Hematology Lecture Exam #3 (Ch 24, 25, 26, & 27) EOC Questions and Summaries
Bernard-Soulier syndrome and Glanzmann's thrombasthenia are both qualitative platelet disorders caused by?
Abnormalities of platelet surface glycoproteins
Qualitative platelet disorders may be caused by?
Abnormalities of platelet surface glycoproteins, deficiencies of platelet granules, or abnormalities of the platelet release mechanism.
Glanzmann's thrombasthenia is a rare autosomal-recessive disorder of platelet function caused by?
Absence or deficiency of the membrane GPIIb/IIIa complex (mediates binding of fibrinogen, vWF, and fibronectin to activated platelets)
Inactivation of factors Va and VIIIa is caused by?
Activated protein C
Which of the following is not characteristic of Glanzmann's thrombasthenia? A) Prolonged bleeding time B) Giant platelets with thrombocytopenia C) Absent platelet aggregation response to ADP, thrombin, collagen, and epinephrine D) Normal platelet aggregation to ristocetin and bovine vWF
B
For a normal PT with an abnormal aPTT, a mixing study should be performed. If the aPTT is corrected with the pooled normal plasma, a deficiency of what factors should be suspected?
Factors VIII:C, IX, XI, XII, prekallikrein (PK), and/or high molecular weight kininogen (HMWK)
An inhibitor to what factors should be suspected if the aPTT is not corrected with a mixing study?
Factors VIII:C,IX, XI, XII, PK, HMWK as well as lupus anticoagulant or heparin.
Which factors are classified as contact group proteins?
Factors XI, XII, PK, & HMWK
What product is responsible for the stabilization of the hemostatic plug?
Fibrin
What is the process of removing unwanted fibrin deposits called?
Fibrinolysis
Thrombin time may be prolonged due to?
Hypofibrinogenemia and dysfibrinogenemia, heparin, fibrin degradation products (FDPs), and pathologic circulating inhibitors.
Activation of second messenger pathways within the platelet leads to intracellular biochemical changes culminating in platelet activation events such as?
Shape change, secretion, cytoskeletal reassembly, and platelet aggregation
Which factors are classified as prothrombin group proteins?
Factors II, VII, IX, & X
Which factors are dependent on vitamin K for synthesis?
Factors II, VII, IX, & X (prothrombin group)
Which factors are unique to the extrinsic system?
Factors III and VII
Which factors are unique to the intrinsic system?
Factors VIII, IX, XI, & XII
What disorders are classically associated with thrombocytosis?
Myeloproliferative syndromes
What is true of acute idiopathic thrombocytopenia (ITP)?
Occurs following a viral infection, spontaneous abortions are common, found primarily in children, and platelet counts are generally lower than in the chronic version.
DIC associated with malignancy can be due to?
Tumor tissue factor-like activity, factor X activation by tumor cysteine protease activity, and endothelial cell disruption by tumor invasion.
What type of purpura is caused by abnormalities of blood vessels without associated platelet or plasma protein defects?
Vascular
The primary inhibitor of the fibrinolytic system is?
a2-Antiplasmin
In DIC presenting clinically as a hypercoaguable state, it is not unusual for which coagulation time to be paradoxically shortened?
aPTT
What test is normally prolonged and is the first indication of lupus anticoagulant (LAC)?
aPTT
Name the 4 platelet-specific proteins secreted from the a granules which are currently used as markers of platelet activation.
b-thromboglobulin, platelet factor 4, thrombospondin, and platelet-derived growth factor (PDGF)
What is the normal size of a platelet?
2-4 um
Which lab test is diagnostic for DIC?
There isn't one.
What is the normal reference range for platelets?
150,000-400,000 cells/uL
Which condition is classified as nonimmunologic thrombocytopenia? A) DIC B) ITP C) Storage pool defects D) Post-transfusion purpura
A
Which of the following clinical manifestations is most characteristic of a platelet disorder: A) Mucosal bleeding B) Hemarthrosis C) Rettroperitoneal hemorrhage D) Deep muscle hematomas
A
What event takes place in the extrinsic system?
Activation of factor VII to VIIa in the presence of calcium (factor III)
What events are involved in the normal formation of a platelet plug?
Activation, adhesion, aggregation, and release action
What is the name for platelet-to-platelet interaction which is an energy dependent process that requires ATP via glycolysis?
Aggregation
What is not considered a test for identification of a lupus anticoagulant?
Anticardiolipin antibodies
Which condition is classified as immunologic thrombocytopenia? A) DIC B) ITP C) Storage pool defects D) Post-transfusion purpura
B
Quantitative and qualitative platelet disorders and vascular disorders are abnormalities of primary hemostasis that result in?
Bleeding and purpura
All of the following statements are true regarding the detection of lupus anticoagulant (LAC) except: A) Platelet-Poor samples are required B) aPTT is frequently prolonged and the first indication of LAC C) A mixture of patient plasma with pooled normal plasma will correct the prolonged aPTT D) The diluted Russell's viper venom time may be used to confirm the presence of LAC
C
Which of the following is not an inherited vascular defect? A) Ehlers-Danlos syndrome B) Marfan syndorme C) Amyloidosis D) Giant hemangiomas
C
Which of the following is not characteristic of Bernard-Soulier syndrome? A) Prolonged bleeding time B) Absent platelet aggregation in response to bovine vWF or human vWF plus ristocetin C) Abnormal platelet aggregation in response to ADP, collagen, and epinephrine D) Abnormality in platelet membrane GPIb/IX
C
If an abnormal PT and aPTT do not correct with mixing studies, an inhibitor to what factors should be suspected?
Factors II, V, or X
Screening tests for coagulation abnormalities should include?
CBC, platelet count, and differential smear. PT, aPTT, fibrinogen, thrombin time, and bleeding time
Normal hemostasis is the result of the balanced interaction of the vascular endothelium and platelets with four biochemical systems. Name the 4 biochemical systems.
Coagulation, fibrinolytic, kinin, and complement
The PT and the aPTT both measure which pathway?
Common pathway
What system is composed of approximately 22 serum proteins that, working together with antibodies and clotting factors, play an important role as mediators of both immune and allergic reactions?
Complement system
On the basis of physical properties, coagulation proteins can be divided into what 3 groups?
Contact proteins, prothrombin proteins, and fibrinogen (thrombin sensitive) proteins
What is the function of thrombin?
Convert fibrinogen to fibrin
D-dimer formation is the result of the action of plasmin on?
Cross-linked fibrin
In primary fibrinolysis, which of the following laboratory tests will be abnormal? A) Platelet count B) D-dimer level C) Fibrinopeptide A level D) Thrombin time
D
Factor abnormality may occur as a result of?
Decreased synthesis, dysfunctional factor molecule(s), or inactivation of factors.
A patient presents with a platelet count of 212 x 10^9/L and a bleeding time of 12 minutes. These results probably suggest?
Defective platelet function
Bernard-Soulier syndrome is a rare autosomal-recessive bleeding disorder caused by?
Deficiency of the platelet GPIb/IX complex. (GPV, a thrombin substrate, has also been documented as being deficient)
The mechanisms responsible for thrombocytopenia include?
Deficient marrow production of platelets, sequestration of platelets in the spleen or hemangiomas, or accelerated loss or destruction of platelets from circulation.
What is the function of plasmin?
Destruction of fibrin
What test may be used to confirm the presence of lupus anticoagulant (LAC)?
Diluted Russell's Viper Venom Time (dRVVT)
The primary tissue source for tissue plasminogen activator (tPA) is?
Endothelial cells
The lysis of a clot in a 5 M urea solution is an indication of what disorder?
F XIII deficiency
For an abnormal PT and a normal aPTT, a mixing study of the PT should be performed using pooled normal plasma. If PT is corrected, what factor deficiency should be suspected?
Factor VII
The factor deficiency that produces a normal aPTT and an abnormal PT is?
Factor VII
The most common inhibitor to a specific clotting factor is?
Factor VIII:C
A patient with amyloidosis can have a deficiency of what factor?
Factor X
Prothrombin fragment F1.2 is formed by the action of which protease action on prothrombin?
Factor Xa
For specimens that have both an abnormal PT and aPTT that corrects with mixing studies, an inhibitor to what factors should be suspected?
Factors I, II, V, and X
Which factors are unique to the common pathway?
Factors I, II, V, and X
Which factors are classified as fibrinogen group proteins?
Factors I, V, VIII, & XIII
An inhibitor to what factors should be suspected if the PT is not corrected with a mixing study?
Factors II, V, VII, and X
What coagulation disorder shows decreased activity of F VIII:C?
Hemophilia A
Name the complex process by which the body spontaneously stops bleeding and maintains blood in the fluid state within the vascular compartment.
Hemostasis
A reptilase time will be normal in the presence of?
Heparin
The reptilase time will be normal in the presence of?
Heparin
Thrombin time will be abnormal in the presence of?
Heparin, afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia, and fibrinogen/fibrin degradation products (FDPs)
Decreased factor synthesis, interference by abnormal molecules, and loss, consumption, or inactivation of factors can lead to?
Impairment of the coagulation system
Aspirin exerts a permanent but limited effect on platelet aggregation by?
Inhibiting the action of the cyclo-oxygenase enzyme and production of thromboxane A2 (TXA2)
What system is activated by both the coagulation and fibrinolytic systems and is important in inflammation, vascular permeability, and chemotaxis?
Kinin system
What is the purpose of the PT test in monitoring hemostasis?
Measures factors of the extrinsic pathway
The organelle zone of a platelet is responsible for?
Metabolic activities
What 3 things are located within the matrix of a platelet?
Microtubules, microfilaments, and submembranous filaments.
What is the purpose of the aPTT test in monitoring hemostasis?
Monitoring heparin therapy (intrinsic)
What 4 things should be included in the patient history?
Physical appearance, site, severity, and frequency of bleeding episodes, patient and family history, drug history, and contributing or underlying illnesses.
The principle mechanism of platelet adhesion involves what 3 components?
Plasma, collagen fibers, and platelet membrane glycoprotein GPIb (receptor for vWF)
Name the molecular components of the fibrinolytic system.
Plasminogen, plasmin, plasminogen activators, plasmin inhibitors, thrombomodulin, thrombin-activatable fibrinolysis inhibitor, and fibrin(ogen)
Name 3 tests for identification of a lupus anticoagulant.
Platelet neutralization procedure (PNP), diluted Russell's viper venom time (dRVVT), and hexagonal phospholipid aPTT.
The lupus anticoagulants may be IgG, IgM, or IgA and can be detected by?
Platelet neutralization procedure (PNP), diluted Russells' viper venom time (dRVVT), or Hexagonal Phospholipid aPTT
What is the name of the mitogen that is stored in and secreted from the a granule of the platelet?
Platelet-derived growth factor (PDGF)
What type of samples are required for detecting of lupus anticoagulant (LAC)?
Platelet-poor
Which stage of hemostasis involves the enzymatic activation of coagulation proteins to produce fibrin from fibrinogen, thereby stabilizing the platelet plug?
Secondary
von Willebrand factor results in a lack of binding of _____________________ that leads to bleeding characteristic of platelet defects?
Platelets at the site of injury
Which stage of hemostasis is defined by platelet adhesion to exposed collagen within the endothelium of the vessel wall (formation of plug)?
Primary
In what 3 ways do platelets participate in hemostasis?
Provide a negatively charged phospholipid surface for factor X and prothrombin activation, release of substances that mediate vasoconstriction, platelet aggregation, coagulation, and vascular repair, and providing surface embrace glycoproteins such as GPIb and IIIa to attach to other platelets via fibrinogen.
What 3 things characterize platelet activation?
Pseudopods form, organelles including a granules and dense bodies are reorganized to the center, and contraction causes the granules to spill their contents into the open canalicular system (OCS)
Clinical conditions associated with DIC include?
Snake bites, sepsis, acute promyelocytic leukemia, placental abruption, trauma, cardiopulmonary bypass, and liver disease.
Coagulation factors may be divided into what 3 categories?
Substrate, cofactor, or enzymes
Biochemical characteristics of the endothelium render the cell surface thromboresistant by?
Synthesis and secretion of a vasodilator prostacyclin (PGI2), secretion of tissue plasminogen activator (t-PA), inactivation and clearance of thrombin, activity of the cofactor thrombomodulin in the thrombodependent activation of protein C, and the degradation of proaggregating substances.
The presence of heparin can be ruled out if what test is normal?
Thrombin time
What tests assesses thrombin-fibrinogen interactions and fibrin polymerization?
Thrombin time
During thrombus formation, what 4 things are incorporated into the clot?
Thrombin, plasminogen, tissue plasminogen activator, and antiplasmin
The role of protein C ( a vitamin K dependent factor) as an anticoagulant is related to the presence of?
Thrombin, thrombomodulin, & protein S
What is the most common primary hemostasis disorder?
Thrombocytopenia
Thrombocytopenia, fever, renal disease. microangiopathic hemolytic anemia, and neurologic complications are hallmark characteristics of?
Thrombotic thrombocytopenia purpura (TTP)
Name the microangiopathic process that leads to thrombocytopenia with thrombosis and bleeding.
Thrombotic thrombocytopenic purpura (TTP)
One of the most common congenital defects of primary hemostasis is?
von Willebrand disease
What coagulation disorder has decreased activity of F VIII:C, vWF:AG, and vWFR:Co, and a prolonged bleeding time test?
von Willebrand disease