Coagulation Studies

Overview

Definition

Coagulation studies are a group of hematologic studies that reflect the function of blood vessels, platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology, and coagulation factors Coagulation factors Endogenous substances, usually proteins, that are involved in the blood coagulation process. Hemostasis, which all work in harmony to achieve hemostasis Hemostasis Hemostasis refers to the innate, stepwise body processes that occur following vessel injury, resulting in clot formation and cessation of bleeding. Hemostasis occurs in 2 phases, namely, primary and secondary. Primary hemostasis involves forming a plug that stops the bleeding temporarily. Secondary hemostasis involves the activation of the coagulation cascade. Hemostasis.

Uses of coagulation studies

• Evaluation of abnormal bleeding or thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus
• Preoperative testing
• Management of anticoagulation Anticoagulation Pulmonary Hypertension Drugs therapy
• Assist in resuscitation Resuscitation The restoration to life or consciousness of one apparently dead. . Neonatal Respiratory Distress Syndrome management during massive transfusions

Review: phases of the hemostatic process

The following is a summary of the hemostatic process:

• Constriction of the blood vessel: limits blood flow Blood flow Blood flow refers to the movement of a certain volume of blood through the vasculature over a given unit of time (e.g., mL per minute). Vascular Resistance, Flow, and Mean Arterial Pressure to the area
• Formation of the platelet plug Platelet plug Hemostasis: the initial, temporary plug formed via the following steps:
  • Adhesion: exposed von Willebrand factor von Willebrand factor A high-molecular-weight plasma protein, produced by endothelial cells and megakaryocytes, that is part of the factor VIII/von Willebrand factor complex. The von Willebrand factor has receptors for collagen, platelets, and ristocetin activity as well as the immunologically distinct antigenic determinants. It functions in adhesion of platelets to collagen and hemostatic plug formation. The prolonged bleeding time in von Willebrand diseases is due to the deficiency of this factor. Hemostasis (VWF) binds to the glycoprotein (Gp) Ib receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors on platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology
  • Aggregation: GpIIb/IIIa receptors Receptors Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors on platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology bind BIND Hyperbilirubinemia of the Newborn fibrinogen Fibrinogen Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides a and b, the proteolytic action of other enzymes yields different fibrinogen degradation products. Hemostasis
  • Secretion: Substances are released that stimulate further platelet activation Platelet activation A series of progressive, overlapping events, triggered by exposure of the platelets to subendothelial tissue. These events include shape change, adhesiveness, aggregation, and release reactions. When carried through to completion, these events lead to the formation of a stable hemostatic plug. Hemostasis and aggregation and initiate the coagulation cascade Coagulation cascade The coagulation cascade is a series of reactions that ultimately generates a strong, cross-linked fibrin clot. Hemostasis.
• Activation of the coagulation cascade Coagulation cascade The coagulation cascade is a series of reactions that ultimately generates a strong, cross-linked fibrin clot. Hemostasis: forms a more stable fibrin Fibrin A protein derived from fibrinogen in the presence of thrombin, which forms part of the blood clot. Rapidly Progressive Glomerulonephritis clot
  • Extrinsic pathway Extrinsic pathway The extrinsic pathway is the primary physiological mechanism by which clotting is initiated Hemostasis: 
    • Primarily responsible for initiation of the cascade
    • Involves (in order): tissue factor, factor VII Factor VII Heat- and storage-stable plasma protein that is activated by tissue thromboplastin to form factor viia in the extrinsic pathway of blood coagulation. The activated form then catalyzes the activation of factor X to factor Xa. Hemostasis, and factor X Factor X Storage-stable glycoprotein blood coagulation factor that can be activated to factor Xa by both the intrinsic and extrinsic pathways. A deficiency of factor X, sometimes called stuart-prower factor deficiency, may lead to a systemic coagulation disorder. Hemostasis
  • Intrinsic pathway Intrinsic pathway The intrinsic pathway is mainly responsible for the amplification of factor X activation Hemostasis: 
    • Primarily involved in amplification of the cascade
    • Can be directly activated by vessel injury
    • Involves (in order): factors XII, XI, IX, VIII, and X
  • Common pathway Common pathway Hemostasis: 
    • The extrinsic and intrinsic pathways join together when factor X Factor X Storage-stable glycoprotein blood coagulation factor that can be activated to factor Xa by both the intrinsic and extrinsic pathways. A deficiency of factor X, sometimes called stuart-prower factor deficiency, may lead to a systemic coagulation disorder. Hemostasis is activated to form the final common pathway Common pathway Hemostasis.
    • Involves (in order): factors X, V, II ( thrombin Thrombin An enzyme formed from prothrombin that converts fibrinogen to fibrin. Hemostasis), I ( fibrin Fibrin A protein derived from fibrinogen in the presence of thrombin, which forms part of the blood clot. Rapidly Progressive Glomerulonephritis), and XIII
• Inhibition of clotting and fibrinolytic phase: 
  • Stops clotting and breaks down the clot once it is no longer necessary
  • Involves: 
    • Plasmin Plasmin A product of the lysis of plasminogen (profibrinolysin) by plasminogen activators. It is composed of two polypeptide chains, light (b) and heavy (a), with a molecular weight of 75, 000. It is the major proteolytic enzyme involved in blood clot retraction or the lysis of fibrin and quickly inactivated by antiplasmins. Hemostasis
    • Antithrombin Antithrombin Endogenous factors and drugs that directly inhibit the action of thrombin, usually by blocking its enzymatic activity. They are distinguished from indirect thrombin inhibitors, such as heparin, which act by enhancing the inhibitory effects of antithrombins. Anticoagulants
    • Proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis C and S

Coagulation Studies

The following studies can assist in diagnosing issues related to hemostasis Hemostasis Hemostasis refers to the innate, stepwise body processes that occur following vessel injury, resulting in clot formation and cessation of bleeding. Hemostasis occurs in 2 phases, namely, primary and secondary. Primary hemostasis involves forming a plug that stops the bleeding temporarily. Secondary hemostasis involves the activation of the coagulation cascade. Hemostasis.

Platelet assessments

Platelet counts:

• Measure platelet number/concentration
• Normal range: 150,000–450,000
• ↑ in thrombocytosis, which can be caused by:
  • Acute blood loss/ iron deficiency anemia Iron Deficiency Anemia Iron deficiency anemia is the most common type of anemia worldwide. This form of anemia is caused by insufficient iron due to a decreased supply, an increased loss, or an increased demand. Iron deficiency anemia is seen across all ages, sexes, and socioeconomic strata; however, children, women of childbearing age, and patients from lower socioeconomic strata are at higher risk. Iron Deficiency Anemia
  • Metastatic cancer
  • Inflammatory conditions: 
    • Rheumatologic disorders
    • Inflammatory bowel disease
    • Kawasaki disease Kawasaki disease An acute, febrile, mucocutaneous condition accompanied by swelling of cervical lymph nodes in infants and young children. The principal symptoms are fever, congestion of the ocular conjunctivae, reddening of the lips and oral cavity, protuberance of tongue papillae, and edema or erythema of the extremities. Kawasaki Disease
    • Nephrotic syndrome Nephrotic syndrome Nephrotic syndrome is characterized by severe proteinuria, hypoalbuminemia, and peripheral edema. In contrast, the nephritic syndromes present with hematuria, variable loss of renal function, and hypertension, although there is sometimes overlap of > 1 glomerular disease in the same individual. Nephrotic Syndrome
  • Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
  • Trauma and burns Burns A burn is a type of injury to the skin and deeper tissues caused by exposure to heat, electricity, chemicals, friction, or radiation. Burns are classified according to their depth as superficial (1st-degree), partial-thickness (2nd-degree), full-thickness (3rd-degree), and 4th-degree burns. Burns
• ↓ in thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia:
  • Immune thrombocytopenic purpura Immune thrombocytopenic purpura Immune thrombocytopenic purpura (ITP), formerly known as idiopathic thrombocytopenic purpura, is a condition that develops secondary to immune-mediated destruction of platelets, resulting in thrombocytopenia (platelet count < 100,000/mm³). Immune thrombocytopenic purpura can be either primary or secondary due to drugs or underlying disease. Immune Thrombocytopenic Purpura
  • Thrombotic thrombocytopenic purpura Thrombotic thrombocytopenic purpura Thrombotic thrombocytopenic purpura (TTP) is a life-threatening condition due to either a congenital or an acquired deficiency of ADAMTS-13, a metalloproteinase that cleaves multimers of von Willebrand factor (VWF). The large multimers then aggregate excessive platelets resulting in microvascular thrombosis and an increase in consumption of platelets. Thrombotic Thrombocytopenic Purpura
  • Gestational thrombocytopenia Gestational Thrombocytopenia Hypocoagulable Conditions
  • HIV HIV Anti-HIV Drugs
  • Drug-induced thrombocytopenia Drug-Induced Thrombocytopenia Thrombocytopenia

Bleeding time Bleeding time Duration of blood flow after skin puncture. This test is used as a measure of capillary and platelet function. Hemostasis (BT):

• Measures the time for bleeding to stop after a lancet incision
• Indirect measure of platelet function
• Normal range: 2–7 minutes
• Prolonged in:
  • Thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia
  • Disseminated intravascular coagulation Disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation ( DIC DIC Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation)
  • Von Willebrand disease Von Willebrand disease Von Willebrand disease (vWD) is a bleeding disorder characterized by a qualitative or quantitative deficiency of von Willebrand factor (vWF). Von Willebrand factor is a multimeric protein involved in the plate adhesion phase of hemostasis by forming a bridge between platelets and damaged portions of the vessel wall. Von Willebrand Disease ( VWD vWD Von Willebrand disease (vWD) is a bleeding disorder characterized by a qualitative or quantitative deficiency of von Willebrand factor (vWF). Von Willebrand factor is a multimeric protein involved in the plate adhesion phase of hemostasis by forming a bridge between platelets and damaged portions of the vessel wall. Von Willebrand Disease)
  • Bernard–Soulier disease
  • Glanzmann thrombasthenia Glanzmann Thrombasthenia Hypocoagulable Conditions
  • Renal failure Renal failure Conditions in which the kidneys perform below the normal level in the ability to remove wastes, concentrate urine, and maintain electrolyte balance; blood pressure; and calcium metabolism. Renal insufficiency can be classified by the degree of kidney damage (as measured by the level of proteinuria) and reduction in glomerular filtration rate. Crush Syndrome
  • NSAID NSAID Nonsteroidal antiinflammatory drugs (NSAIDs) are a class of medications consisting of aspirin, reversible NSAIDs, and selective NSAIDs. NSAIDs are used as antiplatelet, analgesic, antipyretic, and antiinflammatory agents. Nonsteroidal Antiinflammatory Drugs (NSAIDs) and/or aspirin Aspirin The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. Nonsteroidal Antiinflammatory Drugs (NSAIDs) use

Clotting times

These studies are used to assess the amount of time it takes plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products to clot when various substances are added.

• PT: 
  • Measures the time it takes plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products to clot when exposed to tissue factor
  • Measures function of the extrinsic and common pathway
  • Normal range: approximately 11–13 sec
  • Prolonged in:
    • Warfarin Warfarin An anticoagulant that acts by inhibiting the synthesis of vitamin K-dependent coagulation factors. Warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. It is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. Warfarin is also used as a rodenticide. Anticoagulants therapy
    • Vitamin K deficiency Vitamin K Deficiency A nutritional condition produced by a deficiency of vitamin K in the diet, characterized by an increased tendency to hemorrhage (hemorrhagic disorders). Such bleeding episodes may be particularly severe in newborn infants. Fat-soluble Vitamins and their Deficiencies
    • Factor deficiency: II, V, VII, or X
    • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy disease 
    • DIC DIC Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation
• INR:
  • A ratio comparing the patient’s PT to a reference PT set by the WHO
  • Measures function of the extrinsic and common pathways
  • Normal range: approximately 0.8–1.1
• aPTT: 
  • Measures the time it takes plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products to clot when exposed to a negatively charged substance (which activates the intrinsic pathway Intrinsic pathway The intrinsic pathway is mainly responsible for the amplification of factor X activation Hemostasis):
    • Celite
    • Silica
  • Measures function of both the intrinsic and common pathways
  • Normal range: 25–40 sec
  • Prolonged in:
    • Heparin therapy 
    • Hemophilia Hemophilia The hemophilias are a group of inherited, or sometimes acquired, disorders of secondary hemostasis due to deficiency of specific clotting factors. Hemophilia A is a deficiency of factor VIII, hemophilia B a deficiency of factor IX, and hemophilia C a deficiency of factor XI. Patients present with bleeding events that may be spontaneous or associated with minor or major trauma. Hemophilia disorders (abnormal factor VIII Factor VIII Factor VIII of blood coagulation. Antihemophilic factor that is part of the factor viii/von Willebrand factor complex. Factor VIII is produced in the liver and acts in the intrinsic pathway of blood coagulation. It serves as a cofactor in factor X activation and this action is markedly enhanced by small amounts of thrombin. Hemostasis or IX)
    • Von Willebrand disease Von Willebrand disease Von Willebrand disease (vWD) is a bleeding disorder characterized by a qualitative or quantitative deficiency of von Willebrand factor (vWF). Von Willebrand factor is a multimeric protein involved in the plate adhesion phase of hemostasis by forming a bridge between platelets and damaged portions of the vessel wall. Von Willebrand Disease
    • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy disease
    • DIC DIC Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation
• TT: 
  • Time for plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products to clot after exposure Exposure ABCDE Assessment to thrombin Thrombin An enzyme formed from prothrombin that converts fibrinogen to fibrin. Hemostasis
  • Measures the final step in the common pathway Common pathway Hemostasis: the conversion of fibrinogen Fibrinogen Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides a and b, the proteolytic action of other enzymes yields different fibrinogen degradation products. Hemostasis to fibrin Fibrin A protein derived from fibrinogen in the presence of thrombin, which forms part of the blood clot. Rapidly Progressive Glomerulonephritis
  • Normal range: 14–19 sec
  • Prolonged in:
    • ↓ Fibrinogen Fibrinogen Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides a and b, the proteolytic action of other enzymes yields different fibrinogen degradation products. Hemostasis
    • Use of anticoagulants Anticoagulants Anticoagulants are drugs that retard or interrupt the coagulation cascade. The primary classes of available anticoagulants include heparins, vitamin K-dependent antagonists (e.g., warfarin), direct thrombin inhibitors, and factor Xa inhibitors. Anticoagulants that inhibit thrombin Thrombin An enzyme formed from prothrombin that converts fibrinogen to fibrin. Hemostasis: heparin, direct thrombin Thrombin An enzyme formed from prothrombin that converts fibrinogen to fibrin. Hemostasis inhibitors (e.g., Argatroban Argatroban Anticoagulants)
    • DIC DIC Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation
    • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy disease

Coagulation factor assays

Coagulation factor assays primarily used to diagnose specific factor deficiencies. The tests are used to assess the concentration or activity level of individual factors.

• Clot-based assays use PT or aPTT testing calibrated for individual factors.
• Chromogenic assays use cleavage of a chromogenic (colored) substrate Substrate A substance upon which the enzyme acts. Basics of Enzymes to measure factor activity.
• Antigenic assays: ELISAs are used to measure clotting factor levels.
• Fibrinogen Fibrinogen Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides a and b, the proteolytic action of other enzymes yields different fibrinogen degradation products. Hemostasis:
  • The precursor to fibrin Fibrin A protein derived from fibrinogen in the presence of thrombin, which forms part of the blood clot. Rapidly Progressive Glomerulonephritis
  • Abnormally low levels can increase bleeding risk.
  • Normal range: 200–400 mg/dL
  • Abnormal bleeding typically occurs at levels < 100 mg/dL.

Mixing studies

Mixing studies are used to further evaluate an unexplained prolongation of a clotting test, including a prolonged PT, aPTT, or TT.

• Can determine whether an abnormal PT/aPTT is due to:
  • A factor deficiency OR
  • Presence of inhibitor: 
    • Autoantibody to a specific factor
    • Heparins
    • An elevated C-reactive protein
• Measures clotting time of the patient’s plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products when serially diluted with normal plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products
• The normal plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products:
  • Contains all the factors
  • Does not contain enough factors to overcome the presence of inhibitors
• Results: The clotting time will either correct with the addition of normal plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products or fail to correct.
  • If clotting time (PT or aPTT) corrects:
    • Diagnosis: factor deficiency
    • Next step: Identify the specific factor using a coagulation factor assay.
  • If clotting time (PT or aPTT) fails to correct:
    • Diagnosis: presence of a factor inhibitor 
    • Next steps:
      • Consult with hematology.
      • Review medications for potential cause.
      • Determine the titer of antibody present using further serial dilutions.

Clinical Relevance: Hypocoagulable Conditions

Hypocoagulable Hypocoagulable Hypocoagulable conditions, also known as bleeding disorders or bleeding diathesis, are a diverse group of diseases that result in abnormal hemostasis. Physiologic hemostasis is dependent on the integrity of endothelial cells, subendothelial matrix, platelets, and coagulation factors. The hypocoagulable states result from abnormalities in one or more of these contributors, resulting in ineffective thrombosis and bleeding. Hypocoagulable Conditions conditions are a group of diseases that result in abnormal hemostasis Hemostasis Hemostasis refers to the innate, stepwise body processes that occur following vessel injury, resulting in clot formation and cessation of bleeding. Hemostasis occurs in 2 phases, namely, primary and secondary. Primary hemostasis involves forming a plug that stops the bleeding temporarily. Secondary hemostasis involves the activation of the coagulation cascade. Hemostasis. They manifest with minor bleeding ( petechiae Petechiae Primary Skin Lesions, mucocutaneous bleeding) or more severe internal bleeding ( hemarthrosis Hemarthrosis Bleeding into the joints. It may arise from trauma or spontaneously in patients with hemophilia. Hemophilia, intracranial bleeding).

Disorders of formation of the platelet plug Platelet plug Hemostasis

Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with these disorders will most likely have an increased bleeding time Bleeding time Duration of blood flow after skin puncture. This test is used as a measure of capillary and platelet function. Hemostasis but normal PT and aPTT.

• Glanzmann thrombasthenia Glanzmann Thrombasthenia Hypocoagulable Conditions: an autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritance bleeding syndrome characterized by a deficiency of the GpIIb/IIIa receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors, resulting in a lack of platelet aggregation Platelet aggregation The attachment of platelets to one another. This clumping together can be induced by a number of agents (e.g., thrombin; collagen) and is part of the mechanism leading to the formation of a thrombus. Hemostasis
• Bernard–Soulier syndrome: an autosomal recessive Autosomal recessive Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal recessive diseases are only expressed when 2 copies of the recessive allele are inherited. Autosomal Recessive and Autosomal Dominant Inheritance bleeding syndrome characterized by deficiency of the GpIb receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors, resulting in failure of platelet adhesion Platelet adhesion Exposure of the blood to subendothelial components at the site of injury causes platelets to adhere to the injury site. Hemostasis: Bernard–Soulier syndrome can be diagnosed with a ristocetin assay. Ristocetin activates VWF to allow binding to the platelet GpIb receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors; however, in Bernard–Soulier syndrome, platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology will fail to adhere with the assay.
• Thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia: When platelet levels are low, formation of the platelet plug Platelet plug Hemostasis may be impaired. Thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia is usually diagnosed with a CBC with platelet count and morphology assessment. Causes may include immune thrombocytopenic purpura Immune thrombocytopenic purpura Immune thrombocytopenic purpura (ITP), formerly known as idiopathic thrombocytopenic purpura, is a condition that develops secondary to immune-mediated destruction of platelets, resulting in thrombocytopenia (platelet count < 100,000/mm³). Immune thrombocytopenic purpura can be either primary or secondary due to drugs or underlying disease. Immune Thrombocytopenic Purpura ( ITP ITP Immune thrombocytopenic purpura (ITP), formerly known as idiopathic thrombocytopenic purpura, is a condition that develops secondary to immune-mediated destruction of platelets, resulting in thrombocytopenia (platelet count < 100,000/mm³). Immune thrombocytopenic purpura can be either primary or secondary due to drugs or underlying disease. Immune Thrombocytopenic Purpura), thrombotic thrombocytopenic purpura Thrombotic thrombocytopenic purpura Thrombotic thrombocytopenic purpura (TTP) is a life-threatening condition due to either a congenital or an acquired deficiency of ADAMTS-13, a metalloproteinase that cleaves multimers of von Willebrand factor (VWF). The large multimers then aggregate excessive platelets resulting in microvascular thrombosis and an increase in consumption of platelets. Thrombotic Thrombocytopenic Purpura ( TTP TTP Thrombotic thrombocytopenic purpura (TTP) is a life-threatening condition due to either a congenital or an acquired deficiency of adamts-13, a metalloproteinase that cleaves multimers of von Willebrand factor (vWF). The large multimers then aggregate excessive platelets resulting in microvascular thrombosis and an increase in consumption of platelets. Thrombotic Thrombocytopenic Purpura), HIV HIV Anti-HIV Drugs, drug-induced thrombocytopenia Drug-Induced Thrombocytopenia Thrombocytopenia, or other bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types marrow disorders (including malignancy Malignancy Hemothorax).

Disorders of the coagulation cascade Coagulation cascade The coagulation cascade is a series of reactions that ultimately generates a strong, cross-linked fibrin clot. Hemostasis

Hemophilia Hemophilia The hemophilias are a group of inherited, or sometimes acquired, disorders of secondary hemostasis due to deficiency of specific clotting factors. Hemophilia A is a deficiency of factor VIII, hemophilia B a deficiency of factor IX, and hemophilia C a deficiency of factor XI. Patients present with bleeding events that may be spontaneous or associated with minor or major trauma. Hemophilia: a rare blood clotting disorder in which the body lacks blood-clotting factors ( factor VIII Factor VIII Factor VIII of blood coagulation. Antihemophilic factor that is part of the factor viii/von Willebrand factor complex. Factor VIII is produced in the liver and acts in the intrinsic pathway of blood coagulation. It serves as a cofactor in factor X activation and this action is markedly enhanced by small amounts of thrombin. Hemostasis in hemophilia A Hemophilia A The classic hemophilia resulting from a deficiency of factor VIII. It is an inherited disorder of blood coagulation characterized by a permanent tendency to hemorrhage. Hemophilia and factor IX Factor IX Storage-stable blood coagulation factor acting in the intrinsic pathway of blood coagulation. Its activated form, ixa, forms a complex with factor VIII and calcium on platelet factor 3 to activate factor X to Xa. Hemostasis in hemophilia B Hemophilia B A deficiency of blood coagulation factor IX inherited as an X-linked disorder. (also known as Christmas disease, after the first patient studied in detail, not the holiday.) historical and clinical features resemble those in classic hemophilia, but patients present with fewer symptoms. Severity of bleeding is usually similar in members of a single family. Many patients are asymptomatic until the hemostatic system is stressed by surgery or trauma. Treatment is similar to that for hemophilia A. Hemophilia). Affected individuals present with abnormal bleeding that occurred spontaneously or after minor trauma. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship can bleed into joint spaces and can develop life-threatening internal bleeding. Coagulation studies typically reveal a prolonged aPTT due to the abnormalities in the intrinsic pathway Intrinsic pathway The intrinsic pathway is mainly responsible for the amplification of factor X activation Hemostasis, but the PT and platelet counts are normal. Mixing studies will correct, and the level of the specific factor activity in which the patient is deficient will be low.

Mixed disorders affecting both platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology and coagulation factors Coagulation factors Endogenous substances, usually proteins, that are involved in the blood coagulation process. Hemostasis

• Von Willebrand disease Von Willebrand disease Von Willebrand disease (vWD) is a bleeding disorder characterized by a qualitative or quantitative deficiency of von Willebrand factor (vWF). Von Willebrand factor is a multimeric protein involved in the plate adhesion phase of hemostasis by forming a bridge between platelets and damaged portions of the vessel wall. Von Willebrand Disease ( VWD vWD Von Willebrand disease (vWD) is a bleeding disorder characterized by a qualitative or quantitative deficiency of von Willebrand factor (vWF). Von Willebrand factor is a multimeric protein involved in the plate adhesion phase of hemostasis by forming a bridge between platelets and damaged portions of the vessel wall. Von Willebrand Disease): the most commonly inherited disorder of hemostasis Hemostasis Hemostasis refers to the innate, stepwise body processes that occur following vessel injury, resulting in clot formation and cessation of bleeding. Hemostasis occurs in 2 phases, namely, primary and secondary. Primary hemostasis involves forming a plug that stops the bleeding temporarily. Secondary hemostasis involves the activation of the coagulation cascade. Hemostasis, caused by a qualitative or quantitative deficiency in VWF: The three primary types of VWD vWD Von Willebrand disease (vWD) is a bleeding disorder characterized by a qualitative or quantitative deficiency of von Willebrand factor (vWF). Von Willebrand factor is a multimeric protein involved in the plate adhesion phase of hemostasis by forming a bridge between platelets and damaged portions of the vessel wall. Von Willebrand Disease differ in severity, though all tend to present with bleeding abnormalities. Von Willebrand factor von Willebrand factor A high-molecular-weight plasma protein, produced by endothelial cells and megakaryocytes, that is part of the factor VIII/von Willebrand factor complex. The von Willebrand factor has receptors for collagen, platelets, and ristocetin activity as well as the immunologically distinct antigenic determinants. It functions in adhesion of platelets to collagen and hemostatic plug formation. The prolonged bleeding time in von Willebrand diseases is due to the deficiency of this factor. Hemostasis is required for both initial platelet adhesion Platelet adhesion Exposure of the blood to subendothelial components at the site of injury causes platelets to adhere to the injury site. Hemostasis, and it helps stabilize factor VIII Factor VIII Factor VIII of blood coagulation. Antihemophilic factor that is part of the factor viii/von Willebrand factor complex. Factor VIII is produced in the liver and acts in the intrinsic pathway of blood coagulation. It serves as a cofactor in factor X activation and this action is markedly enhanced by small amounts of thrombin. Hemostasis in the intrinsic pathway Intrinsic pathway The intrinsic pathway is mainly responsible for the amplification of factor X activation Hemostasis. Testing shows a normal platelet count, but the aPTT may be prolonged (depending on the reduction of factor VIII Factor VIII Factor VIII of blood coagulation. Antihemophilic factor that is part of the factor viii/von Willebrand factor complex. Factor VIII is produced in the liver and acts in the intrinsic pathway of blood coagulation. It serves as a cofactor in factor X activation and this action is markedly enhanced by small amounts of thrombin. Hemostasis activity). A VWF antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination test, specific functional assays, and genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies can aid in the diagnosis.
• Disseminated intravascular coagulation Disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation: a serious medical condition in which the coagulation cascade Coagulation cascade The coagulation cascade is a series of reactions that ultimately generates a strong, cross-linked fibrin clot. Hemostasis is activated systemically, leading to multiple clots that can lead to permanent end-organ damage and in the process, coagulation factors Coagulation factors Endogenous substances, usually proteins, that are involved in the blood coagulation process. Hemostasis are used up: Disseminated intravascular coagulation Disseminated intravascular coagulation Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation always has a secondary cause. Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease, burns Burns A burn is a type of injury to the skin and deeper tissues caused by exposure to heat, electricity, chemicals, friction, or radiation. Burns are classified according to their depth as superficial (1st-degree), partial-thickness (2nd-degree), full-thickness (3rd-degree), and 4th-degree burns. Burns, and malignancies are among the most common causes, but DIC DIC Disseminated intravascular coagulation (DIC) is a condition characterized by systemic bodywide activation of the coagulation cascade. This cascade results in both widespread microvascular thrombi contributing to multiple organ dysfunction and consumption of clotting factors and platelets, leading to hemorrhage. Disseminated Intravascular Coagulation can also occur during severe postpartum hemorrhage Postpartum hemorrhage Postpartum hemorrhage is one of the most common and deadly obstetric complications. Since 2017, postpartum hemorrhage has been defined as blood loss greater than 1,000 mL for both cesarean and vaginal deliveries, or excessive blood loss with signs of hemodynamic instability. Postpartum Hemorrhage. Laboratory findings include thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia, prolongation of the PT and aPTT, and elevation of D-dimer D-dimer Deep Vein Thrombosis.
• Cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis: The liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy is the primary site of synthesis Synthesis Polymerase Chain Reaction (PCR) for a majority of the clotting factors. In addition to impaired synthesis Synthesis Polymerase Chain Reaction (PCR) of clotting factors, cirrhosis Cirrhosis Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Cirrhosis also may independently result in thrombocytopenia Thrombocytopenia Thrombocytopenia occurs when the platelet count is < 150,000 per microliter. The normal range for platelets is usually 150,000-450,000/µL of whole blood. Thrombocytopenia can be a result of decreased production, increased destruction, or splenic sequestration of platelets. Patients are often asymptomatic until platelet counts are < 50,000/µL. Thrombocytopenia due to splenic sequestration Splenic sequestration Severe Congenital Neutropenia of platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology and decreased thrombopoietin Thrombopoietin A humoral factor that stimulates the production of thrombocytes (blood platelets). Thrombopoietin stimulates the proliferation of bone marrow megakaryocytes and their release of blood platelets. The process is called thrombopoiesis. Platelets: Histology production. Platelets Platelets Platelets are small cell fragments involved in hemostasis. Thrombopoiesis takes place primarily in the bone marrow through a series of cell differentiation and is influenced by several cytokines. Platelets are formed after fragmentation of the megakaryocyte cytoplasm. Platelets: Histology themselves may also be dysfunctional. The platelet count may be low and the PT and aPTT may both be prolonged.