Question 1

What anticoagulant therapy is monitored using the ecarin clotting time (ECT)?

Accepted Answer

A) unfractionated heparin 
B) warfarin 
C) LMWH 
D) direct thrombin inhibitors 
A) unfractionated heparin 
B) warfarin 
C) LMWH 
D) direct thrombin inhibitors D

Question 2

Once a patient is stabilized on warfarin therapy,how often should he or she be monitored?

Accepted Answer

A) once every 6 months 
B) once every week 
C) once a year 
D) once a month 
A) once every 6 months 
B) once every week 
C) once a year 
D) once a month D

Question 3

Low-molecular-weight heparin (LMWH)

Accepted Answer

A) is essentially as effective therapeutically as unfractionated heparin (UFH). 
B) has the same antithrombin effect as UFH. 
C) can be monitored using the PTT. 
D) has a shorter in vivo half-life than UFH. 
A) is essentially as effective therapeutically as unfractionated heparin (UFH). 
B) has the same antithrombin effect as UFH. 
C) can be monitored using the PTT. 
D) has a shorter in vivo half-life than UFH. A

Question 4

All of the following serine proteases are bound and inhibited by antithrombin except

Accepted Answer

A) Xa 
B) IXa 
C) VIIa 
D) XIa 
A) Xa 
B) IXa 
C) VIIa 
D) XIa

Question 5

Why is the platelet count monitored daily for a patient receiving heparin therapeutically?

Accepted Answer

A) Platelets increase when a patient is overheparinized. 
B) Platelets decrease when a patient is overheparinized. 
C) A significant decrease in the platelet count is evidence for heparin-induced thrombocytopenia. 
D) A significant increase in the platelet count is early evidence for heparin-induced thrombocytosis. 
A) Platelets increase when a patient is overheparinized. 
B) Platelets decrease when a patient is overheparinized. 
C) A significant decrease in the platelet count is evidence for heparin-induced thrombocytopenia. 
D) A significant increase in the platelet count is early evidence for heparin-induced thrombocytosis.

Question 6

A clinical laboratory receives a new lot of PTT reagent,so clinical laboratory scientists in the laboratory need to establish the heparin therapeutic range for this new reagent lot.How should this be done?

Accepted Answer

A) Compare PTT results for patient heparinized samples to those for the lot of PTT reagent that is presently being used. 
B) Perform chromogenic Xa and PTT assays on patient heparinized samples, and do a statistical analysis of result comparisons. 
C) Add heparin at various therapeutic concentrations to normal plasma, and perform PTT on each concentration using the new lot of reagent. 
D) Add heparin at high concentration to one normal plasma, make dilutions of this plasma, and then perform PTT on each diluted sample using the new lot of reagent. 
A) Compare PTT results for patient heparinized samples to those for the lot of PTT reagent that is presently being used. 
B) Perform chromogenic Xa and PTT assays on patient heparinized samples, and do a statistical analysis of result comparisons. 
C) Add heparin at various therapeutic concentrations to normal plasma, and perform PTT on each concentration using the new lot of reagent. 
D) Add heparin at high concentration to one normal plasma, make dilutions of this plasma, and then perform PTT on each diluted sample using the new lot of reagent.

Question 7

All of the following are true about the activated clotting time (ACT)except

Accepted Answer

A) it is useful for monitoring warfarin therapy. 
B) it can be performed in the clinic or at the patient's bedside. 
C) it uses diatomaceous earth as the clot activator. 
D) the clinical laboratory scientist inverts the tube until a clot forms. 
A) it is useful for monitoring warfarin therapy. 
B) it can be performed in the clinic or at the patient's bedside. 
C) it uses diatomaceous earth as the clot activator. 
D) the clinical laboratory scientist inverts the tube until a clot forms.

Question 8

After confirmation of a deep vein thrombosis (DVT)and pulmonary embolus in a patient,a baseline coagulation screen and platelet count are obtained.His fibrinogen is 620 mg/dL.When the PTT is performed at 6 hours after initiation of therapy,it is 45 seconds (reference range,25 to 37 seconds).What should be done?

Accepted Answer

A) Report the PTT as not responding. 
B) Monitor the patient with the chromogenic anti-Xa assay. 
C) Add an additional standard amount of heparin to the patient plasma to improve the sensitivity. 
D) Add a standard amount of antithrombin to the patient plasma to improve the sensitivity. 
A) Report the PTT as not responding. 
B) Monitor the patient with the chromogenic anti-Xa assay. 
C) Add an additional standard amount of heparin to the patient plasma to improve the sensitivity. 
D) Add a standard amount of antithrombin to the patient plasma to improve the sensitivity.

Question 9

Which of the following is true related to the use of aspirin to prevent cardiovascular disease?

Accepted Answer

A) It is used to prevent arterial thrombosis. 
B) New studies show it is not effective. 
C) It works well but must be carefully monitored with monthly bleeding times. 
D) Aspirin monitoring tests such as thromboxane B2 are now easy to perform and widely available. 
A) It is used to prevent arterial thrombosis. 
B) New studies show it is not effective. 
C) It works well but must be carefully monitored with monthly bleeding times. 
D) Aspirin monitoring tests such as thromboxane B2 are now easy to perform and widely available.

Question 10

An INR of 6.5 is obtained on a patient taking warfarin.All quality control is acceptable.What should be done?

Accepted Answer

A) Report the result. 
B) Report only the PT in seconds and ignore the INR. 
C) Send an e-mail to the healthcare provider. 
D) Call the healthcare provider immediately. 
A) Report the result. 
B) Report only the PT in seconds and ignore the INR. 
C) Send an e-mail to the healthcare provider. 
D) Call the healthcare provider immediately.

Question 11

Elevated urinary levels of 11-dehydrothromboxane B₂ identify patients who are

Accepted Answer

A) at risk for heparin-induced thrombocytopenia. 
B) overanticoagulated with warfarin. 
C) resistant to aspirin antiplatelet therapy. 
D) resistant to direct thrombin inhibitors. 
A) at risk for heparin-induced thrombocytopenia. 
B) overanticoagulated with warfarin. 
C) resistant to aspirin antiplatelet therapy. 
D) resistant to direct thrombin inhibitors.

Question 12

Warfarin skin necrosis occurs within the first 2 to 3 days after starting warfarin therapy because

Accepted Answer

A) the platelet count decreases to fewer than 100 × 109/L, and significant bleeding occurs. 
B) protein C decreases significantly before full anticoagulation, and skin thrombosis results. 
C) prothrombin decreases rapidly generating less thrombin, and significant bleeding occurs. 
D) plasminogen increases, and rapid clot lysis occurs. 
A) the platelet count decreases to fewer than 100 × 109/L, and significant bleeding occurs. 
B) protein C decreases significantly before full anticoagulation, and skin thrombosis results. 
C) prothrombin decreases rapidly generating less thrombin, and significant bleeding occurs. 
D) plasminogen increases, and rapid clot lysis occurs.

Question 13

A patient is admitted through the hospital emergency department with thrombosis,and heparin is initially begun.Her baseline PTT,before heparin therapy,is prolonged at 68 seconds.Further laboratory studies determine that she has the lupus anticoagulant.What test should be used to monitor her heparin therapy?

Accepted Answer

A) PTT 
B) PTT after first adding antithrombin to her plasma 
C) chromogenic anti-Xa assay 
D) TT after first making a 1:10 dilution of the patient plasma 
A) PTT 
B) PTT after first adding antithrombin to her plasma 
C) chromogenic anti-Xa assay 
D) TT after first making a 1:10 dilution of the patient plasma

Question 14

Why is it important to monitor patients who are receiving anticoagulant therapy?

Accepted Answer

A) Drugs are expensive. 
B) Prophylactic and therapeutic dosage ranges are unknown. 
C) Patients commonly abuse these drugs. 
D) Clinical consequences for overdosing or underdosing are significant. 
A) Drugs are expensive. 
B) Prophylactic and therapeutic dosage ranges are unknown. 
C) Patients commonly abuse these drugs. 
D) Clinical consequences for overdosing or underdosing are significant.

Question 15

Direct thrombin inhibitors include lepirudin and argatroban;they

Accepted Answer

A) require binding to antithrombin to provide their anticoagulant effect. 
B) are usually monitored using the PT. 
C) are used when a patient develops heparin-induced thrombocytopenia. 
D) bind all serine proteases. 
A) require binding to antithrombin to provide their anticoagulant effect. 
B) are usually monitored using the PT. 
C) are used when a patient develops heparin-induced thrombocytopenia. 
D) bind all serine proteases.

Question 16

A patient is stabilized on warfarin therapy and being monitored using the prothrombin time (PT)followed by calculation of the international normalized ratio (INR).The formula for calculating the INR is:
INR = (PTₚₐₜᵢₑₙₜ/PTₙₒᵣₘₐₗ)ᴵˢᴵ (where ISI = international sensitivity index)
What is used for the PTₙₒᵣₘₐₗ?

Accepted Answer

A) arithmetic mean PT for the control 
B) geometric mean PT for the reference population 
C) arithmetic mean PT as found in a standard reference textbook 
D) geometric mean PT reported by the manufacturer of the PT reagent being used 
A) arithmetic mean PT for the control 
B) geometric mean PT for the reference population 
C) arithmetic mean PT as found in a standard reference textbook 
D) geometric mean PT reported by the manufacturer of the PT reagent being used

Question 17

Unfractionated heparin is commonly monitored by the

Accepted Answer

A) PT. 
B) partial thromboplastin time (PTT). 
C) thrombin time (TT). 
D) kinetic fibrinogen. 
A) PT. 
B) partial thromboplastin time (PTT). 
C) thrombin time (TT). 
D) kinetic fibrinogen.

Exam 43: Antithrombotic Therapies and their Laboratory Assessment

What anticoagulant therapy is monitored using the ecarin clotting time (ECT)?

Once a patient is stabilized on warfarin therapy,how often should he or she be monitored?

Low-molecular-weight heparin (LMWH)

All of the following serine proteases are bound and inhibited by antithrombin except

Why is the platelet count monitored daily for a patient receiving heparin therapeutically?

A clinical laboratory receives a new lot of PTT reagent,so clinical laboratory scientists in the laboratory need to establish the heparin therapeutic range for this new reagent lot.How should this be done?

All of the following are true about the activated clotting time (ACT)except

Which of the following is true related to the use of aspirin to prevent cardiovascular disease?

An INR of 6.5 is obtained on a patient taking warfarin.All quality control is acceptable.What should be done?

Elevated urinary levels of 11-dehydrothromboxane B₂ identify patients who are

Warfarin skin necrosis occurs within the first 2 to 3 days after starting warfarin therapy because

Why is it important to monitor patients who are receiving anticoagulant therapy?

Direct thrombin inhibitors include lepirudin and argatroban;they

Unfractionated heparin is commonly monitored by the

An Overview of Clinical Laboratory Hematology

Safety in the Hematology Laboratory

Blood Specimen Collection

Care and Use of the Microscope

Quality Assurance in Hematology and Hemostasis Testing

Cellular Structure and Function

Hematopoiesis

Erythrocyte Production and Destruction

Erythrocyte Metabolism and Membrane Structure and Function

Hemoglobin Metabolism

Iron Kinetics and Laboratory Assessment

Leukocyte Development, Kinetics, and Functions

Platelet Production, Structure, and Function

Manual, Semiautomated and Point-of-Care Testing in Hematology

Automated Blood Cell Analysis

Examination of the Peripheral Blood Film and Correlation with the Complete Blood Count

Bone Marrow Examination

Body Fluid Analysis in the Hematology Laboratory

Anemias: Red Blood Cell Morphology and Approach to Diagnosis

Disorders of Iron Kinetics and Heme Metabolism

Anemias Caused by Defects of DNA Metabolism

Bone Marrow Failure

Introduction to Increased Destruction of Erythrocytes

Intrinsic Defects Leading to Increased Erythrocyte Destruction

Extrinsic Defects Leading to Increased Erythrocyte Destruction Nonimmune Causes

Extrinsic Defects Leading to Increased Erythrocyte Destruction Immune Causes

Hemoglobinopathies (Structural Defects in Hemoglobin)

Thalassemias

Nonmalignant Leukocyte Disorders

Cytogenetics

Molecular Diagnostics in Hematopathology

Flow Cytometric Analysis in Hematologic Disorders

Myeloproliferative Neoplasms

Myelodysplastic Syndromes

Acute Leukemias

Mature Lymphoid Neoplasms

Normal Hemostasis and Coagulation

Hemorrhagic Disorders and Laboratory Assessment

Thrombotic Disorders and Laboratory Assessment

Thrombocytopenia and Thrombocytosis

Qualitative Disorders of Platelets and Vasculature

Laboratory Evaluation of Hemostasis

Hemostasis and Coagulation Instrumentation

Pediatric and Geriatric Hematology and Hemostasis

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