A 35 year old woman has a history of menorrhagia and experiences excessive bleeding after a tooth extraction. She reports no tendency to bruise, no nose bleeds and no petechiae. She has a brother and sister,neither of whom show a bleeding tendency. Her mother has a history similar to her own but her father has no bleeding tendency. Select the most likely disorder from the list below.
A) von Willebrand's Disease
ADP helps promote aggregation by:
D) stimulating platelets to adhere to each other and change shape
Which of the following automated coagulation methods is not sensitive to lipemia?
A) decreased movement of an iron ball in an electromagnetic field when clots form
What is the role of vWF with regard to Factor VIII? Briefly explain why von Willebrand's disease causes a functional Factor VIII deficiency.
vWF is a carrier protein for Factor VIII, which protects Factor VIII from degradation during travel through the body.
vWD causes functional factor VIII disorder because it is directly linked to the quantity of Factor VIII in the body. If vWF is decreased in qty then there is less vWF to "protect" Factor VIII as it travels and it will become damaged and dysfunctional before reaching the site of injury. If vWF is present but qualitatively defective then it will not properly protect Factor VIII and the same absence of functional Factor VIII will occur.
(T/F) The prothrombin time tests the factors in the extrinsic arm of the coagulation cascade and the APTT tests the intrinsic arm. Both the PT and PTT are screening tests. Abnormal results for patients not on anticoagulant therapy should be followed by mixing studies, then testing for specific factor deficiencies.
True
In three words, describe the basic stages of platelet activation in primary hemostasis.
Activation
Adhesion
Aggregation
(T/F) In the platelet function assay (PFA), platelets from a whole blood sample are assessed for adequate function by exposure to collagen and either ADP or epinephrine.
True
(T/F) Platelet factor 4 is a cytokine released by activated platelets which can bind to heparin and interfere with heparin testing.
True
(T/F) Alpha granules contain plasma proteins such as fibrinogen, vWF, Factor V and Factor VIII.
True
The cause of hemophilia A is:
D) deficient or defective Factor VIII
(T/F) Hemophilia A is an Xlinkedrecessive bleeding disorder and the most common life threatening bleeding disorder in the US.
True
What product is responsible for stabilization of the platelet plug?
A) fibrin
Platelet counts below the normal range can be due to conditions involving either decreased production in the bone marrow or increased destruction by the RE system or the immune system. Give an example of a condition that results in decreased platelet counts from each of these categories.
Leukemias (and other marrow disorders) can cause a reduction in platelet production from the marrow.
Increased destruction from HUS?
There are many possible inherited defects or deficiencies of platelets. Name one and briefly describe the defect.
Glanzman thrombothenia is an issue with the platelet membrane which causes lack of aggregation at the site of injury. The initial platelets will still adhere to the site.
The activity of lupus anticoagulant and anti cardiolipin antibodies appears to be directed against:
C) Phospholipid
The reagents in the aPTT assay include:
A) phospholipid, calcium and silica
When cytokines are released after trauma or during the course of cancer, this causes an increased risk for disseminated intravascular coagulation. Why?
A) increased expression of both pro and anticoagulant factors
A patient presents with the following results:
PT normal, PTT prolonged, bleeding time normal
Mixing studies: normal plasma corrects the PTT immediately and after extended incubation. What is the mostlikely disorder from those listed below?
C) Factor IX deficiency
Factor VIIIa is regulated by:
B) spontaneous dissociation
A functional test of Factor V involves comparing aPTT results to an aPTT run after the addition of activated protein C. What will adding protein C do to the clotting time in the second test if the patient has Factor V Leiden?
C) The clotting time in the second test will be less than twice the clotting time in the original test.
(T/F) A deficiency in Factor XII (Hagemann factor) can lead to thrombosis.
True
Glycoprotein 1b is important in:
B) working with von Willebrand's factor to bind to the surface of the blood vessel
A defect in GP1b leads to:
A) Bernard Soulier Disease
Heparin inhibits clotting by:
D) enhancing the action of antithrombin
A patient recovering from a myocardial infarct experiences a sudden drop in platelet count 5 days after surgery. This is most likely due to:
D) heparin induced thrombocytopenia
The INR is important for comparing results from different labs because it:
A) normalizes the PT results based on the strength of the reagents used to induce clot formation
A mixing study is performed using patient plasma mixed with normal platelet poor plasma. The normal plasma initially corrects the prolonged PTT but a second sample, tested after incubation at 37C for 30 minutes is not corrected. What does this mean?
D) the patient has a factor inhibitor (like Correct! anti factor IX)
Two siblings discover they have the prothrombin 20210A mutation after one of their parents is identified as carrying that gene and the whole family is tested. They are heterozygous for the mutation. Their father started experiencing symptoms in his late 40s. Will they experience symptoms?
B) very likely
If a sample is contaminated with tissue factor, what will happen to coag testing?
B) The test will be shorter than expected because of the additional tissue factor present, stimulating coagulation.
Describe the consumptive coagulopathy known as Disseminated Intravascular Coagulation (DIC). Include in your answer a few different circumstances where DIC might occur and which laboratory tests might be used to help diagnose this condition.
DIC is essentially a heightened coagulation response in the body (inhibitory mechanisms are overwhelmed).In acute DIC the use of coagulation factors exceeds the body's ability to produce coagulation factors and severe bleeding can occur.
DIC can occur in the case of excess tissue factor, presence of proteolytic enzymes acting on Factor X or XII, etc.
No single test can confirm DIC, but PT/PTT are indirect tests that can indicate abnormal clotting factor depletion and DDimer can determine if clot formation/breakdown is actively occurring
Coagulation factors affected by coumarin drugs are:
B) II, VII, IX, and X
When cytokines are released after trauma or during the course of cancer, this causes an increased risk for disseminated intravascular coagulation. Why?
A) increased expression of both pro and anticoagulant factors
Heparin inhibits clotting by:
D) enhancing the action of antithrombin
(T/F) Antithrombin is a naturallyoccurringmolecule designed to counter the effects of excess thrombin. It is part ofa feedback loop in the coagulation cascade.
True
Name two disorders in the category of increased destruction of platelets.
HUS and HIT
(T/F) Glanzmann's thromasthenia is caused by a defect or deficiency in the GP IIb/IIIa complex in platelets, which produces a decreased response to agonists in platelet aggregation testing.
True
Which of the following statements is true?
A) The intrinsic and extrinsic pathway models of coagulation accurately describe what happens "in vitro" but do not correctly describe the "in vivo" interactions.
Which of the following describes a function of plasmin?
C) Destruction of fibrin
Thrombin is considered the "driver" of the coagulation cascade. Which of the following describes its main function.
