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A4 - Hematology/Hemostasis&Thrombosis/Urinalysis&BFs - Harr > 2.4 Inhibitors, Thrombotic Disorders, and Anticoagulant Drugs > Flashcards

2.4 Inhibitors, Thrombotic Disorders, and Anticoagulant Drugs Flashcards

1
Q

Which characteristic describes antithrombin (AT)?
A. It is synthesized in megakaryocytes
B. It is activated by protein C
C. It is a cofactor of heparin
D. It is a pathological inhibitor of coagulation

A

C. It is a cofactor of heparin

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2
Q

Which laboratory test is affected by heparin therapy?
A. Thrombin time
B. Fibrinogen assay
C. Protein C assay
D. Protein S assay

A

A. Thrombin time

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3
Q

Abnormal APTT caused by a pathological circulating anticoagulant is:
A. Corrected with factor VIII-deficient plasma
B. Corrected with factor IX-deficient plasma
C. Corrected with normal plasma
D. Not corrected with normal plasma

A

D. Not corrected with normal plasma

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4
Q

The lupus anticoagulant affects which of the following tests?
A. Factor VIII assay
B. Factor IX assay
C. VWF assay
D. Phospholipid-dependent assays

A

D. Phospholipid-dependent assays

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5
Q

Which statement about warfarin (Coumadin) is accurate?
A. It is a vitamin B antagonist
B. It is not recommended for pregnant and lactating women
C. It needs AT as a cofactor
D. APTT test is used to monitor its dosage

A

B. It is not recommended for pregnant and lactating women

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6
Q

Which statement regarding protein C is correct?
A. It is a vitamin K-independent zymogen
B. It is activated by fibrinogen
C. It activates cofactors V and VIII
D. Its activity is enhanced by protein S

A

D. Its activity is enhanced by protein S

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7
Q

Which of the following is an appropriate screening test for the diagnosis of lupus anticoagulant?
A. Thrombin time
B. Diluted Russell viper venom test (DRVVT)
C. D-dimer test
D. Fibrinogen assay

A

B. Diluted Russell viper venom test (DRVVT)

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8
Q

Which of the following is most commonly associated with activated protein C resistance (APCR)?
A. Bleeding
B. Thrombosis
C. Epistaxis
D. Menorrhagia

A

B. Thrombosis

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9
Q

A 50-year-old man has been on heparin for the past 7 days. Which combination of tests is expected to be abnormal?
A. PT and APTT only
B. APTT, TT only
C. APTT, TT, fibrinogen assay
D. PT, APTT, TT

A

D. PT, APTT, TT

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10
Q

Which of the following drugs inhibits ADP-mediated PLT aggregation?
A. Heparin
B. Warfarin
C. Aspirin
D. Prasugrel

A

D. Prasugrel

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11
Q

Thrombin-TM complex is necessary for activation of:
A. Protein C
B. AT
C. Protein S
D. Factors V and VIII

A

B. AT

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12
Q

Which test is used to monitor heparin therapy?
A. INR
B. Chromogenic anti-factor Xa assay
C. TT
D. PT

A

B. Chromogenic anti-factor Xa assay

Heparin dosage can be best monitored by the chromogenic anti-factor Xa assay. In anti-factor Xa assay, the concentration of heparin is determined by inhibition of factor Xa by AT. Anti-factor Xa assay uses a reagent with a fixed concentration of factor Xa and AT. Heparin forms a complex with At and factor Xa reagents. Excess factor Xa combines with the chomogenic substrate to form a colored product; the color intensity is inversely proportional to the concentration of heparin. PT would be prolonged in heparin therapy, but the PT test is not sensitive enough to be used to monitor heparin therapy. Heparin inhibits thrombin and, therefore, causes prolonged TT. The TT test however, is not used to monitor heparin therapy either.

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13
Q

Which test is commonly used to monitor warfarin therapy?
A. INR
B. APTT
C. TT
D. Ecarin time

A

A. INR

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14
Q

Which clotting factors (cofactors) are inhibited by protein S?
A. Factors V and X
B. Factors Va and VIIIa
C. Factors VIII and IX
D. Factors VIII and X

A

B. Factors Va and VIIIa

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15
Q

Which drug promotes fibrinolysis?
A. Warfarin
B. Heparin
C. Urokinase
D. Aspirin

A

C. Urokinase

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16
Q

Diagnosis of lupus anticoagulant is confirmed by which of the following criteria?
A. Decreased APTT
B. Correction of APTT by mixing studies
C. Neutralization of the antibody by high concentration of phospholipids
D. Confirmation that abnormal coagulation tests are related to factor deficiencies

A

C. Neutralization of the antibody by high concentration of phospholipids

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17
Q

Which of the following abnormalities is consistent with the presence of lupus anticoagulant?
A. Decreased APTT/bleeding complications
B. Prolonged APTT/thrombosis
C. Prolonged APTT/thrombocytosis
D. Thrombocytosis/thrombosis

A

B. Prolonged APTT/thrombosis

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18
Q

Which of the following is a characteristic of LMWH?
A. Generally requires monitoring
B. Specifically acts on factors Va
C. Has a longer half-life compared with unfractionated heparin (UFH)
D. Can be used as a fibrinolytic agent

A

C. Has a longer half-life compared with unfractionated heparin (UFH)

19
Q

Which of the following tests is most likely to be abnormal in patients taking aspirin?
A. PLT morphology
B. PLT count
C. PLT aggregation
D. PT

A

C. PLT aggregation

20
Q

Which of the following is associated with AT deficiency?
A. Thrombocytosis
B. Thrombosis
C. Thrombocytopenia
D. Bleeding

A

B. Thrombosis

21
Q

Which of the following may be associated with thrombotic events?
A. Decreased protein C
B. Increased fibrinolysis
C. Afibrinogenemia
D. Idiopathic thrombocytopenic purpura

A

A. Decreased protein C

22
Q

Aspirin resistance may be associated with:
A. Bleeding
B. Factor VIII deficiency
C. Thrombosis
D. Thrombocytosis

A

C. Thrombosis

Up to 22% of patients taking aspirin become resistant to aspirin’s antiplatelet effect. Patients who are aspirin resistant have a high risk of thrombosis (heart attacks and strokes)

23
Q

Prolonged TT is indicative of which of the following antithrombotic agents?
A. Prasugrel
B. Clopidogrel
C. Aspirin
D. Heparin

A

D. Heparin

24
Q

Screening tests for thrombophilia should be performed on:
A. All pregnant women because of the risk of thrombosis
B. Patients with a negative family history
C. Patients with thrombotic events occurring at a young age
D. Patients who are receiving anticoagulant therapy

A

C. Patients with thrombotic events occurring at a young age

25
Q

Prothrombin G20210A is characterized by which of the following causes and conditions?
A. Single mutation of prothrombin molecule/bleeding
B. Single mutation of prothrombin molecule/thrombosis
C. Decreased levels of prothrombin in plasma/thrombosis
D. Increased levels of prothrombin in plasma/bleeding

A

B. Single mutation of prothrombin molecule/thrombosis

26
Q

Factor V Leiden promotes thrombosis by preventing:
A. Inactivation of factor Va
B. Activation of factor V
C. Activation of protein C
D. Activation of protein S

A

A. Inactivation of factor Va

27
Q

What is the approximate incidence of antiphospholipid antibodies in the general population?**
A. Less than 1%
B. 1% - 2%
C. 3% - 8%
D. 10% - 15%

A

B. 1% - 2%

28
Q

Which of the following laboratory tests is helpful in the diagnosis of aspirin resistance?
A. APTT
B. PT
C. PLT count and morphology
D. PLT aggregation

A

D. PLT aggregation

Currently, the PLT aggregation test is considered the gold standard for evaluation of aspirin resistance. In aspirin resistance, PLT aggregation is not inhibited by aspirin ingestion. Aspirin restiance has no effect on PLT count and morphology.

29
Q

Which of the following complications may occur as a result of decreased tissue factor pathway inhibitor
(TFPI)?
A. Increased episodes of hemorrhage
B. Increased risk of thrombosis
C. Impaired PLT plug formation
D. Immune thrombocytopenia

A

B. Increased risk of thrombosis

TFPI is released from the vasculature and is the most important inhibitor of the extrinsic pathway. TFPI inhibits factors Xa and VIIa-TF complex. Therefore, the deficiency of TFPI is associated with thrombosis.

30
Q

Factor VIII inhibitors occur in ________ of patients with factor VIII deficiency.
A. 40% - 50%
B. 30% - 40%
C. 25% - 30%
D. 20% - 25%

A

D. 20% - 25%

31
Q

Which therapy and resulting mode of action are appropriate for the treatment of a patient with a high titer of factor VIII inhibitors?
A. Factor VIII concentrate to neutralize the antibodies
B. Recombinant factor VIIa (rVIIa) to activate factor X
C. Factor X concentrate to activate the common pathway
D. FFP to replace factor VIII

A

B. Recombinant factor VIIa (rVIIa) to activate factor X

32
Q

The Bethesda assay is used for which determination?
A. Lupus anticoagulant titer
B. Factor VIII inhibitor titer
C. Factor V Leiden titer
D. Protein S deficiency

A

B. Factor VIII inhibitor titer

33
Q

Hyperhomocysteinemia may be a risk factor for:
A. Bleeding
B. Thrombocythemia
C. Thrombosis
D. Thrombocytopenia

A

C. Thrombosis

Elevated plasma homocysteine is a risk factor for the development of DVT, coronary heart disease and stroke. Homocystinemia may be inherited or acquired. Acquired homocystinemia is caused by dietary deficiencies of vitamins B6, B12, and folic acid.

34
Q

Which drug may be associated with DVT?
A. Aspirin
B. tPA
C. Oral contraceptives
D. Clopidogrel (Plavix)

A

C. Oral contraceptives

35
Q

Argatroban may be used as an anticoagulant drug in patients with:
A. DVT
B. Hemorrhage
C. TTP
D. Thrombocytosis

A

A. DVT

Argatroban is a direct thrombin-inhibiting drug and may be used as an anticoagulant in patients with HIT to prevent thrombosis. Argatroban is a small synthetic molecule that binds to free and clot-bound thrombin. Argatroban affects TT, PT, APTT, and activated clotting time (ACT) tests. The APTT test is recommended for monitoring the dosage with the target therapeutic range of 1.5 to 3.0 times the mean of the laboratory reference range. In patients with lupus anticoagulant or factor deficiencies, baseline APTT is prolonged; in these conditions, Ecarin time can be used as an alternative assay.

36
Q

Heparin-induced thrombocytopenia (HIT) results from:
A. Antibodies to heparin
B. Antibodies to PLTs
C. Antibodies to PF4
D. Antibodies to heparin-PF4 complex

A

D. Antibodies to heparin-PF4 complex

37
Q

Which laboratory tests is used to screen for APCR?
A. Mixing studies with normal plasma
B. Mixing studies with factor-deficient plasma
C. Modified APTT with and without APC
D. Modified PT with and without APC

A

C. Modified APTT with and without APC

38
Q

Ecarin clotting time may be used to monitor:
A. Heparin therapy
B. Warfarin therapy
C. Fibrinolytic therapy
D. Bivalirudin

A

D. Bivalirudin

Ecarin clotting time, a snake venom-based clotting assay, may be used to monitor bivalirudin therapy in instances when the baseline APTT is prolonged as a result of lupus anticoagulant or factor deficiencies. Heparin therapy is monitored by using the anti-factor Xa assay; warfarin therapy is monitored with the INR. Fibrinolytic therapy may be monitored by using the D-dimer test.

39
Q

Which of the following may interfere with the APCR screening test?
A. Lupus anticoagulant
B. Protein C deficiency
C. AT deficiency
D. Protein S deficiency

A

A. Lupus anticoagulant

The lupus anticoagulant interferes with the APCR screening assay based on the APTT ratio with and without the addition of APC. Persons with the lupus anticoagulant have a prolonged APTT that renders the test invalid for APCR screening.

APCR - activated protein C resistance

40
Q

Thrombophilia may be associated with which of the following disorders?
A. Afibrinogenemia
B. Hypofibrinogenemia
C. Factor VIII inhibitors
D. Hyperfibrinogenemia

A

D. Hyperfibrinogenemia

Hyperfibrinogenemia is a risk factor for thrombophilia (blood can easily form clots). Fibrinogen is an acute-phase reactant and may be increased in inflammation, stress, obesity, smoking, and medications, such as oral contraceptives. Hypofibinogenmia, afibrinogenemia, and factor VIII inhibiotors are associated with bleeding.

41
Q

Which of the following anticoagulant drugs can be used in patients with HIT?
A. Warfarin
B. Heparin
C. Aspirin
D. Argatroban

A

D. Argatroban

Argatroban is a direct thrombin inhibitor drug and used in patients with HIT who cannot tolerate heparin or LMWH therapy. Warfarin should not be used for anticoagulation in persons with HIT because it causes a fall in protein C concentration and vitamin K-dependent coagulation factors. Aspirin is an antiplatelet drug.

42
Q

Which of the following is the preferred method to monitor heparin therapy at the point of care during cardiac surgery?
A. APTT
B. ACT
C. PT
D. TT

A

B. ACT

ACT is a point-of-care coagulation test used to monitor high-dose heparin therapy during cardiac surgery, cardiac angioplasty, hemodialysis, and other major surgeries. It is the preferred method to determine if sufficient heparin was administered to prevent clotting during surgery because it is more rapid than the APTT test. The test uses a clot activator, such as kaolin or Celite, to stimulate coagulation, and the time in seconds is linearly related to the dose of heparin adminstered. The ACT test is available in different formats, and the reference range varies, depending on the method used. At low to moderate heparin doeses, the ACT test does not correlate well with the APTT test or the anti-factor Xa assay.

43
Q

Mrs. Smith has the following laboratory results and no history of bleeding:
_______________________
APTT = prolonged
APTT results on a 1:1 mixture of the patient’s plasma with normal plasma:
Preincubation: prolonged APTT
2-hour incubation: prolonged APTT

These results are consistent with:
A. Factor VIII deficiency
B. Factor VIII inhibitors
C. Lupus anticoagulant
D. Protein C deficiency

A

C. Lupus anticoagulant

Mixing studies differentiate factor deficiencies from factor inhibitors. Lupus anticoagulant is associated with thrombosis, and it is directed against phospholipid-dependent coagulation tests, such as a the APTT test. In patients with lupus anticoagulant, after the patient’s plasma is mixed with normal plasma, APTT remains prolonged immediately after mixing and following 2 hours of incubation. Factor VIII deficiency and factor VIII inhibitor are associated with bleeding.

44
Q

Which test may be used to monitor LMWH therapy?
A. APTT
B. INR
C. Anti-factor Xa heparin assay
D. ACT

A

C. Anti-factor Xa heparin assay

A4 - Hematology/Hemostasis&Thrombosis/Urinalysis&BFs - Harr (18 decks)

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