| |
| CLOT-ED Dictionary for Patients |
|
| The definitions provided in this Dictionary section of the
CLOT-ED web site have either been written by the web site author
or collated from material extracted completely or in part or
paraphrased from any of the following sources: Applicable Guidelines
from the National Commission of Clinical Laboratory Standards
(NCCLS), Wayne, PA; Dorland's Illustrated Medical Dictionary,
30th Edition, Elsevier Science, 2003 (www.mercksource.com);
Stedman's Medical Dictionary, 27 th Edition, 2000; The American
Heritage Dictionary of the English Language, Fourth Edition,
2000 (www.bartleby.com);
Miriam-Webster's Eleventh New Collegiate Dictionary, 2003 (www.m-w.com);
The Merck Manual of Medical Information-Second Home Edition,
2003 (www.mercksource.com);
On-Line Medical Dictionary (www.cancerweb.ncl.ac.uk);
University of Edinburgh, Biology Teaching Organization Genetics
Glossary (www.helios.bto.ed.ac.uk);
Hemostasis and Thrombosis Basic Principles & Clinical Practice,
J.B. Lippincott, 1982; Hemostasis and Thrombosis Basic Principles
& Clinical Practice, 4th Edition, Lippincott Williams & Wilkins,
2001; Hematology 2002, American Society of Hematology Education
Program Book, 2002; Consultative Hemostasis and Thrombosis,
WB Saunders, 2002; Blood Components and Pharmacologic Agents,
AABB Press, 2000. |
| |
| A - B
- C - D
- E - F
- G - H
- I - J
- K - L
- M - N
- O - P
- Q/R - S
- T - U/V/W
- X/Y/Z |
| |
| -A- |
| |
| Activated
Partial Thromboplastin Time Test (APTT) |
| A test performed in the coagulation laboratory that evaluates
how well proteins in the intrinsic
pathway and common
pathway of coagulation work. The test is used as a screening
tool. If the APTT is abnormal, it may indicate that 1) these
proteins are decreased in amount and may cause bleeding or 2)
suggest the presence of an inhibitor such as the Lupus
Anticoagulant that may cause thrombosis.
The assay is also used to monitor therapy with unfractionated
heparin. The APTT is the time in seconds required for a
fibrin clot to form in a platelet
poor plasma sample following the addition
of certain chemicals (activating agent, phospholipids,
and calcium chloride). The slide show entitled Intrinsic
Pathway-APTT shows which coagulation
factors are tested by the APTT. |
| |
| Activated Protein
C (APC) |
| Protein C in the presence of thrombin
and thrombomodulin is converted to Activated Protein C, a natural
anticoagulant that dampens coagulation
by inactivating activated factors VIII
and V. The slide show entitled
Activation
of Protein C by Thrombin shows the relationship among these
components. |
| |
| Activated
Protein C Resistance-APCR |
| APCR is a phenotype in which patients
have a limited response to Activated
Protein C. This leads to an increased risk for thrombosis.
If inherited, APCR is associated with a mutation
in the factor V gene (Factor V Leiden).
The APCR phenotype may also be acquired. |
| |
| Aggregation |
| The clumping together of platelets
that leads to thrombus
formation. In the coagulation laboratory a test (Platelet Aggregation)
can be done that determines if platelets can or cannot form
these clumps. |
| |
| Allele |
| One of two different forms of a gene
that exits at a specific location on a single chromosome |
| |
| Amino Acids |
| Amino acids are a class of organic molecules that contain
an amino group and combine to form proteins.
There are twenty common amino acids. |
| |
| Angina (Angina
Pectoris) |
| Angina is a type of chest pain that results from the heart
not getting enough oxygen due to narrowed coronary
arteries. There are two types of angina: 1) stable wherein
the existing pain is not changing in severity, duration, or
frequency or 2) unstable when existing chest pain increases
in severity, duration, or frequency in response to progressively
less exercise or stimuli. |
| |
| Antibody |
| A protein produced by the immune
system that attacks and eliminates antigens
that are foreign in the blood system. There are two types of
antibodies: alloantibodies (made against substances foreign
to your body) and autoantibodies (antibodies made against proteins
produced by your own body). |
| |
| Anticoagulant |
| Anticoagulants are agents that prevent the clotting of blood
or blood products. They are commonly called blood thinners.
Pharmacological anticoagulants such as coumarin
derivatives, heparin,
LMWH, and
hirudin are used to prevent and treat thrombosis. Blood collected
during blood donation and blood used in coagulation testing
must be kept fluid. This is done by using chemicals also known
as anticoagulants. The body also has naturally occurring anticoagulants
(Antithrombin, Activated
Protein C). |
| |
| Antifibrinolytic |
| Antifibrinolytic refers to a process, protein, or drug that
does not allow for the breakdown of fibrin.
If fibrin can not be destroyed, a clot
will remain. Depending on the physical condition of a patient
(bleeding or thrombotic) this may or may not be of benefit. |
| |
| Antigen |
| A foreign product (protein or carbohydrate) in the blood system
that is introduced by bacteria, viruses, or other foreign proteins
causing the immune system to produce specific antibodies
to attack and eliminate it. |
| |
|
Antithrombin |
| Antithrombin is the major physiological inhibitor
of Thrombin. Binding of heparin
to antithrombin accelerates by nearly 1000 times this shutting
down of thrombin. Antithrombin also inactivates enzymes of the
intrinsic pathway
of coagulation (factors IXa,
Xa, XIa,
and XIIa). |
| |
| Arteries |
| Arteries are hollow pipes that carry blood away from the heart.
They all carry blood rich in oxygen with the exception of the
pulmonary artery. Arteries that carry oxygen directly to heart
tissue are called coronary arteries. |
| |
|
Atherosclerotic Plaque |
| An atherosclerotic plaque is a buildup of cholesterol and
fatty material within an artery due
to the effects of atherosclerotic disease (progressive narrowing
and hardening of arteries over time). |
| |
| Atrium (plural form is Atria) |
| Atria are the two upper chambers (left atrium & right
atrium) of the heart that pump blood into the two lower chambers
(ventricles). |
| |
| Autosomal |
| Term that relates to the non-sex chromosomes
(22 inherited from your mother and 22 very similar ones inherited
from your father). |
| |
| -B- |
| |
| Base Pair |
| Four nucleotides (Adenine [A],
Guanine [G], Thymine [T], and Cytosine [C]), are joined in pairs
(always A & G and T & C). The complimentary bases are
found one in each strand of DNA
(mother & father) and together they form a base pair
(A from mother joins with G from father = base pair). There
are approximately 3.2 billion bases in the human genome. |
| |
| Bethesda Inhibitor
Assay (Titer) |
| A test performed in the coagulation laboratory that measures
the level (titer) of antibodies that
a patient has made to Factor
VIII (Hemophilia A) or Factor
IX (Hemophilia B). |
| |
| Bleeding Time |
| A test performed on a patient's arm that measures the time
needed to stop bleeding from a standardized cut. Historically
the test was used as a screening test for Von
Willebrand Disease or for defects in platelet
function. The test has generally been replaced by a test performed
in the laboratory on a blood sample. |
| |
| Blood |
| The fluid that circulates through the heart, arteries,
and veins consisting of solid elements
such as: red blood cells that carry oxygen to tissues, white
blood cells that fight or destroy disease-causing agents, and
platelets that help to stop bleeding
or contribute to thrombosis. |
| |
| Blood Pressure |
| Force or tension in the walls of arteries
derived from the blood current and measured as diastolic (during
heart relaxation) or systolic (during heart contraction) pressures.
Normal blood pressure is referred to as normotensive in contrast
to high blood pressure that is known as hypertensive. |
| |
| Blood Vessels |
| Blood vessels are hollow tubes (arteries,
veins, arterioles, venules, and capillaries)
that carry blood throughout the body. |
| |
| -C- |
| |
| Carriers |
| Individuals who have (carry) the gene
for a condition but who themselves do not have the condition. |
| |
| Catalyst |
| A catalyst is a substance that can alter the speed of a chemical
reaction but itself does not participate in the reaction or
is changed by it. |
| |
| Cholesterol |
| A soft, fatty, wax-like substance found in blood and cells
throughout your body. It is needed for making cell membranes
and some hormones. Your body makes some cholesterol and the
rest comes from animal products such as meat that you eat. Too
much cholesterol is termed hypercholesterolemia and this may
lead to deposits in artery walls called plaque
(atherosclerosis). |
| |
| Chromosomes |
| Chromosomes are threadlike structures inside the nucleus of
a cell that contain thousands of genes.
Each cell in the human body contains 46 chromosomes (23 pairs)
that are inherited from your parents
(22 from your mother plus either an X or Y chromosome [sex chromosome]
and 22 from your father plus a Y chromosome). Material programmed
by genes on chromosomes allows for information such as green
eyes or potential for disease (Hemophilia) to passed from generation
to generation. |
| |
| Citrate (Sodium Citrate) |
| Chemical (salt or ester of citric acid) agent used as the
anticoagulant in blood collection
tubes (“blue top”) used for coagulation laboratory testing. |
| |
| Clone (Cloning, Cloned) |
| Cloning is a process whereby identical copies of a gene
can be made in the laboratory. |
| |
| Clot (Blood Clot) |
| A soft, non-rigid mass consisting of fibrin
gels in which the solid elements of the blood, principally the
red cells, are trapped. Clots are derived from extravascular
(occurring outside the blood) coagulation.
Situations in which extravascular coagulation occurs include
1) loss of blood into tissues or body cavities, 2) in coagulation
laboratory testing, or 3) after death. Clots are dark red, elastic,
and moist with a glistening surface. Though commonly used
as interchangeable terms, blood clot and thrombus
are not synonymous |
| |
| Coagulation (Clotting) |
| The process by which liquid whole blood or plasma
forms a fibrin clot.
This is done through a series of chemical (enzymatic) reactions
involving coagulation factors
(proteins). For coagulation laboratory testing, the process
is divided into three stages: extrinsic
pathway, intrinsic
pathway, and common
pathway. Coagulation and clotting are similar terms. |
| |
| Coagulation Cascade |
| Blood coagulation is a chain of reactions that takes place
as a series of activation steps, each of which involves the
proteolytic conversion of a zymogen (substrate) to the corresponding
active serine protease (enzyme).
These reactions were viewed historically as a “waterfall” or
“cascade” leading to fibrin clot
formation. The slide show entitled Coagulation
Pathways All Components shows these reactions in detail. |
| |
| Coagulation Factors |
| Coagulation factors are components of the blood coagulation
system necessary to make blood clot. They include the following
factors: |
|
• Factor I (Fibrinogen)
• Factor II (Prothrombin)
• Factor III (thromboplastin,
Tissue Factor)
• Factor IV (calcium)
• Factor V (labile factor)
• Factor VII (stable
factor)
• Factor VIII (Factor
VIII:C, antihemophilic globulin [AHF], antihemophilic factor
A)
• Factor IX (Christmas
factor, antihemophilic factor B)
• Factor X (Stuart-Prower
factor)
• Factor XI (antihemophilic
factor C)
• Factor XII (Hageman
factor, surface factor, contact factor)
• Factor XIII (fibrin
stabilizing factor [FSF])
• Other factors: (Prekallikrein
[Fletcher factor], High
Molecular Weight Kininogen [Williams Fitzgerald factor)
|
| |
| The slide show entitled Coagulation
Pathways All Components shows how all these factors relate
to each other. |
| |
| Coagulopathy |
| A disorder, either congenital or
acquired, that prevents the normal clotting
of blood. |
| |
| Common Pathway
of Coagulation |
| The common pathway is the point at which the extrinsic
and intrinsic
pathways of coagulation meet. Both the APTT
and PT are affected by
components (FX, FV,
FII, FI)
of the common pathway. The slide show entitled Tissue
Factor Pathway (Extrinsic) with Common Pathway (PT) shows
which components are part of this pathway. |
| |
| Congenital |
| A condition with which you are born is termed congenital.
This is in contrast to getting a condition during your lifetime
(acquired). |
| |
| Contact Activation |
| A process that initiates the intrinsic
pathway of coagulation and requires Factor
XII, Prekallikrein, and High
Molecular Weight Kininogen. |
| |
| Coumarin |
| Pharmacological agent that serves as an anticoagulant
(blood thinner) by affecting the production of four coagulation
proteins (FII, FVII,
FIX, FX).
The most common coumarins (or derivatives) in use are warfarin
sodium, acenocoumarol, and phenprocoumon. Coumarins are used
to treat thrombosis and are monitored
by the PT (INR)
test. |
| |
| Cryoprecipitate |
| Cryoprecipitate (“cold precipitate”) is prepared from fresh
frozen (cryo) plasma that has been thawed
at 4 oC and from which the upper liquid portion has been removed.
The remaining denser material settles out (precipitates) and
hence the name. This precipitate is rich in Fibrinogen,
Factor VIII (for treating
Hemophilia A), Factor
XIII (treating FXIII deficiencies), and Von
Willebrand Factor (treating Von
Willebrand Disease). |
| |
| -D- |
| |
| Deep Vein Thrombosis
(DVT) |
| Formation of thrombi
in veins located deep within muscles of
the extremities such as the legs. |
| |
| Deoxyribonucleic Acid
(DNA) |
| DNA is the fundamental substance that makes up genes.
It is technically described as an antiparallel double helix
of nucleotides (having deoxyribose
as their sugars) linked by phosphodiester (sugar-phosphate)
bonds to adjacent nucleotides in the same chain and by hydrogen
bonds to complementary nucleotides in the opposite chain. |
| |
| Desmopressin Acetate
(DDAVP) |
| DDAVP is a synthetic drug similar to the natural pituitary
antidiuretic hormone, 8-arginine vasopressin. It is given to
people with mild Hemophilia A or
Von Willebrand Disease
to stop bleeding. The drug works by stimulating release of Factor
VIII and Von Willebrand
Factor from their storage sites in the body. This causes
a temporary increase in these proteins. The drug can be given
intravenously, subcutaneously,
or by intranasal spray. |
| |
|
Dominant |
| Inheritance is said to be dominant
when an allele produces the same outward
effect (phenotype) whether inherited
with a homozygous or heterozygous
allele. For example if brown hair is dominant in your family
you will have brown hair whether you inherit just one brown
hair gene (from either mother or father) or two (from both mother
and father). |
| |
| Dysfibrinogenemia |
| Dysfibrinogenemia is a condition in which a normal amount
of Fibrinogen protein is made
but it functions inadequately. This abnormality can lead to
either bleeding or thrombotic symptoms. |
| |
| -E- |
| |
| Embolism |
| Embolism is the obstruction or blockage of a blood vessel
by an embolus
that has firmly lodged itself into the vessel. |
| |
| Embolus
(plural form is Emboli) |
| Emboli are broken pieces of thrombi
that have been physically detached from a vessel and have moved
from their origins to another site. For example, thrombi originating
from the deep veins (DVT)
may break away and travel to the pulmonary circulation, lodge
therein, and result in a pulmonary
embolism. |
| |
| Enzyme |
| Enzymes are biological catalysts.
The reactants of enzyme-catalyzed reactions are termed substrates.
Enzymes are specific in character because they act on particular
substrates to produce particular products. |
| |
| Exon |
| Exons are regions of a gene that function
in coding for protein synthesis. Exons
make up the messenger RNA (mRNA) that is translated into protein. |
| |
| Extrinsic
Pathway of Coagulation |
| The extrinsic pathway, also referred to as the tissue factor
pathway, is the physiologically relevant pathway for initiating
coagulation of blood.
In the body, Tissue Factor,
from sources outside the bloodstream, and FVII
from within blood are key components. When they come together
on certain cells, this enzymatic complex has two substrates:
FX and FIX.
In coagulation laboratory testing a thromboplastin
reagent is the source for Tissue Factor. The PT
is affected by FVII and factors in the common
pathway of coagulation. The slide show entitled Tissue
Factor Pathway (Extrinsic) with Common Pathway (PT) shows
the components of this pathway. |
| |
| -F- |
| |
| Factor II |
| See Prothrombin |
| |
| Factor V (FV) |
| A coagulation glycoprotein
synthesized in liver and megakaryocytes (parent cells of platelets)
that functions in the of coagulation. When activated by Thrombin,
activated factor V (FVa) serves as a cofactor in the FXa
conversion of Prothrombin
to Thrombin in the presence of phospholipid
and calcium (prothrombinase complex). FVa is inhibited by Activated
Protein C. The slide show entitled
Activation of Protein C by Thrombin shows the relationship
among these components. See also the slide shows entitled Tissue
Factor Pathway (Extrinsic) with Common Pathway (PT) and
Intrinsic
Pathway-APTT. |
| |
| Factor V Leiden |
| Genotype underlying most causes of
Activated Protein
C Resistance. A single point mutation
in the factor V gene gives rise to a FV
protein that can not be completely
inactivated. The continued procoagulant
activity of this abnormal FV protein gives the patient a lifelong
risk for thrombosis. |
| |
| Factor VII (FVII) |
| A coagulation glycoprotein that
needs vitamin K for synthesis in the
liver. In the presence of Tissue
Factor and calcium, FVIIa (serine
protease) converts FX to FXa.
In addition, FVIIa in the presence of Tissue Factor and calcium
converts FIX to FIXa. FVII
participates in the extrinsic
pathway of coagulation. The FVIIa-tissue factor complex
is inhibited by Tissue Factor Pathway Inhibitor (TFPI). The
slide show entitled Coagulation
Pathways All Components
shows how FVII relates to these components to the other
coagulation factors. See
also the slide show entitled Tissue
Factor Pathway (Extrinsic) with Common Pathway (PT). |
| |
| Factor VIII (FVIII) |
| A coagulation glycoprotein made
in the liver and circulating in blood together with Von
Willebrand Factor. FVIII participates in the intrinsic
pathway of coagulation. It accelerates the conversion of
FX to FXa in the presence of FIXa,
phospholipid, and calcium (tenase
complex). The gene for FVIII is X-linked
and mutations in the gene
give rise to a bleeding disorder called Hemophilia
A. FVIII levels can also be low in people with Von
Willebrand Disease since Von Willebrand Factor carries and
protects FVIII in the blood. The slide show entitled Coagulation
Pathways All Components shows how FVIII relates to the other
coagulation factors. See
also the slide show entitled Intrinsic
Pathway-APTT. |
| |
| Factor IX (FIX) |
| A coagulation glycoprotein that
needs vitamin K for synthesis in the
liver. The zymogen, FIX, is converted to a serine
protease (FIXa) by the enzyme FXIa.
FIXa participates in the intrinsic
pathway of coagulation by converting FX
to FXa in the presence of FVIIIa,
phospholipid, and calcium (tenase
complex). The gene for FIX is X-linked
and mutations in the gene
give rise to a bleeding disorder called Hemophilia
B. The slide show entitled Coagulation
Pathways All Components shows how FIX relates to the other
coagulation factors. See
also the slide show entitled Intrinsic
Pathway-APTT. |
| |
| Factor IX Concentrates |
| Blood products used for replacement treatment in patients
with Hemophilia B (FIX deficiency).
Factor IX products contain very
little or no coagulation factors other than FIX. |
| |
| Factor X (FX) |
| A coagulation glycoprotein that
needs vitamin K for synthesis in the
liver. FX participates in the common
pathway of coagulation and is the meeting point for both
the extrinsic
and intrinsic
pathways of coagulation. It is here that FX becomes functional
by the actions of either pathway (intrinsic: FIXa,
FVIIIa, phospholipid
& calcium [tenase complex] or by the extrinsic: FVIIa
/ Tissue Factor complex).
FX activation by the extrinsic pathway gives rise to an initial
burst of Thrombin whereas the tenase
complex formed via FIXa brings about a subsequent explosive
generation of Thrombin. The slide show entitled Coagulation
Pathways All Components shows how FX relates to the other
coagulation factors. See
also the slide shows entitled Tissue
Factor Pathway (Extrinsic) with Common Pathway (PT) and
Intrinsic
Pathway-APTT. |
| |
| Factor XI (FXI) |
| A coagulation glycoprotein
made in the liver and circulating in blood together with High
Molecular Weight Kininogen (HMWK). Unlike other coagulation
serine proteases, FXIa has two active catalytic
sites. FXI participates in the intrinsic
pathway of coagulation by converting FIX
to FIXa. FXI can be activated either by Thrombin
in a feedback mechanism to make more Thrombin or by autoactivation
in the presence of negatively charged materials. In coagulation
laboratory testing, FXI can be activated by FXIIa
in the presence of HMWK and a negatively charged surface. The
slide show entitled Coagulation
Pathways All Components shows how FXI relates to the other
coagulation factors. See
also the slide show entitled Intrinsic
Pathway-APTT. |
| |
| Factor XII (FXII) |
| FXII is a member of the contact
activation proteins. It is an activator of both the coagulation
and kinin systems. FXII can be converted to FXIIa, a serine
protease, either by autoactivation through contact with
negatively charged surfaces or by the cutting action of kallikrein.
FXIIa can activate Prekallikrein
and FXI. In coagulation laboratory
testing FXII participates in the intrinsic
pathway of coagulation. The slide show entitled Coagulation
Pathways All Components shows how FXII relates to the other
coagulation factors. See
also the slide show entitled Intrinsic
Pathway-APTT. |
| |
| Factor XIII (FXIII) |
| FXIII (fibrin-stabilizing factor) circulates in blood with
Fibrinogen. In the presence
of fibrin, Thrombin
converts FXIII to functionally active FXIIIa. FXIIIa acts as
an intermolecular needle and thread by sewing together chemical
bonds in various substrates such as:
fibrin monomers, alpha- 2-plasmin inhibitor, fibronectin, and
collagen. Therefore FXIII is involved not only in hemostasis
but also wound healing and maintenance of pregnancy. The slide
show entitled Fibrinolytic
Pathway shows how FXIII relates to the other coagulation
factors. |
| |
| Fibrin |
| Fibrin is an insoluble, elastic, whitish product resulting
from Thrombin action on Fibrinogen.
It is the final stage in coagulation.
Fibrin traps platelets and red blood
cells and together they form a web-like mesh that stops bleeding
from a cut. Fibrin is stabilized by FXIIIa.
|
| |
| Fibrinogen (FI) |
| A key coagulation protein
made in the liver and circulating in blood. Thrombin
cuts Fibrinogen and this leads to fibrin monomer formation.
The “sewing” action of FXIIIa
stabilizes the fibrin monomers and results in an insoluble fibrin
mesh. |
| |
|
Fibrinogen Assay |
| A coagulation laboratory test for Fibrinogen
activity. The test measures the rate at which Fibrinogen
is converted to fibrin by the action
of Thrombin. |
| |
| Fibrinolysis |
| Fibrinolysis is a controlled process for dissolving a thrombus
so that vessels can remain open. As coagulation
proceeds, it also sets into motion this process to break down
the fibrin that is being made. Local
activation and control of the fibrinolytic process is due in
large part to the characteristics of the thrombus itself. The
key enzyme of the fibrinolytic system is plasmin.
The slide show entitled Fibrinolytic
Pathway shows the major players in fibrinolyisis. |
| |
| -G- |
| |
| Gene |
| A gene is the basic unit of hereditary that carries information
from one generation to the next. It is an ordered sequence of
nucleotide bases that make up a
segment of DNA and contain
chemical instructions necessary to make a product such as a
protein (Factor VIII). Genes are located
on chromosomes. |
| |
| Gene Locus |
| A gene locus is the specific location on a chromosome
where a can be found. |
| |
| Gene Mutation |
| A gene mutation results from changes within the structure
of a gene that gives rise to a gene
that differs from “normal” (wild-type). |
| |
| Gene Sequence |
| A gene sequence is the order of base
pairs in a gene. |
| |
| Gene Therapy |
| Gene therapy is a method that corrects a gene
mutation by adding an intact (normal) gene
or changing one that is already present. |
| |
| Genetics |
| Genetics is the study of genes,
variation in genes, and the impact of this variability on the
transmission of inherited traits. |
| |
| Genetic Markers |
| Genetic markers are unique pieces of DNA
that are easy to identify but that themselves have nothing to
do with the gene being examined. |
| |
| Genome |
| The genome is all the genetic material in a chromosome
set (all 46 chromosomes). |
| |
| Genotype |
| Genotype is the genetic makeup of an organism. |
| |
| Glycoprotein |
| A glycoprotein is a molecule made up of protein
and carbohydrate (glyco) components. |
| |
| -H- |
| |
| Hemarthrosis |
| Hemarthrosis is the accumulation of blood in a joint or joint
cavity. The joint is the most common bleeding site in patients
with severe hemophilia. |
| |
| Hematoma |
| A mass of coagulated
blood, confined to a tissue or organ, which results from a break
in the wall of a blood vessel. Commonly referred to as a bruise. |
| |
| Hemophilia A |
| Hemophilia A is an X-linked bleeding
disorder and therefore almost exclusively affects males. The
gene mutation is passed from mother
to son or may occur as a spontaneous genetic mutation in about
30% of cases. Mutations in the FVIII
gene lead to a deficiency/abnormality in
Factor VIII. Hemophilia A is classified as severe, moderate,
or mild depending on the amount of protein present. Hemophilia
A is also known as classical hemophilia. |
| |
| Hemophilia B |
| Hemophilia B is an X-linked bleeding
disorder and like Hemophilia A almost exclusively affects males.
The gene mutation is passed
from mother to son. Mutations in the FIX gene
lead to a deficiency of Factor IX. Hemophilia B is classified
as severe, moderate, or mild depending on the amount of protein
present. Hemophilia B is also referred to as Christmas Disease. |
| |
| Hemorrhage |
| Loss of blood from a vessel. Commonly
referred to as bleeding. |
| |
| Hemostasis |
| Pharmaceutical heparins are found in cells from porcine intestinal
mucosa (pig gut) or bovine lung (cow lung). Heparins have no
direct anticoagulant effect but
act through Antithrombin. Heparin
is used for the prevention and treatment of thrombosis. |
| |
| Hereditary Disease |
| A disease that is passed down through a family. |
| |
| Heterozygous |
| An individual is heterozygous for a genetic trait if each
allele at the same genetic
location is different. |
| |
| High
Molecular Weight Kininogen (HMWK) |
| Protein involved with the contact
system. The splitting of HMWK by kallikrein releases bradykinin,
a product that helps in keeping vessels open. The slide show
entitled Coagulation
Pathways All Components shows how HMWK relates to the other
coagulation factors.
See also the slide show entitled Intrinsic
Pathway-APTT. |
| |
|
Homozygous |
| An individual is homozygous for a genetic trait if both alleles
at the same genetic location are
identical. |
| |
| Hypertension |
| Hypertension is popularly known as high blood pressure. The
term generally implies diastolic hypertension. |
| |
| Hypofibrinogenemia |
| A lower than normal amount of Fibrinogen
in the blood. |
| |
| -I- |
| |
| Inheritance |
| Inheritance is that which is transmitted from parent to offspring.
For example, the genetic coding for your green eyes was transmitted
from your father to you. |
| |
| Inhibitor |
| An inhibitor is a substance that depresses the activity of
another substance. In the context of hemostasis,
an inhibitor is an antibody that negatively
affects the action of an enzyme (such
as an antibody to FVIII)
or molecule that in a positive way controls an enzyme (such
as Activated Protein C
retarding the action of activated [functional] factors V
and VIII). |
| |
| INR-International
Normalized Ratio (PT-INR) |
| Number that mathematically compensates for differences (thromboplastin
component) in reagents used to perform the PT.
The INR is a common scale for reporting PT results. |
| |
| Intrinsic
Pathway of Coagulation |
| Pathway in which coagulation
is started by components contained within the blood (independent
of Tissue Factor). In this
pathway FXIa in the presence of calcium activates FIX (in the
extrinsic pathway,
FIX is activated by FVIIa
& Tissue Factor). In the coagulation laboratory test known
as the APTT,
the contact system is needed
to begin the reaction. The APTT is affected by all coagulation
proteins in the intrinsic pathway (FXII,
FXI, FIX,
FVIII) and those of the
common pathway.
The slide show entitled Intrinsic
Pathway-APTT shows the components of this pathway. |
| |
| Intron |
| Introns are sections of DNA
in a gene that do not function in the making
of a protein. |
| |
| Inversion |
| An inversion is mutation that
involves the removal of a piece of chromosome,
turning it 180 degrees, and putting it back in the same place.
This segment can no longer be “read” properly and no protein
is made. Approximately 50% of mutations in severe Hemophilia
A are of this type. |
| |
| In vitro |
| The term means “within glass” and refers to testing or observations
that are done outside the body and under artificial conditions.
Almost all coagulation laboratory tests are in vitro observations. |
| |
| In vivo |
| The term means “in life” and refers to testing or observations
made on tissues not removed from the body. |
| |
| Ischemia |
| Ischemia is the deficiency of blood and oxygen to a part of
the body due to constriction or obstruction of a blood
vessel. When specifically applied to the heart, it indicates
that there is a deficiency of blood supply (and oxygen) to the
heart muscle due to obstruction or constriction of the coronary
arteries. |
| |
| ISI-International
Sensitivity Index |
| A number indicating how sensitive a thromboplastin
reagent used for Prothrombin
Time testing is to a reduction in the vitamin
K-dependent coagulation proteins (FII,
FVII, FIX,
FX). The ISI is used to determine
the INR for
patients receiving coumarin. |
| |
| -J- |
| |
| There are no words in this dictionary that begin with
the letter J |
| |
| -K- |
| |
| There are no words in this dictionary that begin with
the letter K |
| |
| -L- |
| |
| Low
Molecular Weight Heparin (LMWH) |
| LMWH preparations are small fragments made from unfractionated
heparin by chemical means. Similar to unfractionated heparin,
LMWH medications act as anticoagulants
by catalyzing Antithrombin.
LMWHs are used for the prevention and treatment of thrombosis.
LMWH preparations generally do not (or minimally so) prolong
the APTT
and therefore are monitored, if necessary, by an anti-Xa assay. |
| |
| Lupus Anticoagulant
(LA) |
| Lupus Anticoagulants are antibodies
(IgG, IgM, or IgA) that interfere with one or more in
vitro phospholipid dependent
coagulation reactions.
Since there are many different types of these antibodies, no
single laboratory test is capable of identifying every LA. LAs
are grouped into a family of antibodies known as antiphospholipid
antibodies. LAs that are not temporary are usually associated
with an increased risk for venous and arterial thrombosis. |
| |
| -M- |
| |
| Menorrhagia |
| Menstrual bleeding that exceeds 80 milliliters per menstrual
cycle. |
| |
| Mutation |
| See Gene Mutation |
| |
| Myocardial Infarction (MI) |
| Myocardial infarction is a term used to describe irreversible
damage to the heart that occurs when one of the coronary
arteries becomes blocked resulting in a lack of oxygen to
the heart (myocardium) tissue. MI is popularly known as a heart
attack. |
| |
| -N- |
| |
| Nucleic acids |
| Nucleic acids in the form of DNA
and RNA control inheritance and
cellular function. Nucleic acids are many nucleotides
linked together (by 3', 5' phosphodiester linkages). In DNA,
deoxyribonucleic acid, the sugar group is deoxyribose and the
bases consist of the nucleotides, adenine, guanine, thymine
and cytosine. RNA (ribonucleic acid) has ribose as the sugar
and nucleotides adenine, guanine, cytosine and uracil (replaces
thymine). |
| |
| Nucleotides |
| Nucleotides are the basic building blocks (alphabet) of nucleic
acids. There are five nucleotides (bases), Adenine (A),
Guanine (G), Thymine (T), Cytosine (C), and uracil (U). They
are made up of a nitrogen-containing purine or pyrimidine base
linked to a sugar (ribose or deoxyribose) and a phosphate group. |
| |
| -O- |
| |
| There are no words in this dictionary that begin with
the letter O |
| |
| -P- |
| |
| Phenotype |
| Phenotype is the observable physical appearance of an organism.
The characteristics result from interactions between the genotype
of the organism and the environment. |
| |
| Phospholipids |
| Phospholipids are the phosphate containing lipids found in
cell membranes (envelope around a cell). Phospholipids are found
in the membranes of platelets and endothelial
cells. The surfaces of these cells are where coagulation
reactions take place. In coagulation laboratory testing such
as the PT and APTT,
addition of phospholipids is a necessary step in performing
these tests. |
| |
| Plaque |
| See Atherosclerotic Plaque |
| |
|
Plasma |
| The fluid portion of anticoagulated
whole blood that remains after blood has
been spun down (centrifuged or sedimented). It contains nutrients,
electrolytes (dissolved salts), gases, albumin, coagulation
factors, wastes, and hormones. It is different from serum
because the anticoagulant that was present would not allow the
whole blood to clot. Therefore
plasma contains Fibrinogen and
serum does not. Plasma and not serum is used for coagulation
laboratory testing. |
| |
| Plasmapheresis |
| Plasmapheresis is a procedure in which whole blood is separated
into cells and plasma by a device known
as a cell separator. The cells are returned to the person undergoing
treatment, while the plasma that contains harmful components
(antibodies for example) is discarded
and replaced with other fluids such as fresh frozen plasma,
albumin and/or plasma substitute. The procedure is often referred
to as plasma exchange. |
| |
| Plasminogen |
| Plasminogen, a protein synthesized in the liver, is the inactive
form of Plasmin, the main enzyme in the fibrinoytic system.
Plasminogen is converted to Plasmin by activators such as tissue
plasminogen activator (tPA) and Streptokinase. Plasmin binds
to fibrin and breaks it down into small
complexes that can be cleared. One of these degraded products
is the fragment D-dimer. The slide show entitled Fibrinolytic
Pathway shows how Plasminogen participates in fibrinolysis. |
| |
| Platelet |
| Platelets (thrombocytes) are small disc-like fragments that
are released from their parent cell, the megakaryocyte. Platelets
normally circulate in blood for approximately seven days. Platelets
form the initial plug when a blood
vessel is injured and so help to keep blood vessels intact.
They also participate in blood coagulation.
Platelets must be activated in order to become sticky and functional.
Thrombin is the most potent platelet
activator. The slide show entitled
Activation of Platelets by Thrombin shows how a platelet
is affected by Thrombin. |
| |
| Prekallikrein (PK) |
| Prekallikrein is a member of the contact
activation proteins. The slide show entitled Coagulation
Pathways All Components shows how Prekallikrein relates
to the other coagulation factors.
See also the slide show entitled Intrinsic
Pathway-APTT. |
| |
| Prenatal Diagnosis |
| A determination of the disease that produces symptoms in a
child before it is born. |
| |
| Procoagulant |
| The term may be used in two ways: 1) describes the inactive
form of any coagulation factor
(FVII is the procoagulant form [inert zymogen] of FVIIa, the
active form) or 2) applies to any agent that promotes coagulation
or thrombosis (for example, activated
platelets are considered procoagulant). |
| |
| Prophylaxis |
| The prevention of disease. |
| |
| Proteins |
| A large class of organic compounds, found in plants and animals,
which contain carbon, hydrogen, oxygen, sulphur, and most notably
nitrogen. Proteins are essentially a combination of various
amino acids that are linked together.
Twenty different types of amino acids are commonly found in
proteins and each protein has a unique, genetically defined
amino acid sequence that determines how it functions. The coagulation
proteins serve as enzymes. |
| |
|
Prothrombin (FII) |
| A coagulation glycoprotein that
needs vitamin K for synthesis in the
liver. It is the inactive form (zymogen) of the active serine
protease, Thrombin, and participates
in the common pathway
of coagulation. Conversion of Prothrombin to Thrombin is catalyzed
by FXa in the presence of the
cofactor FVa, calcium ions, and
phospholipid (together known as
the prothrombinase complex). The slide show entitled
Coagulation Pathways All Components shows how FII relates
to the other coagulation factors.
See also the slide shows entitled Tissue
Factor Pathway (Extrinsic) with Common Pathway (PT) and
Intrinsic
Pathway-APTT. |
| |
| Prothrombin Time (PT) |
| A test performed in the coagulation laboratory that evaluates
how well proteins in the extrinsic
pathway and common
pathway of coagulation work. The test is used as a screening
tool. If the PT is abnormal it may indicate that proteins in
these pathways are decreased in amount and may cause bleeding
in the patient. The test is also used to monitor oral anticoagulant
therapy. The PT is the time in seconds necessary for a fibrin
clot to form after thromboplastin
and calcium chloride have been added to a plasma
sample. The slide show entitled Tissue
Factor Pathway (Extrinsic) with Common Pathway (PT) shows
which coagulation factors
are tested by the PT. |
| |
| Pulmonary Embolism |
| Pulmonary embolism is the lodging (getting stuck) of an embolus
in the pulmonary artery of a lung.
Pulmonary emboli travel by way of the venous circulation from
veins in the lower extremities (DVT).
Once they come to rest in the pulmonary artery the emboli can
cause severe respiratory dysfunction (shortness of breath, rapid
heart & respiration rate). |
| |
| -Q,
R- |
| |
| Reagent |
| Substance used to detect or measure another substance or to
convert one substance into another by means of the reaction
that it causes. Many different types of reagents are used in
the coagulation laboratory to perform testing. |
| |
|
Receptor |
| A receptor is a specific molecular structure on or within
a cell that can bind to another molecule and cause a specific
effect or action after the binding has taken place. |
| |
| Recessive |
| Inheritance is said to be recessive
when an allele gives rise to a phenotype
only when present in the homozygous
form. In the heterozygous state
its outward effect (phenotype) will be hidden by dominant alleles.
For example if red hair is recessive in your family you will
have red hair only if you inherit a red hair gene from your
mother and a red hair gene from your father. If your mother
has red hair and your father has brown hair, you will have brown
hair because brown is a dominant trait. |
| |
| Recombinant Technology
|
| This process uses genetically engineered or cloned material
to make blood products that do not come from human or animal
plasma. This eliminates the risk for
getting viruses that could potentially be found in human blood
products. Currently recombinant coagulation
factors that are available for patient use are FVII
(rFVIIa), FVIII (rFVIII),
and FIX (rFIX). |
| |
| Reference Interval (Range) |
| Range of values found in an apparently healthy population
(one not afflicted with a noticeable illness). This range defines
what is normal. For example, if 30 normal people had PT
values between 11 and 14 seconds, then any patient result that
falls within that range is considered normal whereas a number
such as 17 seconds would be abnormal. |
| |
| Restriction enzymes |
| Restriction enzymes are enzymes that cut DNA
at specific sites and are used as tools in molecular testing. |
| |
| -S- |
| |
| Serine Proteases |
| Many of the coagulation factors
(FII, FVII, FIX, FX, FXI, FXII, Prekallikrein) belong to a family
of proteins termed serine proteases.
They have in common a core containing the amino
acid serine that is essential for their function in accelerating
chemical reactions. Serine proteases circulate in blood
in a dormant form but when activated act on proteases (proteins
that functions as enzymes) with specific
characteristics. |
| |
| Serum |
| Serum is the clear yellowish fluid that remains after whole
blood, that is not anticoagulated,
is allowed to clot and sediment.
The solid portion consists of cells. Serum differs from plasma
in that serum contains no Fibrinogen
(Fibrinogen is consumed as blood clots). |
| |
|
Specimen |
| A specimen is a distinct portion of body fluid or tissue taken
for examination, study, or analysis. For coagulation laboratory
testing, the specimen is whole blood that
is anticoagulated with sodium
citrate when collected into a specimen tube. |
| |
| Stasis |
| Stasis is the slowing down of normal blood flow in a vessel. |
| |
| Subcutaneous |
| Located beneath the layers of skin. |
| |
|
Substrate |
| A substrate is a substance that is acted upon by an enzyme.
The enzyme accelerates the chemical transformation of this substance.
For example the enzyme Thrombin acts
upon Fibrinogen (one of its
substrates) to convert it to fibrin.
|
| |
| -T- |
| |
| Thrombin |
| Thrombin is the key enzyme in coagulation.
The inactive substance from which it is formed is Prothrombin.
Thrombin can act on many substrates affecting different processes:
1) the clotting reaction (Thrombin conversion of Fibrinogen
to fibrin), 2) activation of FXIII
to further strengthen fibrin, 3) activation of FXI
providing a positive feedback mechanism to make more Thrombin,
4) activation of cofactors FVIII
and FV, 5) activation of Protein
C to form Activated Protein
C, a powerful anticoagulant,
6) cleavage of TAFI to form TAFIa which suppresses plasminogen
activation (inhibits fibrinolysis),
and 7) activation of platelets. The
slide show entitled Coagulation
Pathways All Components shows how Thrombin relates to the
other coagulation factors.
For other slide shows highlighting the critical role of Thrombin,
see: Activation
of Protein C by Thrombin,
Activation of TAFI by Thrombin, Fibrinolytic
Pathway, and
Activation of Platelets by Thrombin. |
| |
|
Thrombocytopenia |
| A decrease in the number of platelets
in the blood leading to a potential for
increased bleeding. |
| |
| Thromboembolism |
| See Embolism |
| |
| Thrombogenesis |
| Thrombogenesis is the formation of thrombi
in blood resulting from an imbalance between
procoagulant factors and protective
anticoagulant mechanisms. |
| |
|
Thrombophilia |
| The term is popularly used to describe any disorder, whether
congenital or acquired, associated
with an increased tendency to venous thromboembolism.
|
| |
| Thromboplastin |
| A phospholipid / Tissue
Factor preparation used for performing the Prothrombin
Time. Thromboplastin (Tissue Factor, factor III) comes from
human brain, rabbit brain/lung, bovine brain, or made by recombinant
technology. Thromboplastins vary in their sensitivity to
reductions in vitamin K-dependent
proteins (FII, FVII,
FIX, and FX). |
| |
| Thrombosis |
| Formation of a thrombus.
Thrombosis can occur in veins, arteries,
throughout the body as in Disseminated Intravascular Coagulation,
or in cardiac chambers. |
| |
|
Thrombus
(plural form is Thrombi) |
| A solid mass or plug formed with in a vessel from constituents
of the blood. Arterial thrombi (white
thrombi) are formed in arteries where
an atherosclerotic plaque
has ruptured and are composed mainly of platelet
clumps bound together by thin fibrin
strands. Venous thrombi (red thrombi) form in areas of stasis
and are composed of red cells with a large amount of interspersed
fibrin and relatively few platelets. Though commonly used
as interchangeable terms, blood clot
and thrombus are not synonymous. |
| |
| Tissue Factor (TF) |
| Tissue Factor is a glycoprotein
associated with phospholipid and
found in cells of blood vessels. Under normal conditions it
is not in direct contact with flowing blood. Atherosclerotic
plaques contain Tissue Factor. Exposure of Tissue Factor
to flowing blood (following an injury to tissue) allows it to
complex with FVIIa. This complex
is the most potent activator of the coagulation
cascade and in coagulation laboratory testing is referred
to as the extrinsic
pathway of coagulation. Tissue Factor used in reagents
for coagulation laboratory testing is called thromboplastin.
The slide show entitled Coagulation
Pathways All Components shows how TF relates to the other
coagulation factors. See
also the slide show entitled Tissue
Factor Pathway (Extrinsic) with Common Pathway (PT). |
| |
| -U,
V, W- |
| |
| Unstable angina |
| See Angina Pectoris |
| |
| Veins |
| Veins are hollow pipes that carry blood
to the heart. All veins, except the pulmonary vein carry oxygen-poor
blood. |
| |
| Ventricles |
| The lower chambers of the heart. |
| |
|
Vitamin K |
| Any of several fat-soluble compounds that are found in alfalfa,
green leafy vegetables, fish-meal, and green tea and are essential
for production and function of the vitamin K-dependent coagulation
proteins (FII, FVII,
FIX, FX). |
| |
| Von Willebrand
Factor (VWF) |
| Von Willebrand Factor is a large glycoprotein
that together with platelets forms
the initial platelet plug that stops bleeding. VWF also carries
the FVIII protein and stabilizes
it in the circulation. VWF is synthesized in endothelial cells
and megakaryocytes. A deficiency or abnormality in VWF leads
to a bleeding condition termed Von
Willebrand Disease. |
| |
|
Von Willebrand
Disease (VWD) |
| Von Willebrand Disease is the most common inherited bleeding
disorder in humans. It is inherited in an autosomal
fashion and therefore affects both males and females equally.
In VWD, Von Willebrand
Factor is reduced and/or abnormal. Since VWF carries and
protects FVIII, those levels
will also be affected by levels of VWF. |
| |
| -X,
Y, Z- |
| |
| X-linked |
| Genes present on the X chromosome are
referred to as X-linked. |
| |
| Dictionary prepared March 2004 |
| |
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