
activators, aggregate, and assemble with fibrin. This series of
events stops bleeding at the site of injury and initiates the
process of wound healing.
[0009] But platelet activation and clot formation can also place a
person at risk of pathological cardiovascular events. For example,
venous blood clot formation in the legs, a condition known as deep
vein thrombosis, creates the risk that the blood clots could
embolize (break apart) and result in clot entrapment in the lungs
or the brain, causing pulmonary embolisms and stroke-related
conditions. Platelet activation and fibrin formation in other
locations in some persons create aggregates and small clots in the
arterial circulation that can also lead to embolization and
strokes.
[0010] In addition to age and genetic and lifestyle risk factors,
implanted medical devices in the blood stream also place patients
at greater risk of clot formation and embolization. Each year,
approximately 500,000 heart valves are implanted in the United
States. Although biomaterial advancement has somewhat reduced the
risk of thrombosis (clot formation), all patients with mechanical
heart valves are at increased risk of clot formation, embolization,
and stroke.
[0011] Arterial stents are another type of device placed in the
circulatory system that place patients at risk from platelet
activation. Arterial stents are placed in clogged coronary and
carotid arteries to provide oxygen to cardiac tissue. They are
typically around 5 mm in diameter and are made from stainless steel
or other materials. Due to the introduction of a foreign material
in the blood stream, platelets can become activated and attach to
the wall of the stented vessel. This leads to reocclusion
(restenosis) of the stented vessel, which is a very significant
risk in patients with arterial stents. Restenosis in the first 28
days is reported in 0.5 to 8% of persons receiving stents.
[0012] In an effort to reduce the risk of embolization and
restenosis, patients receiving heart valves or arterial stents are
commonly placed on anti-coagulant or platelet-inhibiting
medications before, during, and after the procedures.
[0013] Current platelet inhibiting drugs fall into three groups:
(1) aspirin-related drugs, which inhibit the platelet
cyclooxygenase enzyme, thus reducing production of thromboxane
A.sub.2, which is a platelet activator; (2) ADP-receptor inhibiting
drugs, which block a surface membrane receptor on the platelets
that is involved in the activation process; (3) monoclonal
antibodies that block GPIIbIIIa receptors on the platelet surface.
The GPIIbIIIa receptor binds the plasma coagulation factor
fibrinogen, which is involved in both aggregation and in forming a
fibrin clot.
[0014] All three approaches are effective in reducing platelet
activation, however no intervention is successful on all patients.
Aspirin is the least expensive. But the appropriate dose varies
unpredictably from person to person, and up to 30% of individuals
on long-term aspirin therapy do not achieve inhibition of platelet
adhesion. The ADP-inhibiting drugs are more expensive than aspirin,
but are gaining popularity. However, as with aspirin, the required
dose and duration of therapy varies, and a large variation in
platelet adhesion characteristics in patients on the drugs exists.
The GPIIbIIIa-inhibiting drugs are argued to provide the greatest
platelet inhibition, but they are very expensive and still suffer
from patient-to-patient variability in dosing and effectiveness.
Other medications are likely to emerge, but all will probably still
have the patient-to-patient variability seen with other
approaches.
[0015] The failure to determine the proper dose and medication to
inhibit platelets can have a great cost in money, and can cause
unnecessary morbidity and death. For example, patients on
anti-GPIIbIIIa drugs have been reported to have from a 5.8 to 11.2%
incidence of adverse reactions in the first 28 days after stenting.
The adverse reactions were defined as death, myocardial infarction,
or urgent need for reintervention with angioplasty procedures. The
risk was even higher when patients were not treated with the drugs.
(New England J. Med. 330:956-961, 1994; New. England J. Med.
336:1689-96A, 1997; Lancet 349:1429-35, 1997.)
[0016] Thus, anti-platelet drugs have a large patient-to-patient
variability and many patients are refractory to some anti-platelet
drugs. A method is needed to monitor platelet function so the
proper dose of an anti-platelet drug for a particular patient can
be determined, and so a physician can determine whether a
particular patient is refractory to one anti-platelet drug but
responsive to another.
[0017] No reliable point-of-care method currently exists to
specifically determine if platelet adhesion and aggregation have
been inhibited. Thus, there is a need for a method and a device to
measure platelet function, and preferably to measure platelet
adhesion and aggregation as part of the measurement of platelet
function. The need to measure platelet function is particularly
acute in patients receiving arterial stents or other cardiovascular
devices, and in other persons at risk of adverse cardiovascular
events. Such a method would allow an attending physician to ensure
that platelet function has in fact been inhibited in a patient at
risk, and to adjust pharmacologic parameters prior to implanting a
cardiovascular device, which will reduce the risk of adverse events
associated with platelet initiation of clot formation.
[0018] Another need to monitor platelet function arises in platelet
transfusions. Platelets are harvested and used in platelet
transfusions to support patients at risk of bleeding. However,
platelet storage poses problems not found with the storage of whole
blood or other components. Whole blood, red and white cells may be
stored at 4.degree. C. for weeks. However, platelets will aggregate
in cold storage and when allowed to settle. Therefore, the standard
means of storing platelets is at room temperature with gentle
agitation. Even under these conditions, platelets lose function by
about 5 days. Thus, methods and devices for monitoring platelet
function are also needed to determine whether stored platelets have
adequate activity to be transfused into patients.
[0019] Another need to monitor platelet function exists to test
patients undergoing a medical or dental procedure for their risk of
excessive bleeding during the procedure.
[0020] Accordingly, a need exists for a method to measure platelet
function. Preferably, the method would monitor platelet adhesion
and aggregation. Preferably, the method would monitor platelet
function specifically, separately from the other aspects of
clotting such as blood coagulation. Preferably, the method would be
inexpensive. Preferably, the method would not depend upon platelet
activation by any particular chemical platelet activator or group
of chemical platelet activators. Preferably, the method could be
used on whole, unprocessed blood, and could produce results quickly
(e.g., be used at the bedside, during a physician visit, or during
a medical procedure to provide a result almost immediately).
Devices to monitor platelet function are also needed.
SUMMARY OF THE INVENTION
[0021] The invention provides methods and devices for assessing
platelet function, as evidenced by platelet adhesion, and
preferably platelet aggregation. In the methods, blood is drawn
through a passageway, such as a catheter, past or against an
obstruction or irregularity in the passageway, such as a wire
placed in the catheter. The platelets adhere and aggregate on the
obstruction or on the wall of the passageway near the obstruction
or irregularity, and form a platelet mass. It is believed that
shear forces associated with passing or contacting the obstruction
or irregularity in the passageway activate the platelets and induce
them to adhere to the foreign material of the obstruction or the
walls of passageway and to aggregate. When the plug forms, it
occludes the lumen of the passageway and flow stops or slows. The
time of partial or full occlusion of the lumen can be recorded as
the platelet plug formation time.
[0022] Since a plug is the end product of platelet activity,
formation of a plug depends on the functioning of all platelet
activities, including platelet adhesion and, if the plug is thicker
than about 15 microns, platelet aggregation. (If the plug is
thicker than about 15 microns, it involves more than a layer of
platelets that forms due to platelet adhesion to a surface, but
rather involves a mass formed by platelet-to-platelet aggregation.)
This contrasts with some current platelet tests that measure only
one specific platelet activity, such as release of a particular
biochemical, or depend only on platelet adhesion and not
aggregation. It has been found that the platelet mass in the
methods of the present invention contains little or no fibrin or
red or white blood cells. Thus, in at least some embodiments, the
methods of the invention measure platelet function specifically,
independently of the blood coagulation reactions.
[0023] No chemical or biological platelet activators need to be
added to the blood or the passageway for the present methods,
although in some embodiments they optionally can be added. Thus,
the methods do not depend on platelets responding to a particular
biochemical activator or particular group of activators. The
methods are fast and can use whole unprocessed blood. Accordingly,
they can produce results quickly and inexpensively with a small
sample of blood taken at the patient's bedside, during a physician
visit, or during an interventional procedure.
[0024] Thus, the invention provides a method of monitoring platelet
function comprising: passing blood removed from a mammal through a
passageway comprising an obstruction or an irregularity, to contact
the obstruction or the wall of the passageway at the irregularity,
to generate a platelet mass in the passageway; and monitoring the
flow or composition of the blood in the passageway to detect
formation of the platelet mass; wherein the passageway does not
comprise an added biological agent that activates platelets.
[0025] The invention also provides a method of monitoring platelet
function in a mammal comprising: passing blood removed from a
mammal through a passageway comprising an obstruction or an
irregularity, to contact the obstruction or the wall of the
passageway at the irregularity, to generate a platelet mass in the
passageway; and monitoring the flow or composition of the blood in
the passageway to detect formation of the platelet mass; wherein
the platelet mass is substantially depleted in fibrin in comparison
to a natural clot.
[0026] The invention further provides a device for monitoring
platelet function, comprising: (a) a fluid-tight material forming a
passageway; (b) a pump functionally linked to the passageway for
pumping blood through the passageway; (c) an obstruction within the
passageway, arranged such that when blood is pumped through the
passageway to contact the obstruction, a platelet mass
substantially free of fibrin forms on or near the obstruction; and
(d) a means for detecting the flow of blood through the passageway
to detect formation of the platelet mass.
[0027] The invention further provides a device for monitoring
platelet function, comprising: (a) a fluid-tight material forming a
passageway; (b) a pump functionally linked to the passageway for
pumping blood through the passageway; (c) an obstruction within the
passageway, arranged such that when blood is pumped through the
passageway to contact the obstruction, a platelet mass
substantially free of fibrin forms on or near the obstruction; and
(d) a means for detecting the composition of blood in the
passageway to detect formation of the platelet mass.
[0028] The invention also provides a device for monitoring platelet
function, comprising: (a) a fluid-tight material forming a
passageway; (b) a pump functionally linked to the passageway for
pumping blood through the passageway; wherein the passageway
comprises an irregularity arranged such that when blood is pumped
through the passageway to contact the wall of the passageway at the
irregularity, a platelet mass substantially free of fibrin forms on
the wall of the passageway at or near the irregularity; and (c) a
means for detecting the flow of blood through the passageway to
detect formation of the platelet mass.
[0029] The invention also provides a device for monitoring platelet
function, comprising: (a) a fluid-tight material forming a
passageway; (b) a pump functionally linked to the passageway for
pumping blood through the passageway; wherein the passageway
comprises an irregularity arranged such that when blood is pumped
through the passageway to contact the wall of the passageway at the
irregularity, a platelet mass substantially free of fibrin forms on
the wall of the passageway at or near the irregularity; and (c) a
means for detecting the composition of blood in the passageway to
detect formation of the platelet mass.
[0030] The invention further provides a device for monitoring
platelet function, comprising: (a) a fluid-tight material forming a
passageway; (b) a pump functionally linked to the passageway for
pumping blood through the passageway; (c) an obstruction within the
passageway, arranged such that when blood is pumped through the
passageway to contact the obstruction, a platelet mass
substantially free of fibrin forms on or near the obstruction; and
(d) a blood flow detector to detect formation of the platelet
mass.
[0031] The invention further provides a device for monitoring
platelet function, comprising: (a) a fluid-tight material forming a
passageway; (b) a pump functionally linked to the passageway for
pumping blood through the passageway; (c) an obstruction within the
passageway, arranged such that when blood is pumped through the
passageway to contact the obstruction, a platelet mass
substantially free of fibrin forms on or near the obstruction; and
(d) a blood composition detector to detect formation of the
platelet mass.
[0032] The invention also provides a device for monitoring platelet
function, comprising: (a) a fluid-tight material forming a
passageway; (b) a pump functionally linked to the passageway for
pumping blood through the passageway; wherein the passageway
comprises an irregularity arranged such that when blood is pumped
through the passageway to contact the wall of the passageway at the
irregularity, a platelet mass substantially free of fibrin forms on
the wall of the passageway at or near the irregularity; and (c) a
blood flow detector to detect formation of the platelet mass.
[0033] The invention also provides a device for monitoring platelet
function, comprising: (a) a fluid-tight material forming a
passageway; (b) a pump functionally linked to the passageway for
pumping blood through the passageway; wherein the passageway
comprises an irregularity arranged such that when blood is pumped
through the passageway to contact the wall of the passageway at the
irregularity, a platelet mass substantially free of fibrin forms on
the wall of the passageway at or near the irregularity; and (c) a
blood composition detector to detect formation of the platelet
mass.
[0034] The invention also provides an article for use in a device
for monitoring platelet function, the article comprising: a
fluid-tight material forming a passageway; and an obstruction in
the passageway, arranged such that when blood is pumped through the
passageway to contact the obstruction, a platelet mass
substantially free of fibrin forms on or near the obstruction.
[0035] The invention also provides an article for use in a device
for monitoring platelet function, comprising: a fluid-tight
material forming a passageway; wherein the passageway comprises an
irregularity arranged such that when blood is pumped through the
passageway to contact the wall of the passageway at the
irregularity, a platelet mass substantially free of fibrin forms on
the wall of the passageway at or near the irregularity.
[0036] The invention also provides a kit for use in monitoring
platelet function, comprising packaging material containing: (a) an
article comprising: (i) a fluid-tight material forming a
passageway; and (ii) an obstruction in the passageway, arranged
such that when blood is pumped through the passageway to contact
the obstruction, a platelet mass substantially free of fibrin forms
on or near the obstruction; and (b) instruction means indicating
the article is to be used in a device for monitoring platelet
function.
[0037] The invention also provides a kit for use in monitoring
platelet function, comprising packaging material containing: (a) an
article comprising: a fluid-tight material forming a passageway;
wherein the passageway comprises an irregularity arranged such that
when blood is pumped through the passageway past the irregularity,
a platelet mass substantially free of fibrin forms on the wall of
the passageway at or near the irregularity; and (b) instruction
means indicating the article is to be used in a device for
monitoring platelet function.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIGS. 1A-G show passageways for the passage of blood, with
various types of obstructions and irregularities in the
passageways.
[0039] FIG. 2 is a schematic drawing of a device of the
invention.
DETAILED DESCRIPTION
Definitions
[0040] "Platelet function" refers to platelets adhering to a
substrate, changing shape, releasing chemical messengers or
clotting factors stored in the cytoplasm of the platelets, and/or
aggregating with other platelets. "A biological or chemical agent
that activates platelets" refers to a substance that upon contact
with platelets induces platelets to perform any of those platelet
functions (without a requirement that the platelets be exposed to
shear or any other mechanical activator).
[0041] The term "a biological agent that activates platelets"
refers to an agent found naturally in a mammalian body that has the
biological role of activating platelets, such as collagen, ADP,
thrombin, thromboxane A.sub.2, serotonin, and epinephrine.
[0042] "A chemical agent that activates platelets" refers to a
compound that activates platelets other than a mammalian biological
agent. It includes, e.g., lion-biological synthetic compounds,
derivatives of biological agents that activate platelets, or
biological agents found in plants or microorganisms that activate
platelets.
[0043] "An added biological or chemical agent" refers to a compound
or substance that is added to the blood after removal from the
body. An "added agent in the passageway" refers to an agent placed
or incorporated in the passageway prior to addition of blood to the
passageway. The agent could be, for instance, adhered to the wall
of the passageway or to an obstruction in the passageway.
[0044] "Obstruction" refers to an object that partially or fully
obstructs the passageway. Preferably the obstruction partially
obstructs the passageway. Examples of obstructions include (a) a
plug, such as a wire, that occupies a portion of the passageway
(preferably with a space between the plug and the wall of the
passageway), (b) a filter or mesh, or (c) a fiber.
[0045] As used herein, an obstruction in the passageway that is a
"plug" is a solid nonporous object that partially or fully
obstructs the passageway. The plug can be any shape in
cross-section, e.g., circular, square, or rectangular, and can be
composed of any non-porous material, e.g., plastic or metal.
[0046] "Blood" as used herein refers to whole blood or to a blood
fraction containing platelets. Preferably, blood is removed from
the mammal and then passed through the passageway in the methods of
the invention without any processing and without the addition of
any agents (e.g., anti-coagulants or platelet activators). However,
the method will also work with purified platelets or with any blood
fraction enriched in platelets or containing platelets.
Accordingly, the term "blood" includes platelet-containing plasma,
purified platelets, or any blood fraction containing platelets.
[0047] The term "whole blood" refers to blood that has not been
fractionated.
[0048] A "platelet mass" as used herein refers to any mass that is
predominantly platelets. The mass can also contain fibrin and other
cells. Preferably, it is depleted in fibrin and depleted in other
cells as compared to a natural clot. A platelet mass can be less
than about 15 microns thick in one or more dimensions, i.e.,
consisting of a layer of platelets about 5 or fewer platelets thick
and formed by platelet adhesion, with little or no
platelet-to-platelet aggregation. Preferably, however, the platelet
mass is thicker than about 15 microns in all dimensions. The term
"platelet plug" is used interchangeably with "platelet mass."
Description
[0049] The invention provides a method of monitoring platelet
function in a mammal involving passing blood removed from the body
of the mammal through a passageway to contact an obstruction or
irregularity in the passageway to generate a platelet mass in the
passageway, and monitoring the flow or composition of blood in the
passageway. The formation of a platelet mass causes a change in the
flow or composition of the blood in the passageway, and the change
in flow or composition is detected.
[0050] In devices of the invention, blood passes through a
passageway 100, formed by fluid-tight walls 110 of a foreign
material (i.e., any material other than the endothelium of a
natural blood vessel). (FIG. 1A). Preferably, the foreign material
is a non-biological material. It can be, for instance, any type of
plastic, glass, rubber, TEFLON, or metal. Within the passageway is
an obstruction or irregularity. A passageway with obstruction 120
is shown in FIG. 1A. The obstruction is also preferably made of a
foreign material. It can be porous or non-porous. It can be the
same material as the wall of the passageway or a different
material.
[0051] Blood is pumped through the passageway to contact the
obstruction or the wall of the passageway at the irregularity. The
obstruction or irregularity creates areas of high shear and low
shear for fluids passing through the passageway. It is believed
that high shear activates the platelets and areas of low shear
allow the platelets to adhere and form a platelet mass. Preferably,
the blood is pumped past the obstruction or irregularity, until a
platelet mass forms that prevents or resists blood passing.
However, the obstruction can totally occlude the passageway, and
the irregularity can be a closed end of the passageway, where blood
can not pass the obstruction or irregularity. In that case, blood
can be passed back and forth against the occluding obstruction or
irregularity until a platelet mass forms that is detected.
[0052] One example of an obstruction is a wire 120 as shown in FIG.
1A. The obstruction preferably only partially obstructs the
passageway. Preferably the obstruction leaves a gap of at least
about 20 microns between the obstruction and the passageway wall.
Thus, in that case, in order to fully occlude the passageway the
platelet mass must be at least about 20 microns thick. To form a
mass that size, the platelets must not merely adhere to the surface
but must also aggregate to each other. Thus, in this embodiment the
method tests the ability of the platelets to show both the activity
of adhering and the activity of aggregating.
[0053] As blood is pumped past the obstruction 120, a platelet mass
is formed on or near the obstruction. Typically, the platelet mass
forms at a location of low shear, such as on the end of a wire
obstruction. Platelet function can be monitored by measuring the
time until partial or full occlusion of the passageway. Occlusion
of the passageway can be detected by any suitable means. For
instance, a light-emitting diode and a coupled detector can be
placed across one point of the passageway to detect passing of the
red blood past that point. A pressure transducer can be used to
monitor the pressure needed to pump the blood. The passageway can
be placed across the light path of a spectrophotometer, so that the
spectrophotometer detects (a) the passing of red blood past the
light path, (b) an increase in scattering and/or a change in color
at the point of the platelet plug as the platelet plug develops, if
the light path is positioned to pass through the expected point
where the platelet plug forms, or (c) a change in color of the
blood outside of the platelet plug associated with the formation of
the platelet plug. The time it takes the blood to pass from point A
to point B can be measured. Chemical sensors can also be used to
measure the concentrations of particular biochemicals that change,
either in the blood as a whole or in microenvironments at or near
the platelet mass, as the platelet mass forms. For instance, pH,
Mg.sup.++ concentration, K.sup.+ concentration, Na.sup.+
concentration, O.sub.2 concentration, or CO.sub.2 concentration can
be monitored by sensors and methods known in the art.
[0054] The dimensions of the passageway and obstruction or
irregularity can be any dimensions suitable, i.e., wide enough to
allow blood to pass freely through the passageway until a platelet
mass forms, and narrow enough that upon formation of a platelet
mass the occlusion of the passageway can be detected. For instance,
the passageway can be a millimeter or less in diameter or more than
a cm in diameter. A wire obstruction of the passageway can leave,
for instance, a gap of about 50 microns with the passageway wall.
Other larger and smaller gap sizes and dimensions are also
possible.
[0055] Blood can be pumped bidirectionally or unidirectionally
through the passageway. Pumping the blood bidirectionally, i.e.,
back and forth past the obstruction or irregularity, has the
advantage that it allows a smaller volume of blood to be used.
Also, with bidirectional flow, any platelet mass formation time can
be measured with a finite amount of blood. With unidirectional flow
of blood through a linear passageway that is open at both ends,
longer platelet mass formation times will require the use of more
blood.
[0056] Pumping blood unidirectionally through a closed loop, where
the blood can cycle the loop as many times as necessary, has the
same advantages as bidirectional flow, namely allowing the use of
smaller volumes of blood and allowing measurement of extended plug
formation times.
[0057] Thus, some embodiments of the devices and methods of the
invention allow the use of small volumes of blood to monitor
platelet activity. Specifically, in some embodiments, less than
about 2 ml, less than about 1 ml, less than about 0.4 ml, less than
about 0.2 ml, less than about 0.1 ml, or less than 50 .mu.l is
used. In some embodiments, a drop, such as is formed by a finger
prick, can be used.
[0058] Certain embodiments of the obstruction or irregularity are
shown in FIGS. 1A-F. FIG. 1A shows a wire 120 as an obstruction.
The wire 120 can be centered or off-center in the passageway.
Either or both of the passageway 100 and wire 120 can have
non-circular cross-sections. The wire 120 in this embodiment can be
replaced with a plug of any non-porous material. The wire can be
any length, and can be shorter than it is wide.
[0059] The obstruction can be multiple wires or plugs 121, as shown
in FIG. 1B.
[0060] The passageway can comprise an irregularity rather than, or
in addition to, an obstruction. The irregularity can be any angle,
narrowing, expansion, or curve in the passageway that is suitable
to allow formation of a platelet mass. For instance, the
irregularity can be step 130 in the wall of the passageway, as
shown in FIG. 1C. The smaller diameter section of the passageway
could be on the same center as the larger diameter section, or
offset.
[0061] The irregularity could be a narrowed section 131 of the
passageway, as shown in FIG. 1D. The irregularity could also be an
expansion 132 in the passageway 100 (FIG. 1E).
[0062] Another example of a suitable obstruction is an inserted
flow restrictor 122 (FIG. 1F). The flow restrictor could be, for
example, a filter membrane; a single filter or a plurality of
fibers, wires, or ribbons; or a piece of woven or knitted
fabric.
[0063] A plurality of obstructions or irregularities, or a
combination of both obstructions and irregularities can be
used.
[0064] The passageway in the invention can be circular, square, or
any other shape in cross-section. The passageway can be curved or
linear.
[0065] Any flow pattern can be used that produces a platelet mass
in a suitable time. For instance, steady unidirectional, or
oscillating bidirectional flow can be used. With oscillating
bidirectional flow, the oscillation pattern can be sinusoidal, saw
tooth, square wave, asymmetric saw tooth, trapezoidal, asymmetric
trapezoidal, or other patterns. In unidirectional flow, a pulsate
component can be superimposed on the steady flow, and the pulsate
component can have any of the above patterns. The flow patterns can
also vary with time or with measured resistance to reduce the risk
of dislodging a platelet mass once it has started to form. Dwell
periods (no flow) can be introduced to allow aggregation of
platelets activated by shear.
[0066] To achieve the flow patterns described, a pump is preferably
used to draw a predetermined volume of blood at a predetermined
flow rate (although the flow rate can vary with time, as described
above) and a predetermined shear rate into and through the
passageway.
[0067] An example of a device for monitoring platelet function of
the invention is shown in FIG. 2. A three-way y-shaped flow divider
150 with three luer locks 180, 181, and 182 at its openings is
linked to a tube 140 at luer lock 181 to form the passageway 100.
The passageway 100 contains wire 120, which is held in position at
the open end of the passageway. Blood can be placed in the device
by linking a syringe to luer lock 180. Luer lock 182 links the flow
divider 150 to a bidirectional pump 160. The bidirectional pump 160
is coupled to a pressure transducer 170 to monitor the pressure in
the passageway. After blood is placed in the passageway, the
opening at luer lock 180 can be closed. Blood is then pumped back
and forth through the passageway until a platelet mass forms,
slowing or stopping the flow, as detected by the pressure
transducer. The time is recorded as the platelet mass formation
time.
[0068] One embodiment of an article for use in a device for
monitoring platelet function is composed of a rigid
precision-molded plastic piece, with a passageway molded therein.
The article can have an aperture for accepting blood, linked to the
passageway. The ends of the passageway can be open to the air to
allow free flow of blood without pressure buildup. The passageway
in one embodiment is about a millimeter in diameter and a few cm
long, with a stainless steel wire plug of a few millimeters length
fixed to one wall of the passageway. The gap between the wire plug
and the other wall of the passageway can be, for example, about 50
microns. The article can be placed in a flow detection device,
where the device includes a bidirectional pump linked to the
passageway and an LED and a coupled detector are placed across one
end of the passageway. The detector detects the passing of blood
and then air, as the blood is pumped back and forth, until a
platelet mass forms and prevents the passing of blood. The article
can be made of inexpensive plastic so it is disposable.
[0069] One of the advantages of the invention is that no biological
or chemical agent that activates platelets must be added to the
blood or to the passageway through which blood is pumped. Thus, in
some embodiments of the invention, the passageway (prior to
addition of blood) does not contain an added biological agent that
activates platelets. The blood also optionally does not contain an
added biological agent that activates platelets. In some
embodiments both the passageway and blood do not have an added
biological agent that activates platelets.
[0070] In some embodiments, either or both of the passageway and
blood do not comprise an added chemical agent that activates
platelets.
[0071] In some embodiments, the passageway does not comprise a
biological component to which platelets naturally adhere.
[0072] In specific embodiments, the passageway does not comprise
collagen, ADP, epinephrine, or a derivative thereof.
[0073] In some embodiments, no biological or chemical agents are
added to the removed blood. For instance, in some embodiments, no
anti-coagulants are added to the removed blood. In some
embodiments, the passageway and blood do not comprise an added
anti-coagulant.
[0074] However, the methods optionally can also involve use of an
added agent that activates platelets. The agent can be added to the
blood after it is removed from the body of the mammal, or it can be
added to the passageway of the device and thus added to the blood
as the blood passes through the passageway. For instance, the walls
of the passageway, or the walls of an obstruction can be coated
with the agent. If the obstruction is a filter, the filter could be
soaked in the agent. Among the agents that could be used are
thromboxane A.sub.2. Aspirin is believed to inhibit platelet
function primarily by inhibiting production of thromboxane A.sub.2,
so in some embodiments of testing the effectiveness of aspirin
therapy, it may be useful to add thromboxane A.sub.2 to the blood
or passageway. In particular, it may be useful to compare the
platelet mass formation time with and without thromboxane A.sub.2
added to the blood or passageway.
[0075] Other agents that can be added to the removed blood or to
the passageway in some embodiments include any of the activators of
platelets. Among these are ADP, collagen, thrombin, epinephrine,
and serotonin. Other compounds that are not platelet activators but
are beneficial to plug formation could also be added. These include
fibrinogen, fibrin, and von Willebrand factor.
[0076] The invention can be used to monitor platelet function of
patients treated with ADP inhibitors. Among these drugs are
clopidogrel (PLAVIX) and ticlopidine. In the case of patients
treated with ADP inhibitors, if a platelet-activating agent is
added to the removed blood or the passageway, ADP may be useful as
the added agent. In particular, it may be useful to compare the
platelet mass formation time with and without ADP added to the
blood or passageway.
[0077] The invention can also be used to monitor platelet function
of patients treated with GPIIbIIIa inhibitors. Among the GPIIbIIIa
inhibitors are Tirofiban, Eptifibatide, and Abciximab. In the case
of patients treated with GPIIbIIIa inhibitors, if a
platelet-activating agent is added to the removed blood or the
passageway, fibrinogen may be a preferred agent since it binds to
the GPIIbIIIa receptors.
[0078] Thus, the invention also provides a method of monitoring
platelet function comprising: (a) passing blood removed from a
mammal through a passageway comprising an obstruction or
irregularity to contact the obstruction or the wall of the
passageway at the irregularity, to generate a platelet mass in the
passageway; and monitoring the flow or composition of the blood in
the passageway to determine a platelet mass formation time, wherein
the blood and passageway do not comprise an added biological or
chemical agent that activates platelets; and (b) passing blood
removed from a mammal through a passageway comprising an
obstruction or irregularity to contact the obstruction or the wall
of the passageway at the irregularity, to generate a platelet mass
in the passageway; and monitoring the flow or composition of the
blood in the passageway to determine a platelet mass formation
time, wherein the blood and passageway comprise an added biological
or chemical agent that activates platelets; and (c) comparing the
platelet mass formation times.
[0079] The biological or chemical agent that activates platelets
can be, for instance, thromboxane A.sub.2, ADP, or fibrinogen.
[0080] It has been found that the platelet mass formed in some
embodiments of the invention is substantially free of fibrin and of
red and white blood cells. Thus, in some embodiments, the platelet
mass is substantially depleted in fibrin in comparison to a natural
clot. For instance, the platelet mass can contain less than about
50%, less than about 30%, less than about 10%, or less than about
5% of the fibrin per unit mass found in a natural clot in the
peripheral blood system. In other embodiments, the platelet mass
has no detectable fibrin. In certain embodiments, the platelet mass
is substantially depleted in red cells and/or white cells (e.g.,
contains less than about 50%, less than about 30%, less than about
10%, or less than about 5% of the red or white cell found in a
natural clot in the peripheral blood stream or has no detectable
red or white cells).
[0081] In some embodiments of the invention the blood passes (e.g.,
is pumped past) the obstruction or irregularity in the
passageway.
[0082] Platelet mass formation can be detected by monitoring the
flow or the composition of the blood in the passageway. In some
embodiments, the flow is monitored. Flow can be monitored, for
instance, by monitoring the pressure of the blood in the passageway
or optically. The pressure can be monitored with a pressure
transducer. Optical monitoring can be, for instance, with a LED and
a coupled light detector. The optical monitoring, or other methods,
can be used to measure the time for blood to travel a certain
distance in the passageway. Flow can also be monitored by a flow
meter or by volume displacement, as well as by other means known to
those of skill in the art.
[0083] In some embodiments, the composition of the blood in the
passageway is monitored. For instance, formation or size of the
platelet mass can be directly monitored, e.g., by optical means
such as with an LED or a spectrophotometer. The chemical
composition of the blood can also be monitored. For instance, pH or
concentration of O.sub.2, CO.sub.2, Mg.sup.++, or K.sup.+ can be
monitored, as these correlate with platelet mass formation.
[0084] In some embodiments, the passageway comprises an
obstruction. The obstruction can be, for instance, a plug. The plug
can be a metal wire, plastic, ceramic, glass, or any non-porous
substance. The plug can fully or partially obstruct the
passageway.
[0085] In some embodiments the platelet mass develops thickness in
all dimensions. That is, these embodiments of the methods require
platelet aggregation in addition to platelet adhesion. Thus, in
some embodiments, the platelet mass has a thickness in all
dimensions of at least about 20 microns, at least about 30 microns,
at least about 40 microns, at least about 50 microns, at least
about 70 microns, or at least about 100 microns.
[0086] In some embodiments of the invention, the passageway does
not comprise a biological component to which platelets naturally
adhere.
[0087] In some embodiments, the passageway does not comprise
collagen, ADP, epinephrine, or a derivative thereof.
[0088] In some embodiments, the passageway and blood do not
comprise an added anti-coagulant.
[0089] In some embodiments of the methods, the method further
comprises adding a platelet activator to the blood. In some
embodiments the passageway comprises a platelet activator. The
platelet activator can be, for instance, thromboxane A.sub.2.
[0090] In some embodiments of the methods and devices of the
invention, the platelets are activated at least partially by
mechanical forces. In some embodiments, the platelets are activated
solely by mechanical forces. It is believed that the platelets in
the methods of the invention are activated by high shear and adhere
at a point of low shear. However, by varying the dimensions of the
passageway, the velocity of flow generated by the blood pumping,
and the material of the walls of the passageway and of any
obstructions (e.g., the adhesiveness of the material), wide ranges
of shear can be used. Maximum shear rates in different devices in
which platelet mass formation was detected spanned at least the
range of 50 to 5,000 sec.sup.-1.
[0091] In some embodiments, less than 2 ml, less than 1 ml, less
than 0.4 ml, less than 0.2 ml, less than 0.1 ml, or less than 50
.mu.l of blood is removed from the body of the mammal. In some
embodiments, less than these amounts are transferred to the
passageway.
[0092] In some embodiments of the invention, the blood passes
bidirectionally through the passageway. In other embodiments, at
least part of the passageway is a loop (i.e., a closed circuit,
whether circular, oval, square, or another shape) and the blood
passes unidirectionally through the loop.
[0093] In some embodiments of the invention, the blood is whole
blood. In some embodiments, the removed blood is fractionated
before being used in the methods and devices of the invention.
[0094] In some embodiments of the devices and articles of the
invention, the device or article further comprises a fluid-tight
material forming an aperture linked to the passageway.
[0095] In some embodiments of the devices of the invention, the
device operates without a biological agent that activates
platelets. In some embodiments, the device operates without a
chemical agent that activates platelets.
[0096] In some embodiments of the devices and articles of the
invention, the obstruction in the passageway is arranged such that
when blood is pumped through the passageway to contact the
obstruction, a platelet mass that is substantially free of fibrin
and is at least about 20 micron thick in all dimensions forms on or
near the obstruction.
[0097] In some embodiments of the devices and articles of the
invention, the irregularity in the passageway is arranged such that
when blood is pumped through the passageway to contact the wall of
the passageway at the irregularity, a platelet mass that is
substantially free of fibrin and that is at least about 20 micron
thick in all dimensions forms on the wall of the passageway at or
near the irregularity.
[0098] In some embodiments, the blood flows past the obstruction or
irregularity, and the obstruction or irregularity leaves a
passageway at least 20 microns in diameter or width at the
obstruction or irregularity. For instance, the gap between a plug
and the wall of the passageway is at least 20 microns in these
embodiments. For another example, the diameter or width of the
passageway at the narrowest point of the passageway at an
irregularity that narrows the passageway is at least 20 microns in
these embodiments. When a platelet plug forms that fills the
passageway at this point, the passageway is occluded and this is
detected as a change in the flow of the blood in the passageway.
Thus, the method detects the formation of a platelet plug at least
20 microns thick. In other embodiments, the obstruction or
irregularity leaves a passageway of at least 50 microns, at least
100 microns, 20 to 100 microns, or 20 to 200 microns in diameter or
width at the obstruction or irregularity.
[0099] In some embodiments of the invention, the mammal whose
platelet function is monitored is treated with an anti-platelet
agent. In particular embodiments, the anti-platelet agent comprises
a cyclooxygenase inhibitor (e.g., aspirin or other salicylates), an
ADP inhibitor, a GPIIbIIIa inhibitor, or a combination thereof.
[0100] Several uses of the methods and devices of the invention
exist. The methods and devices can be used to monitor the
effectiveness of anti-platelet agents in patients treated with
anti-platelet agents. Such patients include those treated by
interventional cardiology catheterization. This includes
angiograms, angioplasty, and stent placement. In addition, the
methods can be used to monitor the effectiveness of anti-platelet
agents in patients who receive an artificial heart valve.
[0101] The methods and devices can be used to monitor the
effectiveness of aspirin or other anti-platelet agents in patients
taking the agents to prevent a cardiovascular event, such as
coronary thrombosis (heart attack), pulmonary embolism, stroke, or
deep vein thrombosis due to excessive platelet activity.
[0102] The methods and devices can be used to test patients for
their risk of excessive bleeding. This testing can be needed, for
instance, prior to a surgical or dental procedure. For instance,
the methods can be used on patients prior to having a tooth pulled
or wisdom tooth removed to determine their risk of excessive
bleeding. If it is determined that the patient is at risk of
excessive bleeding, appropriate precautions can be taken, such as
doing the procedure in a setting where a blood transfusion or
platelet transfusion is available.
[0103] The methods can also be used to monitor liver function. When
liver function falls, blood flow through the spleen increases. The
spleen, which normally degrades old non-functional platelets, then
begins to degrade good platelets as well and the platelet count
falls. Since a fall in platelet function can be due to low platelet
count, by detecting low platelet function the present methods
provide a quick way of detecting possible low platelet count.
Accordingly, they can be used to screen for liver disease including
hepatitis A, B, and C, cirrhosis, and liver damage due to
alcoholism.
[0104] The invention will now be illustrated by the following
non-limiting examples.
EXAMPLES
Example 1
Characterization of Platelet Mass Adhering to Wire in a Tube
[0105] Methods:
[0106] Platelet mass formation. Human blood was pumped through the
lumen of a TEFLON tube with a 24 gauge stainless steel wire in the
lumen of the tube, the wire being held in place at the end of the
tube. Twenty microliters of blood was pumped in a cycle of 35
seconds at a flow rate of 20/35=1.75 microliters per second. The
flow corresponded to a peak shear rate of 1600 sec.sup.-1.
Following formation of the platelet mass on the end of the wire,
the wire and attached platelet mass were rinsed in 0.9% PBS for 5
minutes, then fixed in 1% glutaraldehyde for 3 hours.
[0107] Antibody staining. The fluorescein-conjugated monoclonal
antibody CD45 (Becton Dickinson) is specific for the surface
receptor GPIb, which is found on platelets and not on other blood
cells. Ten microliters of the fluorescent antibody was added to the
mass on the tip of the wire and incubated in the dark at room
temperature for 30 minutes. Non-specifically bound monoclonal
antibody was removed from the sample with five 5-minute washes with
0.9% PBS. Fluorescent microscopy was then performed.
[0108] Electron microscopy. In another experiment, the mass
attached at the end of the wire and fixed with glutaraldehyde was
characterized by transmission electron microscopy. The wire and
mass were mounted in embedding solution, and cross-sections of the
mass were cut using standard sectioning procedures. The
cross-sections were evaluated by transmission electron
microscopy.
[0109] Results:
[0110] Fluorescent microscopy showed uniform staining of the mass
on the end of the wire with the platelet-specific antibody, with
deeper color at points where the mass was deeper. (Data not shown.)
This shows the mass consisted largely of platelets, and that
platelets were uniformly distributed in the mass.
[0111] Electron microscopy showed that the mass consisted only of
small anucleated cells (i.e., platelets). No cells containing
nuclei (i.e., white blood cells) were seen. In addition, no larger
anucleated cells (red blood cells) were identified. Additionally,
no fibrin strands were visible in the samples viewed by
transmission electron microscopy. Thus, the mass produced by this
device on the end of the wire was a platelet mass that was free of
fibrin and appeared to be free of other blood cells.
Example 2
Monitoring Platelet Activity in Pigs Receiving Aspirin
[0112] Methods:
[0113] Pigs were placed on various platelet inhibitors and then the
platelet function of the pigs was monitored. Twenty-five pigs
received 300 mg aspirin daily for seven days. Ten pigs received 300
mg ticlopidine (an ADP inhibitor) daily. Ten pigs received a
combination of 300 mg aspirin and 300 mg ticlopidine daily.
[0114] Arterial blood was drawn and placed in a device similar to
the device shown in FIG. 2. Twenty microliters of blood were drawn
into the lumen of the tube at a rate of 1.0 microliter per second.
The wire was 0.016 inches in diameter and the inner diameter of the
tube was 0.034 inches in diameter. Blood (20 .mu.l) was delivered
via a three-way flow divider (a Touhy-Borst Connector) into a
TEFLON tube 2 inches long with a stainless steel wire 0.16 inches
in diameter inserted through the tube and extending about
three-fourths of the length of the tube. The wire was held in place
at the end of the tube. The tube was coupled to a Hamilton syringe
pump and to a HP blood pressure transducer for measuring the
pressure in the tube. The platelet plug formation time was
determined as damping of the blood pressure signal.
[0115] Results:
[0116] The results are shown in Tables 1-3 below.
TABLE-US-00001 TABLE 1 Platelet plug formation time of pigs
receiving aspirin. Day Mean platelet plug time (minutes) Before
aspirin 3.25 (.+-. 0.35) After 3 days 3.9 (.+-. 0.25) After 7 days
4.6 (.+-. 0.42)
TABLE-US-00002 TABLE 2 Platelet plug formation time of pigs
receiving ticlopidine. Day Mean platelet plug time (minutes) Before
ticlopidine 3.31 After 3 days 5.67 After 7 days 6.21
TABLE-US-00003 TABLE 3 Platelet plug formation time of pigs
receiving aspirin and ticlopidine. Day Mean platelet plug time
(minutes) Before treatment 2.6 After 1 day 2.6 After 3 days 2.6
After 7 days 18.5
[0117] The results show that the method used allowed detection of a
change in platelet function in the pigs in response to both aspirin
(a cyclooxygenase inhibitor) and ticlopidine (an ADP inhibitor).
Thus, the method successfully monitors response to anti-platelet
drugs, and is not specific for a particular type of anti-platelet
drug.
[0118] All patents, patent documents, and references cited are
incorporated by reference.
* * * * *